Figure 1. The molecular regulators of autophagy. Autophagy induction requires the release of Beclin from Bcl-2, which is then free to form the Class III PI3K that contributes to the formation of the nucleation complex. Two independent conjugation cascades, the LC3-II and the Atg5-12 cascades, serve to elongate the nucleation complex to generate the limiting membrane. The sole transmembrane atg, Atg9, delivers additional membranes for limiting membrane formation. The limiting membrane then sequesters cytosolic cargo and seals upon itself to form an autophagosome. The fusion of autophagosomes to lysosomes results in cargo degradation and release of nutrients into the cytosol. Atg: autophagy gene, LC3: light chain-3, PI3K: phosphoinositide 3-kinase, vps: vacuolar protein sorting.