title: The expression of the thyroid-stimulating hormone (TSH) receptor and the cAMP-dependent protein kinase RII beta regulatory subunit confers TSH-cAMP-dependent growth to mouse fibroblasts.
abstract: TSH activates its specific receptor in thyroid cells and induces cAMP, a robust stimulator of thyroid cell proliferation. Conversely, cAMP is a potent inhibitor of growth in mouse fibroblasts. To dissect the signals mediating cAMP-dependent growth, we have expressed in mouse fibroblasts the human thyrotropin receptor (TSHR) or a constitutively active mutant, under the control of the tetracyclin promoter. Both TSHR and cAMP levels were modulated by tetracyclin. In the presence of serum, activation of TSHR by TSH induced growth arrest. In the absence of serum, cells expressing TSHR stimulated with TSH, replicated their DNA, but underwent apoptosis. Co-expression of cAMP-dependent protein kinase (PKA) regulatory subunit type II (RIIbeta) inhibited apoptosis and stimulated the growth of cells only in the presence of TSH. Expression of RIIbeta-PKA, in the absence of TSHR, induced apoptosis, which was reversed by cAMP. Growth, stimulated by TSHR-RIIbeta-PKA in mouse fibroblasts, was also dependent on Rap1 activity, indicating cAMP-dependent growth in thyroid cells. As for the molecular mechanism underlying these effects, we found that in normal fibroblasts, TSH induced AKT and ERK1/2 only in cells expressing TSHR and RII. Similarly, activation of TSHR increased cAMP levels greatly, but was unable to stimulate CREB phosphorylation and transcription of cAMP-induced genes in the absence of RII. These data provide a simple explanation for the anti-proliferative and proliferative effects of cAMP in different cell types and indicate that RII-PKAII complements TSHR action by stably propagating robust cAMP signals in cell compartments.
authors.affiliation: Dipartimento di Medicina Sperimentale e Patologia, Università La Sapienza, 00161 Roma, Italy. Antoni.Procellini@uniroma1.it
authors.forename: Antonio
authors.initials: A
authors.lastname: Porcellini
authors.forename: Samantha
authors.initials: S
authors.lastname: Messina
authors.forename: Giorgia
authors.initials: G
authors.lastname: De Gregorio
authors.forename: Antonio
authors.initials: A
authors.lastname: Feliciello
authors.forename: Annalisa
authors.initials: A
authors.lastname: Carlucci
authors.forename: Mariavittoria
authors.initials: M
authors.lastname: Barone
authors.forename: Antonietta
authors.initials: A
authors.lastname: Picascia
authors.forename: Antonio
authors.initials: A
authors.lastname: De Blasi
authors.forename: Enrico V
authors.initials: EV
authors.lastname: Avvedimento
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D015152:Blotting, Northern; D015153:Blotting, Western; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D000242:Cyclic AMP / Q000378:metabolism; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D005799:Genes, Dominant; D020287:In Situ Nick-End Labeling; D051379:Mice; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D011989:Receptors, Thyrotropin / Q000096:biosynthesis*; D013752:Tetracycline / Q000494:pharmacology; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D012333:RNA, Messenger; D011989:Receptors, Thyrotropin; D000242:Cyclic AMP; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D013752:Tetracycline