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en: Proteasome dysfunction in T cells causes immunodeficiency via cell cycle disruption and apoptosis

en: Proteasomes are essential molecular complexes that regulate intracellular protein homeostasis by selectively degrading ubiquitinated proteins. Genetic mutations in proteasome subunits lead to proteasome-associated autoinflammatory syndromes (PRAAS) characterized by autoinflammation, partial progressive lipodystrophy, and, in certain cases, immunodeficiency. However, the molecular mechanisms by which proteasome dysfunction results in these phenotypes remain unclear. Here, we established a mouse model carrying a mutation in β5i (encoded by Psmb8) along with T-cell-specific β5 (encoded by Psmb5) deficiency (KIKO mice). The KIKO mice presented severe loss of mature T cells in the spleen but not in the thymus, with reduced proteasome activity leading to the accumulation of ubiquitinated proteins. The CD4+ T cells of KIKO mice presented impaired proliferative activity with cell cycle arrest in the G0/G1 phase following TCR engagement. T cells from KIKO mice underwent rapid cell death through apoptosis, as treatment of T cells with the caspase inhibitor Z-VAD rescued cell viability. Moreover, proteasome dysfunction induced apoptosis in T cells without affecting either mitochondrial functions or ER stress responses. Thus, our data provide insight into the molecular mechanisms underlying not only immunodeficiency in PRAAS patients but also T-cell deficiency associated with other disorders.

en: International Immunology

ja: International Immunology


en: Stimulation of the farnesoid X receptor promotes M2 macrophage polarization.

en: This skewed polarization towards M2 macrophages by an FXR agonist was accompanied by increased expression of signaling molecules related to the retinoic acid receptor. Inhibition of the retinoic acid receptor suppressed FXR agonist-mediated M2 macrophage polarization, indicating that this polarization was, at least, partly dependent on the retinoic acid receptor pathway. These data demonstrate that FXR has a role in polarization toward M2 macrophages and suggest a possible therapeutic potential of FXR agonists in M2 macrophage-related conditions.

en: Frontiers in Immunology

ja: Frontiers in Immunology


en: Blockade of the CXCR3/CXCL10 axis ameliorates inflammation caused by immunoproteasome dysfunction.

en: Immunoproteasomes regulate the degradation of ubiquitin-coupled proteins and generate peptides that are preferentially presented by MHC class I. Mutations in immunoproteasome subunits lead to immunoproteasome dysfunction, which causes proteasome-associated autoinflammatory syndromes (PRAAS) characterized by nodular erythema and partial lipodystrophy. It remains unclear, however, how immunoproteasome dysfunction leads to inflammatory symptoms. Here, we established mice harboring a mutation in Psmb8 (Psmb8-KI mice) and addressed this question. Psmb8-KI mice showed higher susceptibility to imiquimod-induced skin inflammation (IMS). Blockade of IL-6 or TNF-α partially suppressed IMS in both control and Psmb8-KI mice, but there was still more residual inflammation in the Psmb8-KI mice than in the control mice. DNA microarray analysis showed that treatment of J774 cells with proteasome inhibitors increased the expression of the Cxcl9 and Cxcl10 genes. Deficiency in Cxcr3, the gene encoding the receptor of CXCL9 and CXCL10, in control mice did not change IMS susceptibility, while deficiency in Cxcr3 in Psmb8-KI mice ameliorated IMS. Taken together, these findings demonstrate that this mutation in Psmb8 leads to hyperactivation of the CXCR3 pathway, which is responsible for the increased susceptibility of Psmb8-KI mice to IMS. These data suggest the CXCR3/CXCL10 axis as a new molecular target for treating PRAAS.

en: JCI Insight

ja: JCI Insight


en: Necroptosis protects against exacerbation of acute pancreatitis.

en: mice exhibit weight loss, edematous pancreatitis, necrotizing pancreatitis, and acinar cell dedifferentiation in response to tissue damage. Genetic deletion of Mlkl resulted in downregulation of the antiapoptotic genes Bclxl and Cflar in association with increases in the numbers of apoptotic cells, as detected by TUNEL assay. These findings suggest that RIPK3 and MLKL-mediated necroptosis exerts protective effects in AP and caution against the use of necroptosis inhibitors for AP treatment.

en: Cell Death & Disease

ja: Cell Death & Disease


en: Distinct Roles of IL-1 and IL-18 in NLRC4-Induced Autoinflammation.

en: The NLRC4 inflammasome assembles in response to detection of bacterial invasion, and NLRC4 activation leads to the production of IL-1 and IL-18 together with pyroptosis-mediated cell death. Missense activating mutations in cause autoinflammatory disorders whose symptoms are distinctly dependent on the site of mutation and other aspects of the genetic background. To determine the involvement of IL-1 and IL-18 in the inflammation induced by mutation, we depleted IL-1 , IL-18, or both cytokines in Nlrc4-transgenic mice in which mutant is expressed under the MHC class II promoter (Nlrc4-H443P-Tg mice). The deletion of the or gene in Nlrc4-H443P-Tg mice reduced the neutrophil numbers in the spleen, and mice with deletion of both genes had an equivalent number of neutrophils compared to wild-type mice. Deletion of ameliorated but did not eliminate bone marrow hyperplasia, while mice deficient in showed no bone marrow hyperplasia. In contrast, tail bone deformity remained in the presence of deficiency, but deficiency completely abolished bone deformity. The decreased bone density in Nlrc4-H443P-Tg mice was counteracted by but not deficiency. Our results demonstrate the distinct effects of IL-1 and IL-18 on NLRC4-induced inflammation among tissues, which suggests that blockers for each cytokine should be utilized depending on the site of inflammation.


en: Differentiation of preadipocytes and mature adipocytes requires PSMB8.

en: The differentiation of adipocytes is tightly regulated by a variety of intrinsic molecules and also by extrinsic molecules produced by adjacent cells. Dysfunction of adipocyte differentiation causes lipodystrophy, which impairs glucose and lipid homeostasis. Although dysfunction of immunoproteasomes causes partial lipodystrophy, the detailed molecular mechanisms remain to be determined. Here, we demonstrate that Psmb8, a catalytic subunit for immunoproteasomes, directly regulates the differentiation of preadipocytes and additionally the differentiation of preadipocytes to mature adipocytes. Psmb8(-/-) mice exhibited slower weight gain than wild-type mice, and this was accompanied by reduced adipose tissue volume and smaller size of mature adipocytes compared with controls. Blockade of Psmb8 activity in 3T3-L1 cells disturbed the differentiation to mature adipocytes. Psmb8(-/-) mice had fewer preadipocyte precursors, fewer preadipocytes and a reduced ability to differentiate preadipocytes toward mature adipocytes. Our data demonstrate that Psmb8-mediated immunoproteasome activity is a direct regulator of the differentiation of preadipocytes and their ultimate maturation.

en: Scientific Reports

ja: Scientific Reports


en: An inherited mutation in NLRC4 causes autoinflammation in human and mice.

en: Autoinflammatory syndromes cause sterile inflammation in the absence of any signs of autoimmune responses. Familial cold autoinflammatory syndrome (FCAS) is characterized by intermittent episodes of rash, arthralgia, and fever after exposure to cold stimuli. We have identified a missense mutation in the NLRC4 gene in patients with FCAS. NLRC4 has been known as a crucial sensor for several Gram-negative intracellular bacteria. The mutation in NLRC4 in FCAS patients promoted the formation of NLRC4-containing inflammasomes that cleave procaspase-1 and increase production of IL-1. Transgenic mice that expressed mutant Nlrc4 under the invariant chain promoter developed dermatitis and arthritis. Inflammation within tissues depended on IL-1-mediated production of IL-17A from neutrophils but not from T cells. Our findings reveal a previously unrecognized link between NLRC4 and a hereditary autoinflammatory disease and highlight the importance of NLRC4 not only in the innate immune response to bacterial infections but also in the genesis of inflammatory diseases.

en: The Journal of Experimental Medicine

ja: The Journal of Experimental Medicine


en: Differentiation of CD11c+ CX3CR1+ cells in the small intestine requires Notch signaling.

en: The gastrointestinal tract comes into direct contact with environmental agents, including bacteria, viruses, and foods. Intestine-specific subsets of immune cells maintain gut homeostasis by continuously sampling luminal antigens and maintaining immune tolerance. CD11c(+)CX3CR1(+) cells sample luminal antigens in the small intestine and contribute to the trafficking of bacteria to lymph nodes under dysbiotic conditions. The molecular mechanisms crucial for the differentiation of CD11c(+)CX3CR1(+) cells remain unclear. Here we demonstrate that the Notch1- or Notch2-Rbpj axis is essential for the development of CD11c(+)CX3CR1(+) cells. In mice in which Rbpj or Notch1 and Notch2 were deleted from CD11c(+) cells, there was a deficit of CD11c(+)CX3CR1(+) cells and an accumulation of CD11c(low)CX3CR1(+) cells. The CD11c(low)CX3CR1(+) cells could not differentiate to CD11c(+)CX3CR1(+) cells, suggesting that CD11c(low)CX3CR1(+) cells represent a lineage distinct from CD11c(+)CX3CR1(+) cells. These data indicate that Notch signaling is essential for lineage fixation of intestinal CD11c(+)CX3CR1(+) cells.

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