title: G13-dependent activation of MAPK by thyrotropin.
abstract: Stimulation of the thyrotropin receptor (TSHR) activates G proteins of all four subfamilies (G(s), G(i/o), G(q/11), and G(12/13)). Whereas G(s)/cAMP-dependent cellular responses upon TSHR stimulation are well established, other signaling pathways are less characterized. We evaluated TSH-elicited cellular responses in human follicular thyroid carcinoma cells stably expressing the TSHR and in primary, nonneoplastic human thyrocytes. In these cellular models, stimulation with TSH caused activation of p44/42 MAPK and subsequent induction of c-Fos. MAPK stimulation occurred independently of G(s), G(i/o), and G(q/11) signaling. Dominant negative constructs of G(12) or G(13) as well as shRNA-mediated suppression of Galpha(12) or Galpha(13) revealed that MAPK activation was dependent on G(13) but not on G(12) signaling. Furthermore, G(13)-dependent transactivation of the epidermal growth factor receptor was necessary for MAPK activation in follicular carcinoma cells, whereas EGFR was not involved in MAPK activation in nonneoplastic primary thyrocytes. The use of bacterial inhibitors of monomeric GTPases revealed that MAPK activation proceeded independently of Rho proteins but was clostridial toxin B-sensitive, suggesting involvement of Cdc42 or Rac. Thus, our data shed new light on cAMP-independent TSHR signaling and identify the first G(13)-dependent TSHR signaling pathway in human thyrocytes.
authors.affiliation: Institut für Pharmakologie und Toxikologie, Philipps-Universität, Karl-von-Frisch-Strasse 1, Marburg, Germany.
authors.forename: Thomas R H
authors.initials: TR
authors.lastname: Büch
authors.forename: Heike
authors.initials: H
authors.lastname: Biebermann
authors.forename: Hermann
authors.initials: H
authors.lastname: Kalwa
authors.forename: Olaf
authors.initials: O
authors.lastname: Pinkenburg
authors.forename: Denise
authors.initials: D
authors.lastname: Hager
authors.forename: Holger
authors.initials: H
authors.lastname: Barth
authors.forename: Klaus
authors.initials: K
authors.lastname: Aktories
authors.forename: Andreas
authors.initials: A
authors.lastname: Breit
authors.forename: Thomas
authors.initials: T
authors.lastname: Gudermann
mesh_terms: D051702:Activating Transcription Factor 6; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D066246:ErbB Receptors / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011989:Receptors, Thyrotropin / Q000235:genetics / Q000378:metabolism; D013972:Thyrotropin / Q000494:pharmacology*; D015533:Transcriptional Activation / Q000235:genetics
chemical_list: C487807:ATF6B protein, human; D051702:Activating Transcription Factor 6; D050976:Basic-Leucine Zipper Transcription Factors; D021122:Protein Subunits; D016760:Proto-Oncogene Proteins c-fos; D011989:Receptors, Thyrotropin; D013972:Thyrotropin; D066246:ErbB Receptors; D017868:Cyclic AMP-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D043802:GTP-Binding Protein alpha Subunits, Gq-G11