src‐related tyrosine kinases regulate transcriptional activation of the interstitial collagenase gene, MMP‐1, in interleukin‐1‐stimulated synovial fibroblasts

Objective. To characterize tyrosine kinases that contribute to the transcription of interstitial collagenase. Methods. Four thousand six hundred fourteen basepairs of the rabbit collagenase promoter region were cloned and sequenced. Plasmids containing collagenase promoter fragments linked to the luciferase reporter gene were transiently transfected into primary rabbit synovial fibroblasts. Regulation of gene activation by inflammatory mediators and tyrosine kinase inhibitors was assessed. To identify specific tyrosine kinases that contribute to collagenase gene expression, v‐src was transiently expressed in rabbit synovial fibroblasts along with collagenase promoter constructs, and basal and interleukin‐1 (IL‐1)‐induced collagenase transcription was assayed. Results. An inhibitor of src‐related tyrosine kinases, herbimycin A, inhibited increases of collagenase messenger RNA in IL‐1– and phorbol myristate acetate‐treated fibroblasts. Transcriptional activation of collagenase by IL‐1 was also inhibited by herbimycin A. Expression of v‐src in synovial fibroblasts enhanced basal and IL‐1‐inducible transcription. Conclusion. Activation of collagenase transcription by inflammatory mediators involves activation of an src‐related tyrosine kinase.