Plays a central role in autophagy (By similarity). Acts as core subunit of different PI3K complex forms that mediate formation of phosphatidylinositol 3-phosphate and are believed to play a role in multiple membrane trafficking pathways such as initiation of autophagosomes, maturation of autophagosomes and endocytosis (By similarity). Involved in regulation of degradative endocytic trafficking and required for the abcission step in cytokinesis, probably in the context of PI3KC3-C2 (By similarity). Component of the PI3K (PI3KC3/PI3K-III/class III phosphatidylinositol 3-kinase) complex (By similarity). May be proteolytically processed by caspases; the C-terminal fragment(s) may induce apoptosis. Belongs to the beclin family.