Tissue factor-dependent factor VIIa signaling.

Tissue factor (TF) is known primary as a cofactor for factor VIIa-mediated triggering of blood coagulation, which proceeds in a cascade of extracellular reactions. Recent investigations have, however, revealed that intracellular activities can also be induced by the proteolytic activity of factor VIIa bound to cell surface TF. Factor VIIa signal transduction has thus been reported to induce mobilization of intracellular Ca(2+) stores and p44/p42 MAPK phosphorylation and to result in expression of specific genes, which presumably affects a number of cellular functions. The factor VIIa-induced signal transduction is independent of the presence of the TF cytoplasmic domain and it is distinctly different from signaling involving presently known protease-activated receptors (PARs) including receptors for thrombin and factor Xa. This short review summarizes recent advances in our understanding of TF-dependent factor VIIa signaling.