GPBAR1 (TGR5) is a member of the G protein-coupled receptor (GPCR) superfamily and functions as a cell surface receptor for bile acids. Treatment of cells expressing this GPBAR1 with bile acids induces the production of intracellular cAMP, activation of a MAP kinase signaling pathway, and internalization of the receptor. It is implicated in the suppression of macrophage functions and regulation of energy homeostasis by bile acids. GPBAR1 inhibitors may be useful as treatments for polycystic liver disease and cholangiocarcinoma, as it has been found to be overexpressed in cholangiocarcinoma and cystic cholangiocytes and is thought to be involved in promoting proliferation and cyst growth. It has membranous and cytoplasmic positivity in a number of tissues, including the lung, gastrointestinal tract, gallbladder, bladder, pars intermedia of the pituitary gland, and faint to variable positivity in various locations in the central nervous system. References: Semin Liver Dis. 2018 Nov;38(4):333-339, PMID: 30357770