Endoplasmic reticulum protein 29 is involved in endoplasmic reticulum stress in islet beta cells

Abstract

Endoplasmic reticulum stress (ERS) is correlated with insulin resistance and islet-cell function. In the present study, the sub-cellular localization and role of ER protein 29 (Erp29) were investigated in an in vitro ERS model of islet beta cells. The INS-1 islet cell line was treated with various concentrations of tunicamycin to establish the ERS model. Immunofluorescence microscopy demonstrated that Erp29 and anti-ER marker protein calnexin were co-localized in NIH3T3 cells, suggesting that Erp29 is localized to the ER. The ERS model induced by tunicamycin showed significantly increased expression of binding immunoglobulin protein (BIP)/glucose-regulated protein 78 (Grp78), which is a marker for ERS, and the expression of Erp29 was also increased at the mRNA and protein levels. Of note, ERS was blocked following small interfering RNA-mediated silencing of Erp29 expression, as indicated by reduced BIP/Grp78 expression. As an ER protein, Erp29 may have an important role in ERS in islet beta cells.