Identification of glucagon-like peptide-2 (GLP-2)-activated signaling pathways in baby hamster kidney fibroblasts expressing the rat GLP-2 receptor.
Glucagon-like peptide-2 (GLP-2) promotes the expansion of the intestinal epithelium through stimulation of the GLP-2 receptor, a recently identified member of the glucagon-secretin G protein-coupled receptor superfamily. Although activation of G protein-coupled receptors may lead to stimulation of cell growth, the mechanisms transducing the GLP-2 signal to mitogenic proliferation remain unknown. We now report studies of GLP-2R signaling in baby hamster kidney (BHK) cells expressing a transfected rat GLP-2 receptor (BHK-GLP-2R cells). GLP-2, but not glucagon or GLP-1, increased the levels of cAMP and activated both cAMP-response element- and AP-1-dependent transcriptional activity in a dose-dependent manner. The activation of AP-1-luciferase activity was protein kinase A (PKA) -dependent and markedly diminished in the presence of a dominant negative inhibitor of PKA. Although GLP-2 stimulated the expression of c-fos, c-jun, junB, and zif268, and transiently increased p70 S6 kinase in quiescent BHK-GLP-2R cells, GLP-2 also inhibited extracellular signal-regulated kinase 1/2 and reduced serum-stimulated Elk-1 activity. Furthermore, no rise in intracellular calcium was observed following GLP-2 exposure in BHK-GLP-2R cells. Although GLP-2 stimulated both cAMP accumulation and cell proliferation, 8-bromo-cyclic AMP alone did not promote cell proliferation. These findings suggest that the GLP-2R may be coupled to activation of mitogenic signaling in heterologous cell types independent of PKA via as yet unidentified downstream mediators of GLP-2 action in vivo.
Yusta
B
B
Department of Medicine, The Toronto General Hospital, University of Toronto, Toronto, Ontario M5G 2C4, Canada.
Somwar
R
R
Wang
F
F
Munroe
D
D
Grinstein
S
S
Klip
A
A
Drucker
D J
DJ
D000818:Animals; D002455:Cell Division; D002460:Cell Line; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005347:Fibroblasts; D005768:Gastrointestinal Hormones / Q000494:pharmacology / Q000502:physiology; D005934:Glucagon / Q000494:pharmacology; D052216:Glucagon-Like Peptide 1; D053767:Glucagon-Like Peptide 2; D000067757:Glucagon-Like Peptide-1 Receptor; D007668:Kidney; D008156:Luciferases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology* / Q000502:physiology; D010766:Phosphorylation; D011498:Protein Precursors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D018027:Receptors, Glucagon / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
D017362:Cyclic AMP Response Element-Binding Protein; D005768:Gastrointestinal Hormones; C000593835:Glp1r protein, rat; D053767:Glucagon-Like Peptide 2; D000067757:Glucagon-Like Peptide-1 Receptor; D010446:Peptide Fragments; D010455:Peptides; D011498:Protein Precursors; D011518:Proto-Oncogene Proteins; D018027:Receptors, Glucagon; D011994:Recombinant Proteins; D018808:Transcription Factor AP-1; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D008156:Luciferases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases