FIGURE 4.

PP2Ac_α negatively regulates α_IIbβ₃ adhesiveness in 293 cells. A, PP2Ac_α expression as revealed by anti-HA antibody in control and HA-tagged PP2Ac_α-overexpressing cells. This blot was reprobed for actin (loading control) and is a representative of four different experiments. B, effect of HA-PP2Ac_α overexpression on 293 cell adhesion. 293 cells transfected with control vector or vector with PP2Ac_α cDNA were allowed to adhere to fibrinogen in the presence and absence of 10E5 (blocking antibody to α_IIbβ₃), and adhesion was measured by absorbance at 405 nm. Results are mean ± S.E. of 4–7 experiments in triplicate for various time points and 2 experiments for 10E5 blocking studies. Results were significant at #, p = 0.008; *, p = 0.0031; †, p < 0.0001; ♣, p < 0.0001; +, p = 0.002 for 5-, 10-, 15-, 30-, and 60-min adhesion. Error bars were too narrow to be seen with the 10E5 inhibition. C, PP2Ac expression in control and PP2Ac_α-transfected siRNA. The membrane was reprobed for PP1c and actin to demonstrate siRNA specificity and equal loading respectively. Blots are representative of five different experiments. D, effect of PP2Ac_α knockdown on 293 cell adhesion to fibrinogen. Results are mean ± S.E. of 5–6 experiments each performed in triplicate and was significant at *, p = 0.001; †, p = 0.006; ♣, p < 0.001; #, p < 0.0001; ‡, p = 0.01 for 5-, 10-, 15-, 30-, and 60-min adhesion by t test. E, effect of PP2Ac_α knockdown on 293 cell adhesion to von Willebrand factor. Results are mean ± S.E. of three experiments each performed in triplicate and was significant at *, p = 0.0084; ♣, p = 0.0086, for 30 and 60 min.