CCAAT/enhancer-binding protein-homologous protein expression and transcriptional activity are regulated by 3',5'-cyclic adenosine monophosphate in thyroid cells.
The cAMP pathway activates p38-MAPKs in the FRTL-5 rat thyroid cell line, contributing to the increased expression of the Na+/I- symporter (NIS) mRNA. This study investigates the cAMP-dependent expression and transcriptional activity of the p38-MAPK substrate CCAAT/enhancer-binding protein-homologous protein (CHOP). CHOP is expressed in the rat thyroid gland and in confluent PCCL3 and FRTL-5 cells. In FRTL-5 cells, TSH withdrawal induced a rapid down-regulation of CHOP that could be prevented by forskolin (Fk). Moreover, TSH and Fk were able to reinduce CHOP expression. The use of pharmacological inhibitors indicated that cAMP-induced CHOP expression was dependent on protein kinase A (PKA), mammalian target of rapamycin pathway, and reactive oxygen species. Transfection of a CHOP trans- reporting system revealed strong stimulation of the transcriptional activity of CHOP by Fk, by chlorophenylthio-cAMP, and by the catalytic subunit of PKA. CHOP transcriptional activity was significantly reduced by the p38-MAPK inhibitor SB203580, by transfection of a dominant-negative variant of p38alpha-MAPK, or by mutation of two serine residues in CHOP targeted by p38-MAPKs. Finally, cAMP-induced NIS mRNA expression was higher in FRTL-5 cells stably transfected with CHOP cDNA than in control cells. Likewise, the activity of the NIS promoter was higher in cells overexpressing CHOP than in control cells. These findings suggest that the stimulation of CHOP expression and transcriptional activity by the cAMP pathway may contribute to the regulation of genes involved in thyroid cell differentiation.
Pomerance
Martine
M
Unité 486, Institut National de la Santé et de la Recherche Médicale-Paris XI, Faculté de Pharmacie, 5 rue Jean-Baptiste Clément, 92296 Châtenay-Malabry Cédex, France. martine.pomerance@cep.u-psud.fr.
Carapau
Daniel
D
Chantoux
Françoise
F
Mockey
Michaël
M
Correze
Claude
C
Francon
Jacques
J
Blondeau
Jean-Paul
JP
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D002352:Carrier Proteins / Q000494:pharmacology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D027981:Symporters / Q000235:genetics; D013961:Thyroid Gland / Q000166:cytology* / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases; D000099209:Sodium-Iodide Symporters
D000975:Antioxidants; D022762:CCAAT-Enhancer-Binding Proteins; D002352:Carrier Proteins; D005576:Colforsin; D000242:Cyclic AMP; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D012333:RNA, Messenger; D027981:Symporters; D013972:Thyrotropin; D051742:Transcription Factor CHOP; D014157:Transcription Factors; D048051:p38 Mitogen-Activated Protein Kinases; D000099209:Sodium-Iodide Symporters; C497251:Ddit3 protein, rat; C015482:protein kinase modulator