Ubiquitin-like modifier that plays a crucial role in antibacterial autophagy (xenophagy) through the selective binding of CALCOCO2 (PubMed:23022382). Recruits all ATG8 family members to infecting bacteria such as S.typhimurium (PubMed:23022382). May also play a role in aggrephagy, the macroautophagic degradation of ubiquitinated and aggregated proteins (PubMed:28404643). 3 different light chains, LC1, LC2 and LC3, can associate with MAP1A and MAP1B proteins (By similarity). Interacts with TP53INP1 and TP53INP2 (PubMed:22470510). Interacts with CALCOCO2 (PubMed:23022382). Interacts with TECPR2 (PubMed:20562859). Interacts with TBC1D5 (PubMed:22354992). Found in a complex with UBQLN1 and UBQLN2 (PubMed:20529957). Interacts with UBQLN4 (via STI1 1 and 2 domains) (PubMed:23459205). Interacts with UBQLN1 in the presence of UBQLN4 (PubMed:23459205). Interacts with TRIM5 (PubMed:25127057). Interacts with ATG13 (PubMed:24290141). Interacts with MEFV and TRIM21 (PubMed:26347139). Interacts with WDR81; recruits MAP1LC3C to ubiquitinated protein aggregates in the aggrephagy process (PubMed:28404643). Interacts with MOAP1 (via LIR motif) (PubMed:33783314). LC3-II binds to the autophagic membranes. Most abundant in placenta, lung and ovary. The precursor molecule is cleaved by ATG4 (ATG4A, ATG4B, ATG4C or ATG4D) to expose the glycine at the C-terminus and form the cytosolic form, LC3-I (PubMed:15187094, PubMed:20818167, PubMed:30661429, PubMed:31709703). The processed form is then activated by APG7L/ATG7, transferred to ATG3 and conjugated to phosphatidylethanolamine (PE) phospholipid to form the membrane-bound form, LC3-II (PubMed:15187094). During non-canonical autophagy, the processed form is conjugated to phosphatidylserine (PS) phospholipid (PubMed:33909989). ATG4 proteins also mediate the delipidation of PE-conjugated forms (PubMed:33909989, PubMed:31709703). In addition, ATG4B and ATG4D mediate delipidation of ATG8 proteins conjugated to PS during non-canonical autophagy (PubMed:33909989). (Microbial infection) The Legionella effector RavZ is a deconjugating enzyme that hydrolyzes the amide bond between the C-terminal glycine residue and an adjacent aromatic residue in ATG8 proteins conjugated to phosphatidylethanolamine (PE), producing an ATG8 protein that is resistant to reconjugation by the host machinery due to the cleavage of the reactive C-terminal glycine (PubMed:23112293, PubMed:31722778). RavZ is also able to mediate delipidation of ATG8 proteins conjugated to phosphatidylserine (PS) (PubMed:33909989). Phosphorylation at Ser-96 and Ser-98 by TBK1 prevents interaction with ATG4 (ATG4A, ATG4B, ATG4C or ATG4D) (PubMed:31709703). Phosphorylation by TBK1 on autophagosomes prevents their delipidation by ATG4 and premature removal from nascent autophagosomes (PubMed:31709703). Belongs to the ATG8 family.