Plays a role in the translocation of terminally misfolded proteins from the endoplasmic reticulum lumen to the cytoplasm and their degradation by the proteasome (By similarity). Plays a role in lipid droplet formation (By similarity). Induces lipid droplet clustering (By similarity). Recruits ubiquitin-conjugating enzyme UBE2G2 to lipid droplets which facilitates its interaction with ubiquitin ligases AMFR/gp78 and RNF139/TRC8, leading to sterol-induced ubiquitination of HMGCR and its subsequent proteasomal degradation (By similarity). Also required for the degradation of INSIG1, SREBF1 and SREBF2 (By similarity). Plays a role in regulating assembly and secretion of very low density lipoprotein particles and stability of apolipoprotein APOB (By similarity).