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Succination of Protein Disulfide Isomerase Links Mitochondrial Stress and Endoplasmic Reticulum Stress in the Adipocyte During Diabetes.

ABSTRACT: Protein succination by fumarate increases in the adipose tissue of diabetic mice and in adipocytes matured in high glucose as a result of glucotoxicity-driven mitochondrial stress. The endoplasmic reticulum (ER) oxidoreductase protein disulfide isomerase (PDI) is succinated in adipocytes that are matured in high glucose, and in this study we investigated whether succination would alter PDI oxidoreductase activity, directly linking mitochondrial stress and ER stress.Protein succination and the ER stress marker C/EBP homologous protein (CHOP) were diminished after pharmaceutical targeting of mitochondrial stress with the chemical uncoupler niclosamide in adipocytes matured in high-glucose concentrations. PDI was succinated by fumarate on both CXXC-containing active sites, contributing to reduced enzymatic activity. Succinated PDI decreased reductase activity in adipocytes matured in high glucose, and in db/db epididymal adipose tissue, in association with increased levels of CHOP. PDI succination was increased in fumarase knockdown adipocytes, leading to reduced PDI oxidoreductase activity, increased CHOP levels, and pro-inflammatory cytokine secretion, confirming the specific role of elevated fumarate levels in contributing to ER stress. In addition, PDI succination and ER stress were decreased, and PDI reductase activity was restored when exposure to chronic high glucose was limited, highlighting the importance of calorie restriction in the improvement of adipocyte metabolic function.These experiments identify PDI succination as a novel biochemical mechanism linking altered mitochondrial metabolism to ER stress in the adipocyte during diabetes.The current study demonstrates that early biochemical changes in mitochondrial metabolism have important implications for the development of adipocyte stress. Antioxid. Redox Signal. 27, 1281-1296.

SUBMITTER: Manuel AM

PROVIDER: S-EPMC5655420 | biostudies-other | 2017 Dec

REPOSITORIES: biostudies-other

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Succination of Protein Disulfide Isomerase Links Mitochondrial Stress and Endoplasmic Reticulum Stress in the Adipocyte During Diabetes.

Manuel Allison M AM Walla Michael D MD Faccenda Adam A Martin Stephanie L SL Tanis Ross M RM Piroli Gerardo G GG Adam Julie J Kantor Boris B Mutus Bulent B Townsend Danyelle M DM Frizzell Norma N

Antioxidants & redox signaling 20170519 16

<h4>Aims</h4>Protein succination by fumarate increases in the adipose tissue of diabetic mice and in adipocytes matured in high glucose as a result of glucotoxicity-driven mitochondrial stress. The endoplasmic reticulum (ER) oxidoreductase protein disulfide isomerase (PDI) is succinated in adipocytes that are matured in high glucose, and in this study we investigated whether succination would alter PDI oxidoreductase activity, directly linking mitochondrial stress and ER stress.<h4>Results</h4>P ...[more]

PMID: 28376661

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Project description:BACKGROUND: Protein disulfide isomerase (PDI), is sorted to be enzymatic chaperone for reconstructing misfolded protein in endoplasmic reticulum lumen. Recently, PDI has been identified as a link between misfolded protein and neuron apoptosis. However, the potential for PDI to be involved in the pathogenesis of prion disease remains unknown. In this study, we propose that PDI may function as a pleiotropic regulator in the cytotoxicity induced by mutated prion proteins and in the pathogenesis of prion diseases. METHODOLOGY/PRINCIPAL FINDINGS: To elucidate potential alterations of PDI in prion diseases, the levels of PDI and relevant apoptotic executors in 263K infected hamsters brain tissues were evaluated with the use of Western blots. Abnormal upregulation of PDI, Grp78 and Grp58 was detected. Dynamic assays of PDI alteration identified that the upregulation of PDI started at the early stage and persistently increased till later stage. Obvious increases of PDI and Grp78 levels were also observed in cultured cells transiently expressing PrP mutants, PrP-KDEL or PrP-PG15, accompanied by significant cytotoxicities. Excessive expression of PDI partially eased ER stress and cell apoptosis caused by accumulation of PrP-KDEL, but had less effect on cytotoxicity induced by PrP-PG15. Knockdown of endogenous PDI significantly amended cytotoxicity of PrP-PG15, but had little influence on that of PrP-KDEL. A series of membrane potential assays found that apoptosis induced by misfolded PrP proteins could be regulated by PDI via mitochondrial dysfunction. Moreover, biotin-switch assays demonstrated active S-nitrosylated modifications of PDI (SNO-PDI) both in the brains of scrapie-infected rodents and in the cells with misfolded PrP proteins. CONCLUSION/SIGNIFICANCE: Current data in this study highlight that PDI and its relevant executors may function as a pleiotropic regulator in the processes of different misfolded PrP proteins and at different stages during prion infection. SNO-PDI may feed as an accomplice for PDI apoptosis.

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Succination of Protein Disulfide Isomerase Links Mitochondrial Stress and Endoplasmic Reticulum Stress in the Adipocyte During Diabetes.

Publications

Succination of Protein Disulfide Isomerase Links Mitochondrial Stress and Endoplasmic Reticulum Stress in the Adipocyte During Diabetes.

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