The Lnk SH2 domain is required to inhibit Epo-induced signaling pathways in primary erythroid cells. Ter119^- erythroid progenitors were purified, infected with either vector alone, wild-type Lnk, or the Lnk SH2 mutant, and directly cultured in Epo for 14 to 16 hours. Subsequently, the cells were starved for 2 hours and stimulated with Epo for 10 minutes. Protein lysates from equal cell numbers were subjected to Western blotting analysis. Phosphorylation and total protein levels of Stat5 (A), Akt (B), and p42/44MAPK (C) are shown. Lnk protein levels are shown in the bottom panel of A. Five independent experiments were performed and representative results are shown here.