FIGURE 6.

PAK1 activation regulates the procoagulant activity of tissue factor. A and B, monitorization of TF activity in cell lysates from control HeLa cells (CTRL) or cells transiently overexpressing the catalytically active (T423E) (A) and kinase-deficient (K229R) (B) PAK1 mutants under serum starvation/induction conditions. The change in absorbance at 405 nm of the released pNA chromophore, which is directly proportional to the TF enzymatic activity, was recorded each 2 min for 20 min. The average and standard deviation from three independent experiments is shown. Arrows indicate the time points in which the amount of active TF was calculated in C. C, amount of active endogenous TF expressed in lysates from control HeLa cells (CTRL) or cells transiently overexpressing the catalytically active (T423E) and kinase-deficient (K229R) mutants of PAK1 under serum starvation/induction conditions. Values were extrapolated from a standard curve generated with different known concentrations of a recombinant human TF preparation and expressed as pm of TF per 10⁵ cells. The average and standard deviation from triplicates is shown. *, p < 0.005; **, p < 0.001 versus nonstimulated cells. #, p < 0.005 in T423E PAK1 mutant cells (T423E) compared with control HeLa cells (CTRL) under serum stimulation conditions. min, minutes.