Regulation of the transforming growth factor beta-responsive transcription factor CTF-1 by calcineurin and calcium/calmodulin-dependent protein kinase IV.
Transforming growth factor beta (TGF-beta) is a pluripotent peptide hormone that regulates various cellular activities, including growth, differentiation, and extracellular matrix protein gene expression. We previously showed that TGF-beta induces the transcriptional activation domain (TAD) of CTF-1, the prototypic member of the CTF/NF-I family of transcription factors. This induction correlates with the proposed role of CTF/NF-I binding sites in collagen gene induction by TGF-beta. However, the mechanisms of TGF-beta signal transduction remain poorly understood. Here, we analyzed the role of free calcium signaling in the induction of CTF-1 transcriptional activity by TGF-beta. We found that TGF-beta stimulates calcium influx and mediates an increase of the cytoplasmic calcium concentration in NIH3T3 cells. TGF-beta induction of CTF-1 is inhibited in cells pretreated with thapsigargin, which depletes the endoplasmic reticulum calcium stores, thus further arguing for the potential relevance of calcium mobilization in TGF-beta action. Consistent with this possibility, expression of a constitutively active form of the calcium/calmodulin-dependent phosphatase calcineurin or of the calcium/calmodulin-dependent kinase IV (DeltaCaMKIV) specifically induces the CTF-1 TAD and the endogenous mouse CTF/NF-I proteins. Both calcineurin- and DeltaCaMKIV-mediated induction require the previously identified TGF-beta-responsive domain of CTF-1. The immunosuppressants cyclosporin A and FK506 abolish calcineurin-mediated induction of CTF-1 activity. However, TGF-beta still induces the CTF-1 TAD in cells treated with these compounds or in cells overexpressing both calcineurin and DeltaCaMKIV, suggesting that other calcium-sensitive enzymes might mediate TGF-beta action. These results identify CTF/NF-I as a novel calcium signaling pathway-responsive transcription factor and further suggest multiple molecular mechanisms for the induction of CTF/NF-I transcriptional activity by growth factors.
Alevizopoulos
A
A
Laboratory of Molecular Biotechnology, Center of Biotechnology UNIL-EPFL, DC-IGC, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
Dusserre
Y
Y
Rüegg
U
U
Mermod
N
N
D016475:3T3 Cells; D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins; D019703:Calcineurin; D002118:Calcium / Q000378:metabolism; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D016572:Cyclosporine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051379:Mice; D051839:NFI Transcription Factors; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D015398:Signal Transduction; D016559:Tacrolimus / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D022762:CCAAT-Enhancer-Binding Proteins; C077305:CTF-1 transcription factor; D002148:Calmodulin-Binding Proteins; D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D016572:Cyclosporine; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517685:Camk4 protein, mouse; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D002118:Calcium; D016559:Tacrolimus