Contribution of Arp2/3 complex activity to the production of actin filament barbed ends in WAS platelets.

(A) Barbed-end counts were determined in Triton X-100 lysates of normal (░) and WAS (■) platelets activated with 25 μM TRAP or 3 μg/mL CRP for 1 minute using the pyrene-labeled actin assembly assay, as indicated. (B) Barbed-end counts were determined in Triton X-100 lysates of wild-type (░) and WASp-deficient (■) mouse platelets activated with 1 U/mL thrombin for 1 minute as above. (C) Platelet isolated from healthy volunteers (░) and from WAS patients (■) were permeabilized with 0.25% OG in PHEM buffer. The number of barbed ends in OG-permeabilized platelets was determined without any addition (rest), after incubation with 25 μM TRAP for 1 minute (TRAP), or after incubation with GST-CA (3μM) followed by TRAP (TRAP+GST-CA).