The function of RNF183 (ring finger protein 183, ENSG00000165188) is as follows. Acts as an E3 ubiquitin ligase catalyzing the covalent attachment of ubiquitin moieties onto substrate proteins (PubMed:29507230). Triggers apoptosis in response to prolonged ER stress by mediating the polyubiquitination and subsequent proteasomal degradation of BCL2L1 (PubMed:29507230). May collaborate with FATE1 to restrain BIK protein levels thus regulating apoptotic signaling (PubMed:26567849). Mediates the ubiquitination and subsequent lysosomal degradation of ATP1B1 (By similarity). {ECO:0000250|UniProtKB:Q8QZS5, ECO:0000269|PubMed:29507230, ECO:0000305|PubMed:26567849}.