c‐FLIPL is a dual function regulator for caspase‐8 activation and CD95‐mediated apoptosis

Activation of the caspase cascade is a pivotal step in apoptosis and can occur via death adaptor‐mediated homo‐oligomerization of initiator procaspases. Here we show that c‐FLIPL, a protease‐deficient caspase homolog widely regarded as an apoptosis inhibitor, is enriched in the CD95 death‐inducing signaling complex (DISC) and potently promotes procaspase‐8 activation through hetero‐dimerization. c‐FLIPL exerts its effect through its protease‐like domain, which associates efficiently with the procaspase‐8 protease domain and induces the enzymatic activity of the zymogen. Ectopic expression of c‐FLIPL at physiologically relevant levels enhances procaspase‐8 processing in the CD95 DISC and promotes apoptosis, while a decrease of c‐FLIPL expression results in inhibition of apoptosis. c‐FLIPL acts as an apoptosis inhibitor only at high ectopic expression levels. Thus, c‐FLIPL defines a novel type of caspase regulator, distinct from the death adaptors, that can either promote or inhibit apoptosis.

[1]  D. Baltimore,et al.  Autoproteolytic activation of pro-caspases by oligomerization. , 1998, Molecular cell.

[2]  P. Krammer,et al.  TCR-Mediated Up-Regulation of c-FLIPshort Correlates with Resistance Toward CD95-Mediated Apoptosis by Blocking Death-Inducing Signaling Complex Activity1 , 2000, The Journal of Immunology.

[3]  M. Peter,et al.  The death receptors. , 1999, Results and problems in cell differentiation.

[4]  H. Perlman,et al.  Flice-Inhibitory Protein Expression during Macrophage Differentiation Confers Resistance to FAS-Mediated Apoptosis , 1999, The Journal of experimental medicine.

[5]  S. Schreiber,et al.  Identification of an 11-kDa FKBP12-rapamycin-binding domain within the 289-kDa FKBP12-rapamycin-associated protein and characterization of a critical serine residue. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[6]  Brent R. Stockwell,et al.  An Induced Proximity Model for Caspase-8 Activation* , 1998, The Journal of Biological Chemistry.

[7]  R. Siegel,et al.  Membrane Oligomerization and Cleavage Activates the Caspase-8 (FLICE/MACHα1) Death Signal* , 1998, The Journal of Biological Chemistry.

[8]  B. Trask,et al.  MRIT, a novel death-effector domain-containing protein, interacts with caspases and BclXL and initiates cell death. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[9]  M. Peter,et al.  Cytotoxicity‐dependent APO‐1 (Fas/CD95)‐associated proteins form a death‐inducing signaling complex (DISC) with the receptor. , 1995, The EMBO journal.

[10]  J. Blenis,et al.  Death Receptor Recruitment of Endogenous Caspase-10 and Apoptosis Initiation in the Absence of Caspase-8* , 2001, The Journal of Biological Chemistry.

[11]  M. Peter,et al.  Two CD95 (APO‐1/Fas) signaling pathways , 1998, The EMBO journal.

[12]  D. Goeddel,et al.  Casper is a FADD- and caspase-related inducer of apoptosis. , 1997, Immunity.

[13]  Howard Y. Chang,et al.  Proteases for Cell Suicide: Functions and Regulation of Caspases , 2000, Microbiology and Molecular Biology Reviews.

[14]  D. Baltimore,et al.  Essential role of CED-4 oligomerization in CED-3 activation and apoptosis. , 1998, Science.

[15]  T. Griffith,et al.  Intracellular regulation of TRAIL-induced apoptosis in human melanoma cells. , 1998, Journal of immunology.

[16]  S. Srinivasula,et al.  FLAME-1, a Novel FADD-like Anti-apoptotic Molecule That Regulates Fas/TNFR1-induced Apoptosis* , 1997, The Journal of Biological Chemistry.

[17]  Margot Thome,et al.  Inhibition of death receptor signals by cellular FLIP , 1997, Nature.

[18]  D. Baltimore,et al.  Autoimmunity as a consequence of retrovirus-mediated expression of C-FLIP in lymphocytes. , 2009, Immunity.

[19]  R. Gentz,et al.  I-FLICE, a Novel Inhibitor of Tumor Necrosis Factor Receptor-1- and CD-95-induced Apoptosis* , 1997, The Journal of Biological Chemistry.

[20]  Shannon R. Magari,et al.  Redesigning an FKBP-ligand interface to generate chemical dimerizers with novel specificity. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[21]  P. Krammer,et al.  Cellular FLICE-inhibitory Protein Splice Variants Inhibit Different Steps of Caspase-8 Activation at the CD95 Death-inducing Signaling Complex* , 2001, The Journal of Biological Chemistry.

[22]  J. Tschopp,et al.  NF-κB Signals Induce the Expression of c-FLIP , 2001, Molecular and Cellular Biology.

[23]  Ingo Schmitz,et al.  The Role of c-FLIP in Modulation of CD95-induced Apoptosis* , 1999, The Journal of Biological Chemistry.

[24]  M. Hayden,et al.  Cell death attenuation by `Usurpin', a mammalian DED-caspase homologue that precludes caspase-8 recruitment and activation by the CD-95 (Fas, APO-1) receptor complex , 1998, Cell Death and Differentiation.

[25]  Peter Scheurich,et al.  NF-κB Inducers Upregulate cFLIP, a Cycloheximide-Sensitive Inhibitor of Death Receptor Signaling , 2001, Molecular and Cellular Biology.

[26]  J. Blenis,et al.  Essential requirement for caspase-8/FLICE in the initiation of the Fas-induced apoptotic cascade , 1998, Current Biology.

[27]  S. Chen,et al.  CLARP, a death effector domain-containing protein interacts with caspase-8 and regulates apoptosis. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[28]  D. Goeddel,et al.  Requirement for Casper (c-FLIP) in regulation of death receptor-induced apoptosis and embryonic development. , 2000, Immunity.

[29]  H. Chun,et al.  Caspase-10 is an initiator caspase in death receptor signaling , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[30]  R. Offringa,et al.  Immune Escape of Tumors in Vivo by Expression of Cellular Flice-Inhibitory Protein , 1999, The Journal of experimental medicine.

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

[32]  Y. Goltsev,et al.  CASH, a Novel Caspase Homologue with Death Effector Domains* , 1997, The Journal of Biological Chemistry.

[33]  P. Krammer,et al.  FLICE-Inhibitory Proteins: Regulators of Death Receptor-Mediated Apoptosis , 2001, Molecular and Cellular Biology.