Sustained tyrosine phosphorylation of Epo-R^S462A. BaF3 cells expressing either Epo-R^WT or Epo-R^S462A were preincubated with cycloheximide for 30 minutes and stimulated with Epo for the indicated times. Anti-Epo-R immunoprecipitations (IP) using C-236 anti-Epo-R antibodies were analyzed by Western blot using an antiphosphotyrosine (anti-PY) antibody (A) or anti-Epo-R (C-20) antibody (B) and a C = 1.3% polyacrylamide gel. PY Epo-R: tyrosine-phosphorylated Epo-R, Ig: immunoglobulin heavy chains.