Fig. 1.

Key cellular components required for autophagosome formation, transport, and fusion. Adaptor proteins recognize targets for engulfment (Bchs/Alfy recognizes ubiquitin-rich protein aggregates) in conjunction with p62/Sequestosome1/Ref(2)P. The forming autophagosome (phagophore) is initially decorated with Atg5:Atg12 conjugates complexed with Atg16, followed by Atg8/LC3, which is covalently linked to phosphatidylethanolamine (PE). Once the autophagosome seals around its target, externally exposed Atg proteins dissociate (internal LC3 is retained) and the vesicle is transported along microtubules to fuse with a lysosome. The vacuolar proton ATPase acidifies the autophagosome before fusion with a lysosome (also acidified). Upon fusion, the contents of the autophagolysosome are degraded, including LC3