CONICET | Buscador de Institutos y Recursos Humanos

The vacuole membrane protein 1 -VMP1- is an essential autophagy related transmembrane protein conserved from worms to mammals. VMP1 triggers autophagosome formation even under nutrient-replete conditions and its expression functions as a switch for autophagy in human disease, such as pancreatitis. We have previously reported that VMP1 interacts with the evolutionarily conserved autophagic protein Beclin1. The aim of the current study is elucidate the molecular mechanism that explains the essential role of VMP1 in the autophagosome formation site during autophagy in human cells. We perform a series of cell and biochemical studies to characterize the VMP1-Beclin1 interaction and to define the functional significance of this molecular pathway in human cell autophagy. We demonstrate that the VMP1-Atg domain binds to the Beclin1-BH3 domain in a manner that is required for both forming the Beclin1-hVps34 complex and inducing its activity on the autophagosomal membrane. We show that VMP1-Beclin1-hVps34 complex also interacts with ATG16L, promoting its recruitment to the autophagosome formation site. Moreover, the VMP1-Beclin1 interaction induces the topological displacement of Bcl-2 partitioning Beclin 1 to the autophagic pathway. Finally we show that the interplay between endogenous VMP1 and Beclin1-hVps34 complex mediates rapamycin-induced autophagosome formation. Collectively, these results reveal a novel molecular pathway involving VMP1-Beclin1-hVps34-Atg16L interaction that regulates the autophagosome formation in human cells. Our findings provide further understanding of VMP1 role in autophagosome formation. The association of this pathway to disease-related autophagy is of significant relevance to experimental therapeutics.