Physiology of Fas-induced programmed cell death

Programmed cell death has been shown to be very important for the regulation of cellular homeostasis. The present review describes some aspects of apoptosis. In particular it focuses on signal transduction events activated upon the induction of apoptosis. The Fas receptor, an important receptor regulating the peripheral immune response, mediates apoptosis via a stimulation of a cascade of ICE-like proteases and activation of sphingomyelinases, synthesis of ceramide, stimulation of the small G-proteins Pas and Rac 1 and, finally, activation of Jun-N-terminal kinases. Further, Fas receptor triggering mediates the inactivation of n-K+-ion channels and the activation of src-like tyrosine kinases. Inhibition of these signaling cascades prevents Fas-induced cell death showing the significance of the observed signaling events. Thus, the Fas receptor seems to utilize similar signaling pathways as observed by receptors inducing cell differentiation or proliferation. Therefore, the specific biological effect of receptor triggering may be the specific combination of several signaling pathways.