title: Activated G protein-coupled receptor induces tyrosine phosphorylation of STAT3 and agonist-selective serine phosphorylation via sustained stimulation of mitogen-activated protein kinase. Resultant effects on cell proliferation.
abstract: The peptide hormone somatostatin exhibits antiproliferative activity by interacting with the G protein-coupled sst2 or sst5 receptor types. We show here that somatostatin at the human recombinant sst4 receptor induced a concentration-dependent increase in proliferation (EC50 20 nM) with a maximal response 5-fold greater than that produced by its synthetic analog, L-362,855. Analysis of the phosphorylation status of extracellular signal-regulated kinase (ERK)1 and ERK2 showed temporal differences in the changes evoked by the agonists. Phosphorylation induced by somatostatin (100 nM) peaked 10 min after the application and produced a response that continued for at least 4 h. In contrast, L-362,855 (1 microM) showed transient phosphorylation that had declined to basal levels by 1 h. However, both agonists induced rapid and sustained tyrosine phosphorylation of signal transducer and activator of transcription 3 (STAT3) which was pertussis toxin-insensitive. Serine phosphorylation of STAT3 was only apparent after somatostatin treatment and was abolished by pertussis toxin or PD 98059, together with the associated increases in proliferation. Mitogen-activated protein/ERK kinase-1 inhibition also decreased the time interval over which somatostatin-induced ERK phosphorylation was observed (<2 h). We conclude that the difference in the magnitude of the proliferative response evoked by the two agonists at the sst4 receptor can be accounted for by their differential ability to phosphorylate STAT3 on serine residues and supports the concept that selective signaling can be achieved through pharmacological diversity.
authors.affiliation: Glaxo Institute of Applied Pharmacology, Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QJ, United Kingdom.
authors.forename: L A
authors.initials: LA
authors.lastname: Sellers
authors.forename: W
authors.initials: W
authors.lastname: Feniuk
authors.forename: P P
authors.initials: PP
authors.lastname: Humphrey
authors.forename: H
authors.initials: H
authors.lastname: Lauder
mesh_terms: D000818:Animals; D016466:CHO Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D048369:MAP Kinase Kinase 1; D008565:Membrane Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D010456:Peptides, Cyclic / Q000494:pharmacology; D037342:Pertussis Toxin; D010766:Phosphorylation; D015221:Potassium Channels / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins; D017481:Receptors, Somatostatin / Q000819:agonists / Q000378:metabolism*; D050796:STAT3 Transcription Factor; D012694:Serine / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors; D014443:Tyrosine / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D050807:ets-Domain Protein Elk-1
chemical_list: D004268:DNA-Binding Proteins; C091739:L 362855; D008565:Membrane Proteins; D010456:Peptides, Cyclic; D015221:Potassium Channels; D011518:Proto-Oncogene Proteins; D017481:Receptors, Somatostatin; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D010566:Virulence Factors, Bordetella; D050807:ets-Domain Protein Elk-1; C098681:somatostatin receptor subtype-4; D016222:Fibroblast Growth Factor 2; D014443:Tyrosine; D012694:Serine; D037342:Pertussis Toxin; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases