Subcellular localization of tissue factor and human coronary artery smooth muscle cell migration

Summary. Background: Tissue factor (TF) is the most relevant physiological trigger of thrombosis. Additionally TF is a transmembrane receptor with cell signaling functions. Objectives: The aim of this study was to investigate TF subcellular localization, function and signaling in human coronary artery smooth muscle cell migration. Methods: Coronary arteries and primary cultures of vascular smooth muscle cells (HVSMC) were obtained from human explanted hearts. Wound repair and Boyden chamber assays were used to measure migration in vitro. TF‐pro‐coagulant activity (TF‐PCA) was measured in extracted cellular membranes. Analysis of TF distribution was performed by confocal microscopy. A nucleofector device was used for TF and protease activated receptor 2 (PAR2) silencing. mRNA levels were analyzed by RT‐PCR. Results: In migrating HVSMC TF translocates to the leading edge of the cells showing an intense patch‐like staining in the lamellipodia. In the migrating front TF colocalizes with filamin (FLN) in the polarized lipid rafts. TF‐PCA was increased in migrating cells. Silencing of the TF gene inhibits RSK‐induced FLN‐Ser‐2152 phosphorylation, down‐regulates CDC42, RhoA, and Rac1 protein expression and significantly inhibits cell migration. Silencing PAR2 also inhibits cell migration; however, silencing both TF and PAR2 induces a significantly higher effect on migration. Smooth muscle cells expressing TF have been identified in non‐lipid‐rich human coronary artery atherosclerotic plaques. Conclusions: TF translocates to the cell front in association with cytoskeleton proteins and regulates HVSMC migration by mechanisms dependent and independent of factor (F)VIIa/PAR2. These results extend the functional role of TF to smooth muscle cell trafficking in vessel wall remodeling.