Role and regulation of the fibroblast growth factor axis in human thyroid follicular cells.
Thyroidal levels of fibroblast growth factor-2 (FGF-2) and fibroblast growth factor receptor 1 (FGFR1) are elevated in human thyroid hyperplasia. To understand the significance of this, effects of FGFR1 activation on normal human thyrocyte growth and function in vitro and the regulation of FGF-2 and FGFR1 expression have been examined. FGF-2 stimulated cell growth, as measured by cell counting, and inhibited thyroid function as measured by 125I uptake. Sensitivity to FGF-2 disappeared after 7 days, although FGFR1 expression was maintained. Thyroid-stimulating hormone (TSH, 300 mU/l) increased FGFR1 mRNA expression within 4 h and protein expression by 8 h. Exogenous FGF-2 decreased FGFR1 protein. Endogenous FGF-2 levels were low (approximately 1-2 pg/microg protein), and TSH treatment decreased these by 50%. Protein kinase C (PKC) activation increased FGF-2 mRNA and FGF-2 secretion within 2 h. This effect was enhanced (4.4-fold) when cells were cultured in TSH. We conclude that TSH stimulates FGFR1 but not FGF-2 expression. PKC activation stimulates FGF-2 synthesis and secretion, and TSH synergizes with PKC activators. Increases in FGFR1 or FGF-2 or in both may contribute to goitrogenesis.
University of Birmingham, Birmingham B15 2TT, UK.
Helen C
HC
Cocks
Stuart
S
Thompson
Frances E
FE
Turner
Ann
A
Logan
Jayne A
JA
Franklyn
John C
JC
Watkinson
Margaret C
MC
Eggo
D002273:Carcinogens / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006044:Goiter, Nodular / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D007454:Iodides / Q000493:pharmacokinetics; D008934:Mitogens / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D051496:Receptor, Fibroblast Growth Factor, Type 1; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013961:Thyroid Gland / Q000166:cytology* / Q000502:physiology*; D013972:Thyrotropin / Q000494:pharmacology
D002273:Carcinogens; D007454:Iodides; D008934:Mitogens; D012333:RNA, Messenger; D017468:Receptors, Fibroblast Growth Factor; D016222:Fibroblast Growth Factor 2; D013972:Thyrotropin; C496348:FGFR1 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D051496:Receptor, Fibroblast Growth Factor, Type 1; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate