MMP1

Abstract: Mononuclear phagocytes are developmentally and functionally complex cells that play critical roles in extracellular matrix remodeling. We hypothesized that differentiated mononuclear phagocytes, typified by alveolar macrophages, use a spectrum of metalloproteinases to degrade various matrix macromolecules. To test this hypothesis, we have evaluated synthesis and secretion of four metalloproteinases (interstitial collagenase, stromelysin, 72-kD type IV collagenase, and 92-kD type IV collagenase) by human mononuclear phagocytes with regard to (a) the effect of cellular differentiation, (b) regulation of secretion, and (c) comparisons/contrasts with a prototype metalloproteinase-secretory cell, the human fibroblast. We found that regulated secretion of greater quantities and a wider spectrum of metalloenzymes correlated with a more differentiated cellular phenotype. As extreme examples, the 92-kD type IV collagenase was released by peripheral blood monocytes and uninduced U937 monocyte-like cells, whereas stromelysin was secreted only by lipopolysaccharide-stimulated alveolar macrophages. Macrophage production of interstitial collagenase, stromelysin, and 72-kD type IV collagenase was approximately 20%, 10%, and 1-2%, respectively, of that from equal numbers of fibroblasts; secretion of the 92-kD type IV collagenase was not shared by fibroblasts. This work confirms the potential of macrophages to directly degrade extracellular matrix via secreted metalloproteinases in a manner that differs both qualitatively and quantitatively from that of fibroblasts. Moreover, varying regulation of metalloenzyme synthesis, evidenced by distinct patterns of basal and stimulated secretion during differentiation, can be studied at a molecular level in this model system.

Abstract: Objective To profile the expression of all known members of the matrix metalloproteinase (MMP), ADAMTS, and tissue inhibitor of metalloproteinases (TIMP) gene families in normal cartilage and cartilage from patients with osteoarthritis (OA). Methods Human cartilage was obtained from femoral heads at joint replacement for OA or following fracture to the femoral neck. Total RNA was purified, and gene expression was assayed using quantitative real-time polymerase chain reaction. Results Several members of the above gene families were regulated in OA. Genes that showed increased expression in OA were MMP13, MMP28, and ADAMTS16 (all at P < 0.001), MMP9, MMP16, ADAMTS2, and ADAMTS14 (all at P < 0.01), and MMP2, TIMP3, and ADAMTS12 (all at P < 0.05). Genes with decreased expression in OA were MMP1, MMP3, and ADAMTS1 (all at P < 0.001), MMP10, TIMP1, and ADAMTS9 (all at P < 0.01), and TIMP4, ADAMTS5, and ADAMTS15 (all at P < 0.05). Correlation analysis revealed that groups of genes across the gene families were coexpressed in cartilage. Conclusion This is the first comprehensive expression profile of all known MMP, ADAMTS, and TIMP genes in cartilage. Elucidation of patterns of expression provides a foundation with which to understand mechanisms of gene regulation in OA and potentially to refine the specificity of antiproteolytic therapies.

Abstract: Stromelysin is a collagenase-related connective-tissue-degrading metalloproteinase. We have detected RNAs capable of hybridizing to a rat stromelysin cDNA in 11 of 69 human tumours tested. Molecular cloning of cDNAs to these RNAs has identified them as a mixture of stromelysin RNA and a transcript of a hitherto-undescribed related human gene, the stromelysin-2 gene. We have also isolated cDNAs corresponding to a more distantly related new human gene, the pump-1 gene. A comparison of the cDNA-derived amino acid sequences of stromelysin-2 and pump-1 with the known sequences of stromelysin and collagenase reveals significant similarities, with conservation of sequence motifs believed to have functional importance in metalloproteinase action. We conclude that the collagenase gene family in humans consists of at least four members, and speculate that expression of these genes plays a role in cancer.

Abstract: Collagenase is a zinc-dependent endoproteinase and is a member of the matrix metalloproteinase (MMP) family of enzymes. The MMPs participate in connective tissue remodeling events and aberrant regulation has been associated with several pathologies. The 2.4 angstrom resolution structure of the inhibited enzyme revealed that, in addition to the catalytic zinc, there is a second zinc ion and a calcium ion which play a major role in stabilizing the tertiary structure of collagenase. Despite scant sequence homology, collagenase shares structural homology with two other endoproteinases, bacterial thermolysin and crayfish astacin. The detailed description of protein-inhibitor interactions present in the structure will aid in the design of compounds that selectively inhibit individual members of the MMP family. Such inhibitors will be useful in examining the function of MMPs in pathological processes.