ERp44 depletion exacerbates ER stress and aggravates diabetic nephropathy in db/db mice

Diabetic nephropathy (DN) is a major complication of diabetes, and the dysfunction of endoplasmic reticulum (ER) plays an important role in its pathogenesis. ERp44, an ER resident chaperone protein, has been implicated in the modulation of ER stress, however, its role and mechanism in DN are not determined. Here, we show that ERp44 expression is upregulated in the glomeruli of db/db mice, a rodent model of type 2 diabetes. When ERp44 is depleted by in vivo shRNA-mediated knockdown, the features associated with DN including albuminuria level and glomerular basement membrane (GBM) thickness are aggravated, therefore suggesting a detrimental role of ERp44 depletion in DN progression. We further show that ERp44 depletion exacerbates ER stress in DN in db/db mice, and that attenuating ER stress with the chemical chaperone TUDCA remarkably diminishes the aggravated DN features caused by ERp44 depletion. These results suggest that the exacerbated ER stress is a critical factor for the detrimental effect of ERp44 depletion on DN progression in db/db mice. Thus, our study links the role of ERp44 in DN with ER stress regulation and may offer a potential therapeutic strategy to interfere DN progression.