melanin concentrating hormone receptor 1, member of the class A family of seven-transmembrane G protein-coupled receptors
Melanin-concentrating hormone receptor (MCHR) binds melanin concentrating hormone and is presumably involved in the neuronal regulation of food intake and energy homeostasis. Despite strong homology with somatostatin receptors, MCHR does not appear to bind somatostatin. Two MCHRs have been characterized in vertebrates, MCHR1 and MCHR2. MCHR1 is expressed in all mammals, whereas MCHR2 is only expressed in the higher order mammals, such as humans, primates, and dogs, and is not found in rodents. All GPCRs have a common structural architecture comprising of seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops. A general feature of GPCR signaling is agonist-induced conformational changes in the receptors, leading to activation of the heterotrimeric G proteins, which consist of the guanine nucleotide-binding G-alpha subunit and the dimeric G-beta-gamma subunits. The activated G proteins then bind to and activate numerous downstream effector proteins, which generate second messengers that mediate a broad range of cellular and physiological processes.