FIGURE 3.
PI3K p110β is the major isoform involved in thrombin-induced integrin αIIbβ3-mediated clot retraction. A–C, washed human platelets (3 × 108/ml) (A) or those derived from either p110γ+/+, p110γ−/−, p110δ+/+, or p110δ−/− mice (2.5 × 108/ml) (B and C) were preincubated with vehicle alone (DMSO) or various PI3K isoform inhibitors (pan-PI3K, LY294002 (LY; 25 μm); p110β, TGX221 (221; 0.5 μm); p110δ, D-010 (0.5 μm); or p110γ, AS252424 (AS; 1 μm)). Pretreated platelets were supplemented with 0.5 mg/ml fibrinogen prior to stimulation with 1 unit/ml thrombin, and the extent of clot retraction was quantified as described under “Experimental Procedures.” Images depicted in A (i) represent one representative of three independent experiments, quantified in A (ii) (mean ± S.E., n = 3; not significant (ns), p > 0.05; ***, p < 0.001). In B and C, clot retraction was examined in the presence or absence of ADP/TxA2 antagonists, and results are representative of three independent experiments.