miR-155 deficiency activates PAK1 and a PAK1-nucleated apoptotic pathway (JNK/FOXO3/BIM/Caspase 9).

<p>(A) Negatively selected CD4^<b>+</b> T cells from the indicated genotypes were stimulated with αCD3ε/CD4 (10 μg/ml, 3 min.). Ages of the mice were 11 wks (WT), 10 wks (miR155^<b>-/-</b>), 11 wks (LAT-KI), and 12 wks (DM). SDS WCLs were analyzed by WB (n = 3). (B) Jurkat T cells were transfected with Flag-PAK1 and PLC-γ1^<b>CI</b>-HA cDNAs. 24h post-transfection, cells were treated for 4h with MEK inhibitor (U0126, 20 μM) or JNK inhibitor (SP600125, 20 μM). Lamin B-enriched nuclear and tubulin-enriched cytosolic fractions were prepared. PAK1/JNK-mediated FOXO3 nuclear translocation was studied by WB (n = 3). <b>(</b>C) Jurkat T cells were transfected with FOXO3a, BIM/Bcl2l11 or control siRNAs (150 nM). After 24h, cells were super-transfected with siRNAs (150 nM) plus PLC-γ1^<b>CI</b>-HA, Flag-PAK1, or both cDNAs (10 μg). After an additional 36h, cells were lysed. Lysates (75%) were subjected to an active Caspase 9 IP and the 25% remaining lysates were used to make WCLs. Samples were analyzed by WB (n = 3).