Enhances production and/or transport of FGF15 and thus has a role in regulation of bile acid synthesis. Interacts with FGF15. Strongly expressed in epithelial cells of the small intestine. Also detected in kidney cortex, and testis. Viable, with enhanced resistance to diet-induced hypercholesterolemia and atherosclerosis (PubMed:10744778). Increased bile acid levels in blood, liver and gastrointestinal tract, associated with significantly reduced levels of FGF15 in the ileum (PubMed:23747249).