Activation of Akt-FoxO3 in Lyn^+/up erythroid cells during differentiation and in primary Lyn^up/up erythroblasts stimulated with Epo and model of altered signaling in Lyn^+/up cells. (A) Epo-independent activation of Akt-FoxO3 in J2-Lyn^+/up erythroid cells grown in differentiation media. Immunoblot analysis of total cell lysates of J2-WT and J2-Lyn^+/up cell lines for the signaling molecules indicated, cultured in differentiation media (T₃-depleted)²¹  with and without Epo at 0 and 48 hours. Immunoblot analysis was performed on 2 independent experiments producing equivalent results. (B) Altered Epo receptor signaling to GAB2 and Akt/FoxO3 in primary Lyn^up/up CD71⁺ splenic erythroblasts. Immunoblot analysis of total cell lysates of Lyn^+/+ and Lyn^up/up CD71⁺ spleen cells 0, 10, and 30 minutes after Epo stimulation for the signaling molecules indicated. Immunoblot analysis was performed on 2 independent experiments producing equivalent results. (C) Model of altered signaling in (right) J2-Lyn^+/up cells compared with (left) J2-Lyn^WT cells. Thickness and darkness of arrows indicate relative intensity of signaling connections. S, serine phosphorylation; Y, tyrosine phosphorylation.