VPS34, vacuolar protein sorting 34, is the only identified Class III phosphoinositide-3 kinase (PI3K) in mammals and is ubiquitously expressed in all eukaryotic cells. VPS34 is a 100 kDa protein responsible for phosphorylating phosphatidylinositol to produce phosphatidylinositol 3-phosphate (PI3P). PI3P is an important intermediate in the development of the double-membraned autophagosome during autophagy, indicating a role for VPS34 in autophagy initiation. PI3P allows VPS34 to form complexes with ATG14L during the elongation of the autophagosome membrane.
