Somatostatin receptor type 2 and Somatostatin receptor type 5 (SSTR2 and SSTR5)

Somatostatin receptor type 2 (SSTR2) and type 5 (SSTR5) are G protein-coupled receptors (GPCRs) that mediate the inhibitory physiological effects of the peptide hormone somatostatin. They are widely distributed in the pituitary gland, pancreas, gastrointestinal tract, and central nervous system, where they regulate the secretion of hormones such as growth hormone, insulin, glucagon, and ACTH. In oncology, these receptors are frequently overexpressed in neuroendocrine tumors (NETs) and pituitary adenomas, serving as critical targets for both diagnostic imaging and therapeutic intervention. Drugs targeting these receptors, such as octreotide and pasireotide, act as agonists to suppress hormone hypersecretion and inhibit tumor growth through cell cycle arrest and apoptosis. Furthermore, SSTR2 is the primary target for peptide receptor radionuclide therapy (PRRT), which delivers cytotoxic radioisotopes directly to tumor cells. Therapeutic challenges include the management of side effects like hyperglycemia, particularly with SSTR5-targeting agents, and the potential for tumor resistance due to receptor downregulation.

Other names

Somatostatin receptor 2Somatostatin receptor 5sst2sst5SRIF-2SRIF-5SS2RSS5R

Somatostatin receptor agonists bind to SSTR2 and SSTR5 to activate inhibitory G proteins (Gi), which leads to the inhibition of adenylate cyclase and a subsequent decrease in intracellular cyclic AMP (cAMP) levels. This signaling cascade modulates calcium and potassium channels to inhibit hormone exocytosis and activates phosphotyrosine phosphatases (such as SHP-1 and SHP-2) to induce antiproliferative effects and apoptosis. Additionally, radiolabeled ligands (PRRT) bind to these receptors to deliver targeted ionizing radiation to tumor cells.