It is localized in the endoplasmic reticulum (ER) and seems to be expressed in all tissues, especially in liver.

Importantly, the protein encoded by this gene plays a critical role in regulating cholesterol concentrations in cells.

There are two other proteins whose sterol-binding sites show a great similarity to the ones of SCAP and HMG-CoA-reductase and who might thus be regulated by INSIG1 as well: Oxysterols regulate cholesterol homeostasis through liver X receptor (LXR) and sterol regulatory element-binding protein (SREBP) mediated signaling pathway.

Alternatively spliced transcript variants encoding distinct isoforms have been observed.

CL-6, INSIG-1, Insulin-induced gene 1 protein, MGC1405 (source: iHOP) INSIG1 has been shown to interact with SREBF2.