ECM regulates MT1-MMP localization with β1 or αvβ3 integrins at distinct cell compartments modulating its internalization and activity on human endothelial cells

Regulation of membrane-type 1 matrix metalloproteinase (MT1-MMP) by different extracellular matrices (ECMs) on human endothelial cells (ECs) has been investigated. First, MT1-MMP is found at the intercellular contacts of confluent ECs grown on beta1 integrin-dependent matrix such as type 1 collagen (COL 1), fibronectin (FN), or fibrinogen (FG), but not on gelatin (GEL) or vitronectin (VN). The novel localization of MT1-MMP at cell-cell contacts is assessed by confocal videomicroscopy of MT1-MMP-GFP-transfected ECs. Moreover, MT1-MMP colocalizes with beta1 integrins at the intercellular contacts, whereas it is preferentially found with alphanubeta3 integrin at motility-associated structures on migrating ECs. In addition, clustered integrins recruit MT1-MMP and neutralizing anti-beta1 or anti-alphanu integrin mAb displace MT1-MMP from its specific sites, pointing to a biochemical association that is finally demonstrated by coimmunoprecipitation assays. On the other hand, COL 1, FN, or FG up-regulate cell surface MT1-MMP on confluent ECs by an impairment of its internalization, whereas expression and internalization are not modified on GEL or VN. In addition, MT1-MMP activity is diminished in confluent ECs on COL 1, FN, or FG. Finally, MT1-MMP participates and cooperates with beta1 and alphanubeta3 integrins in the migration of ECs on different ECM. These data show a novel mechanism by which ECM regulates MT1-MMP association with beta1 or alphanubeta3 integrins at distinct cellular compartments, thus modulating its internalization, activity, and function on human ECs.