CELL-SURFACE BINDING OF TIMP-2 AND PRO-MMP-2 TIMP-2 COMPLEX/

Tissue inhibitor of metalloproteinases (TIMP-2) is a low molecular wei ght proteinase inhibitor capable of inhibiting activated matrix metall oproteinases (MMPs). TIMP-2 is found both free and in a 1:1 stoichiome tric complex with the pro-enzyme form of MMP-2 (pro-MMP-2/TIMP-2 compl ex). We have measured the binding of recombinant TIMP-2 to intact HT-1 080 and MCF-7 cells, HT-1080 cells in suspension bound I-125-labeled r TIMP-2 with a K-d of 2.5 nM and 30,000 sites/cell. Monolayers of MCF-7 cells were similarly found to bind [I-125]rTIMP-2 with a K-d of 1.6 n M and 25,000 sites/cell. Specific binding of MMP-2 alone to HT-1080 ce lls was not observed; however, pro-MMP-2/TIMP-2 complex was capable of binding to the surface of HT-1080 cells in a TIMP-2-dependent manner. Binding of rTIMP-2 was not competed by the presence of TIMP-1. These results suggest that rTIMP-2 alone binds directly to the cell surface of HT-1080 and MCF-7 cell lines, and TIMP-2 is capable of localizing M MP-2 to the surface of HT-1080 cells via interaction with a specific b inding site.