Identification of Low-Density Lipoprotein Receptor-Related Protein 1 as a CXCL14 Receptor Using Chemically Synthesized Tetrafunctional Probes


CA9 and PRELID2; hypoxia-responsive potential therapeutic targets for pancreatic ductal adenocarcinoma as per bioinformatics analyses.

A strong hypoxic environment has been observed in pancreatic ductal adenocarcinoma (PDAC) cells, which contributes to drug resistance, tumor progression, and metastasis. Therefore, we performed bioinformatics analyses to investigate potential targets for the treatment of PDAC. To identify potential genes as effective PDAC treatment targets, we selected all genes whose expression level was related to worse overall survival (OS) in The Cancer Genome Atlas (TCGA) database and selected only the genes that matched with the genes upregulated due to hypoxia in pancreatic cancer cells in the dataset obtained from the Gene Expression Omnibus (GEO) database. Although the extracted 107 hypoxia-responsive genes included the genes that were slightly enriched in angiogenic factors, TCGA data analysis revealed that the expression level of endothelial cell (EC) markers did not affect OS. Finally, we selected CA9 and PRELID2 as potential targets for PDAC treatment and elucidated that a CA9 inhibitor, U-104, suppressed pancreatic cancer cell growth more effectively than 5-fluorouracil (5-FU) and PRELID2 siRNA treatment suppressed the cell growth stronger than CA9 siRNA treatment. Thus, we elucidated that specific inhibition of PRELID2 as well as CA9, extracted via exhaustive bioinformatic analyses of clinical datasets, could be a more effective strategy for PDAC treatment.


Enhanced tumor specific drug release by hypoxia sensitive dual-prodrugs based on 2-nitroimidazole

Hypoxia in cancer is important in the development of cancer-selective medicines. Here, a novel hypoxia-responsible dual-prodrug is described. We designed and synthesized 2-nitroimidazole derivatives which spontaneously release both a PYG inhibitor and gemcitabine under hypoxic conditions. One such derivative, a prodrug 9 was found to be stable against chemical and enzymatic hydrolysis, and upon chemical reduction of the nitro group on imidazole, successfully releases both drugs. In an in vitro proliferation assay using human pancreatic cells, compound 9 exhibited significant anti-proliferative effects in hypoxia but fewer effects in normoxia. Consequently, prodrug 9 should be useful for cancer treatment due to its improved cancer selectivity and potential to overcome drug resistance.

Bioorganic & Medicinal Chemistry Letters


Residue-selective CH sulfenylation enabled by acid-activated S-acetamidomethyl cysteine sulfoxide with application to one-pot stapling and lipidation sequence


Development of a novel tocopheryl ester for suppression of lipid accumulation without cytotoxicity by optimization of dicarboxylic ester moiety


S-Protected cysteine sulfoxide-enabled tryptophan-selective modification with application to peptide lipidation


Identification of an endoplasmic reticulum proteostasis modulator that enhances insulin production in pancreatic β cells.

Perturbation of endoplasmic reticulum (ER) proteostasis is associated with impairment of cellular function in diverse diseases, especially the function of pancreatic β cells in type 2 diabetes. Restoration of ER proteostasis by small molecules shows therapeutic promise for type 2 diabetes. Here, using cell-based screening, we report identification of a chemical chaperone-like small molecule, KM04794, that alleviates ER stress. KM04794 prevented protein aggregation and cell death caused by ER stressors and a mutant insulin protein. We also found that this compound increased intracellular and secreted insulin levels in pancreatic β cells. Chemical biology and biochemical approaches revealed that the compound accumulated in the ER and interacted directly with the ER molecular chaperone BiP. Our data show that this corrector of ER proteostasis can enhance insulin storage and pancreatic β cell function.


Late-stage macrolactonisation enabled by tandem acyl transfers followed by desulphurisation

Intramolecular -acylation of a thiol-installed threonine with a thioester unit, followed by S-O acyl transfer and subsequent desulphurisation, allows the synthesis of lactone peptides. A protocol has been developed enabling the cyclisation of a linear peptide, a reaction which has not been achieved by conventional methods.


Copper (II)-mediated C-H sulphenylation or selenylation of tryptophan enabling macrocyclization of peptides


Peptide Cyclization Mediated by Metal-Free S-Arylation: S-Protected Cysteine Sulfoxide as an Umpolung of Cysteine Nucleophile


Identification of Functional Domains of CXCL14 Involved in High-Affinity Binding and Intracellular Transport of CpG DNA


Discovery of a Macropinocytosis-Inducing Peptide Potentiated byMedium-Mediated Intramolecular Disulfide Formation


Sequence-independent traceless method for preparation of peptide/protein thioesters using CPaseY-mediated hydrazinolysis

Proteins incorporating artificial moieties such as fluorophores and drugs have enjoyed increasing use in chemical biology and drug development research. Preparation of such artificial protein derivatives has relied mainly on native chemical ligation in which peptide/protein thioesters chemoselectively react with N-terminal cysteine peptides to afford protein molecules. The protein thioesters derived from expressed proteins represent thioesters that are very useful for the preparation of artificial proteins by native chemical ligation with synthetic peptides with N-terminal Cys. We recently have developed a traceless thioester-producing protocol using carboxypeptidase Y (CPaseY) which is compatible with an expressed protein. The traceless character is ensured by CPaseY-mediated hydrazinolysis of C-terminal Xaa (X)-Cys-Pro-Leu-OH sequence followed by an auto-processing of the Cys-Pro (CP) dipeptide unit, affording the corresponding X-thioester (X-SR). However, hydrazinolysis of the amide bond in the prolyl leucine junction depends significantly on the nature of X. In the case of hydrophobic X residues, the hydrazinolysis overreacts to give several hydrazides while the reaction of hydrophilic X residues proceeds slowly. In this research, we attempted to develop an X-independent CPaseY-mediated protocol and found that the incorporation of a triple CP sequence into the C-terminal end (X-(CP)-Leu-OH) allows for efficient X-SR formation in a manner that is independent of X.


Deprotection of S-Acetamidomethyl Cysteine with Copper (II) and 1,2-Aminothiols under Aerobic Conditions


Sulfanylmethyldimethylaminopyridine as a Useful Thiol Additive for Ligation Chemistry in Peptide/Protein Synthesis

Sulfanylmethyl-installed dimethylaminopyridine, 2-sulfanylmethyl-4-dimethylaminopyridine (), has an acidic thiol group comparable to that in aryl thiols due to the formation of a zwitterion consisting of a thiolate anion and a pyridinium cation. It can be used as an additive for native chemical ligation. The alkyl thiol in allows it to be used for the one-pot native chemical ligation-desulfurization protocol in peptide synthesis. The utility of in the synthesis of cyclic peptides is demonstrated.


Copper-mediated deprotection of thiazolidine and selenazolidine derivatives applied to native chemical ligation


Development of a 1,3a,6a-triazapentalene derivatives as a compact and thiol-specific fluorescent labeling reagent


Asymmetric Synthesis of α-Amino Phosphonic Acids Using Stable Imino Phosphonate as a Universal Precursor


Traceless synthesis of protein thioesters using enzyme-mediated hydrazinolysis and subsequent self-editing of cysteinyl prolyl sequence


A photo-activatable peptide mimicking functions of apolipoprotein A-I

Apolipoprotein A-I (apoA-I) plays a critical role in high-density lipoprotein (HDL) biogenesis, function and structural dynamics. Peptides that mimic apoA-I have a short amphipathic α-helical structure that can functionally recapitulate many of the same biologic properties of full-length apoA-I in HDL. Hence, they might be expected to have clinical applications in the reduction of atherosclerosis. However, nonspecific cellular efflux of cholesterol induced by apoA-I mimetic peptides might cause side effects that are, as yet, unidentified. In this study, we developed a photo-activatable peptide, 2F*, which is an 18 amino acid peptide mimicking apoA-I bearing an internal photocleavable caging group that is designed to assume an α-helical structure in response to a light stimulus and trigger efflux of cholesterol from cells. Without light irradiation, 2F* peptide showed a low tendency for the formation of α-helices, and therefore did not associate with lipids and failed to induce efflux of cholesterol. In addition, 2F* did not cause hemolysis under our experimental condition. Mass spectrometry indicated that, after light exposure, the caging group detached from 2F* and it assumed the α-helical structure in the presence of lipids, and enhanced cholesterol efflux from cells. Photo-activatable peptides such as 2F* that control cholesterol efflux following light stimulus may be useful for future atherosclerosis-reducing therapies.


Development of a turn-on fluorescent traceable linker employing N-sulfanylethylcoumarinyl amide for enrichment and visualization of target proteins Current Topic Drug Discovery: Recent Progress and the Future


A recyclable hydrophobic anchor-tagged asymmetric amino thiourea catalyst


ProteoFind: A script for finding proteins that are suitable for chemical synthesis


Direct enantioselective indolylation of peptidyl imine for the synthesis of indolyl glycine-containing peptides


Light-induced propulsion of a giant liposome driven by peptide nanofibre growth

Light-driven nano/micromotors are attracting much attention, not only as molecular devices but also as components of bioinspired robots. In nature, several pathogens such as Listeria use actin polymerisation machinery for their propulsion. Despite the development of various motors, it remains challenging to mimic natural systems to create artificial motors propelled by fibre formation. Herein, we report the propulsion of giant liposomes driven by light-induced peptide nanofibre growth on their surface. Peptide-DNA conjugates connected by a photocleavage unit were asymmetrically introduced onto phase-separated giant liposomes. Ultraviolet (UV) light irradiation cleaved the conjugates and released peptide units, which self-assembled into nanofibres, driving the translational movement of the liposomes. The velocity of the liposomes reflected the rates of the photocleavage reaction and subsequent fibre formation of the peptide-DNA conjugates. These results showed that chemical design of the light-induced peptide nanofibre formation is a useful approach to fabricating bioinspired motors with controllable motility.


Resin-bound crypto-thioester for native chemical ligation


Effect of phosphatidylserine and cholesterol on membrane-mediated fibril formation by the N-terminal amyloidogenic fragment of apolipoprotein A-I

Here, we examined the effects of phosphatidylserine (PS) and cholesterol on the fibril-forming properties of the N-terminal 1-83 fragment of an amyloidogenic G26R variant of apoA-I bound to small unilamellar vesicles. A thioflavin T fluorescence assay together with microscopic observations showed that PS significantly retards the nucleation step in fibril formation by apoA-I 1-83/G26R, whereas cholesterol slightly enhances fibril formation. Circular dichroism analyses demonstrated that PS facilitates a structural transition from random coil to α-helix in apoA-I 1-83/G26R with great stabilization of the α-helical structure upon lipid binding. Isothermal titration calorimetry measurements revealed that PS induces a marked increase in capacity for binding of apoA-I 1-83/G26R to the membrane surface, perhaps due to electrostatic interactions of positively charged amino acids in apoA-I with PS. Such effects of PS to enhance lipid interactions and inhibit fibril formation of apoA-I were also observed for the amyloidogenic region-containing apoA-I 8-33/G26R peptide. Fluorescence measurements using environment-sensitive probes indicated that PS induces a more solvent-exposed, membrane-bound conformation in the amyloidogenic region of apoA-I without affecting membrane fluidity. Since cell membranes have highly heterogeneous lipid compositions, our findings may provide a molecular basis for the preferential deposition of apoA-I amyloid fibrils in tissues and organs.


Current Topics - Drug Discovery: Recent Progress and the Future Foreward


CXCL14 acts as a specific carrier of CpG into dendritic cells and activates Toll-like receptor 9-mediated adaptive immunity

CXCL14 is a primordial chemokine that plays multiple roles in tumor suppression, autoimmune arthritis, and obesity-associated insulin resistance. However, the underlying molecular mechanisms are unclear. Here, we show that CXCL14 transports various types of CpG oligodeoxynucleotide (ODN) into the endosomes and lysosomes of bone marrow-derived dendritic cells (DCs), thereby activating Toll-like receptor 9 (TLR9). A combination of CpG ODN (ODN2395) plus CXCL14 induced robust production of IL-12 p40 by wild-type, but not Tlr9-knockout, DCs. Consistent with this, ODN2395-mediated activation of DCs was significantly attenuated in Cxcl14-knockout mice. CXCL14 bound CpG ODN with high affinity at pH7.5, but not at pH6.0, thereby enabling efficient delivery of CpG ODN to TLR9 in the endosome/lysosome. Furthermore, the CXCL14-CpG ODN complex specifically bound to high affinity CXCL14 receptors on DCs. Thus, CXCL14 serves as a specific carrier of CpG DNA to sensitize TLR9-mediated immunosurveillance.


Chemical synthetic platform for chlorpromazine oligomers that were reported as photo-degradation products of chlorpromazine

A synthetic platform for chlorpromazine (CPZ) oligomers, which could be generated via photo-reaction of CPZ, is essential to promote their biological and structural studies. In this paper, the first synthetic platform for CPZ oligomers is described. A photo-irradiation experiment of CPZ to confirm whether the structure of the CPZ dimer generated by the photo-irradiation was identical to that prepared by our synthetic method is also reported.


Cysteine-free intramolecular ligaiton of N-sulfanylethylanilide peptide using 4-mercaptobenzylphosphonic acid: Synthesis of cyclic peptide, trichamide


Stapled BIG3 helical peptide ERAP potentiates anti-tumour activity for breast cancer therapeutics.

Estradiol (E2) and the oestrogen receptor-alpha (ER) signalling pathway play pivotal roles in the proliferative activity of breast cancer cells. Recent findings show that the brefeldin A-inhibited guanine nucleotide-exchange protein 3-prohibitin 2 (BIG3-PHB2) complex plays a crucial role in E2/ER signalling modulation in breast cancer cells. Moreover, specific inhibition of the BIG3-PHB2 interaction using the ER activity-regulator synthetic peptide (ERAP: 165-177 amino acids), derived from -helical BIG3 sequence, resulted in a significant anti-tumour effect. However, the duration of this effect was very short for viable clinical application. We developed the chemically modified ERAP using stapling methods (stapledERAP) to improve the duration of its antitumour effects. The stapledERAP specifically inhibited the BIG3-PHB2 interaction and exhibited long-lasting suppressive activity. Its intracellular localization without the membrane-permeable polyarginine sequence was possible via the formation of a stable -helix structure by stapling. Tumour bearing-mice treated daily or weekly with stapledERAP effectively prevented the BIG3-PHB2 interaction, leading to complete regression of E2-dependent tumours in vivo. Most importantly, combination of stapledERAP with tamoxifen, fulvestrant, and everolimus caused synergistic inhibitory effects on growth of breast cancer cells. Our findings suggested that the stapled ERAP may be a promising anti-tumour drug to suppress luminal-type breast cancer growth.


Inside Front Cover: Elucidation of inhibitor-binding pocket of D-amino acid oxidase using docking simulation and N-sulfanylethylanilide-based labeling technology


Elucidation of inhibitor-binding pocket of D-amino acid oxidase using docking simulation and N-sulfanylethylanilide-based labeling technology


An aromatic amino acid within intracellular loop 2 of the prostaglandin EP2 receptor is a prerequisite for selective association and activation of Gas

We previously demonstrated that the aromatic moiety of Tyr(143) within the intracellular loop 2 (ICL2) region of the prostaglandin EP2 receptor plays a crucial role in Gs coupling. Here we investigated whether the ICL2 of the EP2 receptor directly binds to Gs and whether an aromatic moiety affects this interaction. In Chinese hamster ovary cells, mutations of Tyr(143) reduced the ability of the EP2 receptor to interact with G proteins as demonstrated by GTPS sensitivity, as well as the ability of agonist-induced cAMP formation, with the rank order of Phe>Tyr (wild-type)=Trp>Leu>Ala (=0). We found that the wild-type ICL2 peptide (i2Y) and its mutant with Phe at Tyr(143) (i2F) inhibited receptor-G protein complex formation of wild-type EP2 in membranes, whereas the Ala-substituted mutant (i2A) did not. Specific interactions between these peptides and the Gs protein were detected by surface plasmon resonance, but Gs showed different association rates, with a rank order of i2F>i2Yi2A, with similar dissociation rates. Moreover, i2F and i2Y, but not i2A activated membrane adenylyl cyclase. These results indicate that the ICL2 region of the EP2 receptor is its potential interaction site with Gs, and that the aromatic side chain moiety at position 143 is a determinant for the accessibility of the ICL2 to the Gs protein.

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids


A convenient method for preparation of -imino carboxylic acid derivatives and application to the asymmetric synthesis of unnatural -amino acid derivative

We describe herein a manganese(IV) oxide-mediated oxidation of N-p-methoxyphenyl (PMP)-protected glycine derivatives for the synthesis of -imino carboxylic acid derivatives. Using this methodology, utilization of unstable glyoxic acid derivatives was avoided. Furthermore, using this methodology we synthesized novel -imino carboxylic acid derivatives such as -imino phenyl ester, perfluoroalkyl etsers, imides, and thioester. The asymmetric Mannich reaction of those novel imine derivatives with 1,3-dicarbonyl compound is also described, and the novel -imino imide gave improved chemical yield and stereoselectivity compared with those obtained by the use of the conventional -imino ester-type substrate.


N-Sulfanylethylaminooxybutyramide (SEAoxy): A Crypto-Thioester Compatible with Fmoc Solid-Phase Peptide Synthesis

An N-sulfanylethylaminooxybutyramide (SEAoxy) has been developed as a novel thioester equivalent for native chemical ligation. SEAoxy peptide was straightforwardly synthesized by conventional Fmoc solid-phase peptide synthesis without a problem. Moreover, SEAoxy peptide could be directly applied to native chemical ligation owing to the intramolecular N-to-S acyl shift that releases the peptide-thioester in situ. This methodology was successfully applied to the synthesis of two bioactive peptides.


Heparin promotes fibril formation of the N-terminal fragment of amyloidogenic aplipoprotein A-I

Glycosaminoglycans are known to be associated with extracellular amyloid deposits of various amyloidogenic proteins. In this study, we found that the glycosaminoglycan heparin greatly accelerates the elongation step in fibril formation by the N-terminal 1-83 fragment of human apolipoprotein A-I (apoA-I), especially in the amyloidogenic W50R variant. Using fragment peptides, we demonstrate that heparin significantly promotes β-transition and fibril formation of the highly amyloidogenic region spanning residues 44-65 and colocalizes with fibrils formed by the W50R variant. These results suggest the possible role of glycosaminoglycans in fibril formation by amyloidogenic apoA-I variants.


Development of an anilide-type scaffold for the thioester precursor N-sulfanylethylcoumarinyl amide

N-Sulfanylethylcoumarinyl amide (SECmide) peptide, which was initially developed for use in the fluorescence-guided detection of promoters of N-S acyl transfer, was successfully applied to a facile and side reaction-free protocol for N-S acyl-transfer-mediated synthesis of peptide thioesters. Additionally, 4-mercaptobenzylphosphonic acid (MBPA) was proven to be a useful catalyst for the SECmide or N-sulfanylethylanilide (SEAlide)-mediated NCL reaction.


Back Cover: Tailored synthesis of 162-residue S-monoglycosylated GM2-activator protein (GM2AP) analogues that allows access to protein library


Tailored synthesis of 162-residue S-monoglycosylated GM2-activator protein (GM2AP) analogues that allows access to protein library


Labelling of endogenous target protein via N-S acyl transfer-mediated activation of N-sulfanylethylanilide


An N-Sulfanylethylanilide-based traceable linker for enrichment and selective labelling of target proteins


Facile preparation of peptides with C-terminal N-alkylamide via radical-initiated dethiocarboxylation

A new synthetic method has been developed to prepare peptides bearing a C-terminal N-alkylamide from peptide thioacids via a radical-initiated dethiocarboxylation process. This method enables the introduction of various alkyl groups to C-terminal amides simply by replacing the amino acid building block. Its application to the preparation of anti-cancer drug ABT-510 is also reported.


Enthalpy-driven interactions with sulfated glycosaminoglycans promote cell membrane penetration of arginine peptides

The first step of cell membrane penetration of arginine peptides is thought to occur via electrostatic interactions between positive charges of arginine residues and negative charges of sulfated glycosaminoglycans (GAGs) on the cell surface. However, the molecular interaction of arginine peptides with GAG still remains unclear. Here, we compared the interactions of several arginine peptides of Tat, R8, and Rev and their analogues with heparin in relation to the cell membrane penetration efficiency. The high-affinity binding of arginine peptides to heparin was shown to be driven by large favorable enthalpy contributions, possibly reflecting multidentate hydrogen bondings of arginine residues with sulfate groups of heparin. Interestingly, the lysine peptides in which all arginine residues are substituted with lysine residues exhibited negligible binding enthalpy despite of their considerable binding to heparin. In CHO-K1 cells, arginine peptides exhibited a great cell-penetrating ability whereas their corresponding lysine peptides did not penetrate into cells. The degree of cell penetration of arginine peptides markedly decreased by the chlorate treatment of cells which prevents the sulfation of GAG chains. Significantly, the cell penetration efficiency of arginine peptides was found to be correlated with the favorable enthalpy of binding to heparin. These results suggest that the enthalpy-driven strong interaction with sulfated GAGs such as heparan sulfate plays a critical role in the efficient cell membrane penetration of arginine peptides.

Biochimica et Biophysica Acta (BBA) - Biomembranes


Identification of SNAIL1 Peptide-Based Irreversible Lysine Specific Demethylase 1-Selective Inactivators

Inhibition of lysine-specific demethylase 1 (LSD1), a flavin-dependent histone demethylase, has recently emerged as a new strategy for treating cancer and other diseases. LSD1 interacts physically with SNAIL1, a member of the SNAIL/SCRATCH family of transcription factors. This study describes the discovery of SNAIL1 peptide-based inactivators of LSD1. We designed and prepared SNAIL1 peptides bearing a propargyl amine, hydrazine, or phenylcyclopropane moiety. Among them, peptide 3, bearing hydrazine, displayed the most potent LSD1-inhibitory activity in enzyme assays. Kinetic study and mass spectrometric analysis indicated that peptide 3 is a mechanism-based LSD1 inhibitor. Furthermore, peptides 37 and 38, which consist of cell-membrane-permeable oligoarginine conjugated with peptide 3, induced a dose-dependent increase of dimethylated Lys4 of histone H3 in HeLa cells, suggesting that they are likely to exhibit LSD1-inhibitory activity intracellularly. In addition, peptide 37 decreased the viability of HeLa cells. We believe this new approach for targeting LSD1 provides a basis for development of potent selective inhibitors and biological probes for LSD1.


Protease-resistant modified human β-hexosaminidase B ameliorates symptoms in GM2 gangliosidosis model

GM2 gangliosidoses, including Tay-Sachs and Sandhoff diseases, are neurodegenerative lysosomal storage diseases that are caused by deficiency of β-hexosaminidase A, which comprises an αβ heterodimer. There are no effective treatments for these diseases; however, various strategies aimed at restoring β-hexosaminidase A have been explored. Here, we produced a modified human hexosaminidase subunit β (HexB), which we have termed mod2B, composed of homodimeric β subunits that contain amino acid sequences from the α subunit that confer GM2 ganglioside-degrading activity and protease resistance. We also developed fluorescent probes that allow visualization of endocytosis of mod2B via mannose 6-phosphate receptors and delivery of mod2B to lysosomes in GM2 gangliosidosis models. In addition, we applied imaging mass spectrometry to monitor efficacy of this approach in Sandhoff disease model mice. Following i.c.v. administration, mod2B was widely distributed and reduced accumulation of GM2, asialo-GM2, and bis(monoacylglycero)phosphate in brain regions including the hypothalamus, hippocampus, and cerebellum. Moreover, mod2B administration markedly improved motor dysfunction and a prolonged lifespan in Sandhoff disease mice. Together, the results of our study indicate that mod2B has potential for intracerebrospinal fluid enzyme replacement therapy and should be further explored as a gene therapy for GM2 gangliosidoses.


Facile synthesis of C-terminal peptide thioacids under mild conditions from N-sulfanylethylanilide peptides


Formation of stable nanodiscs by bihelical apolipoprotein A-I mimetic peptide

Nanodiscs are composed of scaffold protein or peptide such as apolipoprotein A-I (apoA-I) and phospholipids. Although peptide-based nanodiscs have an advantage to modulate the size of nanodiscs by changing phospholipid/peptide ratios, they are usually less stable than apoA-I-based nanodiscs. In this study, we designed a novel nanodisc scaffold peptide (NSP) that has proline-punctuated bihelical amphipathic structure based on apoA-I mimetic peptides. NSP formed -helical structure on 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) nanodiscs prepared by cholate dialysis method. Dynamic light scattering measurements demonstrated that diameters of NSP nanodiscs vary depending upon POPC/NSP ratios. Comparison of thermal unfolding of nanodiscs monitored by circular dichroism measurements demonstrated that NSP forms much more stable nanodiscs with POPC than monohelical peptide, 4F, exhibiting comparable stability to apoA-I-POPC nanodiscs. Intrinsic Trp fluorescence measurements showed that Trp residues of NSP exhibit more hydrophobic environment than that of 4 F on nanodiscs, suggesting the stronger interaction of NSP with phospholipids. Thus, the bihelical structure of NSP appears to increase the stability of nanodiscs because of the enhanced interaction of peptides with phospholipids. In addition, NSP as well as 4F spontaneously solubilized POPC vesicles into nanodiscs without using detergent. These results indicate that bihelical NSP forms nanodiscs with comparable stability to apoA-I and has an ability to control the size of nanodiscs simply by changing phospholipid/peptide ratios. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.


Development of an intein-inspired amide cleavage chemical device

A photoresponsive amide cleavage device was developed based on the asparagine imidation-mediated cleavage of peptide bonds during intein-mediated protein splicing. The chemical environment of the protein splicing process was mimicked by the incorporation of geminal dimethyl groups and a secondary amine unit in asparagine scaffold. Furthermore, the resulting photoresponsive device could induce the phototriggered cleavage of an amide bond by the protection of the secondary amine unit with an o-nitrobenzyloxycarbonyl group.


One-pot/sequential native chemical ligation using photo-caged crypto-thioester

A practical and efficient methodology for the chemical synthesis of peptides/proteins using a one-pot/sequential ligation is described. It features the use of photocleavable S-protection on an N-sulfanylethylaniline moiety. Removal of the S-protecting ligated materials under UV irradiation provides a readily usable mixture for subsequent native chemical ligation.


Preparation of peptide thioesters from naturally occurring sequences using reaction sequence consisting of regioselective S-cyanylation and hydrazinolysis

The vital roles of peptide/protein thioesters in protein chemistry, including chemical or semi-synthesis of proteins, have encouraged studies on the development of methods for the preparation of such chemical units. Biochemical protocols using intein or sortase have proved to be useful in protein chemistry as methods suitable for naturally occurring sequences, including recombinant proteins. Although chemical protocols are potential options for thioester preparation, only a few are applicable to naturally occurring sequences, because standard chemical protocols require an artificial chemical device for producing thioesters. In this context, the chemical preparation of thioesters based on a reaction sequence consisting of regioselective S-cyanylation and hydrazinolysis was investigated. Regioselective S-cyanylation, which is required for cysteine-containing thioesters, was achieved with the aid of a zinc-complex formation of a CCHH-type zinc-finger sequence. Free cysteine residues that are not involved in complex formation were selectively protected with a 6-nitroveratryl group followed by S-cyanylation of the zinc-binding cysteine. Hydrazinolysis of the resulting S-cyanopeptide and subsequent photo-removal of the 6-nitroveratryl group yielded the desired peptide hydrazide, which was then converted to the corresponding thioester. The generated thioester was successfully used in N-to-C-directed one-pot/sequential native chemical ligation using an N-sulfanylethylanilide peptide to give a 64-residue peptide toxin. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 531-546, 2016.


Amyloidogenic Mutation Promotes Fibril Formation of the N-terminal Apolipoprotein A-I on Lipid Membranes

The N-terminal amino acid 1-83 fragment of apolipoprotein A-I (apoA-I) has a strong propensity to form amyloid fibrils at physiological neutral pH. Because apoA-I has an ability to bind to lipid membranes, we examined the effects of the lipid environment on fibril-forming properties of the N-terminal fragment of apoA-I variants. Thioflavin T fluorescence assay as well as fluorescence and transmission microscopies revealed that upon lipid binding, fibril formation by apoA-I 1-83 is strongly inhibited, whereas the G26R mutant still retains the ability to form fibrils. Such distinct effects of lipid binding on fibril formation were also observed for the amyloidogenic prone region-containing peptides, apoA-I 8-33 and 8-33/G26R. This amyloidogenic region shifts from random coil to -helical structure upon lipid binding. The G26R mutation appears to prevent this helix transition because lower helical propensity and more solvent-exposed conformation of the G26R variant upon lipid binding were observed in the apoA-I 1-83 fragment and 8-33 peptide. With a partially -helical conformation induced by the presence of 2,2,2-trifluoroethanol, fibril formation by apoA-I 1-83 was strongly inhibited, whereas the G26R variant can form amyloid fibrils. These findings suggest a new possible pathway for amyloid fibril formation by the N-terminal fragment of apoA-I variants: the amyloidogenic mutations partially destabilize the -helical structure formed upon association with lipid membranes, resulting in physiologically relevant conformations that allow fibril formation.


Efficient one-pot synthesis of CXCL14 and its derivative using an N-sulfanylethylanilide peptide as a peptide thioester equivalent and their biological evaluation

CXCL14 is a CXC-type chemokine that exhibits chemotactic activity for immature dendritic cells, activated macrophages, and activated natural killer cells. However, its specific receptor and signaling pathway remain obscure. Recently, it was reported that CXCL14 binds to CXCR4 with high affinity and inhibits CXCL12-mediated chemotaxis. Furthermore, the CXCL14 C-terminal -helical region is important for binding to its receptor. In this context, we chemically synthesized CXCL14 and its derivative with a one-pot method using N-sulfanylethylanilide peptide as a thioester equivalent. The synthetic CXCL14 proteins possessed inhibitory activities to CXCL12-mediated chemotaxis comparable with that of recombinant CXCL14. Moreover, we proved that chemically biotinylated CXCL14 binds to CXCR4 on cells by flow cytometry analysis.


Safe removal of the allyl protecting groups of allyl esters using a recyclable, low-leaching and ligand-free palladium nanoparticle Catalyst


Design and synthesis of a hydrogen peroxide-responsive amino acid that induces peptide bond cleavage after exposure to hydrogen peroxide


Photo-triggered fluorescent labelling of recombinant proteins in live cells

A method to photo-chemically trigger fluorescent labelling of proteins in live cells is developed. The approach is based on photo-caged split-intein mediated conditional protein trans-splicing reaction and enabled background-free fluorescent labelling of target proteins with the necessary spatiotemporal control.


The total chemical synthesis of the monoglycosylated GM2 ganglioside activator using a novel cysteine surrogate

We describe a novel peptide ligation/desulfurization strategy using a -mercapto-N-glycosylated asparagine derivative. The newly developed procedure was successfully applied to the total chemical synthesis of the GM2 ganglioside activator protein bearing a monosaccharide on the native glycosylation site.


Synthesis of lactam-bridged cyclic peptides by using olefin metathesis and diimide reduction


Development of chemical methodology for preparation of peptide thioesters applicable to naturally occurring peptides using a sequential quadruple acyl transfer system


Inside Back Cover: A photoinduced growth system of peptide nanofibres addressed by DNA hybridization

Spatiotemporal control of peptide nanofibre growth was achieved by photocleavage of a DNA-conjugated -sheet forming peptide that is linked through a photoresponsive amino acid residue. Peptide nanofibres were selectively formed by photocleaving the conjugate on a complementary DNA-immobilised glass substrate.


A photoinduced growth system of peptide nanofibres addressed by DNA hybridization


Molecular Complex Composed of -Cyclodextrin-Grafted Chitosan and pH-Sensitive Amphipathic Peptide for Enhancing Cellular Cholesterol Efflux under Acidic pH

Excess of cholesterol in peripheral cells is known to lead to atherosclerosis. In this study, a molecular complex composed of -cyclodextrin-grafted chitosan (BCC) and cellular cholesterol efflux enhancing peptide (CEEP), synthesized by modifying pH sensitive amphipathic GALA peptide, is introduced with the eventual aim of treating atherosclerosis. BCC has a markedly enhanced ability to induce cholesterol efflux from cell membranes compared to -cyclodextrin, and the BCC-CEEP complex exhibited a 2-fold increase in cellular cholesterol efflux compared to BCC alone under weakly acidic conditions. Isothermal titration calorimetry and fluorescence spectroscopy measurements demonstrated that the random coil structure of CEEP at neutral pH converted to the -helical structure at acidic pH, resulting in a three-order larger binding constant to BCC (K = 3.7 × 10(7) at pH 5.5) compared to that at pH 7.4 (K = 7.9 × 10(4)). Such high-affinity binding of CEEP to BCC at acidic pH leads to the formation of 100-nm-sized aggregate with positive surface charge, which would efficiently interact with cell membranes and induce cholesterol efflux. Since the cholesterol efflux ability of HDL is thought to be impaired under acidic environments in advanced atherosclerotic lesions, the BCC-CEEP complex might serve as a novel nanomaterial for treating atherosclerosis.


Liquid-phase synthesis of bridged peptides using olefin metathesis of protected peptide with long aliphatic chain anchor

Bridged peptides including stapled peptides are attractive tools for regulating protein-protein interactions (PPIs). An effective synthetic methodology in a heterogeneous system for the preparation of these peptides using olefin metathesis and hydrogenation of protected peptides with a long aliphatic chain anchor is reported.


Development of a fluoride-responsive amide bond cleavage device that is potentially applicable to a traceable linker


Development of a traceable linker containing a thiol-responsive amino acid for the enrichment and selective labelling of target proteins

A traceable linker that is potentially applicable to identification of a target protein of bioactive compounds was developed. It enabled not only thiol-induced cleavage of the linker for enrichment of the target protein but also selective labelling to pick out the target from contaminated non-target proteins for facile identification.


Development of caged non-hydrolyzable phosphoamino acids and application to photo-control of binding affinity of phosphopeptide mimetic to phosphopeptide-recognizing protein

The design and synthesis of caged non-hydrolyzable phospho-serine, -threonine, and -tyrosine derivatives that generate parent non-hydrolyzable phosphoamino acids, containing a difluoromethylene unit instead of the oxygen of a phosphoester, after UV-irradiation are described. The caged non-hydrolyzable amino acids were incorporated into peptides by standard Fmoc solid-phase peptide synthesis, and the obtained peptides were successfully converted to the parent non-hydrolyzable phosphopeptides by UV-irradiation. Application of the caged non-hydrolyzable phosphoserine-containing peptide to photo-control the binding affinity of the peptide to 14-3-3 protein is also reported.


Examination of native chemical ligation using peptidyl prolyl thioester

Peptidyl prolyl thioesters, which have been regarded as too unreactive for practical use in native chemical ligations (NCLs), were proven to be versatile reagents in peptide coupling. Tuning the reactivity of prolyl thioesters enabled a one-pot/sequential NCL reaction based on kinetically controlled ligation.


The extreme N-terminal region of human apolipoprotein A-I has a strong propensity to form amyloid fibrils.

The N-terminal 1-83 residues of apolipoprotein A-I (apoA-I) have a strong propensity to form amyloid fibrils, in which the 46-59 segment was reported to aggregate to form amyloid-like fibrils. In this study, we demonstrated that a fragment peptide comprising the extreme N-terminal 1-43 residues strongly forms amyloid fibrils with a transition to -sheet-rich structure, and that the G26R point mutation enhances the fibril formation of this segment. Our results suggest that in addition to the 46-59 segment, the extreme N-terminal region plays a crucial role in the development of amyloid fibrils by the N-terminal fragment of amyloidogenic apoA-I variants.


Dimeric peptides of the C-terminal region of CXCL14 function as CXCL12 inhibitors

We recently reported that CXCL14 binds to CXCR4 with high affinity and inhibits CXCL12-mediated chemotaxis. Here we found that the C-terminal 51-77 amino acid residues of CXCL14 are responsible for CXCR4 binding. A disulfide dimer peptide of CXCL14(51-77) bound to CXCR4 with comparable affinity to full length CXCL14, and exhibited CXCL12 inhibitor activity. CXCR4 was efficiently internalized upon binding of dimeric CXCL14(51-77), thereby being reduced on the cell surface. Substitution of 5 amino acid residues in combination with the use of an oxime linker for dimerization increased the solubility and chemical stability of the dimeric CXCL14(51-77).


Chemical synthesis of biologically active monoglycosylated GM2-activator protein analog using N-sulfanylethylanilide peptide

Going to SEA(lide): Total chemical synthesis of a 162-residue glycoprotein analogue of the monoglycosylated human GM2-activator protein (GM2AP) was achieved. Key steps were the use of N-sulfanylethylanilide (SEAlide) peptides in the kinetic chemical ligation synthesis of a large peptide fragment, and a convergent native chemical ligation for final fragment assembly.


CXCL14 is a natural inhibitor of the CXCL12-CXCR4 signaling axis

Activation of the CXCL12-CXCR4 pathway is crucial for the migration of hematopoietic stem cells, various immune cells, and malignant tumor cells. Here, we show that another CXC chemokine, CXCL14, specifically binds to CXCR4 with high affinity and inhibits the CXCL12-mediated chemotaxis of human leukemia-derived cell lines and CD34(+) hematopoietic progenitor cells. Thus, CXCL14 functions as a natural inhibitor of CXCL12. Our observations suggest that CXCL14 represents, along with CXCR7, molecules that co-evolved with the CXCL12-CXCR4 axis to modulate important physiological processes in development, stem cell maintenance, and immune responses.


Synthetic procedure for N-Fmoc amino acyl-N-sulfanylethylaniline linker as crypto-peptide thioester precursor with application to native chemical ligation

N-sulfanylethylanilide (SEAlide) peptides 1, obtainable using Fmoc-based solid-phase peptide synthesis (Fmoc SPPS), function as crypto-thioesters in native chemical ligation (NCL), yielding a wide variety of peptides/proteins. Their acylating potential with N-terminal cysteinyl peptides 2 can be tuned by the presence or absence of phosphate salts, leading to one-pot/multifragment ligation, operating under kinetically controlled conditions. SEAlide peptides have already been shown to be promising for use in protein synthesis; however, a widely applicable method for the synthesis of N-Fmoc amino acyl-N-sulfanylethylaniline linkers 4, required for the preparation of SEAlide peptides, is unavailable. The present study addresses the development of efficient condensation protocols of 20 naturally occurring amino acid derivatives to the N-sulfanylethylaniline linker 5. N-Fmoc amino acyl aniline linkers 4 of practical use in NCL chemistry, except in the case of the proline- or aspartic acid-containing linker, were successfully synthesized by coupling of POCl(3)- or SOCl(2)-activated Fmoc amino acid derivatives with sodium anilide species 6, without accompanying racemization and loss of side-chain protection. Furthermore, SEAlide peptides 7 possessing various C-terminal amino acids (Gly, His, Phe, Ala, Asn, Ser, Glu, and Val) were shown to be of practical use in NCL chemistry.


Fmoc-based solid phase synthesis of adenylylated peptides using diester-type adenylylated amino acid derivatives


Development of a reduction-responsive amino acid that induces peptide bond cleavage in hypoxic cells

Hypoxia-responsive amino acids are indispensable in the preparation of hypoxic tumor-specific peptidyl prodrugs. In this paper, the design and synthesis of a reduction-responsive amino acid that induces peptide bond cleavage after reduction of the nitro group are described. Application to hypoxia-responsive peptide bond cleavage system is also reported.


Dual kinetically-controlled native chemical ligation using a combination of sulfanylproline and sulfanylethylanilide peptide

Dual kinetically controlled native chemical ligation using a newly developed sulfanylproline-mediated reaction in combination with an N-sulfanylethylanilide peptide was successfully applied to a previously unreported sequential coupling of peptide fragments added simultaneously to the reaction.


Development of UV-responsive catch-and-release system of a cysteine protease model peptide


N-Sulfanylethylanilide Peptide as a Crypto-Thioester Peptide


Application of N-C- or C-N-directed sequential native chemical ligation to the preparation of CXCL14 analogs and their biological evaluation

CXCL14 is a chemokine that exhibits chemoattractant activity for activated macrophages, immature dendric cells, natural killer cells, and epithelial tumor cells. Its potential role as a metabolic regulator has recently been disclosed. However, a complete understanding of its physiological roles remains elusive. This is partly due to the lack of appropriate CXCL14-based molecular probes to explore the biological functions of CXCL14. In this context, we have developed synthetic protocols that provide access to a wide variety of CXCL14 analogs. Two sequential native chemical ligation (NCL) protocols, which proceed in opposite directions, have been used to assemble CXCL14 analogs from peptide fragments. The first involved a conventional C-N-directed sequential NCL, and afforded wild-type CXCL14. The other used peptide thioacids in N-C-directed elongation, and yielded CXCL14 analogs with molecular diversity at the C-terminal fragment. The CXCL14 analogs prepared showed biological activity on human monocytic leukemia-derived THP-1 cells that was comparable to that of wild-type CXCL14.


Design and synthesis of caged ceramide: UV-responsive ceramide releasing system based on UV-induced amide bond cleavage followed by O-N acyl transfer


Enantioselective synthesis of stimulus-responsive amino acid via asymmetric -amination of aldehyde


A structure activity relationship study elucidating the mechanism of sequence-specific collagen recognition by the chaperone HSP47

Heat-shock protein 47 (HSP47) is a chaperone that facilitates the proper folding of procollagen. Our previous studies showed that the high-affinity HSP47-binding motif in the collagen triple helix is Xaa-(Thr/Pro)-Gly-Xaa-Arg-Gly. In this study, we further investigated structural requirements for the HSP47-binding motif, using synthetic triple-helical collagen-model peptides with systematic amino acid substitutions at either the Thr/Pro (=Yaa(-3)) or the Arg (=Yaa(0)) position. Results obtained from in vitro binding assays indicated that HSP47 detects the side-chain structure of Arg at the Yaa(0)-position, while the Yaa(-3) amino acid serves as the secondary recognition site that affects affinity to HSP47.


Development and photo-responsive peptide bond cleavage reaction of two-photon near-infrared excitation responsive peptide


Sequential native chemical ligation utilizing peptide thioacids derived from newly developed Fmoc-based synthetic method


Development of thiol-responsive amide bond cleavage device and its application for peptide nucleic acid-based DNA releasing system


Proline cis/trans isomerase Pin1 regulates peroxisome proliferators-activated receptor g activity through the direct binding to the AF-1 domain

The important roles of a nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) are widely accepted in various biological processes as well as metabolic diseases. Despite the worldwide quest for pharmaceutical manipulation of PPARgamma activity through the ligand-binding domain, very little information about the activation mechanism of the N-terminal activation function-1 (AF-1) domain. Here, we demonstrate the molecular and structural basis of the phosphorylation-dependent regulation of PPARgamma activity by a peptidyl-prolyl isomerase, Pin1. Pin1 interacts with the phosphorylated AF-1 domain, thereby inhibiting the polyubiquitination of PPARgamma. The interaction and inhibition are dependent upon the WW domain of Pin1 but are independent of peptidyl-prolyl cis/trans-isomerase activity. Gene knockdown experiments revealed that Pin1 inhibits the PPARgamma-dependent gene expression in THP-1 macrophage-like cells. Thus, our results suggest that Pin1 regulates macrophage function through the direct binding to the phosphorylated AF-1 domain of PPARgamma.


Structural and functional analyses of minimal phosphopeptides targeting the polo-box domain of polo-like kinase 1

Polo-like kinase-1 (Plk1) has a pivotal role in cell proliferation and is considered a potential target for anticancer therapy. The noncatalytic polo-box domain (PBD) of Plk1 forms a phosphoepitope binding module for protein-protein interaction. Here, we report the identification of minimal phosphopeptides that specifically interact with the PBD of human PLK1, but not those of the closely related PLK2 and PLK3. Comparative binding studies and analyses of crystal structures of the PLK1 PBD in complex with the minimal phosphopeptides revealed that the C-terminal SpT dipeptide functions as a high-affinity anchor, whereas the N-terminal residues are crucial for providing specificity and affinity to the interaction. Inhibition of the PLK1 PBD by phosphothreonine mimetic peptides was sufficient to induce mitotic arrest and apoptotic cell death. The mode of interaction between the minimal peptide and PBD may provide a template for designing therapeutic agents that target PLK1.


Synthesis of amide-type fluoroalkene dipeptide isosteres by an intramolecular redox reaction

We previously achieved NHC-mediated preparation of ester-type fluoroalkene dipeptide isosteres (ES-FADIs, 4) by an intramolecular redox reaction. In the present study, a cyanide ion-mediated reaction was successfully applied to the conversions of gamma,gamma-difluoro-alpha,beta-enoylsilane 1 or 2 to amide-type fluoroalkene isosteres (AM-FADIs, 5 or 6). The use of catalytic cyanide ion allowed synthesis of chiral auxiliary incorporated FADI 15b which was then subjected to a diastereoselective alpha-alkylation reaction to yield alpha-substituted FADIs 17. Furthermore, the presented amidation protocol was used for straightforward incorporation of FADI into peptidyl resin.


Synthesis of fluoroalkene dipeptide isosteres by an intramolecular redox reaction utilizing N-heterocyclic carbenes (NHCs)

(Z)-Fluoroalkene dipeptide isosteres (FADIs 16) have served as potential dipeptide mimetics possessing the substitution of fluoroalkenes for parent peptide bonds. Previously, we synthesized FADIs by reduction of gamma,gamma-difluoro-alpha,beta-enoates with organocoppers or SmI(2), which prompted us to use an intramolecular redox reaction mediated by N-heterocyclic carbenes (NHCs) for the preparation of FADIs. Instead of the enoates, gamma,gamma-difluoro-alpha,beta-enal 20 and gamma,gamma-difluoro-alpha,beta-enoylsilane 34 were converted to FADIs by an NHC-mediated intramolecular redox reaction, whereby aldehyde components reduced the allylic difluoride component in an S(N)2' manner with accompanying monodefluorination.


N→S acyl-transfer-mediated synthesis of peptide thioesters using anilide derivatives

N-->S acyl-transfer-mediated synthesis of peptide thioesters utilizing an N-aminoacyl-N-sulfanylethylaminobenzoic acid derivative has been examined. The developed synthetic methodology for peptide thioesters is compatible with Fmoc solid-phase peptide synthesis (SPPS).


FRET-based assay of the processing reaction kinetics of stimulus-responsive peptides: Influence of amino acid sequence on reaction kinetics


Electrostatically constrained alpha-helical peptide inhibits replication of HIV-1 resistant to Enfuvirtide

Alpha-helical peptides, such as T-20 (enfuvirtide) and C34, derived from the gp41 carboxyl-terminal heptad repeat (C-HR) of HIV-1, inhibit membrane fusion of HIV-1 and the target cells. Although T-20 effectively suppresses the replication of multi-drug resistant HIV variants both in vitro and in vivo, prolonged therapy with T-20 induces emergence of T-20 resistant variants. In order to suppress the emergence of such resistant variants, we introduced charged and hydrophilic amino acids, glutamic acid (E) and lysine (K), at the solvent accessible site of C34. In particular, the modified peptide, SC34EK, demonstrates remarkably potent inhibition of membrane fusion by the resistant HIV-1 variants as well as wild-type viruses. The activity was specific to HIV-1 and little influenced by serum components. We found a strong correlation between the anti-HIV-1 activities of these peptides and the thermostabilities of the 6-helix bundles that are formed with these peptides. We also obtained the crystal structure of SC34EK in complex with a 36 amino acid sequence (N36) comprising the amino-terminal heptad repeat of HIV-1. The EK substitutions in the sequence of SC34EK were directed toward the solvent and generated an electrostatic potential, which may result in enhanced alpha-helicity of the peptide inhibitor. The 6-helix bundle complex of SC34EK with N36 appears to be structurally similar to that of C34 and N36. Our approach to enhancing alpha-helicity of the peptide inhibitor may enable future design of highly effective and specific HIV-1 inhibitors.

The International Journal of Biochemistry & Cell Biology


Identification of minimal sequence for HIV-1 fusion inhibitors

Emergence of multi-drug resistant HIV-1 is a serious problem for AIDS treatment. Recently, the virus-cell membrane fusion process has been identified as a promising target for the development of novel drugs against these resistant variants. In this study, we identified a 29-residue peptide fusion inhibitor, SC29EK, which shows activity comparable to the previously reported inhibitor SC35EK. Some residues in SC29EK not required for interaction with virus gp41 heptad repeat 1 (HR1) were replaced with a non-proteinogenic amino acid, 2-aminoisobutyric acid (Aib), to stabilize the alpha-helix structure and to provide resistance to peptidases.


Heptad Repeat-Derived Peptides Block Protease-Mediated Direct Entry from the Cell Surface of Severe Acute Respiratory Syndrome Coronavirus but Not Entry via the Endosomal Pathway

The peptides derived from the heptad repeat (HRP) of severe acute respiratory syndrome coronavirus (SCoV) spike protein (sHRPs) are known to inhibit SCoV infection, yet their efficacies are fairly low. Recently our research showed that some proteases facilitated SCoV's direct entry from the cell surface, resulting in a more efficient infection than the previously known infection via endosomal entry. To compare the inhibitory effect of the sHRP in each pathway, we selected two sHRPs, which showed a strong inhibitory effect on the interaction of two heptad repeats in a rapid and virus-free in vitro assay system. We found that they efficiently inhibited SCoV infection of the protease-mediated cell surface pathway but had little effect on the endosomal pathway. This finding suggests that sHRPs may effectively prevent infection in the lungs, where SCoV infection could be enhanced by proteases produced in this organ. This is the first observation that HRP exhibits different effects on virus that takes the endosomal pathway and virus that enters directly from the cell surface.


Synthesis of a stimulus-responsive processing device and its application to a nucleocytoplasmic shuttle peptide


Development of copper-mediated allylation of c-activated-a,b-unsaturated lactam toward peptide mimetic synthesis


Synthesis of (Z)-alkene-containing cis-proline dipeptide mimetics using samarium(II) diiodide (SmI2)-mediated reductive alkylation reaction.


A novel one-pot reaction involving organocopper-mediated reduction/transmetalation/asymmetric alkylation, leading to the diastereoselective synthesis of functionalized (Z)-fluoroalkene dipeptide isosteres.

By a novel one-pot reaction sequence involving consecutive organocopper-mediated reduction, transmetalation and asymmetric alkylation, a highly diastereoselective synthesis of functionalized (Z)-fluoroalkene dipeptide isosteres was achieved in good to excellent yields.


Stereoselective Synthesis of (Z)-alkene-containing proline dipeptide mimetics

In peptides and proteins, the peptide bond between an amino acid and proline exists as an equilibrium mixture of the cis-imide and trans-imide due to the low energy barrier in their interconversion. This feature greatly influences the structure and function of the proline-containing peptides and proteins. Therefore, restricting the amide bond with an (E)- or (Z)-alkene should provide a promising method for elucidating the structure-activity relationships of the peptide and the proteins. In this report, the regio- and stereoselective synthesis of cis-alanylproline (Ala-Pro) type (Z)-alkene dipeptide mimetic is described. The key steps of this synthesis are to introduce a C3 unit onto a gamma-phosphoryloxy-alpha,beta-unsaturated-delta-lactam with an organocopper-mediated anti-S(N)2' reaction and subsequently construct a five-membered proline-like cyclic structure with an intramolecular Suzuki coupling reaction. Hydrolysis of the amide bond in the resulting bicyclic lactam yields the desired cis-Ala-Pro type (Z)-alkene dipeptide isostere. The presented synthetic methodology should be applicable to the general syntheses of other cis-aminoacylproline type (Z)-alkene dipeptide mimetics.


Synthesis of (Z)-Alkene and (E)-Fluoroalkene-Containing Diketopiperazine Mimetics Utilizing Oraganocopper-Mediated Reduction-Alkylation and Diastereoselectivity Examination Using DFT Calculations.

We have carefully examined the organocopper-mediated reduction-alkylation of gamma-acetoxy or gamma,gamma-difluoro-alpha,beta-unsaturated-delta-lactams for the synthesis of (Z)-alkene- or (E)-fluoroalkene-containing diketopiperazine mimetics. Reduction of acetates 2, 12, 14, and difluorolactam 18 with higher-order cuprate reagents (Me3CuLi2 x LiI x 3 LiBr), followed by trapping the resulting metal dienolate with an electrophile in a one-pot procedure gave alpha-alkylated-beta,gamma-unsaturated-delta-lactams in good yields. Because of side-chain steric repulsion, we found that alkylation using relatively large electrophiles such as BnBr gave mostly 3,6-trans isomers by kinetic trapping of metal enolates. On the other hand, MeI-mediated alkylations predominantly provided the unexpected 3,6-cis isomers despite the presence of a bulky benzyl side chain. Based on density functional theory calculations, we concluded that formation of the 3,6-cis isomers was due to the occurrence of oxa-pi-allyllithium complexes 29 and 31.


Stereoselective Synthesis of 3,6-Disubstituted-3,6-dihydropyridin-2-ones as Potential Diketopiperazine Mimetics Using Organocopper-Mediated anti-SN2' Reactions and Their Use in the Preparation of Low-Molecule CXCR4 Antagonists.

Organocopper-mediated anti-SN2' reactions of gamma-phosphoryloxy-alpha,beta-unsaturated-delta-lactams were used to prepare highly functionalized diketopiperazine mimetics. The substrate phosphates 24, 32, and 47 were prepared from alpha-amino acid-derived allylic alcohols 10 by a sequence of reactions that included ring-closing metathesis. In the reactions of phosphates with organocopper reagents, the addition of LiCl dramatically improved anti-SN2' selectivity, indicating that an organocopper cluster containing lithium chloride plays an important role in the determination of regioselectivity. This reaction system was applied to the preparation of novel low molecular weight CXCR4-chemokine receptor antagonists.


Specific recognition of the collagen triple helix by chaperone HSP47. II. The HSP47-binding structural motif in collagens and related proteins

The endoplasmic reticulum-resident chaperone heat-shock protein 47 (HSP47) plays an essential role in procollagen biosynthesis. The function of HSP47 relies on its specific interaction with correctly folded triple-helical regions comprised of Gly-Xaa-Yaa repeats, and Arg residues at Yaa positions have been shown to be important for this interaction. The amino acid at the Yaa position (Yaa(-3)) in the N-terminal-adjoining triplet containing the critical Arg (defined as Arg(0)) was also suggested to be directly recognized by HSP47 (Koide, T., Asada, S., Takahara, Y., Nishikawa, Y., Nagata, K., and Kitagawa, K. (2006) J. Biol. Chem. 281, 3432-3438). Based on this finding, we examined the relationship between the structure of Yaa(-3) and HSP47 binding using synthetic collagenous peptides. The results obtained indicated that the structure of Yaa(-3) determined the binding affinity for HSP47. Maximal binding was observed when Yaa(-3) was Thr. Moreover, the required relative spatial arrangement of these key residues in the triple helix was analyzed by taking advantage of heterotrimeric collagen-model peptides, each of which contains one Thr(-3) and one Arg(0). The results revealed that HSP47 recognizes the Yaa(-3) and Arg(0) residues only when they are on the same peptide strand. Taken together, the data obtained led us to define the HSP47-binding structural epitope in the collagen triple helix and also define the HSP47-binding motif in the primary structure. A motif search against human protein database predicted candidate clients for this molecular chaperone. The search result indicated that not all collagen family proteins require the chaperoning by HSP47.


a2 Isoform-specific activation of 5 adenosine monophosphate-activated protein kinase by 5-aminoimidazole-4-carboxamide-1-b-D-ribonucleoside at a physiological level activates glucose transport and increases glucose transporter 4 in mouse skeletal muscle

5'Adenosine monophosphate-activated protein kinase (AMPK) has been implicated in exercise-induced stimulation of glucose metabolism in skeletal muscle. Although skeletal muscle expresses both the alpha1 and alpha2 isoforms of AMPK, the alpha2 isoform is activated predominantly in response to moderate-intensity endurance exercise in human and animal muscles. The purpose of this study was to determine whether activation of alpha2 AMPK plays a role in increasing the rate of glucose transport, promoting glucose transporter 4 (GLUT4) expression, and enhancing insulin sensitivity in skeletal muscle. To selectively activate the alpha2 isoform, we used 5-aminoimidazole-4-carboxamide-1-beta-d-ribonucleoside (AICAR), which is metabolized in muscle cells and preferentially stimulates the alpha2 isoform. Subcutaneous administration of 250 mg/kg AICAR activated the alpha2 isoform for 90 minutes, but not the alpha1 isoform in hind limb muscles of the C57/B6J mouse. The maximal activation of the alpha2 isoform was observed 30 to 60 minutes after administration of AICAR and was similar to the activation induced by a 30-minute swim in a current pool. The increase in alpha2 activity paralleled the phosphorylation of Thr(172), the essential residue for full kinase activation, and the activity of acetyl-coenzyme A carboxylase beta, a known substrate of AMPK in skeletal muscle. Subcutaneous injection of AICAR rapidly increased, by 30%, the rate of 2-deoxyglucose (2DG) transport into soleus muscle; 2DG transport increased within 30 minutes and remained elevated for 4 hours after administration of AICAR. Repeated intraperitoneal injection of AICAR, 3 times a day for 4 to 7 days, increased soleus GLUT4 protein by 30% concomitant with a significant 20% increase in insulin-stimulated 2DG transport. These data suggest that moderate endurance exercise promotes glucose transport, GLUT4 expression, and insulin sensitivity in skeletal muscle at least partially via activation of the alpha2 isoform of AMPK.


Unequivocal Synthesis of (Z)-Alkene and (E)-Fluoroalkene Dipeptide Isosters to Probe Structural Requirements of Peptide Transporter PEPT1.

[reaction: see text] Described is a novel synthetic route for dipeptide isosteres containing (Z)-alkene and (E)-fluoroalkene units as cis-amide bond equivalents via organocopper-mediated reduction of gamma-acetoxy- or gamma,gamma-difluoro-alpha,beta-unsaturated-delta-lactams. The synthesized isosteres were evaluated in terms of their affinities for the peptide transporter PEPT1. trans-Amide isosteres tended to possess higher affinities for PEPT1 as compared to the corresponding cis-amide bond equivalents.


Application of Tri- and Tetrasubstituted Alkene Dipeptide Mimetics to Conformational Studies of Cyclic RGD Peptides.


Cysteine-Derived S-Protected Oxazolidinones: Potential Chemical Devices for the Preparation of Peptide Thioesters

[reaction: see text]. An N-S acyl-transfer-mediated preparation of peptide thioesters using the S-protected oxazolidinone derived from cysteine has been developed and applied to the synthesis of a 32-mer biologically active peptide by native chemical ligation protocols.


Design and synthesis of downsized metastin (45-54) analogs with maintenance of high GPR54 agonistic activity

Metastin has been identified as a metastasis suppressor gene product that mediates its function through a G protein coupled receptor, GPR54. To refine insight into the critical pharmacophore for the activation of GPR54, we have conducted alanine and d-amino acid scanning on a biologically active metastin fragment (45-54). Based on these data and structures of peptides previously reported to activate GPR54, a series of shortened metastin (45-54) derivatives were synthesized and tested for the ability to induce GPR54 signaling. These biological experiments were performed in yeast containing human GPR54 that was coupled to the pheromone response pathway and a pheromone responsive lacZ reporter gene. Compounds 32, 33, and 39, which possess an N-terminal basic group and a C-terminal RW-amide motif, were strong agonists, similar to the level of metastin. This may provide an approach to reverse the pro-metastatic effect of metastin deletion in multiple malignant tumors.

Bioorganic & Medicinal Chemistry Letters


Structure activity relationship studies on CXCR4 antagonists having cyclic pentapeptide scaffolds

Structure-activity relationship studies on CXCR4 antagonists, which were previously found by using cyclic pentapeptide libraries, were performed to optimize side-chain functional groups, involving conformationally constrained analogues. In addition, a new lead of cyclic pentapeptides with the introduction of a novel pharmacophore was developed.


Photolabile Protection for One-Pot Sequential Native Chemical Ligation


Development of Anti-HIV Agents Targeting Dynamic Supramolecular Mechanism: Entry and Fusion Inhibitors Based on CXCR4/CCR5 Antagonists and gp41-C34-Remodeling Peptides

A molecular mechanism involved both in HIV-entry and -fusion steps has been disclosed in detail: The interaction of an HIV envelope protein, gp120, with chemokine receptors, CXCR4 and CCR5, which were identified as major co-receptors in association with CD4, triggers conformational changes in the gp120-gp41 (another envelope protein) complex, and subsequently forms the trimer-of-hairpins structure of gp41 followed by virus-cell membrane fusion. The elucidation of the above dynamic supramolecular mechanism in HIV-entry and -fusion has provided insights into new type of drugs that can block HIV infection. Based on this, we have developed not only coreceptor antagonists (1) but also fusion inhibitors (2). (1) Potent CXCR4 antagonists, T22 and T140, have been developed through the structure-activity relationship studies on tachyplesins and polyphemusins that are horseshoe crabs' antimicrobial peptides. T22, which was initially found to bind gp120 and CD4, and T140 selectively suppress T-cell line-tropic HIV-1 (X4-HIV-1) entry based on their specific binding to CXCR4. Furthermore, molecular-size reduction of T140 using cyclic pentapeptide templates brought us to find low molecular weight CXCR4 antagonists, such as FC131. (2) Artificial remodeling of a gp41 fragment, C34, has led to development of strong inhibitors of HIV-fusion into cells. These fusion inhibitors effectively block the formation of the trimer-of-hairpins structure of gp41. HIV-entry/fusion inhibitors such as CXCR4 antagonists and C34 analogs would improve the clinical chemotherapy of AIDS and HIV-infected patients. This review article focuses on our recent research on the development of the above two types of inhibitors, including comparative studies with several CXCR4 antagonists besides T22/T140-related compounds and other fusion inhibitors such as Fuzeon (T-20).


Facile access to (Z)-alkene-containing diketopiperazine mimetics utilizing organocopper-mediated anti-SN2 reactions


Identification of Novel Low Molecular Weight CXCR4 Antagonists by Structural Tuning of Cyclic Tetrapeptide Scaffolds

A highly potent CXCR4 antagonist, compound 2, was previously found by using two orthogonal cyclic pentapeptide libraries involving conformation-based and sequence-based libraries based on the pharmacophore of a 14-mer peptidic antagonist, 1. Herein, cyclic tetrapeptides derived from replacements of the dipeptide unit (Nal-Gly) with a gamma-amino acid and pseudopeptides cyclized by disulfide and olefin bridges were synthesized to find novel scaffold structures different from that of cyclic pentapeptides. These compounds contain a reduced number of peptide bonds compared to compound 2. Furthermore, several analogues with chemical modification of the side chain of Arg(4) in 2 were also prepared. From these, several new leads possessing high to moderate CXCR4-antagonistic activity were characterized.


Stereoselective Synthesis of [L-Arg-L/D-3-(2-naphthyl)alanine]-Type (E)-Alkene Dipeptide Isosteres and Its Application to the Synthesis and Biological Evaluation of Pseudopeptide Analogues of the CXCR4 Antagonist FC131

L,L-Type and L,D-type (E)-alkene dipeptide isosteres (EADIs) that have unnatural side chains at the alpha-position were synthesized by the combination of stereoselective aziridinyl ring-opening reactions and organozinc-copper-mediated anti-S(N)2' reactions toward a single substrate of gamma,delta-cis-gamma,delta-epimino (E)-alpha,beta-enoate. The utility of this methodology was demonstrated by the stereoselective synthesis of a set of diastereomeric EADIs of L-Arg-L/D-3-(2-naphthyl)alanine (Nal) that is contained in a small CXCR4 antagonist FC131 [cyclo(-D-Tyr-Arg-Arg-Nal-Gly-)]. Furthermore, a (Nal-Gly)-type EADI was synthesized by samarium diiodide (SmI(2))-induced reduction of a gamma-acetoxy-alpha,beta-enoate. Several FC131 analogues, in which these EADIs were inserted for reduction of their peptide character, were synthesized with analogues containing reduced amide-type dipeptide isosteres to investigate the importance of these amide bonds for anti-HIV and CXCR4-antagonistic activity.


Mutations Conferring Resistance to Human Immunodeficiency Virus Type 1 Fusion Inhibitors Are Restricted by gp41 and Rev-Responsive Element Functions

One of the human immunodeficiency virus (HIV) envelope proteins, gp41, plays a key role in HIV fusion. A gp41-derived peptide, T-20, efficiently inhibits HIV fusion and is currently approved for treatment of HIV-infected individuals. Although resistant variants have been reported, the mechanism of the resistance remains to be defined. To elucidate the mechanism in detail, we generated variants resistant to C34, a peptide derived from the gp41 carboxyl terminus heptad repeat (C-HR) in vitro. The resistant variants had a 5-amino-acid deletion in gp120 and a total of seven amino acid substitutions in gp41. Binding assays revealed that an I37K substitution in the N-terminal heptad repeat (N-HR) impaired the binding of C34, whereas an N126K substitution in the C-HR enhanced the binding to mutated N-HR, indicating that both mutations were directly involved in resistance. On the other hand, substitutions for A30 and D36 seemed to be secondary mutations, located complementary to each other in the Rev-responsive element (RRE), and were mutated simultaneously to maintain the secondary structure of the RRE that was impaired by the mutations at I37. Thus, HIV acquired resistance to C34 by mutations in N-HR, which directly interacted with C34. However, since this region also encoded the RRE, additional mutations were required to maintain viral replication. These results suggest that HIV fusion is one of the attractive targets for HIV chemotherapy.


Identification of a CXCR4 antagonist, a T140 analog, as an anti-rheumatoid arthritis agent

Several recent papers support the involvement of an interaction between stromal cell-derived factor-1 (SDF-1/CXCL12) and its receptor, chemokine receptor CXCR4, in memory T cell migration in the inflamed rheumatoid arthritis (RA) synovium. Analogs of the 14-mer peptide T140 were previously found to be specific CXCR4 antagonists that were characterized as not only HIV-entry inhibitors but also anti-cancer-metastatic agents. In this study, a T140 analog, 4F-benzoyl-TN14003, was proven to inhibit CXCL12-mediated migration of human Jurkat cells and mouse splenocyte in a dose-dependent manner in vitro (IC(50)=0.65 and 0.54 nM, respectively). Furthermore, slow release administration by subcutaneous injection (s.c.) of 4F-benzoyl-TN14003 using an Alzet osmotic pump significantly suppressed the delayed-type hypersensitivity response induced by sheep red blood cells in mice, and significantly ameliorated clinical severity in collagen-induced arthritis in mice. As such, T140 analogs might be attractive lead compounds for chemotherapy of RA.


Possible involvement of the α1 isoform of 5'AMP-activated protein kinase in oxidative stress-stimulated glucose transport in skeletal muscle

Recent studies have suggested that 5'AMP-activated protein kinase (AMPK) is activated in response to metabolic stresses, such as contraction, hypoxia, and the inhibition of oxidative phosphorylation, which leads to insulin-independent glucose transport in skeletal muscle. In the present study, we hypothesized that acute oxidative stress increases the rate of glucose transport via an AMPK-mediated mechanism. When rat epitrochlearis muscles were isolated and incubated in vitro in Krebs buffer containing the oxidative agent H(2)O(2), AMPKalpha1 activity increased in a time- and dose-dependent manner, whereas AMPKalpha2 activity remained unchanged. The activation of AMPKalpha1 was associated with phosphorylation of AMPK Thr(172), suggesting that an upstream kinase is involved in the activation process. H(2)O(2)-induced AMPKalpha1 activation was blocked in the presence of the antioxidant N-acetyl-l-cysteine (NAC), and H(2)O(2) significantly increased the ratio of oxidized glutathione to glutathione (GSSG/GSH) concentrations, a sensitive marker of oxidative stress. H(2)O(2) did not cause an increase in the conventional parameters of AMPK activation, such as AMP and AMP/ATP. H(2)O(2) increased 3-O-methyl-d-glucose transport, and this increase was partially, but significantly, blocked in the presence of NAC. Results were similar when the muscles were incubated in a superoxide-generating system using hypoxanthine and xanthine oxidase. Taken together, our data suggest that acute oxidative stress activates AMPKalpha1 in skeletal muscle via an AMP-independent mechanism and leads to an increase in the rate of glucose transport, at least in part, via an AMPKalpha1-mediated mechanism.

American Journal of Physiology, Endocrinology and Metabolism


Facile synthesis of membrane-embedded peptides utilizing lipid bilayer-assisted chemical ligation

Lipid bilayer-assisted chemical ligation between thiolester and N-terminal cysteine peptides has been developed with successful application to the synthesis of membrane protein segments possessing both two transmembrane and one extracellular regions.


HIV protease inhibitor nelfinavir inhibits replication of SARS-associated coronavirus

A novel coronavirus has been identified as an etiological agent of severe acute respiratory syndrome (SARS). To rapidly identify anti-SARS drugs available for clinical use, we screened a set of compounds that included antiviral drugs already in wide use. Here we report that the HIV-1 protease inhibitor, nelfinavir, strongly inhibited replication of the SARS coronavirus (SARS-CoV). Nelfinavir inhibited the cytopathic effect induced by SARS-CoV infection. Expression of viral antigens was much lower in infected cells treated with nelfinavir than in untreated infected cells. Quantitative RT-PCR analysis showed that nelfinavir could decrease the production of virions from Vero cells. Experiments with various timings of drug addition revealed that nelfinavir exerted its effect not at the entry step, but at the post-entry step of SARS-CoV infection. Our results suggest that nelfinavir should be examined clinically for the treatment of SARS and has potential as a good lead compound for designing anti-SARS drugs.

Biochemical and Biophysical Research Communications


Topochemical exploration of potent compounds using retro-enantiomer libraries of cyclic pentapeptides

Cyclic pentapeptides have been adopted as conformationally restricted peptide templates to dispose pharmacophores of bioactive peptides. In our recent study, use of two orthogonal cyclic pentapeptide libraries involving conformation-based and sequence-based libraries containing critical residues of a bioactive peptide led to the discovery of potent downsized peptides that possess activity comparable to that of the parent peptide. The present study demonstrates that a third library consisting of retro-enantiomers (retro-inverso peptides) that possess not only all residues with the opposite configuration to those in the corresponding original peptide but also amino acid sequences with reversed arrangement, is important as an alternative library for rationally finding active compounds.


SmI2-Mediated Reduction of γ,γ-Difluoro-α,β-enoates with Application to the Synthesis of Functionalized (Z)-Fluoroalkene-Type Dipeptide Isosteres

A samarium diiodide (SmI(2))-mediated reduction of gamma,gamma-difluoro-alpha,beta-enoates (15, 29, and 34) was successfully applied to the synthesis of (Z)-fluoroalkene dipeptide isosteres (23, 30, and 35), which have served as potential dipeptide mimetics. Reduction of the gamma,gamma-difluoro-alpha,beta-enoates by SmI(2) proceeded via successive two-electron transfers to form dienolate species which upon kinetically controlled trapping with t-BuOH yielded Xaa-Gly-type fluoroalkene isosteres exemplified by 23, 30, and 35. Replacement of the t-BuOH kinetic trapping agent with aldehydes or ketones provided access to alpha-substituted fluoroalkene isosteres (43 and 45) through aldol reactions of Sm-dienolates with the carbonyl compounds. Of particular note, the use of the SmI(2)-HCHO reagent system with chiral enoate 34 provided D-Phe-psi[(Z)-CF[double bond]CH]-D/L-Ser isosteres (45), which could be converted to enantiomerically pure isosteres (49-52) that bore a variety of side chain functionalities at the alpha-position. This was achieved by a sequence of manipulations consisting of beta-lactone formation followed by chromatographic separation and ring-opening with soft nucleophiles. Included in the present work is the first utilization of a Rh-catalyzed Reformatsky reaction of chiral imines for the stereoselective preparation of alpha,alpha-difluoro-beta-amino acid derivatives (28 and 33). The appropriate choice of reagents (carbonyl compounds for kinetic trapping or ring-opening nucleophiles and imines for Reformatsky reactions) allows the presented methodology to yield various fluoroalkene isosteres possessing a wide range of side chain functionalities.


Enhancement of the T140-based pharmacophores leads to the development of more potent and bio-stable CXCR4 antagonists

A CXCR4 antagonistic peptide, T140, and its bio-stable analogs, such as Ac-TE14011, were previously developed. These peptides inhibit the entry of T cell line-tropic strains of HIV-1 (X4-HIV-1) into T cells. Herein, a series of TE14011 analogs having modifications in the N-terminal region were synthesized to develop effective compounds with increased biostability. Among these analogs, 4F-benzoyl-TE14011 (TF14013) showed the strongest anti-HIV activity derived from CXCR4-antagonism, suggesting that a 4-fluorobenzoyl moiety at the N-terminus of T140 analogs constitutes a novel T140-based pharmacophore for CXCR4 antagonists. Structure-activity relationship (SAR) studies on TE14011 analogs with N(alpha)-acylation by several benzoic acid derivatives have disclosed a significant relationship between the anti-HIV activity and the Hammett constant (sigma) of substituted benzoic acids. TF14013 was found to be stable in mouse serum, but not completely stable in rat liver homogenate due to deletion of the C-terminal Arg14-NH2 from the parent peptide. This biodegradation was completely suppressed by N-alkyl-amidation at the C-terminus. Taken together, the enhancement of the T140-based pharmacophores led to development of a novel CXCR4 antagonist, 4F-benzoyl-TE14011-Me (TF14013-Me), which has very high anti-HIV activity and increased biostability.


Synthesis of potent CXCR4 inhibitors possessing low cytotoxicity and improved biostability based on T140 derivatives

A peptidic CXCR4 antagonist T140 efficiently blocks the entry of T cell line-tropic strains of HIV-1 (X4-HIV-1) into target cells. In this study, a series of T140 derivatives, replacing the basic amino acid residues with Glu (D-Glu) and/or L-citrulline (Cit), were synthesized in order to reduce non-specific binding and cytotoxicity. Among them, TE14011 ([Cit6, D-Glu8]-T140 with the C-terminal amide) exhibited strong anti-HIV activity and low cytotoxicity. TE14011 was found to be stable in mouse serum, but unstable in rat liver homogenate due to the deletion of the N-terminal Arg1-Arg2-L-3-(2-naphthyl)alanine (Nal)3 residues from the parent peptide. N-Terminal acetylation of TE14011 led to the development of a novel lead compound, Ac-TE 14011, which possesses a high selectivity index as well as increased stability in serum and liver homogenate.


T140 analogs as CXCR4 antagonists identified as anti-metastatic agents in the treatment of breast cancer

A chemokine receptor, CXCR4, and its endogenous ligand, stromal cell-derived factor-1 (SDF-1), have been recognized to be involved in the metastasis of several types of cancers. T140 analogs are peptidic CXCR4 antagonists composed of 14 amino acid residues that were previously developed as anti-HIV agents having inhibitory activity against HIV-entry through its co-receptor, CXCR4. Herein, we report that these compounds effectively inhibited SDF-1-induced migration of human breast cancer cells (MDA-MB-231), human leukemia T cells (Sup-T1) and human umbilical vein endothelial cells at concentrations of 10-100 nM in vitro. Furthermore, slow release administration by subcutaneous injection using an Alzet osmotic pump of a potent and bio-stable T140 analog, 4F-benzoyl-TN14003, gave a partial, but statistically significant (P</=0.05 (t-test)) reduction in pulmonary metastasis of MDA-MB-231 in SCID mice, even though no attempt was made to inhibit other important targets such as CCR7. These results suggest that T140 analogs have potential use for cancer therapy, and that small molecular CXCR4 antagonists could potentially replace neutralizing antibodies as anti-metastatic agents for breast cancer.


Application of samarium diiodide (SmI2)-induced reduction of γ-acetoxy-α,β-enoates with α-specific kinetic electrophilic trapping for the synthesis of amino acid derivatives

Gamma-acetoxy-alpha,beta-enoates were easily reduced by samarium diiodide (SmI2) in THF to generate samarium dienolates which were kinetically trapped with ease at their alpha-positions by electrophiles (proton, aldehydes or ketones) to yield (E)-alkene dipeptide isosteres or gamma-amino acid derivatives in high chemical yields.


Molecular-Size Reduction of a Potent CXCR4-Chemokine Antagonist Using Orthogonal Combination of Conformation- and Sequence-Based Libraries


Synthesis of potent beta-secretase inhibitors containing a hydroxyethylamine dipeptide isostere and their structure-activity relationship studies

Several beta-secretase inhibitors were designed based on hydroxyethylamine dipeptide isostere (HDI) structures and were synthesized by a methodology using the aza-Payne rearragement and O,N-acyl transfer reactions to study their structure-activity relationships. Among these pseudopeptides, effective compounds were developed as the first beta-secretase inhibitors containing the HDI transition state mimic with potent enzyme inhibitory activity (IC50 < 100 nM).


Reduction of Peptide Character of HIV Protease Inhibitors That Exhibit Nanomolar Potency against Multidrug Resistant HIV-1 Strains

Novel HIV protease inhibitors containing a hydroxyethylamine dipeptide isostere as a transition state-mimic king structure were synthesized by combining substructures of known HIV protease inhibitors. Among them, TYA5 and TYB5 were proven to be not only potent enzyme inhibitors (K(i) = 0.12 nM and 0.10 nM, respectively) but also strong anti-HIV agents (IC(50) = 9.5 nM and 66 nM, respectively), even against viral strains with multidrug resistance. Furthermore, insertion of an (E)-alkene dipeptide isostere at the P(1)-P(2) position of TYB5 led to development of a purely nonpeptidic protease inhibitor, TYB1 (K(i) = 0.38 nM, IC(50) = 160 nM).


Diastereoselective Synthesis of New Ψ [(E)-CH=CMe]- and Ψ [(Z)-CH=CMe]-type Alkene Dipeptide Isosteres by Organocopper Reagents and Application to Conformationally Restricted Cyclic RGD Peptidomimetics

Diastereoselective synthesis of new psi[(E)-CH=CMe]- and psi[(Z)-CH=CMe]-type alkene dipeptide isosteres corresponding to dipeptides having one N-methylamino acid, and application to bioactive peptides, are described. In a key reaction introducing the chiral alpha-alkyl group of the isosteres, organocopper-mediated alkylation of syn-beta-methylated gamma-mesyloxy-alpha,beta-enoate 26a afforded E- and Z-isomers of anti-S(N)2' products in a solvent-dependent manner. The resulting two isosteres, D-Phe-psi[(E)-CH=CMe]-L-Val 27a and D-Phe-psi[(Z)-CH=CMe]-L-Val 28b, which corresponded to trans- and cis-conformers of D-Phe-L-MeVal, respectively, were utilized in a structure-activity relationship study on cyclic RGD peptides 1 and 2, in company with a psi[(E)-CH=CH]-type alkene dipeptide isostere, D-Phe-psi[(E)-CH=CH]-L-Val. The cyclic isostere-containing pseudopeptides 3, 4, and 40 were synthesized and biological activity against integrin alpha(V)beta(3) and alpha(IIb)beta(3) receptors were also evaluated.


Regio- and Stereoselective Synthesis of (E)-Alkene trans-Xaa-Pro Dipeptide Mimetics Utilizing Organocopper-Mediated Anti-SN2' Reactions

Proline dipeptides (Xaa-Pro) exist as an equilibrium mixture of cis- and trans-rotamers, which depends on the energy barriers for imide isomerization. This conformation mixture contributes to both structure and function of proline-containing peptides and proteins. Structural motifs resembling these cis- or trans-conformers have served as useful tools for elucidating contributions of proline residues in the physicochemical and biological profiles of structures which contain them. Among such motifs are alkene dipeptide isosteres which mimic cis- or trans-imide using (Z)- or (E)-alkene, respectively. In this report, the first regio- and stereoselective syntheses of (E)-alkene dipeptide isosteres (20, 31, and 35) corresponding to trans-proline dipeptides are described. Key to the synthesis of these mimetics is the anti-S(N)2' reaction of vinyl aziridines such as 15 or vinyl oxazolidinones such as 28 and 32 with organocopper reagents "RCu" (R = CH(2)SiMe(2)(Oi-Pr)). Reaction of cis-vinylaziridine 15 derived from L-serine with organocopper reagent gave a precursor of the trans-L-Ser-D-Pro type alkene isosteres 20, accompanied by an S(N)2 side product. One limitation with the use of such aziridine-mediated methodology is formation of the corresponding trans-aziridine 22, which leads to L-L type isosteres, that is unstable and obtainable only in low yield. On the other hand, both isomers of oxazolidinone derivatives can be easily obtained from N-Boc-protected amino alcohols. The reaction of trans- 28 or cis-oxazolidinone derivative 32 with organocopper reagents proceeds quantitatively with high regio- and diastereoselectivities in anti-S(N)2' fashion. Subsequent oxidative treatment of the newly introduced isopropoxydimethylsilylmethyl group yields trans-L-Ser-L-Pro 31 or trans-L-Ser-D-Pro type isosteres 35, respectively. Of note, synthesized isostere 31 can also be converted to trans-phosphoSer-Pro 42 and trans-Cys-Pro mimetics 44. The present synthetic methodology affords trans-Xaa-Pro alkene-type dipeptide isosteres in high yield with relatively simple manipulation.


Remodeling of gp41-C34 Peptide Leads to Highly Effective Inhibitors of the Fusion of HIV-1 with Target Cells


Identification of Cell Binding Sites in the Laminin α5-Chain G Domain

The laminins consist of at least 11 polypeptides (5 alpha-chains, 3 beta-chains, and 3 gamma-chains) specific to basement membranes. Here we investigate the biological activity associated with the G domain of the newly identified laminin alpha5-chain using 113 overlapping synthetic peptides (positions 2679-3635). Using HT-1080 cells, 21 peptides showed attachment activity either on peptide-coated tissue culture plates or to peptide-conjugated Sepharose beads. Heparin inhibited cell attachment to 16 peptides, while ethylenediaminetetraacetic acid exhibited no inhibitory activity. Peptides A5G-27, A5G-65, and A5G-71 showed the strongest cell attachment, with the minimum active core sequences of the peptides being GIIFFL, HQNMGSVNVSV, and YLQFVG, respectively. Furthermore, these 16 peptides were tested for their ability to stimulate neurite outgrowth in the PC12 cells. A5G-3, A5G-33, A5G-71, A5G-73, A5G-81, and A5G-101 were the only peptides of the 16 that demonstrated the ability to promote neurite outgrowth. These results demonstrate that synthetic peptides with alpha5-chain G domain primary amino acid sequences possess some of the same biological activities attributable to the whole laminin and the alpha5-chain G domain. Therefore, these peptides may be useful in the investigation of laminin-receptor interactions and possibly mechanisms of laminin signal transduction.


Certification of the Critical Importance of L-3-(2-Naphthyl)alanine at Position 3 of a Specific CXCR4 Inhibitor, T140, Leads to an Exploratory Performance of Its Downsizing Study

We have previously found that a 14-amino acid residue-peptide, T140, inhibits infection of target cells by T cell line-tropic HIV-1 (X4-HIV-1) through its specific binding to a chemokine receptor, CXCR4. Here, the importance of an L-3-(2-naphthyl)alanine (Nal) residue at position 3 in T140 for high anti-HIV activity and inhibitory activity against Ca(2+) mobilization induced by stromal cell-derived factor (SDF)-1alpha-stimulation through CXCR4 has initially been shown by the synthesis and biological evaluation of several analogues, where Nal(3) is substituted by diverse aromatic amino acids. Next, the order of the N-terminal 3 residues (Arg(1)-Arg(2)-Nal(3)) has been proved to be important from the structure--activity relationship (SAR) study shuffling these residues. Based on these results, we have found 10-residue peptides possessing modest anti-HIV activity by systematic antiviral evaluation of a series of synthetic, shortened analogues of T140.


Diastereoselective synthesis of psi[(E)-CH=CMe]- and psi[(Z)-CH=CMe]-type dipeptide isosteres by organocopper-mediated anti-S(N)2' reaction

[reaction: see text] Acyclic psi[(E)-CH=CMe]- and psi[(Z)-CH=CMe]-type dipeptide isosteres were efficiently synthesized. In a key reaction, alpha-alkylation of gamma-mesyloxy-beta-methyl-alpha,beta-unsaturated esters with organocyanocuprates in diethyl ether or tetrahydrofuran preferentially afforded the psi[(E)-CH=CMe]- or psi[(Z)-CH=CMe]-isomer, respectively, via anti-S(N)2' mechanism.


Diastereoselective synthesis of psi[(E)-CMe=CH]- and psi[(E)-CMe=CMe]- type dipeptide isosteres based on organocopper-mediated anti-S(N)2' reaction

[reaction: see text] A straightforward synthetic route for the synthesis of diastereomerically pure psi[(E)-CMe=CH]- and psi[(E)-CMe=CMe]-type dipeptide isosteres was developed on the basis of regio- and stereoselective anti-S(N)2' alkylation of 3-(N-Boc-5-methyl-4-substituted-oxazolidin-2-on-5-yl)acrylates with organocopper reagents.


Trojan p16 Peptide Suppresses Pancreatic Cancer Growth and Prolongs Survival in Mice

The tumor suppressor gene p16INK4A is inactivated frequently in a large number of human cancers, and many investigators have attempted to restore the function of p16 using the p16 wild-type gene and viral vectors. In this study, we treated the tumor-bearing animals with the p16-derived synthetic peptide coupled with the Antennapedia carrier sequence, which we designated as Trojan p16 peptide. Injections (i.p.) of the Trojan p16 peptide (100 microg/mouse/day) were given for 3 weeks in the AsPC-1 and BxPC-3 s.c. tumor models. Tumor growth, histopathology, and TUNEL staining of the tumor and toxicity of the animals were evaluated. To examine its influence on the survival of tumor-bearing mice, Trojan p16 was administered in the AsPC-1 peritoneal dissemination model. In the AsPC-1 s.c. tumor model, a significant growth inhibition was obtained by the Trojan p16 treatment when compared with the three control treatments, i.e., vehicle, unconjugated form of p16, or Trojan peptide alone. Tumor growth inhibition was almost complete in the BxPC-3 tumor, a relatively slow growing tumor. Neither hematological cytotoxicity or body weight loss were observed. Histopathology of the BxPC-3 s.c. tumor in the Trojan p16 treatment group revealed marked vacuole formation and apoptotic death of cancer cells. In the AsPC-1 peritoneal dissemination model, the survival curve of mice treated with Trojan p16 was significantly longer than that of control. These results provide evidence that the Trojan p16 peptide system, a gene-oriented peptide coupled with a peptide vector, functions for experimental pancreatic cancer therapy.


Synthesis and evaluation of pseudopeptide analogues of a specific CXCR4 inhibitor, T140: The insertion of an (E)-alkene dipeptide isostere into the βII' -turn moiety

A 14-residue peptide, T140, strongly inhibits the T-cell line-tropic HIV-1 (X4-HIV-1) infection, since this peptide functions as a specific antagonist against a chemokine receptor, CXCR4. T140 takes an antiparallel beta-sheet structure with a type II' beta-turn. In the present paper, we have designed and synthesized several T140 analogues, in which an (E)-alkene dipeptide isostere was inserted into the type II' beta-turn moiety, as a bridging study to develop nonpeptidic CXCR4 inhibitors. It has been proven that the turn region of T140 can be replaced by the above surrogate with the maintenance of strong anti-HIV activity.

Bioorganic & Medicinal Chemistry Letters


Notch receptor cleavage depends on but is not directly executed by presenilins

Proceedings of the National Academy of Sciences of the United States of America


Regio- and stereoselective ring-opening of chiral 1,3-oxazolidin-2-one derivatives by organocopper reagents provides novel access to di-, tri- and tetra-substituted alkene dipeptide isosteres

Journal of the Chemical Society, Perkin Transactions 1


Efficient stereoselective synthesis of peptidomimetics containing hydroxyethylamine dipeptide isosteres utilizing the aza-Payne rearrangement and O, N-acyl transfer reactions


Heterodimer Formation between the Antimicrobial Peptides Magainin 2 and PGLa in Lipid Bilayers: A Cross-Linking Study

The antimicrobial peptides magainin 2 and PGLa, isolated from the skin of the African clawed frog Xenopus laevis, show marked synergism [Westerhoff, H. V., Zasloff, M., Rosner, J. L., Hendler, R. W., de Waal, A., Vaz Gomes, A., Jongsma, A. P. M., Riethorst, A., and Juretic, D. (1995) Eur. J. Biochem. 228, 257-264]. We suggested previously that these peptides form a potent heterodimer composed of either parallel or antiparallel helices in membranes [Matsuzaki, K., Mitani, Y., Akada, K., Murase, O., Yoneyama, S., Zasloff, M., and Miyajima, K. (1998) Biochemistry 37, 15144-15153]. To detect the putative heterodimer by chemical cross-linking, analogues of magainin 2 and PGLa with a Cys residue at either terminus were synthesized. These cross-linking experiments suggested that both peptides form a parallel heterodimer in membranes composed of phosphatidylglycerol/phosphatidylcholine but not in either buffer or a helix-promoting 2,2,2-trifluoroethanol/buffer mixture. The isolated parallel heterodimers exhibited an order of magnitude higher membrane permeabilization activity compared with the monomeric species, indicating that the observed synergism is due to heterodimer formation.


New access to α-substituted (Z)-fluoroalkene dipeptide isosteres utilizing organocopper reagents under `reduction oxidative alkylation (R-OA)' conditions


Synthesis and evaluation of bifunctional anti-HIV agents based on specific CXCR4 antagonists-AZT conjugation

We have previously found that T140, a 14-amino acid residue peptide, inhibits infection of target cells by T cell-line-tropic strains of HIV-1 (X4-HIV-1) through its specific binding to a chemokine receptor, CXCR4. Here, we report synthesis and evaluation of bifunctional anti-HIV compounds, which are composed of T140 analogues and a reverse transcriptase inhibitor, 3'-azido-3'-deoxythymidine (AZT). Novel conjugated analogues have been proved to have the ability for controlled release of AZT in neutral aqueous media as well as mouse and feline sera, and high selectivity indexes (SIs, 50% cytotoxic concentration/50% effective concentration) caused by a synergistic effect of two different regenerating agents. Thus, these bifunctional compounds have several potential advantages. T140 analogues can possibly work as a carrier of AZT targeting T cells due to their specific affinity for CXCR4 on T cells. A synergistic effect by two types of regenerating agents may enable drug dosage to be reduced, and thus it may effectively suppress toxic side effects and the appearance of drug-resistant virus.