Defective αIIbβ3 signaling in CD148-deficient platelets. Platelets from wild-type (WT) and CD148 transmembrane-knockout (KO) mice were plated on BSA- and fibrinogen-coated surfaces for 45 minutes. Whole cell lysates (WCLs) were prepared of BSA (BSA) nonadherent and fibrinogen (fib) adherent platelets. (A) Equal amounts of total protein were resolved by SDS-PAGE and Western blotted with an anti-phosphotyrosine antibody (p-Tyr). (B) Syk and (C) PLCγ2 were immunoprecipitated from equal amounts of WCLs and blotted with an anti-phosphotyrosine antibody. Membranes were subsequently stripped and reblotted with anti-Syk and anti-PLCγ2 antibodies. (Di-vi) WCLs were Western blotted with (Di) an anti-Src p-Tyr-529 antibody, (Diii) an anti-Lyn p-Tyr-507 antibody, and (Dv) an anti-Src family kinase (SFK) activation loop p-Tyr antibody. Blots are representative of 4 to 6 experiments. (Dii, iv, vi) Band intensities were quantified from 4 separate experiments (mean ± SEM; *P < .05, **P < .01).