Component of the ERLIN1/ERLIN2 complex which mediates the endoplasmic reticulum-associated degradation (ERAD) of inositol 1,4,5- trisphosphate receptors (IP3Rs). Involved in regulation of cellular cholesterol homeostasis by regulation the SREBP signaling pathway (PubMed:37683630). Binds cholesterol and may promote ER retention of the SCAP-SREBF complex (PubMed:24217618). {ECO:0000269|PubMed:19240031, ECO:0000269|PubMed:24217618, ECO:0000269|PubMed:37683630}. (Microbial infection) Required early in hepatitis C virus (HCV) infection to initiate RNA replication, and later in the infection to support infectious virus production. . This is the function of ERLIN1 (ER lipid raft associated 1, Ensembl gene identifier ENSG00000107566).