Signal transduction of the GLP-1-receptor cloned from a human insulinoma.
GLP-1 (glucagon-like peptide 1 (7-36) amide) plays an important role in the regulation of insulin secretion and proinsulin gene expression of pancreatic beta-cells. Patients with insulinoma tumors show uncontrolled insulin hypersecretion. This study demonstrates the molecular cloning of a cDNA for the GLP-1 receptor from a human insulinoma employing a lambda-gt11 cDNA library. The cloned cDNA encoded a seven transmembrane domain protein of 463 amino acids which showed high homology to the GLP-1 receptor in normal human pancreas. Four amino acid exchanges were found in comparison to a receptor sequence obtained from regular pancreatic islets. When transfected transiently into COS-7 or stably into fibroblast CHL cells a high affinity receptor was expressed which coupled to the adenylate cyclase with normal basal cAMP and increasing intracellular cAMP levels under GLP-1 stimulation. The receptor accepted GLP-1 and the non-mammalian agonist exendin-4 as high affinity ligands. In transfected COS-7 cells, GLP-1 did not influence intracellular calcium, whereas in the stably transfected fibroblasts GLP-1 transiently increased intracellular calcium to a small extent. The understanding of GLP-1 receptor regulation and signal transduction will aid in the discovery of compounds that act as agonists of the GLP-1 receptor for potential use in the treatment of diabetes and will facilitate the understanding of its expression under normal and pathophysiological conditions.
van Eyll
B
B
Clinical Research Unit for Gastrointestinal Endocrinology, Philipps University of Marburg, Germany.
Lankat-Buttgereit
B
B
Bode
H P
HP
Göke
R
R
Göke
B
B
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D005934:Glucagon; D052216:Glucagon-Like Peptide 1; D004763:Glucagon-Like Peptides; D006801:Humans; D007340:Insulinoma / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D012313:RNA / Q000302:isolation & purification; D051381:Rats; D018027:Receptors, Glucagon / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014162:Transfection
D010446:Peptide Fragments; D018027:Receptors, Glucagon; D011994:Recombinant Proteins; C055453:glucagon-like peptide 1 (7-36)amide; D004763:Glucagon-Like Peptides; D012313:RNA; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D002118:Calcium