Fig. 5. Effect of IEX-1 on the kinetics and dose–response of growth factor-mediated ERK activation. CHO-ER cells were transfected with HA-ERK along with either empty pcDNA (V) or pcDNA-HA-IEX-1. Twenty-four hours post-transfection, cells were either harvested directly (non-starved) or starved of serum overnight prior to stimulation with 1–10 U/ml EPO for 10 min (A), or 4 U/ml EPO for various times (B). The activity of HA-tagged ERK was analyzed in anti-HA-immuno precipitates.