We have recently identified the fifth member of the membrane-type matrix metalloproteinase subfamily, MT5-MMP/MMP24, which is expressed in a brain specific manner (Duanqing Pei (1999) J. Biol. Chem. 274, 8925-8932). To further characterize its enzymic properties, an expression construct was engineered to produce MT5-MMP as a soluble and active form by truncating its transmembrane domain. Stable expression cell lines were subsequently established from MDCK cells transfected with this construct. Unfortunately, purification of MT5-MMP from the culture media in large quantity proves to be difficult initially due to its rapid turnover via a mechanism which can be inhibited by a broad spectrum metalloproteinase inhibitor, BB94. Thus, BB94 was included in the cell culture medium and throughout the purification process except the final step of chromatography to protect MT5-MMP from destruction. Purified to homogeneity and free of the synthetic inhibitor, MT5-MMP can activate progelatinase A efficiently in a TIMP2 sensitive fashion. A preliminary screen for its potential substrates among extracellular matrix components identified the proteoglycans as the preferred substrates for MT5-MMP. Furthermore, it is determined that the stability of purified MT5-MMP is temperature dependent with rapid destruction at 37°C, but being relatively stable at temperatures 4°C or lower. These observations establish MT5-MMP as a proteoglycanase with a short half-life at body temperature, which may be critical for tightly controlled turnover of ECM components such as those in the brain. Copyright (C) 1999 Federation of European Biochemical Societies.
Bibliographical noteFunding Information:
The author wishes to thank Dr. R. Fridman (Wayne State University) for providing TIMP1 and 2; Helen Mills of British Biotech for providing BB94; Drs. Stephen J. Weiss and Hideaki Nagase for encouragement. This study was supported in part by Grant CA76308 from the National Cancer Institute, American Heart Association Grant-in-Aid 9750197N, Elsa Pardee Foundation, University of Minnesota grant-in-aid, Minnesota Medical Foundation.
- ECM degradation