Transforming growth factor-beta1 induces interleukin-6 expression via activating protein-1 consisting of JunD homodimers in primary human lung fibroblasts.
Transforming growth factor (TGF)-beta1 induces extracellular matrix deposition and proliferation of mesenchymal cells. We recently reported that interleukin (IL)-6 is an essential mediator of growth factor-induced proliferation of lung fibroblasts. Here, we demonstrate by reverse transcriptase polymerase chain reaction and enzyme-linked immunoassay that TGF-beta1 is a potent inducer of IL-6 mRNA and protein in primary human lung fibroblasts. Transient transfections of fibroblasts with a luciferase reporter gene construct containing nucleotides -651 to +1 of the human IL-6 promoter revealed that TGF-beta1 also potently activated IL-6 promoter activity. Progressive 5'-deletions and site-directed mutagenesis of the parental construct located the TGF-beta1-responsive cis-regulatory element to a known activating protein-1 (AP-1) sequence (nucleotides -284 to -276). Gel shift analyses revealed that AP-1 DNA binding activity in nuclear extracts was increased 30 min after stimulation with TGF-beta1. In contrast, neither CCAAT enhancer-binding protein-beta, NF-kappaB, nor Sp1 were activated by TGF-beta1. Supershift analyses demonstrated that the AP-1 complex induced by TGF-beta1 was composed of Jun isoforms and absent of Fos isoforms. Moreover, this complex was found to be a JunD homodimer. Our data thus demonstrate that TGF-beta1 is a potent inducer of IL-6 in primary human lung fibroblasts. The TGF-beta1-activated JunD homodimer may be essential for a majority of the biological effects induced by TGF-beta1 in this cell type, such as proliferation and extracellular matrix synthesis.
Eickelberg
O
O
Department of Research and Internal Medicine, University Hospital, 4031 Basel, Switzerland. oliver.eickelberg@yale.edu
Pansky
A
A
Mussmann
R
R
Bihl
M
M
Tamm
M
M
Hildebrand
P
P
Perruchoud
A P
AP
Roth
M
M
D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D019281:Dimerization; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics*; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D017931:DNA Primers; D015850:Interleukin-6; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta