Schematic presentation of the hypothetical role of Mcl-1 in IL-5 and SCF antiapoptotic signaling pathways.

LY indicates LY294002 and is the PI-3K inhibitor. PD indicates PD98059 and is the MEK inhibitor. Both MEK/MAPK and PI-3K/Akt pathways were shown to be essential for the antiapoptotic activity of cytokines IL-5 and SCF, which results in the induction of the antiapoptotic protein Mcl-1. An additional JAK/STAT5 pathway, which is insensitive to both inhibitors, is involved only in IL-5 signaling and may also contribute to the survival effect of IL-5. A PI-3K–dependent MEK activation pathway, which is sensitive to LY treatment, is also indicated.