An Induced Proximity Model for Caspase-8 Activation*

The assembly of the CD-95 (Fas/Apo-1) receptor death-inducing signaling complex occurs in a hierarchical manner; the death domain of CD-95 binds to the corresponding domain in the adapter molecule Fas-associated death domain (FADD) Mort-1, which in turn recruits the zymogen form of the death protease caspase-8 (FLICE/Mach-1) by a homophilic interaction involving the death effector domains. Immediately after recruitment, the single polypeptide FLICE zymogen is proteolytically processed to the active dimeric species composed of large and small catalytic subunits. Since all caspases cleave their substrates after Asp residues and are themselves processed from the single-chain zymogen to the two-chain active enzyme by cleavage at internal Asp residues, it follows that an upstream caspase can process a downstream zymogen. However, since FLICE represents the most apical caspase in the Fas pathway, its mode of activation has been enigmatic. We hypothesized that the FLICE zymogen possesses intrinsic enzymatic activity such that when approximated, it autoprocesses to the active protease. Support for this was provided by (i) the synthesis of chimeric Fpk3FLICE molecules that can be oligomerizedin vivo by the synthetic cell-permeable dimerizer FK1012H2. Cells transfected with Fpk3FLICE underwent apoptosis after exposure to FK1012H2; (ii) the creation of a nonprocessable zymogen form of FLICE that retained low but detectable protease activity.

[1]  A. Chinnaiyan,et al.  The cell-death machine , 1996, Current Biology.

[2]  Matthias Mann,et al.  FLICE, A Novel FADD-Homologous ICE/CED-3–like Protease, Is Recruited to the CD95 (Fas/APO-1) Death-Inducing Signaling Complex , 1996, Cell.

[3]  E. Reinherz,et al.  T‐cell receptor ligation by peptide/MHC induces activation of a caspase in immature thymocytes: the molecular basis of negative selection , 1997, The EMBO journal.

[4]  S. Schreiber,et al.  Functional analysis of Fas signaling in vivo using synthetic inducers of dimerization , 1996, Current Biology.

[5]  S. Schreiber,et al.  Controlling signal transduction with synthetic ligands. , 1993, Science.

[6]  G. Salvesen,et al.  Molecular Ordering of Apoptotic Mammalian CED-3/ICE-like Proteases* , 1996, The Journal of Biological Chemistry.

[7]  M. Saraste,et al.  FEBS Lett , 2000 .

[8]  D. Goeddel,et al.  TRAF2-mediated activation of NF-kappa B by TNF receptor 2 and CD40 , 1995, Science.

[9]  J. Tschopp,et al.  The death domain motif found in Fas (Apo‐1) and TNF receptor is present in proteins involved in apoptosis and axonal guidance , 1995, FEBS letters.

[10]  H. Steller.  Mechanisms and genes of cellular suicide , 1995, Science.

[11]  G. Salvesen,et al.  FLICE Induced Apoptosis in a Cell-free System , 1997, The Journal of Biological Chemistry.

[12]  Seamus J. Martin,et al.  Protease activation during apoptosis: Death by a thousand cuts? , 1995, Cell.

[13]  Patrick R. Griffin,et al.  Identification and inhibition of the ICE/CED-3 protease necessary for mammalian apoptosis , 1995, Nature.

[14]  A. Heguy,et al.  Amino acids conserved in interleukin-1 receptors (IL-1Rs) and the Drosophila toll protein are essential for IL-1R signal transduction. , 1992, The Journal of biological chemistry.

[15]  G. Salvesen,et al.  Target Protease Specificity of the Viral Serpin CrmA , 1997, The Journal of Biological Chemistry.

[16]  R. Black,et al.  Viral inhibition of inflammation: Cowpox virus encodes an inhibitor of the interleukin-1β converting enzyme , 1992, Cell.

[17]  J. Camonis,et al.  A Novel Protein That Interacts with the Death Domain of Fas/APO1 Contains a Sequence Motif Related to the Death Domain (*) , 1995, The Journal of Biological Chemistry.

[18]  S. Srinivasula,et al.  Molecular ordering of the Fas-apoptotic pathway: the Fas/APO-1 protease Mch5 is a CrmA-inhibitable protease that activates multiple Ced-3/ICE-like cysteine proteases. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[19]  David Wallach,et al.  Involvement of MACH, a Novel MORT1/FADD-Interacting Protease, in Fas/APO-1- and TNF Receptor–Induced Cell Death , 1996, Cell.

[20]  Arul M. Chinnaiyan,et al.  FADD, a novel death domain-containing protein, interacts with the death domain of fas and initiates apoptosis , 1995, Cell.

[21]  P. Henkart.  ICE family proteases: mediators of all apoptotic cell death? , 1996, Immunity.

[22]  M. Raff,et al.  Social controls on cell survival and cell death , 1992, Nature.

[23]  Matthias Mann,et al.  FLICE is activated by association with the CD95 death‐inducing signaling complex (DISC) , 1997, The EMBO journal.

[24]  S. Schreiber,et al.  A composite FKBP12-FK506 surface that contacts calcineurin , 1993 .