VMP1 triggers autophagy and cancer cell death through the interaction with BH3 domain of Beclin1.

MOLEJON, MI; LO RE, A; PARDO, R; GRASSO, D; BOGGIO, V; ROPOLO, A; VACCARO, MI

Encuentro; 43rd Meeting of the European Pancreatic Club (EPC); 2011

1. Autophagy has recently elicited significant attention as a mechanism that either protects cells or promotes cancer cell death. However, different pathways that could explain autophagy function in cancer remain to be elucidated. We recently showed that VMP1-mediated autophagy leads to cell death in Mia-Paca and Panc1 pancreatic cancer cells. 2. Here we report a thorough cellular and biochemical characterization of VMP1 mediated autophagosome formation and cell death in human pancreatic cancer cells. We demonstrate that VMP1 triggers autophagy and cell death interacting with the tumor suppressor protein Beclin1. 3-4. Using recombinant Beclin1 peptides and mutated peptides, coimmunoprecipitation assays show that VMP1 interacts with the BH3 domain of Beclin1, which is essential for VMP1-Beclin1 interaction. FRET analyses confirm the VMP1-Beclin1 in vivo direct interaction. Moreover, VMP1-Beclin1 interaction enhances PI3K activity recruiting Beclin1-hVsp34 complex to the autophagosomal membrane. Also, VMP1 deficient mutant, (VMP1?´Atg), which is not able to interact with Beclin1, fails to recruit PI3K complex to the autophagosome. Finally, we found that VMP1-Beclin1 interaction displaces Bcl2 from the BH3 domain of Beclin1, favoring autophagy and leading to pancreatic cancer cell death. Also, VMP1?´Atg expression does not alter cell survival. 5. These data characterizes the VMP1-Beclin1 interaction and reveals the molecular pathway by which VMP1 expression leads to autophagic cell death in human pancreatic cancer cells. Our findings provide further understanding of the VMP1-autophagy molecular mechanism and are potentially relevant to therapeutic strategies in pancreatic cancer.