Background: Apoptosis and autophagy are two closely related systems that induce cell death. Results: X-box-binding protein 1 (XBP1) mRNA splicing regulates BECLIN-1 transcriptional activation, a fundamental player in the initiation of autophagy. Conclusion: XBP1 splicing induces an autophagic response in endothelial cells. Significance: XBP1 could be used as an important pharmacological target that can regulate the autophagic machinery and endothelial cell death.

Autophagy is an intracellular degradation process to clear up aggregated proteins or aged and damaged organelles. The Beclin1-Vps34-Atg14L complex is essential for autophagosome formation. However, how the complex formation is regulated is unclear. Here, we show that Dapper1 (Dpr1) acts as a critical regulator of the Beclin1-Vps34-Atg14L complex to promote autophagy. Dpr1 ablation in the central nervous system results in motor coordination defect and accumulation of p62 and ubiquitinated proteins. Dpr1 increases autophagosome formation as indicated by elevated puncta formation of LC3, Atg14L and DFCP1 (Double FYVE-containing protein 1). Conversely, loss of Dpr1 impairs LC3 lipidation and causes p62/SQSTM1 accumulation. Dpr1 directly interacts with Beclin1 and Atg14L and enhances the Beclin1-Vps34 interaction and Vps34 activity. Together, our findings suggest that Dpr1 enhances the Atg14L-Beclin1-Vps34 complex formation to drive autophagy.

Background: Protein aggregates could be degraded through autophagy. Results: Dpr1 promotes pVHL-induced Dvl2 ubiquitination and mediates the Vps34-Beclin1 complex formation induced by protein aggregates. Conclusion: Protein aggregates stimulate autophagy initiation in a Dpr1-dependent manner. Significance: This study shows that protein aggregates can induce autophagy to facilitate their clearance.