Dapper1Promotes Autophagy By Enhancing The Beclin1-Vps34-Atg14l Complex Formation

Autophagy is a regulated self-eating process that selectively eliminatesthe cellularmaterials, such as aggregated cytoplasmic proteins or aging and damaged organellesthrough the lysosomal degradationin response to starvation and other metabolic stress.Althoughautophagy is usually induced by starvation, this process also occurs undernutrient-rich conditions (referred to as basal autophagy or constitutive autophagy), andbasal autophagy contributes to turnover of long-lived proteins and prevents theaccumulation of disease-associated proteins. However,the molecular mechanism totrigger autophagy iniatation is poorly understood.Here we show that ablation of Dapper1(Dpr1) in mice results in impaired basalautophagy, as evidenced by more p62/SQSTM1and accumulation of ubiquitinatedproteins inbrain tissues and motor control defects of Dpr1fl/fl;Nestin-Cre mice. Thepathologycial changes including loss of Purkinje cells, elevated glial cells, andincreased apoptosis can be observed in the cerebral cortex and cerebellum ofDpr1fl/fl;Nestin-Cremice, indicating that Dpr1deficiency impairs basal autophagy in thecentral nervous system.Loss of Dpr1also causes the impairment of LC3lipidation and p62accumulation inDpr1-/-mouse embryonic fibroblasts (MEFs), indicating the important function of Dpr1in autophagy. Consistently, overexpression of Dpr1increases autophagosome formationas indicated by elevated puncta formation of LC3, Atg14L and DFCP (double FYVEdomain-containing protein). Mechanistically, Dpr1directly interacts with Beclin1andAtg14L but not with UVRAG, and specifically enhances theBeclin1-Vps34-Atg14Lcomplex formation and Vps34lipid kinase activity,which isrequired for autophagy initiation.We further observed that some aggregation-prone proteins, such as Dishevelled2(Dvl2), p62and the hungtingtin mutant Htt103Q, which have been shown to bedegraded via the autophagy-lysosome pathway,could promote autophagy inaDpr1-dependent manner. Htt103Q, Dvl2and p62, but not their aggregation-deficientmutants, can also increase the Beclin1-Vps34interaction and promote puncta formationof Atg14L and LC3.Our findings suggest that Dpr1acts as a critical regulator of the autophagy initiating machinery Atg14L-Beclin1-Vps34complex to drive autophagy forclearing up protein aggregates.