The calmodulin inhibitor W7 causes Sema4D cleavage in platelets. Sema4D shedding detectable as a decrease in full-length Sema4D and an increase in soluble Sema4D. (A) Gel-filtered platelets were incubated with 150 µM W7 for 2 to 60 minutes at 37°C. Platelet pellets and supernatants were separated and immunoblotted for full-length and soluble Sema4D. Actin was used to confirm equal sample loading. *P < .05; **P < .01; ***P < .001. N.S., not significant (n = 3). (B) Platelets were incubated with 5 to 300 μΜ W7 for 60 minutes, blotted, and analyzed for intact and soluble Sema4D.