Somatostatin receptor subtypes 3 and 5 (SSTR3, SSTR5)

Somatostatin receptor type 3 (SSTR3) and somatostatin receptor type 5 (SSTR5) are members of the G protein-coupled receptor (GPCR) superfamily, encoded by separate genes and characterized by seven transmembrane domains. They are primarily responsible for mediating the inhibitory effects of the peptide hormone somatostatin on hormone secretion and cell proliferation. SSTR3 is highly expressed in the brain and pancreatic islets, is functionally coupled to adenylyl cyclase via inhibitory G proteins, and is strongly linked to apoptosis and cell cycle arrest. SSTR5, widely expressed in endocrine and neuroendocrine tissues, also plays major roles in hormone regulation, especially in pituitary tumors. Both receptors are validated therapeutic targets in neuroendocrine tumors and pituitary adenomas. Their activity is the target of several clinically used drugs, including somatostatin analogues such as pasireotide, octreotide, and lanreotide. Therapeutic use can be limited by safety concerns such as hyperglycemia and general suppression of physiological hormone secretion

Other names

Somatostatin receptor 3Somatostatin receptor 5SSTR3SSTR5SST3sst3SST5sst5

Activation by agonists leads to coupling with inhibitory G proteins (mainly G\(_i\)), resulting in:\n- Inhibition of adenylyl cyclase, decreasing cAMP\n- Modulation of ion channels (Ca\(^2+\), K\(^+\)), leading to decreased hormone/neurotransmitter release\n- Induction of apoptosis and cell cycle arrest mainly via SSTR3 and SSTR5\n- Regulation of downstream pathways such as the MAPK cascade and tyrosine phosphatase activation