A PLASMA MEMBRANE-ASSOCIATED COMPONENT OF OVARIAN ADENOCARCINOMA CELLS ENHANCES THE CATALYTIC EFFICIENCY OF MATRIX METALLOPROTEINASE-2

Several recent investigations have demonstrated that matrix metallopro teinase-2 (MMP-2) binds to the cell surface and undergoes zymogen acti vation via a plasma membrane associated activity, The purpose of this study was to determine if association of MMP-2 with the plasma membran e also modulates the catalytic efficiency of the active enzyme. Using density gradient centrifugation, we isolated the plasma membrane fract ions of two ovarian adenocarcinoma cell lines, DOV 13 and OVCA 432, pr eviously described either to express MMP-2 or to express no gelatinoly tic: metalloproteinases, respectively, While DOV 13 cells contained pl asma membrane-associated MMP-2 and OVCA 432 did not, both cell types w ere able to bind exogenous MMP-2. Furthermore, plasma membrane fractio ns from these cells significantly enhanced the rate of cleavage of [C- 14]gelatin I substrate by both MMP-2 tissue inhibitor of metalloprotei nases-2 (TIMP-2) complex (2.5-8-fold) and TIMP-2-free MMP-2 (5.9-fold) , This stimulatory activity was dose-dependent, soluble in Triton X-10 0, and abolished by trypsin treatment of the membranes, but was stable to heat treatment, Plasma membrane stimulation of MMP-2 resulted in a 3.8-4.6-fold increase in the catalytic efficiency of gelatinolysis. T hese data suggest that, in addition to promoting zymogen activation, c ell surface binding of MMP-2 may regulate enzyme activity by increasin g the rate of substrate cleavage. Via this mechanism, tumor cell types that do not express MMPs (such as OVCA 432) nevertheless may be able to utilize exogenous MMP-2 to mediate proteolysis associated with inva sion and metastasis.