The neutral proteinase collagenase is the only enzyme initiating breakdown of the interstitial collagens, Tupes I, II, and III, the body's most abundant structural proteins. Collagen remodeling occurs in normal processes, such as uterine resorption and wound healing, and in pathophysiological conditions, such as tumor invasion and rheumatoid arthritis. Nowhere is the impact of collagenase more apparent than in this latter disease where there is gross destruction of cartilage, tendon and bone, with subsequent deformity and loss of joint function. Our work focuses on mechanisms operating at the level of the gene to control collagenase production in rheumatoid arthritis. For these studies, we use a model system of monolayer cultures of rabbit synovial fibroblasts. These cells are readily available, grow well in culture, and importantly, can be induced to synthesize and secrete large quantities of collagenase, Mr. 57K and 61K. Equally attractive is the fact that collagenase synthesis can be suppressed by glucocorticoids or the synthetic Vitamin A analogues, the retinoids. Along with collagenase, another protein, Mr 52K and 54K, that functions to activate latent collagenase is also induced and repressed. Both inducers and repressors appear to affect collagenase and its activator by acting transcriptionally. Confirmation of this hypothesis is one aim of this proposal. Our studies to date have resulted in the isolation and characterization of both cDNA and genomic clones for synovial cell collagenase and these are appropriate tools for extending our work. Specifically, we will (1) determine whether steroids and retinoids affect collagenase mRNA 1/2 life; (2) isolate the 5' end of the collagenase gene and characterize its promoter regions; (3) study the coordinate regulation of collagenase and its activator protein by isolating and characterizing cDNA and genomic clones for this activator; (4) determine the chromosomal location(s) for the rabbit synovial cell collagenase gene(s) so as to investigate the genetic basis for multiple forms of collagenase protein (e.g., macrophage, neutrophil, synovial cell collagenase); and (5) sequence the cDNA and genomic clones for collagenase and its activator. Results of these studies are important to our understanding not only of how the destructive potential of synovial cells is regulated in rheumatoid arthritis but also to the control of collagenolysis by various other cell types throughout the body.
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