Ethanolamine Is a New Anti-Prion Compound

Prion diseases are a group of fatal neurodegenerative disorders caused by accumulation of proteinaceous infectious particles, or prions, which mainly consist of the abnormally folded, amyloidogenic prion protein, designated PrP. PrP is produced through conformational conversion of the cellular isoform of prion protein, PrP, in the brain. To date, no effective therapies for prion diseases have been developed. In this study, we incidentally noticed that mouse neuroblastoma N2a cells persistently infected with 22L scrapie prions, termed N2aC24L1-3 cells, reduced PrP levels when cultured in advanced Dulbecco's modified eagle medium (DMEM) but not in classic DMEM. PrP levels remained unchanged in prion-uninfected parent N2aC24 cells cultured in advanced DMEM. These results suggest that advanced DMEM may contain an anti-prion compound(s). We then successfully identified ethanolamine in advanced DMEM has an anti-prion activity. Ethanolamine reduced PrP levels in N2aC24L1-3 cells, but not PrP levels in N2aC24 cells. Also, oral administration of ethanolamine through drinking water delayed prion disease in mice intracerebrally inoculated with RML scrapie prions. These results suggest that ethanolamine could be a new anti-prion compound.

International Journal of Molecular Sciences


Neurotropic influenza A virus infection causes prion protein misfolding into infectious prions in neuroblastoma cells.


Vaporized Hydrogen Peroxide and Ozone Gas Synergistically Reduce Prion Infectivity on Stainless Steel Wire.

Prions are infectious agents causing prion diseases, which include Creutzfeldt-Jakob disease (CJD) in humans. Several cases have been reported to be transmitted through medical instruments that were used for preclinical CJD patients, raising public health concerns on iatrogenic transmissions of the disease. Since preclinical CJD patients are currently difficult to identify, medical instruments need to be adequately sterilized so as not to transmit the disease. In this study, we investigated the sterilizing activity of two oxidizing agents, ozone gas and vaporized hydrogen peroxide, against prions fixed on stainless steel wires using a mouse bioassay. Mice intracerebrally implanted with prion-contaminated stainless steel wires treated with ozone gas or vaporized hydrogen peroxide developed prion disease later than those implanted with control prion-contaminated stainless steel wires, indicating that ozone gas and vaporized hydrogen peroxide could reduce prion infectivity on wires. Incubation times were further elongated in mice implanted with prion-contaminated stainless steel wires treated with ozone gas-mixed vaporized hydrogen peroxide, indicating that ozone gas mixed with vaporized hydrogen peroxide reduces prions on these wires more potently than ozone gas or vaporized hydrogen peroxide. These results suggest that ozone gas mixed with vaporized hydrogen peroxide might be more useful for prion sterilization than ozone gas or vaporized hydrogen peroxide alone.


Strain-Dependent Prion Infection in Mice Expressing Prion Protein with Deletion of Central Residues 91-106.

Conformational conversion of the cellular prion protein, PrP, into the abnormally folded isoform, PrP, is a key pathogenic event in prion diseases. However, the exact conversion mechanism remains largely unknown. Transgenic mice expressing PrP with a deletion of the central residues 91-106 were generated in the absence of endogenous PrP, designated Tg(PrP∆91-106)/ mice and intracerebrally inoculated with various prions. Tg(PrP∆91-106)/ mice were resistant to RML, 22L and FK-1 prions, neither producing PrP∆91-106 or prions in the brain nor developing disease after inoculation. However, they remained marginally susceptible to bovine spongiform encephalopathy (BSE) prions, developing disease after elongated incubation times and accumulating PrP∆91-106 and prions in the brain after inoculation with BSE prions. Recombinant PrP∆91-104 converted into PrP∆91-104 after incubation with BSE-PrP-prions but not with RML- and 22L-PrP-prions, in a protein misfolding cyclic amplification assay. However, digitonin and heparin stimulated the conversion of PrP∆91-104 into PrP∆91-104 even after incubation with RML- and 22L-PrP-prions. These results suggest that residues 91-106 or 91-104 of PrP are crucially involved in prion pathogenesis in a strain-dependent manner and may play a similar role to digitonin and heparin in the conversion of PrP into PrP.


Prion protein signaling induces M2 macrophage polarization and protects from lethal influenza infection in mice.

The cellular prion protein, PrPC, is a glycosylphosphatidylinositol anchored-membrane glycoprotein expressed most abundantly in neuronal and to a lesser extent in non-neuronal cells. Its conformational conversion into the amyloidogenic isoform in neurons is a key pathogenic event in prion diseases, including Creutzfeldt-Jakob disease in humans and scrapie and bovine spongiform encephalopathy in animals. However, the normal functions of PrPC remain largely unknown, particularly in non-neuronal cells. Here we show that stimulation of PrPC with anti-PrP monoclonal antibodies (mAbs) protected mice from lethal infection with influenza A viruses (IAVs), with abundant accumulation of anti-inflammatory M2 macrophages with activated Src family kinases (SFKs) in infected lungs. A SFK inhibitor dasatinib inhibited M2 macrophage accumulation in IAV-infected lungs after treatment with anti-PrP mAbs and abolished the anti-PrP mAb-induced protective activity against lethal influenza infection in mice. We also show that stimulation of PrPC with anti-PrP mAbs induced M2 polarization in peritoneal macrophages through SFK activation in vitro and in vivo. These results indicate that PrPC could activate SFK in macrophages and induce macrophage polarization to an anti-inflammatory M2 phenotype after stimulation with anti-PrP mAbs, thereby eliciting protective activity against lethal infection with IAVs in mice after treatment with anti-PrP mAbs. These results also highlight PrPC as a novel therapeutic target for IAV infection.


The N-Terminal Polybasic Region of Prion Protein Is Crucial in Prion Pathogenesis Independently of the Octapeptide Repeat Region

Conformational conversion of the cellular isoform of prion protein, designated PrP, into the abnormally folded, amyloidogenic isoform, PrP, is an essential pathogenic event in prion diseases. However, the exact conversion mechanism remains largely unknown. Lines of evidence indicate that the N-terminal domain, which includes the N-terminal, positively charged polybasic region and the octapeptide repeat (OR) region, is important for PrP to convert into PrP after infection with prions. To further gain insights into the role of the polybasic region and the OR region in prion pathogenesis, we generated two different transgenic mice, designated Tg(PrP3K3A)/Prnp and Tg(PrP3K3A∆OR)/Prnp mice, which express PrP with lysine residues at codons 23, 24, and 27 in the polybasic region mutated with or without a deletion of the OR region on the Prnp background, respectively, and intracerebrally inoculated them with RML and 22L prions. We show that Tg(PrP3K3A)/Prnp mice were highly resistant to the prions, indicating that lysine residues at 23, 24, and 27 could be important for the polybasic region to support prion infection. Tg(PrP3K3A∆OR)/Prnp mice also had reduced susceptibility to RML and 22L prions equivalent to Tg(PrP3K3A)/Prnp mice. The pre-OR region, including the polybasic region, of PrP3K3A∆OR, but not PrP3K3A, was unusually converted to a protease-resistant structure during conversion to PrP3K3A∆OR. These results suggest that, while the OR region could affect the conformation of the polybasic region during conversion of PrP into PrP, the polybasic region could play a crucial role in prion pathogenesis independently of the OR region.


Analysis of the immunoglobulin G (IgG) secretion efficiency in recombinant Chinese hamster ovary (CHO) cells by using Citrine-fusion IgG.

Biopharmaceuticals represented by immunoglobulin G (IgG) are produced by the cultivation of recombinant animal cells, especially Chinese hamster ovary (CHO) cells. It is thought that the intracellular secretion process of IgG is a bottleneck in the production of biopharmaceuticals. Many studies on the regulation of endogenous secretory protein expression levels have shown improved productivity. However, these strategies have not universally improved the productivity of various proteins. A more rational and efficient establishment of high producer cells is required based on an understanding of the secretory processes in IgG producing CHO cells. In this study, a CHO cell line producing humanized IgG1, which was genetically fused with fluorescent proteins, was established to directly analyze intracellular secretion. The relationship between the amount of intracellular and secreted IgG was analyzed at the single cell level by an automated single-cell analysis and isolation system equipped with dual color fluorescent filters. The amounts of intracellular and secreted IgG showed a weak positive correlation. The amount of secreted IgG analyzed by the system showed a weak negative linear correlation with the specific growth of isolated clones. An immunofluorescent microscopy study showed that the established clones could be used to analyze the intracellular secretion bottleneck. This is the first study to report the use of fluorescent protein fusion IgG as a tool to analyze the secretion of recombinant CHO cells.


Secretion analysis of intracellular difficult-to-express immunoglobulin G (IgG) in Chinese hamster ovary (CHO) cells

The Chinese hamster ovary (CHO) cell line is the most widely used host cell for therapeutic antibody production. Although its productivity has been improved by various strategies to satisfy the growing global demand, some difficult-to-express (DTE) antibodies remain at low secretion levels. To improve the production of various therapeutic antibodies, it is necessary to determine possible rate-limiting steps in DTE antibody secretion in comparison with other high IgG producers. Here, we analyzed the protein secretion process in CHO cells producing the DTE immunoglobulin G (IgG) infliximab. The results from chase assays using a translation inhibitor revealed that infliximab secretion could be nearly completed within 2 h, at which time the cells still retained about 40% of heavy chains and 65% of light chains. Using fluorescent microscopy, we observed that these IgG chains remained in the endoplasmic reticulum and Golgi apparatus. The cells inefficiently form fully assembled heterodimer IgG by making LC aggregates, which may be the most serious bottleneck in the production of DTE infliximab compared with other IgG high producers. Our study could contribute to establish the common strategy for constructing DTE high-producer cells on the basis of rate-limiting step analysis.


Analysis of intracellular IgG secretion in Chinese hamster ovary cells to improve IgG production.

The production of biopharmaceutical immunoglobulin G (IgG) using cultured mammalian cells, especially Chinese hamster ovary (CHO) cells is well established and has been markedly improved through the modification of cells and cell culture engineering technologies. The establishment of high-production cell lines remains a challenge. The intracellular secretion of IgG has been investigated to identify and solve the rate-limiting steps in antibody production. However, strategies that regulate the expression of proteins that are related to antibody secretory pathway have not consistently improved their production. In this study, key features and limitations of the antibody secretion process in recombinant CHO cells were analyzed to develop more efficient approaches for establishing high-production cells. By chase assay with protein translation inhibitors, IgG secretion reached a plateau when at least 20% of IgG remained in the cells. The secretion kinetics and retention ratio of IgG varied between IgG subclasses (two types of IgG1 and an IgG3 subclass). Immunofluorescent microscopy and size exclusion chromatography showed that the remaining intracellular IgG localized mainly within the endoplasmic reticulum (ER) and less with the cis-Golgi network, despite the formation of fully assembled IgG. These results show that remaining intracellular IgG is a target for enhancing antibody secretion, even in high-production CHO cells.

Journal of Bioscience and Bioengineering


Prion protein protects mice from lethal infection with influenza A viruses.

The cellular prion protein, designated PrPC, is a membrane glycoprotein expressed abundantly in brains and to a lesser extent in other tissues. Conformational conversion of PrPC into the amyloidogenic isoform is a key pathogenic event in prion diseases. However, the physiological functions of PrPC remain largely unknown, particularly in non-neuronal tissues. Here, we show that PrPC is expressed in lung epithelial cells, including alveolar type 1 and 2 cells and bronchiolar Clara cells. Compared with wild-type (WT) mice, PrPC-null mice (Prnp0/0) were highly susceptible to influenza A viruses (IAVs), with higher mortality. Infected Prnp0/0 lungs were severely injured, with higher inflammation and higher apoptosis of epithelial cells, and contained higher reactive oxygen species (ROS) than control WT lungs. Treatment with a ROS scavenger or an inhibitor of xanthine oxidase (XO), a major ROS-generating enzyme in IAV-infected lungs, rescued Prnp0/0 mice from the lethal infection with IAV. Moreover, Prnp0/0 mice transgenic for PrP with a deletion of the Cu-binding octapeptide repeat (OR) region, Tg(PrPOR)/Prnp0/0 mice, were also highly susceptible to IAV infection. These results indicate that PrPC has a protective role against lethal infection with IAVs through the Cu-binding OR region by reducing ROS in infected lungs. Cu content and the activity of anti-oxidant enzyme Cu/Zn-dependent superoxide dismutase, SOD1, were lower in Prnp0/0 and Tg(PrPOR)/Prnp0/0 lungs than in WT lungs. It is thus conceivable that PrPC functions to maintain Cu content and regulate SOD1 through the OR region in lungs, thereby reducing ROS in IAV-infected lungs and eventually protecting them from lethal infection with IAVs. Our current results highlight the role of PrPC in protection against IAV infection, and suggest that PrPC might be a novel target molecule for anti-influenza therapeutics.


Structural and mechanistic aspects influencing the ADAM10-mediated shedding of the prion protein.

Proteolytic processing of the prion protein (PrP<superscript>C</superscript>) by endogenous proteases generates bioactive membrane-bound and soluble fragments which may help to explain the pleiotropic roles of this protein in the nervous system and in brain diseases. Shedding of almost full-length PrP<superscript>C</superscript> into the extracellular space by the metalloprotease ADAM10 is of peculiar relevance since soluble PrP stimulates axonal outgrowth and is protective in neurodegenerative conditions such as Alzheimer's and prion disease. However, molecular determinates and mechanisms regulating the shedding of PrP are entirely unknown. We produced an antibody recognizing the neo-epitope of shed PrP generated by ADAM10 in biological samples and used it to study structural and mechanistic aspects affecting the shedding. For this, we investigated genetically modified cellular and murine models by biochemical and morphological approaches. We show that the novel antibody specifically detects shed PrP in cell culture supernatants and murine brain. We demonstrate that ADAM10 is the exclusive sheddase of PrP<superscript>C</superscript> in the nervous system and reveal that the glycosylation state and type of membrane-anchorage of PrP<superscript>C</superscript> severely affect its shedding. Furthermore, we provide evidence that PrP shedding can be modulated by pharmacological inhibition and stimulation and present data suggesting that shedding is a relevant part of a compensatory network ensuring PrP<superscript>C</superscript> homeostasis of the cell. With the new antibody, our study introduces a new tool to reliably investigate PrP-shedding. In addition, this study provides novel and important insight into the regulation of this cleavage event, which is likely to be relevant for diagnostic and therapeutic approaches even beyond neurodegeneration.


Prion Protein Devoid of the Octapeptide Repeat Region Delays BSE Pathogenesis in Mice.

Conformational conversion of the cellular isoform of prion protein, PrP, into the abnormally folded, amyloidogenic isoform, PrP, is a key pathogenic event in prion diseases, including Creutzfeldt-Jakob disease in humans and scrapie and bovine spongiform encephalopathy (BSE) in animals. We previously reported that the octapeptide repeat (OR) region could be dispensable for converting PrP into PrP after infection with RML prions. We demonstrated that mice transgenically expressing mouse PrP with deletion of the OR region on the PrP knockout background, designated Tg(PrPΔOR)/ mice, did not show reduced susceptibility to RML scrapie prions, with abundant accumulation of PrPΔOR in their brains. We show here that Tg(PrPΔOR)/ mice were highly resistant to BSE prions, developing the disease with markedly elongated incubation times after infection with BSE prions. The conversion of PrPΔOR into PrPΔOR was markedly delayed in their brains. These results suggest that the OR region may have a crucial role in the conversion of PrP into PrP after infection with BSE prions. However, Tg(PrPΔOR)/ mice remained susceptible to RML and 22L scrapie prions, developing the disease without elongated incubation times after infection with RML and 22L prions. PrPΔOR accumulated only slightly less in the brains of RML- or 22L-infected Tg(PrPΔOR)/ mice than PrP in control wild-type mice. Taken together, these results indicate that the OR region of PrP could play a differential role in the pathogenesis of BSE prions and RML or 22L scrapie prions. Structure-function relationship studies of PrP conformational conversion into PrP are worthwhile to understand the mechanism of the conversion of PrP into PrP We show here that, by inoculating Tg(PrPΔOR)/ mice with the three different strains of RML, 22L, and BSE prions, the OR region could play a differential role in the conversion of PrP into PrP after infection with RML or 22L scrapie prions and BSE prions. PrPΔOR was efficiently converted into PrPΔOR after infection with RML and 22L prions. However, the conversion of PrPΔOR into PrPΔOR was markedly delayed after infection with BSE prions. Further investigation into the role of the OR region in the conversion of PrP into PrP after infection with BSE prions might be helpful for understanding the pathogenesis of BSE prions.


Novel Amplification Mechanism of Prions through Disrupting Sortilin-Mediated Trafficking.

Conformational conversion of the cellular prion protein, PrP, into the abnormally folded isoform of prion protein, PrP, which leads to marked accumulation of PrP in brains, is a key pathogenic event in prion diseases, a group of fatal neurodegenerative disorders caused by prions. However, the exact mechanism of PrP accumulation in prion-infected neurons remains unknown. We recently reported a novel cellular mechanism to support PrP accumulation in prion-infected neurons, in which PrP itself promotes its accumulation by evading the cellular inhibitory mechanism, which is newly identified in our recent study. We showed that the VPS10P sorting receptor sortilin negatively regulates PrP accumulation in prion-infected neurons, by interacting with PrP and PrP and trafficking them to lysosomes for degradation. However, PrP stimulated lysosomal degradation of sortilin, disrupting the sortilin-mediated degradation of PrP and PrP and eventually evoking further accumulation of PrP in prion-infected neurons. These findings suggest a positive feedback amplification mechanism for PrP accumulation in prion-infected neurons.


Prions amplify through degradation of the VPS10P sorting receptor sortilin.

Prion diseases are a group of fatal neurodegenerative disorders caused by prions, which consist mainly of the abnormally folded isoform of prion protein, PrPSc. A pivotal pathogenic event in prion disease is progressive accumulation of prions, or PrPSc, in brains through constitutive conformational conversion of the cellular prion protein, PrPC, into PrPSc. However, the cellular mechanism by which PrPSc is progressively accumulated in prion-infected neurons remains unknown. Here, we show that PrPSc is progressively accumulated in prion-infected cells through degradation of the VPS10P sorting receptor sortilin. We first show that sortilin interacts with PrPC and PrPSc and sorts them to lysosomes for degradation. Consistently, sortilin-knockdown increased PrPSc accumulation in prion-infected cells. In contrast, overexpression of sortilin reduced PrPSc accumulation in prion-infected cells. These results indicate that sortilin negatively regulates PrPSc accumulation in prion-infected cells. The negative role of sortilin in PrPSc accumulation was further confirmed in sortilin-knockout mice infected with prions. The infected mice had accelerated prion disease with early accumulation of PrPSc in their brains. Interestingly, sortilin was reduced in prion-infected cells and mouse brains. Treatment of prion-infected cells with lysosomal inhibitors, but not proteasomal inhibitors, increased the levels of sortilin. Moreover, sortilin was reduced following PrPSc becoming detectable in cells after infection with prions. These results indicate that PrPSc accumulation stimulates sortilin degradation in lysosomes. Taken together, these results show that PrPSc accumulation of itself could impair the sortilin-mediated sorting of PrPC and PrPSc to lysosomes for degradation by stimulating lysosomal degradation of sortilin, eventually leading to progressive accumulation of PrPSc in prion-infected cells.


Effects of prion protein devoid of the N-terminal residues 25-50 on prion pathogenesis in mice.

The N-terminal polybasic region of the normal prion protein, PrP(C), which encompasses residues 23-31, is important for prion pathogenesis by affecting conversion of PrP(C) into the pathogenic isoform, PrP(Sc). We previously reported transgenic mice expressing PrP with residues 25-50 deleted in the PrP-null background, designated as Tg(PrPpreOR)/Prnp (0/0) mice. Here, we produced two new lines of Tg(PrPpreOR)/Prnp (0/0) mice, each expressing the mutant protein, PrPpreOR, 1.1 and 1.6 times more than PrP(C) in wild-type mice, and subsequently intracerebrally inoculated RML and 22L prions into them. The lower expresser showed slightly reduced susceptibility to RML prions but not to 22L prions. The higher expresser exhibited enhanced susceptibility to both prions. No prion transmission barrier was created in Tg(PrPpreOR)/Prnp (0/0) mice against full-length PrP(Sc). PrP(Sc)preOR accumulated in the brains of infected Tg(PrPpreOR)/Prnp (0/0) mice less than PrP(Sc) in control wild-type mice, although lower in RML-infected Tg(PrPpreOR)/Prnp (0/0) mice than in 22L-infected mice. Prion infectivity in infected Tg(PrPpreOR)/Prnp (0/0) mice was also lower than that in wild-type mice. These results indicate that deletion of residues 25-50 only slightly affects prion susceptibility, the conversion of PrP(C) into PrP(Sc), and prion infectivity in a strain-specific way. PrPpreOR retains residues 23-24 and lacks residues 25-31 in the polybasic region. It is thus conceivable that residues 23-24 rather than 25-31 are important for the polybasic region to support prion pathogenesis. However, other investigators have reported that residues 27-31 not 23-24 are important to support prion pathogenesis. Taken together, the polybasic region might support prion pathogenesis through multiple sites including residues 23-24 and 27-31.


Mouse-Hamster Chimeric Prion Protein (PrP) Devoid of N-terminal Residues 23-88 Restores Susceptibility to 22L Prions, But Not to RML Prions in PrP-Knockout Mice.

Prion infection induces conformational conversion of the normal prion protein PrPC, into the pathogenic isoform PrPSc, in prion diseases. It has been shown that PrP-knockout (Prnp0/0) mice transgenically reconstituted with a mouse-hamster chimeric PrP lacking N-terminal residues 23-88, or Tg(MHM223-88)/Prnp 0/0 mice, neither developed the disease nor accumulated MHM2Sc23-88 in their brains after inoculation with RML prions. In contrast, RML-inoculated Tg(MHM223-88)/Prnp 0/+ mice developed the disease with abundant accumulation of MHM2Sc23-88 in their brains. These results indicate that MHM223-88 itself might either lose or greatly reduce the converting capacity to MHM2Sc23-88, and that the co-expressing wild-type PrPC can stimulate the conversion of MHM223-88 to MHM2Sc23-88 in trans. In the present study, we confirmed that Tg(MHM223-88)/Prnp 0/0 mice remained resistant to RML prions for up to 730 days after inoculation. However, we found that Tg(MHM223-88)/Prnp 0/0 mice were susceptible to 22L prions, developing the disease with prolonged incubation times and accumulating MHM2Sc23-88 in their brains. We also found accelerated conversion of MHM223-88 into MHM2Sc23-88 in the brains of RML- and 22L-inoculated Tg(MHM223-88)/Prnp 0/+ mice. However, wild-type PrPSc accumulated less in the brains of these inoculated Tg(MHM223-88)/Prnp 0/+ mice, compared with RML- and 22L-inoculated Prnp 0/+ mice. These results show that MHM223-88 itself can convert into MHM2Sc23-88 without the help of the trans-acting PrPC, and that, irrespective of prion strains inoculated, the co-expressing wild-type PrPC stimulates the conversion of MHM223-88 into MHM2Sc23-88, but to the contrary, the co-expressing MHM223-88 disturbs the conversion of wild-type PrPC into PrPSc.


Development of in vitro model of insulin receptor cleavage induced by high glucose in HepG2 cells.

Soluble insulin receptor (sIR), the ectodomain of IR, has been detected in human plasma, and its concentration parallels that of blood glucose in patients with diabetes. IR has a pivotal role in glucose homeostasis and diabetes development; therefore, cleavage of IR promoted by hyperglycemia is involved in insulin resistance and glucose toxicity. To elucidate the physiology of sIR, we developed an in vitro model mimicking the changes in sIR levels in plasma from patients with diabetes. Among four human cell lines that expressed IR, spontaneous cleavage of IR occurred only in HepG2 cells. The molecular characteristics of sIR derived from HepG2 cells were similar to those of sIR detected in human plasma. The concentration of sIR in the medium did not differ between basal and high-glucose conditions in the initial 24-h period, but increasing the duration of pre-stimulation (>48 h) led to a significant increase in sIR levels in cells exposed to high glucose. Additionally, glucose-dependent increment of sIR was reversible in this model. These results are consistent with the observation of plasma sIR in patients with diabetes. Using this model, O-linked N-acetylglucosamine modification was determined to be involved in high-glucose-induced IR cleavage. A calcium-dependent protease was shown to cleave IR extracellularly. These findings show that this in vitro model could be useful for determining the molecular mechanism underlying IR cleavage.

Biochemical and Biophysical Research Communications


Disturbed vesicular trafficking of membrane proteins in prion disease.

The pathogenic mechanism of prion diseases remains unknown. We recently reported that prion infection disturbs post-Golgi trafficking of certain types of membrane proteins to the cell surface, resulting in reduced surface expression of membrane proteins and abrogating the signal from the proteins. The surface expression of the membrane proteins was reduced in the brains of mice inoculated with prions, well before abnormal symptoms became evident. Prions or pathogenic prion proteins were mainly detected in endosomal compartments, being particularly abundant in recycling endosomes. Some newly synthesized membrane proteins are delivered to the surface from the Golgi apparatus through recycling endosomes, and some endocytosed membrane proteins are delivered back to the surface through recycling endosomes. These results suggest that prions might cause neuronal dysfunctions and cell loss by disturbing post-Golgi trafficking of membrane proteins via accumulation in recycling endosomes. Interestingly, it was recently shown that delivery of a calcium channel protein to the cell surface was impaired and its function was abrogated in a mouse model of hereditary prion disease. Taken together, these results suggest that impaired delivery of membrane proteins to the cell surface is a common pathogenic event in acquired and hereditary prion diseases.


Prions disturb post-Golgi trafficking of membrane proteins.

Conformational conversion of normal cellular prion protein PrP(C) into pathogenic PrP(Sc) is central to the pathogenesis of prion diseases. However, the pathogenic mechanism remains unknown. Here we show that post-Golgi vesicular trafficking is significantly delayed in prion-infected N2a cells. Accordingly, cell surface expression of membrane proteins examined, including PrP(C), insulin receptor involved in neuroprotection, and attractin, whose mutation causes prion disease-like spongiform neurodegeneration, is reduced. Instead, they accumulate in the Golgi apparatus. PrP(Sc) is detected throughout endosomal compartments, being particularly abundant in recycling endosome. We also show reduced surface expression of PrP(C) and insulin receptor in prion-infected mouse brains well before the onset of disease. These results suggest that prion infection might impair post-Golgi trafficking of membrane proteins to the cell surface in neurons via PrP(Sc) accumulated in recycling endosome, and eventually induce neuronal dysfunctions associated with prion diseases.


Biological and biochemical characterization of mice expressing prion protein devoid of the octapeptide repeat region after infection with prions.

Accumulating lines of evidence indicate that the N-terminal domain of prion protein (PrP) is involved in prion susceptibility in mice. In this study, to investigate the role of the octapeptide repeat (OR) region alone in the N-terminal domain for the susceptibility and pathogenesis of prion disease, we intracerebrally inoculated RML scrapie prions into tg(PrPOR)/Prnp(0/0) mice, which express mouse PrP missing only the OR region on the PrP-null background. Incubation times of these mice were not extended. Protease-resistant PrPOR, or PrP(Sc)OR, was easily detectable but lower in the brains of these mice, compared to that in control wild-type mice. Consistently, prion titers were slightly lower and astrogliosis was milder in their brains. However, in their spinal cords, PrP(Sc)OR and prion titers were abundant and astrogliosis was as strong as in control wild-type mice. These results indicate that the role of the OR region in prion susceptibility and pathogenesis of the disease is limited. We also found that the PrP(Sc)OR, including the pre-OR residues 23-50, was unusually protease-resistant, indicating that deletion of the OR region could cause structural changes to the pre-OR region upon prion infection, leading to formation of a protease-resistant structure for the pre-OR region.


VCIP135 deubiquitinase and its binding protein, WAC, in p97ATPase-mediated membrane fusion.

Two distinct p97 membrane fusion pathways are required for Golgi biogenesis: the p97/p47 and p97/p37 pathways. VCIP135 is necessary for both pathways, while its deubiquitinating activity is required only for the p97/p47 pathway. We have now identified a novel VCIP135-binding protein, WAC. WAC localizes to the Golgi as well as the nucleus. In Golgi membranes, WAC is involved in a complex containing VCIP135 and p97. WAC directly binds to VCIP135 and increases its deubiquitinating activity. siRNA experiments revealed that WAC is required for Golgi biogenesis. In an in vitro Golgi reformation assay, WAC was necessary only for p97/p47-mediated Golgi reassembly, but not for p97/p37-mediated reassembly. WAC is hence thought to function in p97/p47-mediated Golgi membrane fusion by activating the deubiquitinating function of VCIP135. We also showed that the two p97 pathways function in ER membrane fusion as well. An in vitro ER reformation assay revealed that both pathways required VCIP135 but not its deubiquitinating activity for their ER membrane fusion. This was consistent with the finding that WAC is unnecessary for p97-mediated ER membrane fusion.


The Rab GTPase-Activating Protein AS160 as a Common Regulator of Insulin- and Gαq-Mediated Intracellular GLUT4 Vesicle Distribution

Akt substrate of 160kDa (AS160) is a Rab GTPase activating protein (GAP) and was recently identified as a component of the insulin signaling pathway of glucose transporter type 4 (GLUT4) translocation. We and others, previously reported that the activation of Galphaq protein-coupled receptors (GalphaqPCRs) also stimulated GLUT4 translocation and glucose uptake in several cell lines. Here, we report that the activation of GalphaqPCRs also promoted phosphorylation of AS160 by the 5'-AMP activated protein kinase (AMPK). The suppression of AS160 phosphorylation by the siRNA mediated AMPKalpha1 subunit knockdown promoted GLUT4 vesicle retention in intracellular compartments. This suppression did not affect the ratio of non-induced cell surface GLUT4 to Galphaq-induced it. Rat 3Y1 cells lacking AS160 did not show insulin-induced GLUT4 translocation. The cells stably expressing GLUT4 revealed GLUT4 vesicles that were mainly localized in the perinuclear region and less frequently on the cell surface. After expression of exogenous AS160, GLUT4 on the cell surface decreased and GLUT4 vesicles were redistributed throughout the cytoplasm. Although PMA-induced or sodium fluoride-induced GLUT4 translocation was significantly increased in these cells, insulin did not affect GLUT4 translocation. These results suggest that AS160 is a common regulator of insulin- and GalphaqPCR activation-mediated GLUT4 distribution in the cells.


p37is a p97 adaptor required for Golgi and ER biogenesis in interphase and at the end of mitosis.

We previously reported that p97/p47-assisted membrane fusion is important for the reassembly of organelles at the end of mitosis, but not for their maintenance during interphase. We have now identified a p97 adaptor protein, p37, which forms a complex with p97 in the cytosol and localizes to the Golgi and ER. siRNA experiments revealed that p37 is required for Golgi and ER biogenesis. Injection of anti-p37 antibodies into cells at different cell cycle stages showed that p37 plays an important role in both Golgi and ER maintenance during interphase as well as in their reassembly at the end of mitosis. In an in vitro Golgi reassembly assay, the p97/p37 complex has membrane fusion activity. In contrast to the p97/p47 pathway, this pathway requires p115-GM130 tethering and SNARE GS15, but not syntaxin5. Interestingly, although VCIP135 is also required, its deubiquitinating activity is unnecessary for p97/p37-mediated activities.


NSF/SNAPs and p97/p47/VCIP135 are sequentially required for cell cycle-dependent reformation of the ER network.

The endoplasmic reticulum (ER) has a characteristic polygonal structure with hallmark three-way junctions. In a previous paper, we reconstituted the disruption of the pre-existing ER network using mitotic cytosol from HeLa cells in streptolysin O (SLO)-permeabilized CHO-HSP cells (stably expressing GFP-HSP47). In addition, we found that interphase cytosol induced reformation of the disrupted ER network into a continuous network structure. Here, we show that the reformation of the ER network is accomplished through two sequential fusion reactions. The first process is mediated by NSF/alpha and gamma-SNAPs, and involves the generation of typical membranous intermediate structures that connect the disrupted ER tubules. A subsequent fusion is mediated by p97/p47/VCIP135, which has been shown to be required for homotypic fusion events in Golgi cisternae regrowth after mitosis. In addition, we also found that both fusion processes involve the t-SNARE, syntaxin 18.


Structure, dynamics and interactions of p47, a major adaptor of the AAA ATPase, p97.

p47 is a major adaptor molecule of the cytosolic AAA ATPase p97. The principal role of the p97-p47 complex is in regulation of membrane fusion events. Mono-ubiquitin recognition by p47 has also been shown to be crucial in the p97-p47-mediated Golgi membrane fusion events. Here, we describe the high-resolution solution structures of the N-terminal UBA domain and the central domain (SEP) from p47. The p47 UBA domain has the characteristic three-helix bundle fold and forms a highly stable complex with ubiquitin. We report the interaction surfaces of the two proteins and present a structure for the p47 UBA-ubiquitin complex. The p47 SEP domain adopts a novel fold with a betabetabetaalphaalphabeta secondary structure arrangement, where beta4 pairs in a parallel fashion to beta1. Based on biophysical studies, we demonstrate a clear propensity for the self-association of p47. Furthermore, p97 N binding abolishes p47 self-association, revealing the potential interaction surfaces for recognition of other domains within p97 or the substrate.


Structural basis of the interaction between p97/VCP and its adaptor protein p47.

The AAA ATPase p97/VCP is involved in many cellular events including ubiquitin-dependent processes and membrane fusion. In the latter, the p97 adaptor protein p47 is of central importance. In order to provide insight into the molecular basis of p97 adaptor binding, we have determined the crystal structure of p97 ND1 domains complexed with p47 C-terminal domain at 2.9 A resolution. The structure reveals that the p47 ubiquitin regulatory X domain (UBX) domain interacts with the p97 N domain via a loop (S3/S4) that is highly conserved in UBX domains, but is absent in ubiquitin, which inserts into a hydrophobic pocket between the two p97 N subdomains. Deletion of this loop and point mutations in the loop significantly reduce p97 binding. This hydrophobic binding site is distinct from the predicted adaptor-binding site for the p97/VCP homologue N-ethylmaleimide sensitive factor (NSF). Together, our data suggest that UBX domains may act as general p97/VCP/CDC48 binding modules and that adaptor binding for NSF and p97 might involve different binding sites. We also propose a classification for ubiquitin-like domains containing or lacking a longer S3/S4 loop.


The localization and phosphorylation of p47 are important for Golgi disassembly-assembly during the cell cycle.

In mammalian cells, the Golgi apparatus is disassembled at the onset of mitosis and reassembled at the end of mitosis. This disassembly-reassembly is generally believed to be essential for the equal partitioning of Golgi into two daughter cells. For Golgi disassembly, membrane fusion, which is mediated by NSF and p97, needs to be blocked. For the NSF pathway, the tethering of p115-GM130 is disrupted by the mitotic phosphorylation of GM130, resulting in the inhibition of NSF-mediated fusion. In contrast, the p97/p47 pathway does not require p115-GM130 tethering, and its mitotic inhibitory mechanism has been unclear. Now, we have found that p47, which mainly localizes to the nucleus during interphase, is phosphorylated on Serine-140 by Cdc2 at mitosis. The phosphorylated p47 does not bind to Golgi membranes. An in vitro assay shows that this phosphorylation is required for Golgi disassembly. Microinjection of p47(S140A), which is unable to be phosphorylated, allows the cell to keep Golgi stacks during mitosis and has no effect on the equal partitioning of Golgi into two daughter cells, suggesting that Golgi fragmentation-dispersion may not be obligatory for equal partitioning even in mammalian cells.


VCIP135, a novel essential factor for p97/p47-mediated membrane fusion, is required for Golgi and ER assembly in vivo.

NSF and p97 are ATPases required for the heterotypic fusion of transport vesicles with their target membranes and the homotypic fusion of organelles. NSF uses ATP hydrolysis to dissociate NSF/SNAPs/SNAREs complexes, separating the v- and t-SNAREs, which are then primed for subsequent rounds of fusion. In contrast, p97 does not dissociate the p97/p47/SNARE complex even in the presence of ATP. Now we have identified a novel essential factor for p97/p47-mediated membrane fusion, named VCIP135 (valosin-containing protein [VCP][p97]/p47 complex-interacting protein, p135), and show that it binds to the p97/p47/syntaxin5 complex and dissociates it via p97 catalyzed ATP hydrolysis. In living cells, VCIP135 and p47 are shown to function in Golgi and ER assembly.


Effect of C/N ratio and starch concentration on ethanol production from sago starch using recombinant yeast.

World Journal of Microbiology & Biotechnology


Partial purification and characterization of amylolytic enzymes obtained from direct fermentation of Sago starch to ethanol by recombinant yeast


Characterization of bacteriocin N15 produced by Enterococcus faecium N15 and cloning of the related genes.

Enterococcus faecium N15 was isolated from nuka (Japanese rice-bran paste), which is utilized as starter in the fermenting of vegetables, and was found to produce a bacteriocin that exhibited a broad spectrum of activity, including activity against Listeria monocytogenes and Bacillus circulans JCM2504. The bacteriocin was sensitive to proteases (alpha-chymotrypsin, proteinase K, trypsin, and pepsin) and alpha-amylase, but it was resistant to lipase. The bacteriocin was resistant to heat treatment at 100 degrees C for 2 h, but its activity was completely lost after autoclaving at 121 degrees C for 15 min. It was active over a wide pH range from 2.0 to 10.0. The bacteriocin showed bactericidal activity against Lactobacillus sake JCM1157 at a concentration of 40 AU/ml. Its molecular weight was estimated by SDS-PAGE to be about 3-5 kDa. PCR primers were designed based on the conserved amino acid sequences of class IIa bacteriocins. A 3-kb DNA fragment was amplified and three open reading frames (ORFs) were found. The first encodes a probable immunity protein of 103 amino acid residues and shows complete homology with the putative immunity protein of E. faecium DPC1146. The second and third ORFs respectively encode a probable transposase gene and an inducing factor. The upstream region of the immunity gene, in which the bacteriocin structural gene is located, was amplified. A homology search revealed that the bacteriocin produced by E. faecium N15 exhibits complete identity to enterocin A, a bacteriocin produced by E. faecium DPC1146. PCR using the primers designed in this study is a rapid and sufficient method of screening for bacteriocin-producing strains.

Journal of Bioscience and Bioengineering


Modeling and optimization of alpha-amylase production in a recombinant yeast fed-batch culture taking account of the cell cycle population distribution.


Maximum glucoamylase production by a temperature-sensitive mutant of Saccharomyces cerevisiae in batch culture.

Journal of Industrial Microbiology & Biotechnology


Bioprocess fault detection by nonlinear multivariate analysis: application of an artificial autoassociative neural network and wavelet filter bank.


On-line fault diagnosis for an optimal rice -amylase production process of temperature-sensitive mutant of Saccharomyces cerevisiae by autoassociative neural network.

Journal of Fermentation and Bioengineering


Cell cycle dependency of rice alpha-amylase production in a recombinant yeast.


Optimization of rice alpha-amylase production using temperature-sensitive mutants of Saccharomyces cerevisiae for the PHO regulatory system.