Somatostatin Receptors

Somatostatin (SST) is a small cyclic peptide that was first identified as a powerful inhibitor of the secretion of various hormones including growth hormone (GH), thyroid-stimulating hormone (TSH) and prolactin from the pituitary, as well as practically every major hormone from the intestinal tract. SST consists of two major bioactive forms, SST-14 and the N-terminus extended peptide SST-28, that can be produced by a wide variety of neuroendocrine, inflammatory and immune cells. In target cells, SST induces a variety of physiological functions that include neuromodulation, cell secretion, cell proliferation and smooth muscle contractility. SST acts on its multiple cell targets via a family of six receptors that originate from five genes: SSTR1, SSTR2a, SSTR2b, SSTRR3, SSTR4, SSTR5. The SSTRs are members of the G-protein coupled receptor superfamily and they modulate cell response via multiple second messenger systems such as inhibition of adenylate cyclase, modulation of conductance of ion channels and protein dephosphorylation.