TRAIL transiently increases Ack1 levels. Ack1 levels were analyzed by Western blotting following TRAIL treatment of MCF10A for the times indicated (A), and band intensities were quantified (B). Error bars represent S.D. (n = three independent experiments). C, Western blot analysis of NCI-H460 cells subjected to Ack1 or non-targeting siRNA transfection followed by treatment with the lysosomal inhibitor chloroquine. D, quantification of Ack1 by densitometry of Western blots of NCI-H460 cells pretreated with chloroquine followed by treatment with TRAIL for the indicated times (n = 5). E, Western blot analysis of NCI-H460 cells subjected to Ack1 or non-targeting siRNA transfection followed by treatment with the proteasomal inhibitor MG132 for 16 h (representative of three independent experiments). F, TRAIL-induced cleavage of caspase-8 levels determined by Western blot analysis after a 2-h preincubation with the selective TRAIL inhibitor AIM-100 (10 μm) or vehicle alone (mock). G, Western blot analysis of Tyr-284 phosphorylation of ectopically expressed Ack1 (pAck1) treated with AIM-100 as described for F.