PKCθ negatively regulates CRP-induced ATP secretion. Mouse (A-B) or human (C) platelets were prepared as described by Nagy et al. Mouse platelets were treated with indomethacin (10 μM), and human platelets were treated with aspirin (1 mM), to exclude the effects of thromboxane. CRP-induced ATP secretion was measured using luciferin-luciferase in a lumi-aggregometer (Chrono-Log). Platelets were magnetically stirred at 1000 rpm. In B and C, platelets were treated with Vθ1-1-TAT (1 μM), TAT alone (1 μM), or equivalent volume of buffer (−) for 15 minutes before stimulation. In panel B, mouse platelets were stimulated by 1 μg/mL CRP. Sigmoidal concentration-response relationships were fitted using Prism 4 software (GraphPad Software Inc). Data shown are mean ± SEM (n = 3-4) and were analyzed for statistical significance by 2-way ANOVA. *P < .05; **P < .01. n.s. indicates not significant.