The Beclin-1 complex (ATG14:PIK3C3:PIK3R4:BECN1) is essential for autophagosome formation (Matsunaga et al. 2009, 2010). PIK3C3 (VPS34), the catalytic component of this complex, is a class III phosphatidylinositol 3-kinase that phosphorylates phosphatidylinositol (PI) producing phosphatidylinositol 3-phosphate (PI3P). PIK3C3 is essential for the early stages of autophagy and colocalizes strongly with early autophagosome markers (Axe et al. 2008). The role of PI3P in autophagosome formation is to recruit WIPI2b (Dooley et al. 2014) a member of the WIPI family (Proikas-Cezanne et al. 2004, 2015, Polson et al. 2010).
1-phosphatidylinositol-3-kinase activity of ATG14:PIK3C3:PIK3R4:p-S15-BECN1 [endoplasmic reticulum membrane]