Expression of the Gβ5/R7-RGS protein complex in pituitary and pancreatic islet cells

Abstract

Heterotrimeric G protein subunit Gβ5 is expressed primarily in the nervous system and retina and, among Gβ isoforms, is unique in its ability to heterodimerize with regulator of G protein signaling (RGS) proteins of the R7 subfamily (R7-RGS) [see [1, 2] for recent reviews]. The R7-RGS subfamily consists of RGS proteins 6, 7, 9, and 11 which can form tight heterodimers with the G protein β5 subunit through a Gγ-like (GGL) domain [1, 2]. R7-RGS subfamily members are unstable in the absence of Gβ5 [3]. Previous study from our laboratory showed that in addition to its expression in brain and neural cell lines, Gβ5 was also expressed in the αT3-1 gonadotrophic pituitary cell line [4]. We show now that the Gβ5/R7-RGS complex is expressed in corticotroph-derived pituitary AtT-20 cells, pituitary gland and purified pancreatic islets. The expression of Gβ5 in various endocrine cell lines and native tissues raises the possibility that hormone secretion, and not just neurotransmission and phototransduction, may be regulated by the Gβ5/R7-RGS complex.