Figure 2.

Activated R-Ras rescues the suppression of integrin activation by H-Ras(G12V) and Raf-CAAX. (A) αβ-py cells were transiently transfected with 2 μg of an expression vector encoding Tac-α₅ alone and Tac-α₅ plus H-Ras(G12V). In a separate transfection Tac-α₅ plus H-Ras(G12V) was cotransfected with 3 μg of a plasmid encoding R-Ras(G38V). After 48 h, cells were harvested and stained for Tac expression (y-axis) and PAC1 binding (x-axis). Left, In the H-Ras(G12V)-transfected cells, there is a leftward shift of the dot plot in the upper quadrants representing a reduction in PAC1 binding. Middle, This shift is reversed by the cotransfection with activated R-Ras(G38V). Right, In the empty vector control transfection, there was no suppression of PAC1 binding in the Tac-α₅–expressing cells. (B) αβ-py cells were cotransfected with 4 μg of an expression vector encoding Raf-CAAX and H-Ras(G12V). In separate transfections Raf-CAAX or H-Ras(G12V) expression vectors were simultaneously cotransfected with 3 μg of a plasmid encoding R-Ras(G38V). After 48 h, integrin activation was determined by PAC1 binding. Depicted is the mean percent inhibition of integrin activation relative to that of the empty vector ± SE of three independent determinations.