Mediates the endoplasmic reticulum-associated degradation (ERAD) of inositol 1,4,5-trisphosphate receptors (IP3Rs). Promotes sterol-accelerated ERAD of HMGCR. Involved in regulation of cellular cholesterol homeostasis by regulation the SREBP signaling pathway (By similarity). Associated with lipid raft-like domains of the endoplasmic reticulum membrane. Belongs to the band 7/mec-2 family.