EXPERIMENTAL FIGURE 15-10 Activation by the hormone erythropoietin (Epo) of three signal transduction proteins via their phosphorylation. Mouse erythrocyte progenitor cells were treated for 10 minutes with different concentrations of the hormone erythropoietin (Epo). Extracts of the cells were analyzed by Western blotting with three different antibodies specific for the phosphorylated forms of three signal transduction proteins and three other antibodies that recognize a nonphosphorylated segment of amino acids in each of the same proteins. The data show that with increasing concentrations of Epo, the three proteins become phosphorylated. Treatment with 1 unit Epo/ml is sufficient to maximally phosphorylate and thus activate all three pathways. Stat5 = transcription factor phosphorylated on tyrosine 694; Akt = kinase phosphorylated on serine 473; p42/p44 = p42/p44 MAP kinase phosphorylated on threonine 202 and tyrosine 204. See Zhang et al., 2003, Blood 102:3938.

[Courtesy Jing Zhang.]