Figure 3.

Fas-mediated signaling pathways. Engagement of the Fas receptor induces DISC formation and subsequently caspase 8 activation. The active caspase 8 can either directly activate caspase 3 to initiate apoptosis, or active caspase 8 may cleave and activate Bid (tBid). tBid interacts with Bax to activate the caspase 9 cascade to induce apoptosis. On the other hand, Fas signaling may also lead to activation of cellular proliferation. Therefore, Fas engagement may leads to two conflicting cellular processes: apoptosis and survival. The molecular mediators controlling the switcher between these two opposing pathways remain to be determined.