Related Experiment Videos
Involvement of protein kinase A in fibroblast growth factor-2-activated transcription
J P Pursiheimo1, M Jalkanen, K Taskén
1Turku Centre for Biotechnology, University of Turku, Tykistökatu 6B, BioCity, FIN-20520 Turku, Finland.
Abstract:
Polypeptide growth factors activate common signal transduction pathways, yet they can induce transcription of different target genes. The mechanisms that control this specificity are not completely understood. Recently, we have described a fibroblast growth factor (FGF)-inducible response element, FiRE, on the syndecan-1 gene. In NIH 3T3 cells, the FiRE is activated by FGF-2 but not by several other growth factors, such as platelet-derived growth factor or epidermal growth factor, suggesting that FGF-2 activates signaling pathways that diverge from pathways activated by other growth factors. In this paper, we report that the activation of FiRE by FGF-2 requires protein kinase A (PKA) in NIH 3T3 cells. The PKA-specific inhibitor H-89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide) blocked the FGF-2-induced activation of FiRE, the transcription of the syndecan-1 gene, and cell proliferation. Also, expression of a dominant-negative form of PKA inhibited the FGF-2-induced FiRE activation and the transcription of the syndecan-1 gene. The binding of activator protein-1 transcription-factor complexes, required for the activation of FiRE, was blocked by inhibition of PKA activity before FGF-2 treatment. In accordance with the growth factor specificity of FiRE, the activity of PKA was stimulated by FGF-2 but not by platelet-derived growth factor or epidermal growth factor. Furthermore, a portion of the PKA catalytic subunit pool was translocated to the nucleus by FGF-2. Noticeably, the total cellular cAMP concentration was not affected by FGF-2 stimulus. We propose that the FGF-2-selective transcriptional activation through FiRE is caused by the ability of FGF-2 to control PKA activity.
Insights
Fibroblast growth factor-2 (FGF-2) selectively activates the syndecan-1 gene through a specific DNA element (FiRE) by engaging protein kinase A (PKA). This FGF-2-induced PKA activation, independent of cAMP, is crucial for FiRE-mediated gene transcription and cell proliferation.
Area of Science:
- Molecular Biology
- Cell Signaling
- Gene Regulation
Background:
- Polypeptide growth factors trigger common signaling pathways but can elicit distinct gene expression profiles.
- Specificity mechanisms controlling differential gene transcription remain incompletely understood.
- A fibroblast growth factor (FGF)-inducible response element (FiRE) in the syndecan-1 gene is activated by FGF-2 but not other growth factors.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying FGF-2-specific transcriptional activation of the syndecan-1 gene via FiRE.
- To investigate the role of protein kinase A (PKA) in FGF-2-mediated signaling and gene regulation.
Main Methods:
- Utilized NIH 3T3 cells for experiments.
- Employed the PKA-specific inhibitor H-89 and a dominant-negative PKA construct.
- Assessed FiRE activation, syndecan-1 gene transcription, cell proliferation, activator protein-1 (AP-1) complex binding, and PKA activity/localization.
Main Results:
- FGF-2-induced FiRE activation, syndecan-1 transcription, and cell proliferation were blocked by PKA inhibition.
- FGF-2 specifically stimulated PKA activity, not other growth factors, and caused PKA catalytic subunit translocation to the nucleus.
- AP-1 binding to FiRE was dependent on PKA activity prior to FGF-2 stimulation; cellular cAMP levels remained unaffected.
Conclusions:
- FGF-2 selectively activates syndecan-1 transcription through FiRE by modulating PKA activity, not by altering overall cAMP levels.
- PKA acts as a critical mediator in the FGF-2 signaling pathway, controlling the binding of transcription factors necessary for gene activation.
- This study reveals a novel mechanism of growth factor-specific gene regulation involving PKA-dependent signaling pathways.