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.
Jinnin
Masatoshi
M
Department of Dermatology, Faculty of Medicine, University of Tokyo, Tokyo, Japan.
Ihn
Hironobu
H
Asano
Yoshihide
Y
Yamane
Kenichi
K
Trojanowska
Maria
M
Tamaki
Kunihiko
K
D001483:Base Sequence; D020405:Dermis / Q000166:cytology / Q000378:metabolism; D005260:Female; D005347:Fibroblasts; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D050783:Proto-Oncogene Proteins c-ets / Q000737:chemistry / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D020218:Response Elements; D015398:Signal Transduction; D019063:Tenascin / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects
D010982:Platelet-Derived Growth Factor; D050783:Proto-Oncogene Proteins c-ets; D012333:RNA, Messenger; D019063:Tenascin; D014157:Transcription Factors; D019869:Phosphatidylinositol 3-Kinases