E3 ubiquitin-protein ligase which can target both itself and other proteins including CD3D and APOB for proteasomal degradation. Mediates polyubiquitination of CYP3A4. Specific receptor for the autocrine motility factor. Mediates tumor invasion and metastasis. Component of a complex required to couple deglycosylation and proteasome-mediated degradation of misfolded proteins in the endoplasmic reticulun that are retrotranslocated in the cytosol. Promotes ubiquitination of misfolded proteins such as mutant CFTR; proposed to mediate sequential ubiquitination by recognizing already ubiquitin-conjugated substrates and to cooperate with E3 ubiquitin-protein ligase RNF5.