Transforming growth factor-beta upregulates the expression of integrin and related proteins in MRC-5 human myofibroblasts.
Myofibroblasts are defined as fibroblasts that express certain features of smooth muscle differentiation. Activation of myofibroblasts plays a central role in fibrosis. Transforming growth factor-beta (TGF-beta) is a potent activator of myofibroblasts; namely, TGF-beta causes changes in myofibroblast phenotypes including morphological alterations and the expression of alpha-smooth muscle actin (alpha-SMA), a marker of myofibroblasts. Because it has been well known that humoral factors, especially, TGF-beta, and extracellular matrix components cause myofibroblast activation, we examined the expression of integrin and related proteins during activation of MRC-5 human myofibroblasts with TGF-beta. Western blot analysis revealed that TGF-beta treatment for 3 days increased the expression of alpha-SMA, which was also immunocytochemically observed as actin stress fibers. In the early phase of TGF-beta treatment, fibronectin expression was greatly increased, followed by the increased expression of integrin alphav and alpha11 and integrin beta1 and beta3. Co-immunoprecipitation assays revealed that the integrin alphav subunit was co-precipitated with integrin beta1 and beta3, and that integrin beta1 was co-precipitated with alpha11, alphav, alpha2, and alpha5. The expression of focal adhesion kinase and integrin-linked kinase proteins was also upregulated by treatment with TGF-beta. In addition, the expression of type I collagen mRNA was increased by TGF-beta, but not type III collagen mRNA, as judged by real-time PCR analysis. These results suggest the possibility that TGF-beta induces fibronectin expression in MRC-5 cells, which subsequently induces the expression of integrin receptors, alphavbeta3, alphavbeta1, and alpha11beta1. This report also shows that expression of integrin alpha11 is upregulated during the TGF-beta-mediated activation of myofibroblasts.
Honda
Eiko
E
Life Science Research Institute, Kinki University, Sayama, Osaka, Japan.
Yoshida
Koji
K
Munakata
Hiroshi
H
D000199:Actins / Q000378:metabolism; D000818:Animals; D048430:Cell Shape; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology*; D015854:Up-Regulation
D000199:Actins; D005353:Fibronectins; D016023:Integrins; D021122:Protein Subunits; D016212:Transforming Growth Factor beta