Somatostatin receptor 4 (SSTR4)

Somatostatin receptor 4 (SSTR4) is a G protein-coupled receptor encoded by the SSTR4 gene. It is one of five somatostatin receptor subtypes (SSTR1-5) that mediate the biological effects of somatostatin (SRIF/GHIH). SSTR4 is predominantly expressed in the brain, particularly in the cortex and hippocampus, and also in lung tissue. It functions as a receptor for somatostatin-14, inhibiting adenylyl cyclase through G protein coupling. SSTR4 plays roles in inhibiting hormone secretion (including growth hormone, thyroid-stimulating hormone, insulin, and glucagon), learning and memory processes, and mediates cytostatic effects. Due to its expression pattern and functions, SSTR4 is considered a promising therapeutic target for CNS disorders affecting learning and memory (such as Alzheimer's disease) and certain cancers. Ligands include the endogenous peptide somatostatin-14 and small-molecule agonists like J-2156. Structural studies using cryo-electron microscopy have provided insights into SSTR4 function and ligand binding. Its activity can be regulated by other proteins, such as CD26, in specific contexts.

Activation of SSTR4, typically by agonists, leads to G protein coupling and inhibition of adenylyl cyclase, mediating downstream cellular effects including inhibition of hormone secretion and potential cytostatic effects.