Role of cholesterol in ligand binding and G-protein coupling of serotonin_1A receptors solubilized from bovine hippocampus

The serotonin_1A (5-HT_1A) receptor is an important member of the superfamily of seven transmembrane domain G-protein-coupled receptors. We report here that solubilization of the hippocampal 5-HT _1A receptor by the zwitterionic detergent CHAPS is accompanied by loss of membrane cholesterol which results in a reduction in specific agonist binding activity and extent of G-protein coupling. Importantly, replenishment of cholesterol to solubilized membranes using MβCD-cholesterol complex restores the cholesterol content of the membrane and significantly enhances the specific agonist binding activity and G-protein coupling. These novel results provide useful information on the role of cholesterol in solubilization of G-protein-coupled receptors, an important step for molecular characterization of these receptors.