Figure 5. Effect of phosphatase inhibitors on the activity of ERK8 in HEK-293 cells.

The cells were transfected with a vector encoding wild-type HA–ERK8 as in Figure 4(A). At 36 h post-transfection, the cells were incubated for 1 h with or without 1 μM okadaic acid, 1 mM sodium orthovanadate (Na₃VO₄), or both phosphatase inhibitors, and lysed. ERK8 was immunoprecipitated from cell extracts using an anti-HA antibody and assayed for activity using MBP as a substrate.