Figure 2. The point mutation S707Y augments the responsiveness of PLCγ₂ to constitutively active Rac2, wild-type Rac2, and constitutively active Vav1.

COS-7 cells were transfected as indicated with 50 ng/well of vector encoding wild-type PLCγ₂ (WT) or PLCγ₂S707Y (S707Y) and increasing amounts of vector encoding Rac2^G12V (left panel). Center panel, COS-7 cells were transfected as in the left panel except that 150 ng/well of vector encoding PLCγ₂ and increasing amounts of vector encoding wild-type Rac2 was used as indicated at the abscissa. Right panel, COS-7 cells were transfected as in the left panel except that increasing amounts of vector encoding Vav1ΔN was used as indicated at the abscissa. Twenty four hours after transfection, the cells were incubated for 18 h with myo-[2-³H]inositol, and inositol phosphate formation was then determined. The ED₅₀ values of vectors encoding Rac2^G12V, Rac2, or Vav1ΔN for the stimulation of wild-type or mutant PLCγ₂ activity obtained by non-linear curve fitting are shown above the graphs in nanograms/well.