期刊
BIOSCIENCE REPORTS
卷 37, 期 -, 页码 -出版社
PORTLAND PRESS LTD
DOI: 10.1042/BSR20170898
关键词
-
资金
- National Institutes of Health [K99 HL122354, R00 HL122354, R01 HL098435, R01 HL133497]
C/EBP-homologous protein (CHOP) is a ubiquitously expressed stress-inducible transcription factor robustly induced by maladaptive endoplasmic reticulum (ER) stresses in a wide variety of cells. Here, we examined a novel function of Sigma 1 receptor (Sigmar-1) in regulating CHOP expression under ER stress in cardiomyocytes. We also defined Sigmar1-dependent activation of the adaptive ER-stress pathway in regulating CHOP expression. We used adenovirus-mediated Sigmar1 overexpression as well as Sigmar1 knockdown by siRNA in neonatal rat ventricular cardiomyocytes (NRCs); to induce ER stress, cardiomyocytes were treated with tunicamycin. Sigmar1-siRNA knockdown significantly increased the expression of CHOP and significantly induced cellular toxicity by sustained activation of ER stress in cardiomyocytes. Sigmar1 overexpression decreased the expression of CHOP and significantly decreased cellular toxicity in cells. Using biochemical and immunocytochemical experiments, we also defined the specific ER-stress pathway associated with Sigmar1-dependent regulation of CHOP expression and cellular toxicity. We found that Sigmar1 overexpression significantly increased inositol requiring kinase 1 alpha (IRE1 alpha) phosphorylation and increased spliced X-box-binding proteins (XBP1s) expression as well as nuclear localization. In contrast, Sigmar1 knockdown significantly decreased IRE1 alpha phosphorylation and decreased XBP1s expression as well as nuclear transport. Taken together, these results indicate that Sigmar1-dependent activation of IRE1 alpha-XBP1s ER-stress response pathways are associated with inhibition of CHOP expression and suppression of cellular toxicity. Hence, Sigmar1 is an essential component of the adaptive ER-stress response pathways eliciting cellular protection in cardiomyocytes.
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