FIG. 7.
Proposed pathways for the cytokine regulation of Baf-3 cell survival. Signals arising from the membrane-proximal portion of the βc chain contribute to the rapid and stable expression of Bcl-xL through activation of STAT5 but downregulate Bim only transiently. By contrast, signals from the membrane-distal domain of the βc chain activate the P13-K/mTOR and Raf/MAPK pathways through Ras stimulation. Either pathway can downregulate Bim expression. When suppressed, Bim cannot inhibit the antiapoptotic functions of Bcl-2 and Bcl-xL and thus contributes to the cytokine-mediated survival of Baf-3 cells.