Differential effects of the immunosuppressant FK-506 on human alpha2(I) collagen gene expression and transforming growth factor beta signaling in normal and scleroderma fibroblasts.
OBJECTIVE
To investigate the effects of FK-506 on the expression of the human alpha2(I) collagen gene and transforming growth factor beta (TGFbeta) signaling in normal and scleroderma fibroblasts.


METHODS
The expression levels of type I procollagen protein and alpha2(I) collagen messenger RNA (mRNA) were analyzed by immunoblotting and Northern blotting, respectively. The promoter activities of alpha2(I) collagen gene and 3TP-Lux were determined by transient transfection assay. Interaction between TGFbeta receptor type I and FK-506 binding protein 12 (FKBP12) was evaluated by immunoprecipitation.


RESULTS
FK-506 did not affect the basal expression of type I procollagen protein or alpha2(I) collagen mRNA, but it significantly reduced the TGFbeta1-induced expression of type I procollagen protein and alpha2(I) collagen mRNA in normal fibroblasts. The effect of FK-506 was regulated posttranscriptionally, but not transcriptionally. In scleroderma fibroblasts, FK-506 significantly reduced the expression of type I procollagen protein and alpha2(I) collagen mRNA through posttranscriptional regulation, but not transcriptional regulation. FK-506 increased the basal activity of the 3TP-Lux promoter, but it did not affect the TGFbeta1-induced promoter activity in normal fibroblasts. In contrast, FK-506 did not affect the basal or the TGFbeta1-induced 3TP-Lux promoter activity in scleroderma fibroblasts. Furthermore, FKBP12, which protects TGFbeta receptor type I from ligand-independent activation by TGFbeta receptor type II, constitutively dissociated from TGFbeta receptor type I in scleroderma fibroblasts.


CONCLUSIONS
FK-506 inhibits alpha2(I) collagen gene expression by reducing the stability of mRNA without exhibiting its activation effect on TGFbeta signaling in scleroderma fibroblasts.
Asano
Yoshihide
Y
University of Tokyo, Tokyo, Japan.
Ihn
Hironobu
H
Yamane
Kenichi
K
Jinnin
Masatoshi
M
Mimura
Yoshihiro
Y
Tamaki
Kunihiko
K
D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D011347:Procollagen / Q000235:genetics / Q000378:metabolism; D012595:Scleroderma, Systemic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D016559:Tacrolimus / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*
D024042:Collagen Type I; D007166:Immunosuppressive Agents; D011347:Procollagen; D016212:Transforming Growth Factor beta; D016559:Tacrolimus