Characterization of specific calcitonin gene-related peptide receptors present in hamster pancreatic beta cells.
Calcitonin gene-related peptide (CGRP) shares about 46% and 20% amino acid sequence homology with islet amyloid polypeptide (IAPP) and salmon calcitonin (sCT). We investigated whether these related peptides could cross-react with the specific binding of 125I-[His]hCGRP I to the CGRP receptor in hamster insulinoma cell membranes. A rapid dissociation of membrane bound 125I-[His]hCGRP I could be induced in the presence of 1 microM chicken CGRP (cCGRP). The specific 125I-[His]hCGRP I binding was inhibited by the related peptides and their half-maximal inhibitory concentrations (IC50) were: cCGRP (0.1 nM), rat CGRP I and human CGRP I and II (1.0-2.0 nM), fragment of hCGRP I (8-37) (150 nM), human IAPP (440 nM). The non-amidated form of hIAPP; human diabetes-associated peptide (hDAP) did not inhibit the binding of 125I-[His]hCGRP I and sCT was only effective at a high concentration (1 microM). Binding of 125I-[His]hCGRP I was dose dependently inhibited by guanosine-5'-O-(3-thiotriphosphate) or (GTP gamma S) and a 70% reduction of binding was obtained with 0.1 mM GTP gamma S. The IC50 value of cCGRP (0.1 nM) was increased 100-fold in the presence of 0.1 mM GTP gamma S. Human CGRP I and cCGRP at 2.5 microM did not stimulate the activity of hamster insulinoma cell membranes adenylate cyclase, while glucagon (1 microM) induced a 2-fold increase. Thus, specific CGRP receptors present in hamster beta cells are associated with G protein (s) and IAPP can interact with these receptors. These results and the observation that cCGRP and hCGRP I did not influence adenylate cyclase activity provide further evidence for CGRP receptor subtypes.
Barakat
A
A
Institut National de la Santé et de la Recherche Médicale U.55, Hôpital Saint-Antoine, Paris, France.
Rosselin
G
G
Marie
J C
JC
D000255:Adenosine Triphosphate / Q000378:metabolism; D000682:Amyloid / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002116:Calcitonin / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002645:Chickens; D006224:Cricetinae; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D007340:Insulinoma / Q000378:metabolism*; D058228:Islet Amyloid Polypeptide; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D051381:Rats; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000378:metabolism*
D000682:Amyloid; D058228:Islet Amyloid Polypeptide; D018015:Receptors, Calcitonin Gene-Related Peptide; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide