VPS34, also known as phosphoinositide-3-kinase p100 subunit or PIK3C3 (phosphoinositide-3-kinase, class III), is a member of the PI3/PI4-kinase family. It is ubiquitously expressed with predominant expression in skeletal muscle and is believed to participate in endosome to lysosome transport, multivesicular body formation, autophagy and retrograde endosome to Golgi transport. VPS34 is the catalytic subunit of class III PI3Ks and forms a heterodimer with p150, a regulatory subunit of class 3 PI3Ks. It exclusively phosphorylates phosphatidylinositol to produce PtdIns3P. The activity of VPS34 is enhanced by manganese and can be regulated by nutrients, suggesting an important role of VPS34 in the regulation of mTOR protein synthesis. VPS34 also forms a complex with Beclin1 that promotes autophagy and tumor supression.