title: Functional studies of a glucagon receptor isolated from frog Rana tigrina rugulosa: implications on the molecular evolution of glucagon receptors in vertebrates.
abstract: In this report, the first amphibian glucagon receptor (GluR) cDNA was characterized from the liver of the frog Rana tigrina rugulosa. Functional expression of the frog GluR in CHO and COS-7 cells showed a high specificity of the receptor towards human glucagon with an EC(50) value of 0.8+/-0.5 nM. The binding of radioiodinated human glucagon to GluR was displaced in a dose-dependent manner only with human glucagon and its antagonist (des-His(1)-[Nle(9)-Ala(11)-Ala(16)]) with IC(50) values of 12.0+/-3. 0 and 7.8+/-1.0 nM, respectively. The frog GluR did not display any affinity towards fish and human GLP-1s, and towards glucagon peptides derived from two species of teleost fishes (goldfish, zebrafish). These fish glucagons contain substitutions in several key residues that were previously shown to be critical for the binding of human glucagon to its receptor. By RT-PCR, mRNA transcripts of frog GluR were located in the liver, brain, small intestine and colon. These results demonstrate a conservation of the functional characteristics of the GluRs in frog and mammalian species and provide a framework for a better understanding of the molecular evolution of the GluR and its physiological function in vertebrates.
authors.affiliation: Department of Zoology, University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: E S
authors.initials: ES
authors.lastname: Ngan
authors.forename: L S
authors.initials: LS
authors.lastname: Chow
authors.forename: D L
authors.initials: DL
authors.lastname: Tse
authors.forename: X
authors.initials: X
authors.lastname: Du
authors.forename: Y
authors.initials: Y
authors.lastname: Wei
authors.forename: S
authors.initials: S
authors.lastname: Mojsov
authors.forename: B K
authors.initials: BK
authors.lastname: Chow
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D016466:CHO Cells / Q000378:metabolism; D019556:COS Cells; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D019143:Evolution, Molecular; D000077270:Exenatide; D005934:Glucagon / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D052216:Glucagon-Like Peptide 1; D006801:Humans; D020128:Inhibitory Concentration 50; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000378:metabolism / Q000494:pharmacology; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D010455:Peptides / Q000378:metabolism / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011498:Protein Precursors / Q000378:metabolism / Q000494:pharmacology; D011898:Ranidae / Q000235:genetics*; D018027:Receptors, Glucagon / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012633:Secretin / Q000378:metabolism / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism / Q000494:pharmacology; D014688:Venoms; D014714:Vertebrates / Q000502:physiology*; D015027:Zebrafish
chemical_list: C495401:ADCYAP1 protein, human; D009479:Neuropeptides; D010446:Peptide Fragments; D010455:Peptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011498:Protein Precursors; D018027:Receptors, Glucagon; D011994:Recombinant Proteins; D014688:Venoms; C121627:glucagon-amide, desHis(1)-Nle(9)-Ala(11,16)-; D012633:Secretin; D014660:Vasoactive Intestinal Peptide; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000077270:Exenatide; D000242:Cyclic AMP