Restoration of Growth Hormone-Releasing Hormone (GHRH) Responsiveness in Pituitary GH3 Cells by Adenovirus-Directed Expression of the Human GHRH Receptor

Abstract

GH-secreting GH3 cells lack GH-releasing hormone (GHRH) re- ceptors. In this study we used adenoviral vectors to transfer the human GHRH receptor to GH3 cells in an effort to restore GHRH responsiveness. A replication-deficient recombinant adenovirus (AdGHRH-R) was designed to allow cytomegalovirus promoter-driven expression of the GHRH receptor messenger RNA. COS-7 cells and GH-producing GH3 cells infected with AdGHRH-R showed GHRH receptor expression on their membranes and exhibited specific GHRH binding. The addition of GHRH to GH3 cells infected with AdGHRH-R increased cAMP levels, induced cAMP response element-binding pro- tein phosphorylation and restored GH secretory responsiveness. GHRH treatment also caused activation of mitogen-activated-protein kinase, induction of c-fos, stimulation of GH promotor activity, and increased cellular proliferation. These findings indicate that adeno- viral vectors carrying human GHRH receptor are useful for in vitro studies of GHRH receptor biology and represent a first step toward the development of gene therapy for dwarfism caused by GHRH receptor mutations. (Endocrinology 142: 414 - 420, 2001)