Biophysical evidence for differential gallated green tea catechins binding to membrane type-1 matrix...

Membrane type-1 matrix metalloproteinase (MT1-MMP) is a transmembrane MMP which triggers intracellular signaling and regulates extracellular matrix proteolysis, two functions that are critical for tumor-associated angiogenesis and inflammation. While green tea catechins, particularly epigallocatechin gallate (EGCG), are considered very effective in preventing MT1-MMP-mediated functions, lack of structure-function studies and evidence regarding their direct interaction with MT1-MMP-mediated biological activities remain. Here, we assessed the impact in both cellular and biophysical assays of four ungallated catechins along with their gallated counterparts on MT1-MMP-mediated functions and molecular binding partners. Concanavalin-A (ConA) was used to trigger MT1-MMP-mediated proMMP-2 activation, expression of MT1-MMP and of endoplasmic reticulum stress biomarker GRP78 in U87 glioblastoma cells. We found that ConA-mediated MT1-MMP induction was inhibited by EGCG and catechin gallate (CG), that GRP78 induction was inhibited by EGCG, CG, and gallocatechin gallate (GCG), whereas proMMP-2 activation was inhibited by EGCG and GCG. Surface plasmon resonance was used to assess direct interaction between catechins and MT1-MMP interactors. We found that gallated catechins interacted better than their ungallated analogs with MT1-MMP as well as with MT1-MMP binding partners MMP-2, TIMP-2, MTCBP-1 and LRP1-clusterIV. Overall, current structure-function evidence supports a role for the galloyl moiety in both direct and indirect interactions of green tea catechins with MT1-MMP-mediated oncogenic processes.