EpoR is not constitutively activated in HS2 cells.

HS1 cells (663) and HS2 cells (606) were stimulated or not stimulated with 10 U/mL Epo for 10 minutes. Cell lysates were immunoprecipitated (IP) with anti-EpoR antibodies and analyzed by Western blotting (WB) with anti-PY antibodies (upper panel) or with anti-EpoR antibodies (lower panel). Arrows point to phosphorylated EpoR (upper panel) and EpoR (lower panel).