Mouse gelatinase B

Gelatinase B is a regulated matrix metalloproteinase with an important role in the remodelling of extracellular matrices and of basement membranes. To study the structure and function of gelatinase B in the mouse, the cDNA was cloned from a macrophage cell line (WEHI-3). Using this cDNA, a cosmid clone with the mouse gene was isolated. The complete gene (8 kbp) was sequenced and compared with the human gene structure. There was 78% similarity at the cDNA level and the exon/intron structure of the murine gene was similar to the human counterpart. At the 5' untranslated side, 1200 bp of the promoter/enhancer region were sequenced and found to contain several transacting-factor-binding sites. The mRNA transcription-initiation site was determined by non-isotopic primer-extension analysis. Polymerase-chain-reaction amplification of cDNAs yielded indirect evidence for a reverse-transcription stop in WEHI-3 cell mRNA. The DNA-derived mouse-protein structure exhibited 82% similarity with the human one. This similarity was functionally reflected by cross-reactivity of the mouse protein with an antiserum against human gelatinase B. The production of murine gelatinase B was studied at the protein level by zymography and at the mRNA level by Northern blot analysis. In WEHI-3 cells the gelatinase B protein is induced by bacterial lipopolysaccharide, phorbol ester, double-stranded RNA and the cytokine interleukin-1. Regulation of activity and structural heterogeneity of gelatinase B in WEHI-3 cells were shown to occur at the gene regulatory level, by expression of the matrix metalloproteinase inhibitor TIMP-1, and by glycosylation of the secreted protein.