Figure 6.
Imatinib mesylate inhibits phosphorylation/activation of p70 S6 kinase and the S6 ribosomal protein. (A) KT-1 cells were treated with imatinib mesylate (1 μM) for different time points, as indicated. Top panel shows immunoblotting of total cell lysates with an anti-phospho-Thr421/Ser-424 p70 S6 kinase antibody. Bottom panel shows reprobing of the same blot with an anti-p70 S6K antibody. (B) KT-1 cells were treated with imatinib mesylate for different times as indicated. Top panel shows an immunoblot of total cell lysates with an antibody against the phosphorylated form of the S6 ribosomal protein on serines 235/236. Bottom panel shows reprobing of the same blot with an anti-S6 ribosomal protein antibody. (C) KT-1 cells were treated with imatinib mesylate for different time points, as indicated. Top panel shows an immunoblot with an antibody against the phosphorylated form of the S6 ribosomal protein on serines 240/244. Bottom panel shows reprobing of the same blot with an anti-S6 ribosomal protein antibody. (D) K562 cells were treated with imatinib mesylate (1 μM) for different times, as indicated. Top panel shows immunoblotting of total cell lysates with an anti-phospho-Thr421/Ser-424 p70 S6 kinase antibody. Bottom panel shows reprobing of the same blot with an anti-p70 S6 kinase antibody. (E) K562 cells were treated with imatinib mesylate for different times as indicated. Top panel shows an immunoblot of total cell lysates with an antibody against the phosphorylated form of the S6 ribosomal protein on serines 235/236. Bottom panel shows reprobing of the same blot with an anti-S6 ribosomal protein antibody. (F) K562 cells were treated with imatinib mesylate and/or rapamycin for 120 minutes, as indicated. Top panel shows immunoblotting of total cell lysates with an antibody against the phosphorylated form of the S6 ribosomal protein on serines 235/236. Bottom panel shows reprobing of the same blot with an anti-S6 ribosomal protein antibody. (G) Similar experiment to the one shown in panel F, except that an antibody against the phosphorylated form of the S6 ribosomal protein on serines 240/244 was used for immunoblotting in the top panel.