Figure 4.

EGFR phosphorylation upon proteasome inhibition is p38 MAPK dependent. ARPE-19 cells were cultured in the presence or absence of epoxomicin (A and C) and epoxomicin plus SB203580 (B and D) in serum-free medium for 8 h. Levels of endogenous phospho-EGFR (Tyr1045 and Tyr1068), total EGFR, and actin were detected by Western blot using polyclonal (to phosphorylated and total EGFR) and monoclonal antibodies (to actin). (A and B) EGFR phosphorylation at Tyr1045 position is shown. (C and D) EGFR phosphorylation at Tyr1068 position is shown. The figures are representative of three independent experiments with similar results.