Human Somatostatin Receptor, SSTR2, Is Coupled to Adenylyl Cyclase in the Presence of Giα1 Protein

Abstract

Somatostatin has been shown to exert diverse biological effects in various tissues. Recently, the human genes encoding five subtypes of somatostatin receptor (SSTR1-SSTR5) were cloned. Among these subtypes SSTR2, is present in many endocrine tumors as well as normal tissues and may mediate the effects of somatostatin analog, SMS301-995. In this study, we have investigated the intracellular effect of SSTR2 stably expressed in Chinese hamster ovary cells. Somatostatin-14 does not affect the forskolin stimulated cAMP formation when human SSTR2 is expressed in CHO cells, which lack internal Giα1 protein. However, somatostatin-14 inhibits the adenylyl cyclase in a dose dependent and pertussis toxin-sensitive manner when human SSTR2, is co-expressed with Giα1 in CHO cells. These results indicate that human SSTR2, is functionally coupled to Giα1 protein but not to Giα2 or Giα3 when expressed in CHO cells.