Retrotransposon-derived protein that forms virion-like capsids (By similarity). Acts as an effector of BAX during apoptosis: enriched at outer mitochondria membrane and associates with BAX upon induction of apoptosis, facilitating BAX-dependent mitochondrial outer membrane permeabilization and apoptosis (PubMed:11060313, PubMed:16199525). Required for death receptor-dependent apoptosis (PubMed:11060313). When associated with RASSF1, promotes BAX conformational change and translocation to mitochondrial membranes in response to TNF and TNFSF10 stimulation (PubMed:15949439). Also promotes autophagy: promotes phagophore closure via association with ATG8 proteins (PubMed:33783314). Acts as an inhibitor of the NFE2L2/NRF2 pathway via interaction with SQSTM1: interaction promotes dissociation of SQSTM1 inclusion bodies that sequester KEAP1, relieving inactivation of the BCR(KEAP1) complex (PubMed:33393215). Homodimer (PubMed:15949439). Under normal circumstances, held in an inactive conformation by an intramolecular interaction (PubMed:15949439). Interacts with BAX (PubMed:11060313, PubMed:16199525). Binding to RASSF1 isoform A (RASSF1A) relieves this inhibitory interaction and allows further binding to BAX (PubMed:15949439). Binds also to BCL2 and BCLX (PubMed:11060313). Recruited to the TNFRSF1A and TNFRSF10A complexes in response to their respective cognate ligand, after internalization (PubMed:15949439). Interacts with TRIM39 (PubMed:19100260). Interacts with RASSF6 (By similarity). Interacts with ATG8 proteins MAP1LC3A, MAP1LC3B and MAP1LC3C (PubMed:33783314). Does not interact with ATG8 proteins GABARAPL1, GABARAPL2 and GABARAP (PubMed:33783314). Interacts with SQSTM1; promoting dissociation of SQSTM1 inclusion bodies that sequester KEAP1 (PubMed:33393215). Forms virion-like extracellular vesicles that are released from cells. Widely expressed, with high levels in heart and brain. The protein is evolutionarily related to retrotransposon Gag proteins: it contains the capsid (CA)subdomain of gag. The BH3-like domain is required for association with BAX and for mediating apoptosis (PubMed:11060313). The three BH domains (BH1, BH2, and BH3) of BAX are all required for mediating protein-protein interaction (PubMed:11060313). The LIR motif (LC3-interacting region) is required for the interaction with the ATG8 family proteins MAP1LC3A, MAP1LC3B and MAP1LC3C. Ubiquitinated and degraded during mitotic exit by APC/C-Cdh1, this modification is inhibited by TRIM39. Belongs to the PNMA family.