Association of CIB1 with α_IIb is needed for platelet spreading but not filopodia formation.

<p>(A) Western blot analysis of anti-CIB1 immunoprecipitates of lysates from platelets incorporated with either α_IIb peptide (2.5 μM) or anti-CIB1 antibody (0.1 mg/ml) as indicated. DMSO, scrambled α_IIb peptide (2.5 μM) and irrelevant isotype specific antibody (cIgG, 0.1 mg/ml) were used as control. Upper blot shows the co-immunoprecipitation of α_IIb. Same blot was reprobed with anti-CIB1 to ensure equal amount of protein in the immunoprecipitates (lower blot). Input represents sample of platelet lysate prior to immunoprecipitation. (B) Quantitation of α_IIb bands from (A) normalized to corresponding CIB1 band. (<i>*P<0</i>.<i>05)</i> (C) Confocal images of platelets incorporated with α_IIb peptide, anti-CIB1 or corresponding controls DMSO, scrambled α_IIb peptide, or cIgG and were allowed to spread on Fg for 45 min and stained for F-actin; boxed area is enlarged to visualize colocalization (arrows); non-specific red speckles are shown by arrowheads; original magnification, X 1600. (D) Quantitation of platelets from C showing CIB1 staining at the filopodia (***<i>P<0</i>.<i>001</i>). Error bars indicate mean ± SEM of at least three independent experiments.