title: Somatostatin activation of mitogen-activated protein kinase via somatostatin receptor 1 (SSTR1).
abstract: Hormones and growth factors regulate cell growth via the mitogen-activated protein (MAP) kinase cascade. Here we examine the actions of the hormone somatostatin on the MAP kinase cascade through one of its two major receptor subtypes, the somatostatin receptor 1 (SSTR1) stably expressed in CHO-K1 cells. Somatostatin antagonizes the proliferative effects of fibroblast growth factor in CHO-SSTR1 cells via the SSTR1 receptor. However, in these cells, somatostatin robustly activates MAP kinase (also called extracellular signal regulated kinase; ERK) and augments fibroblast growth factor-stimulated ERK activity. We show that the activation of ERK via SSTR1 is pertussis toxin sensitive and requires the small G protein Ras, phosphatidylinositol 3-kinase, the serine/threonine kinase Raf-1, and the protein tyrosine phosphatase SHP-2. The activation of ERK by SSTR1 increased the expression of the cyclin-dependent protein kinase inhibitor p21(cip1/WAF1). Previous studies have suggested that somatostatin-stimulated protein tyrosine phosphatase activity mediates the growth effects of somatostatin. Our data suggest that SHP-2 stimulation by SSTR1 may mediate some of these effects through the activation of the MAP kinase cascade and the expression of p21(cip1/WAF1).
authors.affiliation: Institute of Pharmacology, School of Medicine, University of Genoa, Italy.
authors.forename: T
authors.initials: T
authors.lastname: Florio
authors.forename: H
authors.initials: H
authors.lastname: Yao
authors.forename: K D
authors.initials: KD
authors.lastname: Carey
authors.forename: T J
authors.initials: TJ
authors.lastname: Dillon
authors.forename: P J
authors.initials: PJ
authors.lastname: Stork
mesh_terms: D000818:Animals; D016466:CHO Cells / Q000187:drug effects / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D002455:Cell Division; D006224:Cricetinae; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D037342:Pertussis Toxin; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D013004:Somatostatin / Q000378:metabolism* / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D047908:Intracellular Signaling Peptides and Proteins; D017481:Receptors, Somatostatin; D011994:Recombinant Proteins; D010566:Virulence Factors, Bordetella; C101130:somatostatin receptor type 1; D016222:Fibroblast Growth Factor 2; D013004:Somatostatin; D037342:Pertussis Toxin; D011505:Protein-Tyrosine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D019204:GTP-Binding Proteins; D018631:ras Proteins