Tissue factor cytoplasmic domain stimulates migration by activation of the GTPase Rac1 and the mitogen-activated protein kinase p38.
BACKGROUND
Tissue factor (TF), the surface receptor for the serine protease factor VIIa (FVIIa) and the initiator of the extrinsic coagulation cascade, supports vessel development and tumor metastasis by activation of extracellular, protease-dependent signaling pathways. The molecular mechanisms that do not require proteolytic activity of FVIIa are not yet known. The aim of the study, therefore, was to investigate the effects of active-site-inhibited FVIIa (FFR-FVIIa) on TF-mediated signaling.


RESULTS
After stimulation with FVIIa and FFR-FVIIa, migration and activation of the GTPase Rac (Rac1) or the mitogen-activated protein kinase p38 (p38) were analyzed in J82 cells. FVIIa and FFR-FVIIa stimulated migration and activation of Rac1 and p38 in a TF-specific, dose- and time-dependent manner. Enhancement of migration required activation of Rac1 and p38, because it was abolished after inhibition with SB203580 or overexpression of dominant negative p38 and Rac1. The cytoplasmic domain of TF was necessary because no effects of FFR-FVIIa could be detected after transfection of a TF deletion mutant lacking the cytoplasmic domain.


CONCLUSIONS
We identified a novel signaling pathway through which TF stimulates migration by activation of p38 and Rac1 independent of the proteolytic activity of FVIIa but dependent on the cytoplasmic domain of TF. Binding of FFR-VIIa to TF may stimulate vessel wall remodeling by enhancement of migration through activation of Rac1 and p38. This novel link may provide an insight into the understanding of the nonhemostatic functions of TF.
Ott
Ilka
I
Deutsches Herzzentrum und 1. Medizinische Klinik der Technischen Universität München, Munich, Germany. ott@dhm.mhn.de
Weigand
Berthold
B
Michl
Ruth
R
Seitz
Isabell
I
Sabbari-Erfani
Nooshin
N
Neumann
Franz-Josef
FJ
Schömig
Albert
A
D045744:Cell Line, Tumor; D002465:Cell Movement; D003593:Cytoplasm / Q000378:metabolism; D004789:Enzyme Activation; D015942:Factor VIIa / Q000494:pharmacology / Q000502:physiology; D006801:Humans; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D013925:Thromboplastin / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
D013925:Thromboplastin; D048051:p38 Mitogen-Activated Protein Kinases; D015942:Factor VIIa; D020744:rac GTP-Binding Proteins