ATG4B is one of the four mammalian Atg4 homologues, also known as autophagins, mediating both proteolytic activation and delipidation of ATG8 family proteins [, ]. It is required for Required for canonical autophagy (macroautophagy), non-canonical autophagy as well as for mitophagy []. ATG4B is a cysteine protease required for autophagy and acts to proteolytically prime and recycle its substrate MAP1LC3B (also referred to as LC3), where cleavage generates a C-terminal glycine required for LC3 conjugation to lipids in autophagosomes [, ].
