49-OR: Synergistic Effect of ERAD and Autophagy in Preventing Proinsulin Aggregation and Promoting Beta-Cell Survival

Decline of proteostasis in the endoplasmic reticulum (ER) is thought to underlie molecular changes in β cell function and drive the pathogenesis of diabetes. ER-associated degradation (ERAD) and macroautophagy (hereafter “autophagy”) are two principal quality-control mechanisms responsible for the clearance of ER-resident proteins or protein aggregates, respectively, in the cell. However, the physiological significance of ERAD-autophagy crosstalk remains unexplored. Previously, using β cell-specific knockout mouse models, we reported that ERAD deficiency leads to β cell dedifferentiation, while autophagy deficiency leads to β cell loss by 4-5 months of age. Interestingly, we observed that loss of ERAD in β cells triggered activation of autophagy pathways, as monitored by LC3 flux. Furthermore, chloroquine-mediated inhibition of autophagy in ERAD-deficient islets led to an increased proinsulin aggregation. In mice, combined deletion of ERAD and autophagy in β cells caused marked hyperglycemia soon after weaning, with extensive loss of β cells and premature death at 2-3 months of age. Thus, our data demonstrate that ERAD and autophagy act synergistically to prevent proinsulin aggregation and promote β cell survival. This study reveals a critical role for crosstalk between the ERAD and autophagy pathways in preventing diabetes and provides the first evidence for synergism between ERAD and autophagy in vivo.