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 islet­cell function. In the present study, the sub­cellular localization and role of ER protein 29 (Erp29) were investigated in an in vitro ERS model of islet beta cells. The INS­1 islet cell line was treated with various concentrations of tunicamycin to establish the ERS model. Immunofluorescence microscopy demonstrated that Erp29 and anti­ER marker protein calnexin were co­localized 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)/glucose­regulated 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 RNA­mediated 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.