Caspase-dependent cleavage of cytoskeletal proteins induces a shear-specific defect in platelet membrane tether stability. (A) DiIC12-labeled washed human platelets in the presence of 1 mg/mL ristocetin were perfused over human VWF-coated microchannels and allowed to adhere for 10 minutes in the absence of shear. Shear was applied (at a rate of 600 or 1800 s−1), and platelet adhesive behavior was captured using Metamorph software. Single frame fluorescence images (after subjecting to a low pass filter of 3) show the formation of long membrane tethers from ABT-737–treated (1μM) platelets, which is prevented by pretreatment with Q-VD-OPh (50μM). Scale bar represents 10 μm. (B) Quantitation of mean tether length from 3 independent experiments demonstrates a significant increase in membrane tether length in ABT-737–treated platelets compared with control and QV-D-OPh–treated platelets. ***P < .001. (C) DIC images of platelets demonstrating membrane tethers and the loss of discoid platelet morphology after treatment with ABT-737 and prevention by Q-VD-OPh are shown under the same shear conditions as in panel A. Scale bar represents 10 μm.
