Platelet derived growth factor induced tenascin-C transcription is phosphoinositide 3-kinase/Akt-dependent and mediated by Ets family transcription factors.
Previous studies have identified several cytokines as inducers of tenascin-C (TN-C) expression in various tissue culture systems. However, the signaling pathways of the regulation of TN-C expression are almost unknown. In this study, we clarified the molecular mechanism(s) underlying the regulation of the TN-C gene by platelet derived growth factor (PDGF) in cultured human dermal fibroblasts. PDGF induced the expression of TN-C protein as well as mRNA in a dose-dependent manner. Actinomycin D, an RNA synthesis inhibitor, significantly blocked the PDGF- mediated upregulation of TN-C mRNA expression, whereas cycloheximide, a protein synthesis inhibitor, did not. The PDGF- mediated induction of TN-C expression was inhibited by the treatment of fibroblasts with a selective phosphoinositide 3-kinase ( PI3K) inhibitor, wortmannin, or LY294002. These results suggest that PDGF induced the expression of TN-C at a transcriptional level via phosphoinositide3-kinase/Akt signaling pathways. We performed serial 5' deletions and a transient transfection analysis to define the region in the TN-C promoter mediating the responsiveness to PDGF. Overexpression of Sp1, Ets1, or Ets2 activated the TN-C promoter and superinduced TN-C promoter activity stimulated by PDGF, whereas overexpression of Fli1 inhibited the effects of PDGF on TN-C expression. Mutation of the Sp1/3 binding sites or Ets binding sites in the TN-C promoter region responsible to PDGF abrogated the PDGF-inducible promoter activity. Immunoprecipitation analysis revealed that Sp1, Ets1, and Ets2 form a transcriptionally active complex. On the other hand, the interaction of Fli1 with Sp1 decreased after PDGF treatment. These results suggest that the upregulation of TN-C expression by PDGF involves Ets family transcription factors, co-operating with Sp1.[1]References
- Platelet derived growth factor induced tenascin-C transcription is phosphoinositide 3-kinase/Akt-dependent and mediated by Ets family transcription factors. Jinnin, M., Ihn, H., Asano, Y., Yamane, K., Trojanowska, M., Tamaki, K. J. Cell. Physiol. (2006) [Pubmed]
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