somatostatin receptor type 3, member of the class A family of seven-transmembrane G protein-coupled receptors
G protein-coupled somatostatin receptors (SSTRs) are composed of five distinct subtypes (SSTR1-5) that display strong sequence similarity with opioid receptors. All five receptor subtypes bind the natural somatostatin (somatotropin release inhibiting factor), a polypeptide hormone that regulates a wide variety of physiological functions such as neurotransmission, cell proliferation, contractility of smooth muscle cells, and endocrine signaling as well as inhibition of the release of many secondary hormones. SSTR3 is coupled to inward rectifying potassium channels. SSTR3 plays critical roles in growth hormone secretion, endothelial cell cycle arrest and apoptosis. Furthermore, SSTR3 is expressed in the normal human pituitary and in nearly half of pituitary growth hormone adenomas.