Androgen receptor inclusions acquire GRP78/BiP to ameliorate androgen-induced protein misfolding stress in embryonic stem cells

Abstract

Commitment of differentiating embryonic stem cells (ESCs) toward the various lineages is influenced by many factors, including androgens. However, the mechanisms underlying proteotoxic stress conferred by androgen receptor (AR) actions on embryonic cell fate remains unclear. Here we show that mouse ESCs display stress-related cellular phenotypes in response to androgens during early phase of differentiation. Androgen induced a significant increase in the percentage of ESCs and embryoid bodies with the intranuclear and juxtanuclear AR inclusions, which were colocalized with the E3 ubiquitin ligase, C terminus of Hsc70-interacting protein. Caspase-3 activity corresponded with AR expression, was enhanced in cells engaged more differentiation phenotypes. Androgen-mediated accumulation of AR aggregates exacerbated endoplasmic reticulum (ER) stress and rendered ESCs susceptible to apoptosis. Increasing expression levels of the ER chaperones, GRP78/BiP and GRP94, as well as ER stress markers, such as ATF6, phosphorylated PERK, GADD153/CHOP and spliced XBP-1 mRNA, were dramatically elevated in ESCs overexpressing AR. We found that androgen induced GRP78/BiP to dissociate from ATF6, and act as an AR-interacting protein, which was recruited into AR inclusions in ESCs. GRP78/BiP was also colocalized with AR inclusions in the cells of spinal bulbar muscular atrophy transgenic mouse model. Overexpression of GRP78/BiP suppressed ubiquitination of AR aggregates and ameliorated the misfolded AR-mediated cytopathology in ESCs, whereas knockdown of GRP78/BiP increased the accumulation of AR aggregates and significantly higher levels of caspase-3 activity and cell apoptosis. These results generate novel insight into how ESCs respond to stress induced by misfolded AR proteins and identify GRP78/BiP as a novel regulator of the AR protein quality control.

Oxidative damage to osteoblasts can be alleviated by early autophagy through the endoplasmic reticulum stress pathway—Implications for the treatment of osteoporosis

“…The possible reason was that autophagy through the ER stress signaling pathway was indispensable for the survival of osteoblasts regardless of whether under oxidative stress or not. Similar findings have been reported by Yang et al [77]. Our findings suggested that the protective role of autophagy against ROS injury was dependent on the up-regulation of PERK and GRP78, although apoptosis of the cells could also be caused by ROS via non ER-stress-mediated cell death pathways [78][79][80].…”

Gartanin, an isoprenylated xanthone from the mangosteen fruit (Garcinia mangostana), is an androgen receptor degradation enhancer

“…This suggests a possible interplay between AR signaling and the UPR pathway. It has been reported that AR signaling activated ER stress/UPR in embryonic stem cells . For example, dihydrotestosterone treatment induced significantly higher CHOP mRNA level in embryonic stem cells stably expressing AR than in parental embryonic stem cells.…”

Upregulated ATF6 contributes to chronic intermittent hypoxia-afforded protection against myocardial ischemia/reperfusion injury

“…BiP is involved in the action of ATF6 and plays an important role in initiating adaptive ER stress and inhibiting apoptotic ER stress ( 34 ). Androgen induces BiP to dissociate from ATF6 and act as an androgen receptor-interacting protein, suggesting that BiP is a regulator of androgen receptor protein quality control ( 35 ). Thus, we would expect BiP expression levels to increase with the 50-kDa cleaved form of ATF6.…”