In exponentially growing erythroid progenitor cells, mature EPOR-T forms, unlike mature wild-type EPOR's, become hyper-phosphorylated.

<p><b>A</b>] UT7-wtEPOR, UT7-EPOR-T392 and UT7-EPOR-T374 cells were cultured in EPO at either 0.3 or 3 U/mL (as detailed above, legend to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029064#pone-0029064-g008" target="_blank">Figure 8</a>). Levels of PY-EPOR then were assessed via western blotting and also determined quantitatively (lower panel). <b>B</b>] <u>Left panel</u>: In the above cells (samples), levels of PY-JAK2 also were analyzed. <u>Right panel</u>: Heightened EPO-dependent expansion of UT7-EPOR-T392 cells. UT7epo cells expressing the wtEPOR or EPOR-T-392 at matched levels were cultured in EPO at the indicated concentrations, and at 48 hours viable cell numbers were determined.