Xa receptor EPR-1.

Cellular inflammatory responses and early mechanisms of vascular injury are invariably associated with activation of blood coagulation and deposition of insoluble fibrin. This process occurs on vascular cell surfaces through the ability of the coagulation protease factor Xa to generate thrombin. However, experimental evidence accumulated during the past decade underscores how prothrombin activation is only one of the biological consequences of factor Xa assembly on vascular cells. Instead, binding of factor Xa to leukocytes, endothelium, and smooth muscle cells triggers complex pathways of intracellular signal transduction that participate, directly or indirectly, in the regulation of cellular growth. One of the cellular binding sites for factor Xa, designated effector cell protease receptor-1 (EPR-1), has recently emerged as a novel potential regulator of factor Xa-mediated mitogenic signaling. For its activation-dependent phenotype on leukocyte subsets, its ability to costimulate lymphocyte proliferation through release of intracellular second messengers, and its regulated cellular expression by alternative mRNA splicing, EPR-1 may influence vascular cell growth and aberrantly contribute to the earliest pathogenetic processes of vascular diseases.