Glucagon is a 29 amino acid pancreatic hormone that counteracts the blood glucose lowering action of insulin by stimulation of hepatic glycogenolysis and gluconeogenesis. Hormone activation of adenylate cyclase requires at least three membrane components; hormone receptor, catalytic subunit and GTP-regulatory component (Gs) that couples hormone binding to cyclase activation. Isolation and characterization of these components is essential for understanding the mechanism of the sequential events that begin with hormone binding and end with increase in cyclase activity. Although glucagon regulation of adenylate cyclase activity has been extensively studied, our knowledge about glucagon receptor itself lags behind the understanding of insulin or beta-adrenergic receptors. Recently we have identified glucagon receptor as a 62 kda glycoprotein that contains intrachain disulfide bonds and N-linked carbohydrate. To aid in studies of the glucagon receptor we prepared monoclonal antibodies (MAbs) that recognize the glucagon receptor. These antibodies were used to clone the cDNA encoding the glucagon receptor, from the expression library. In this proposal we outlined our planes for further characterization of the glucagon receptor and of its gene. The rat and human genomic sequences will be isolated by screening library with cDNA probe, and the glucagon receptor gene will be characterized with respect to intron/exon organization, regulatory features of the 5'end, and transcription initiation site. In the separate line of experiments we will study the postranslational modifications of the receptor such as phosphorylation and fatty acid acylation and the role these modification play in the ability of the receptor to activate adenylate cyclase. It is hoped that the results of the proposed experiments will contribute to our understanding of the mechanism of glucagon action.
| Simonson, G D; Iwanij, V (1995) Genomic organization and promoter sequence of a gene encoding a rat liver-specific type-I transport protein. Gene 154:243-7 |
| Iwanij, V (1995) Canine kidney glucagon receptor: evidence for a structurally-different, tissue-specific variant of the glucagon receptor. Mol Cell Endocrinol 115:21-8 |
| Simonson, G D; Vincent, A C; Roberg, K J et al. (1994) Molecular cloning and characterization of a novel liver-specific transport protein. J Cell Sci 107 ( Pt 4):1065-72 |
