FLICE, A Novel FADD-Homologous ICE/CED-3–like Protease, Is Recruited to the CD95 (Fas/APO-1) Death-Inducing Signaling Complex

Abstract

To identify CAP3 and CAP4, components of the CD95 (Fas/APO-1) death-inducing signaling complex, we utilized nano-electrospray tandem mass spectrometry, a recently developed technique to sequence femtomole quantities of polyacrylamide gel-separated proteins. Interestingly, CAP4 encodes a novel 55 kDa protein, designated FLICE, which has homology to both FADD and the ICE/CED-3 family of cysteine proteases. FLICE binds to the death effector domain of FADD and upon overexpression induces apoptosis that is blocked by the ICE family inhibitors, CrmA and z-VAD-fmk. CAP3 was identified as the FLICE prodomain which likely remains bound to the receptor after proteolytic activation. Taken together, this is unique biochemical evidence to link a death receptor physically to the proapoptotic proteases of the ICE/CED-3 family.

Caspase-8/FLICE functions as an executioner caspase in anticancer drug-induced apoptosis

“…In the death receptor pathway, recruitment of FADD causes the binding of procaspase-8, which in turn undergoes oligomerization-induced activation (Muzio et al, 1996). Depending on the cell type, caspase-8 directly activates downstream caspases including caspase-3 and -6.…”

MyD genes in negative growth control

“…To activate NF-kB, TRADD interacts with serine/threonine kinase RIP and TRAF2, that are linked to the NIK/IkK cascade, and trigger the phosphorylation and degradation of IkB (Hsu et al, 1996a,b). On the other hand, to induce cell death, TRADD interacts with FADD, which in turn triggers the apoptotic caspase cascade (Boldin et al, 1996;Grimm et al, 1996;Hsu et al, 1996a;Muzio et al, 1996). Since in IL-1 signaling, MyD88 is responsible for recruiting IRAK, which interacts with TRAF6, it is the functional equivalent of TRADD in NF-kB activation by IL-1.…”

Caspase-dependent cleavage and inactivation of the Vav1 proto-oncogene product during apoptosis prevents IL-2 transcription

“…Ligation of the CD95 receptor leads to the induced binding of the adaptor protein FADD, which in turn recruits procaspase-8 to the receptor complex (Muzio et al, 1996). Procaspase-8 is then activated by autoproteolysis, resulting in the release of active caspase-8 from the receptor complex .…”