CSF-1–mediated caspase-8 interaction with FADD and RIP1 depends on PI3K. (A) Monocytes were exposed for 4 days in the absence or presence of Y294002 (LY, 10 μmol/L) or U0126 (U0, 10 μmol/L) added either 30 minutes before CSF-1 (P) and at indicated times after the beginning of CSF-1 treatment and the expression of procaspase-3 and caspase-3 cleavage (C3*) was analyzed by immunoblot. HSC70 indicates loading control. (B) Monocytes were analyzed before any treatment or after exposure to CSF-1 for 72 hours in the presence or absence of LY (10 μmol/L) added 24 hours after the beginning of CSF-1 treatment. Cell lysates were used for immunoblotting before (lysates) or after (IP: caspase 8) immunoprecipitation with an anti–caspase-8 antibody. Molecular weight (MW) is given in kilodaltons. One representative of 3 independent experiments is shown.