Expression of TEL/PDGFβR augments IL-3–induced signaling cascades. BaF/3 clone TP2 was incubated in the presence (+ Tet) or absence (– Tet) of 2 μg/mL Tet for 24 hours. Cells were washed free of IL-3 and serum and incubated in serum-free media for 1 hour prior to being stimulated for the indicated period of time (in minutes) with 10 ng/mL rmIL-3 or left untreated (0). Whole cell lysates were prepared and 20 or 40 μg protein/sample was immunoblotted (IB) with the following antibodies: (A) Upper panel, 4G10 specific for tyrosine-phosphorylated proteins and in the lower panel anti-PDGFβR. (B) Antiphospho Ser473 of PKB (pPKB, upper panel); this blot was stripped and reprobed with a pan-PKB antibody (PKB, lower panel). (C) Antibody specific for phosphotyrosine 694/699 of STAT5a/b (pSTAT5, upper panel); this immunoblot was stripped and reprobed with an anti-STAT5 antibody to assess loading (STAT5, lower panel). (D) An antibody specific for dually phosphorylated ERK 1 and 2 (pERK1/2, upper panel); this blot was stripped and reprobed with an anti-panErk antibody (ERK, lower panel). (E) An antibody specific for dually phosphorylated p38 MAPK (pp38); this blot was stripped and reprobed with an anti-panp38 antibody (p38, lower panel). (F) An antibody specific for dually phosphorylated JNK1 and 2 (pJNK); this blot was stripped and reprobed with an anti-panJNK antibody (JNK2, lower panel). Positions of the phosphorylated and nonphosphorylated proteins are indicated, as are the molecular weight standards, in kilodaltons.