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Loss of Nix in Pdx1-deficient mice prevents apoptotic and necrotic β cell death and diabetes.

ABSTRACT: Mutations in pancreatic duodenal homeobox (PDX1) are linked to human type 2 diabetes and maturity-onset diabetes of the young type 4. Consistent with this, Pdx1-haploinsufficient mice develop diabetes. Both apoptosis and necrosis of β cells are mechanistically implicated in diabetes in these mice, but a molecular link between Pdx1 and these 2 forms of cell death has not been defined. In this study, we introduced an shRNA into mouse insulinoma MIN6 cells to deplete Pdx1 and found that expression of proapoptotic genes, including NIP3-like protein X (Nix), was increased. Forced Nix expression in MIN6 and pancreatic islet β cells induced programmed cell death by simultaneously activating apoptotic and mitochondrial permeability transition-dependent necrotic pathways. Preventing Nix upregulation during Pdx1 suppression abrogated apoptotic and necrotic β cell death in vitro. In Pdx1-haploinsufficient mice, Nix ablation normalized pancreatic islet architecture, β cell mass, and insulin secretion and eliminated reactive hyperglycemia after glucose challenge. These results establish Nix as a critical mediator of β cell apoptosis and programmed necrosis in Pdx1-deficient diabetes.

SUBMITTER: Fujimoto K

PROVIDER: S-EPMC2964996 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Loss of Nix in Pdx1-deficient mice prevents apoptotic and necrotic β cell death and diabetes.

Fujimoto Kei K Ford Eric L EL Tran Hung H Wice Burton M BM Crosby Seth D SD Dorn Gerald W GW Polonsky Kenneth S KS

The Journal of clinical investigation 20101011 11

Mutations in pancreatic duodenal homeobox (PDX1) are linked to human type 2 diabetes and maturity-onset diabetes of the young type 4. Consistent with this, Pdx1-haploinsufficient mice develop diabetes. Both apoptosis and necrosis of β cells are mechanistically implicated in diabetes in these mice, but a molecular link between Pdx1 and these 2 forms of cell death has not been defined. In this study, we introduced an shRNA into mouse insulinoma MIN6 cells to deplete Pdx1 and found that expression ...[more]

PMID: 20978346

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Project description:UnlabelledKeratins, formerly known as cytokeratins, are the major epithelial-specific subgroup of intermediate filament proteins. Adult hepatocytes express keratin polypeptides 8 and 18 (K8/K18), whereas cholangiocytes express K8/K18 and keratins 7 and 19 (K7/K19). Keratins function primarily to protect hepatocytes from apoptosis and necrosis, which was revealed using several genetic mouse models. This cytoprotective function was further clarified by the identification of natural human keratin variants that are normally silent, but become pathogenic by predisposing their carriers to apoptosis during acute or chronic liver injury mediated by toxins, virus infection, or metabolic stress. During apoptosis, caspases cleave K18 and K19 at conserved aspartates (human K18/K19: (235) Val-Glu-Val-Asp(↓) ) and K18 at a unique aspartate (human K18: (394) Asp-Ala-Leu-Asp(↓) ), with the latter exposed epitope becoming recognized by the M30 antibody in blood and tissues. Additional K18-containing protein backbone epitopes are detected using the M6 and M5 (termed M65) antibodies. Intact K18 and its associated fragments, which are released into blood during apoptosis and necrosis in various diseases, have been analyzed by enzyme-linked immunosorbent assay using the M30/M65 antibodies or their signal ratios. Furthermore, M30/M65 levels have been used as diagnostic and prognostic biomarkers in acute and chronic liver diseases, including nonalcoholic steatohepatitis and acute liver failure. Other keratin biomarkers include K8/K18/K19-related tissue polypeptide antigen, K18-related tissue polypeptide-specific antigen, and K19-related CYFRA-21-1, which have been evaluated mostly in patients with epithelial tumors.ConclusionKeratins and their fragments are released into blood during liver and other epithelial tissue injury. The epithelial specificity of K18/K19, epitope unmasking upon caspase digestion, keratin abundance, and relative keratin stability render them useful biomarkers for hepatocyte and cholangiocyte apoptosis and necrosis. However, the precise biochemical nature and release mechanism of circulating keratins remain unknown. (Hepatology 2016;64:966-976).

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Loss of Nix in Pdx1-deficient mice prevents apoptotic and necrotic β cell death and diabetes.

Publications

Loss of Nix in Pdx1-deficient mice prevents apoptotic and necrotic β cell death and diabetes.

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