Interleukin-1 beta induction of matrix metalloproteinase-1 transcription in chondrocytes requires ERK-dependent activation of CCAAT enhancer-binding protein-beta.
Interleukin-1 beta (IL-1beta) is a central mediator of inflammation and connective tissue destruction in rheumatoid arthritis. IL-1beta activates articular chondrocytes to produce matrix metalloproteinase-1 (MMP-1), an enzyme capable of dismantling the collagen scaffold of articular cartilage. To define the transcription factors and signaling intermediates that activate MMP-1 transcription in chondrocytes, we performed transient transfection of MMP-1 promoter constructs followed by reporter assays. These studies identified an IL-1beta-responsive region of the human MMP-1 promoter that contains a consensus CCAAT enhancer-binding protein (C/EBP) binding site. Deletion of this site reduced overall transcriptional activity of the MMP-1 promoter, as well as decreased fold induction by IL-1beta. IL-1beta stimulation of chondrocytes increased binding of C/EBP-beta to the MMP-1 C/EBP site. Extracellular signal regulated kinase (ERK) pathway-dependent phosphorylation of C/EBP-beta on threonine 235 activates this transcription factor. Here we show that IL-1beta stimulation of chondrocytes induced phosphorylation of C/EBP-beta on threonine 235, and that the ERK pathway inhibitor PD98059 reduced this phosphorylation. We further show that PD98059 reduces IL-1beta-induced MMP-1 mRNA expression in chondrocytes. Moreover, inhibition of the ERK pathway by expression of dominant-negative forms of ERK1 and ERK2 impaired the ability of IL-1beta to transactivate the MMP-1 promoter. Our findings demonstrate a novel role for C/EBP-beta in IL-1beta-induced connective tissue disease and define a new nuclear target for the ERK pathway in MMP-1 gene activation.
Raymond
Lauren
L
Department of Medicine, Dartmouth Medical School, Lebanon, New Hampshire, USA.
Eck
Sarah
S
Mollmark
Jessica
J
Hays
Ezra
E
Tomek
Ivan
I
Kantor
Stephen
S
Elliott
Sarah
S
Vincenti
Matthew
M
D000818:Animals; D001483:Base Sequence; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D020935:MAP Kinase Signaling System; D020781:Matrix Metalloproteinase 1 / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011817:Rabbits; D014158:Transcription, Genetic / Q000235:genetics; D015533:Transcriptional Activation
D022782:CCAAT-Enhancer-Binding Protein-beta; D007375:Interleukin-1; D048049:Extracellular Signal-Regulated MAP Kinases; D020781:Matrix Metalloproteinase 1