Arp2/3 complex distribution in the active mouse platelet cytoskeleton.

Wild-type (A) and WASp-deficient (B) mouse platelets were activated by 1 U/mL thrombin on anti-GPIbα antibody-coated glass coverslips and permeabilized with 0.75% Triton X-100 in PHEM buffer. Cytoskeletons were labeled with a mixture of rabbit polyclonal anti-Arp3 and anti–p34-Arc antibodies and 10 nm colloidal gold coated with goat antirabbit IgG. Cytoskeletons were fixed, washed into water, rapidly frozen, freeze-dried, and metal-coated. Bars represent 200 nm; lm indicates lamellae; f, filopodia; arrows, foci of gold labeling.