Abstract 3913: Emmprin (cd147) Is a Novel Receptor for Platelet GPVI and Mediates Platelet Rolling via GPVI-Emmprin Interaction
Background: The Extracellular Matrix Metalloproteinase Inducer (EMMPRIN, CD147) is an immunoglobulin like receptor which is known to induce the synthesis of matrix metalloproteinases in various cell types. Recently, we have identified EMMPRIN as a novel platelet receptor and have shown that platelet-monocyte interactions augment nuclear factor κB-dependent inflammatory processes apart from MMPs in monocytes by involvement of EMMPRIN. On the other hand, we have shown that EMMPRIN binding to platelets can induce platelet degranulation as detected by upregulation of p-selectin and CD40L on the cell surface. To our knowledge EMMPRIN has not been shown to serve as adhesion receptor, yet. Here we characterize platelet GPVI as a novel adhesion receptor for EMMPRIN.
Methods and Results: Human freshly isolated platelets were prestimulated with ADP (5 μM) and perfused over immobilized recombinant EMMPRIN-Fc (fusion protein, 25 μg/mL) or Fc-fragments (5 μg/mL) under arterial shear conditions. ADP-stimulated platelets showed significantly enhanced rolling (but not enhanced firm adhesion) on immobilized EMMPRIN-Fc compared to Fc. Pretreatment of platelets with blocking mAbs anti-EMMPRIN or anti-GPVI lead to a significant reduction of rolling platelets on immobilized EMMPRIN-Fc, whereas pretreatment with blocking anti-p-selectin, anti-α4 or antibody against the GPIIb/IIIa complex (20μg/mL each) had no effect. Consistently, chinese hamster ovary (CHO) cells who were stably transfected with GPVI showed enhanced rolling (but not adhesion) on immobilized EMMPRIN-Fc in comparison to non-transfected CHO cells. Similarly, CHO cells who were stably transfected with EMMPRIN showed enhanced rolling on immobilized GPVI-Fc compared to non transfected CHO-cells. Finally, a direct binding assay showed specific binding of recombinant GPVI-Fc on immobilized EMMPRIN-Fc.
Conclusion: Platelet GPVI is a novel receptor for EMMPRIN and mediates platelet rolling via GPVI-EMMPRIN interaction.