Caspase 7 can cleave tumor necrosis factor receptor-I (p60) at a non-consensus motif, in vitro.

Ligand binding to tumor necrosis factor receptor-I (TNFRI) can promote cell survival or activate the apoptotic caspase cascade. Cytoplasmic interaction of TNFRI with TRAF2 and RIP allows for the activation of JNK and NFkappaB pathways. Alternatively, a carboxy terminal death domain protein interaction motif can recruit TRADD, which then recruits FADD/MORT1, and finally procaspase 8. Aggregation of these components form a death inducing signaling complex, leading to the cleavage and activation of caspase 8. We have found that during apoptosis human TNFRI protein is lost in a caspase-dependent manner. The cytoplasmic tail of human TNFRI was found to be susceptible to caspase cleavage but not by caspase 8. Instead, the downstream executioner caspase 7 was the only caspase capable of cleaving TNFRI, in vitro. Identification and characterization of the cleavage site revealed a derivative of the classic EXD motif that incorporates a glutamate (E) in the P1 position. Using several criteria to establish that caspase activity was responsible for cleavage at this site, we confirmed that caspase 7 can cleave at a GELE motif. Mutation of the cleavage site prevented the apoptosis-associated cleavage of TNFRI. This ability of caspase 7 to cleave at a non-EXD or -DXXD motif suggests that the specificity of caspases may be broader than is currently held.

[1]  G. Salvesen,et al.  Caspases: Intracellular Signaling by Proteolysis , 1997, Cell.

[2]  Shahrooz Rabizadeh,et al.  The DCC gene product induces apoptosis by a mechanism requiring receptor proteolysis , 1998, Nature.

[3]  C. Belka,et al.  Tumor necrosis factor (TNF)‐alpha activates c‐raf‐1 kinase via the p55 TNF receptor engaging neutral sphingomyelinase. , 1995, The EMBO journal.

[4]  G. Häcker,et al.  Activation of caspase‐3‐like enzymes in non‐apoptotic T cells , 1998, European journal of immunology.

[5]  L. Tartaglia,et al.  A novel domain within the 55 kd TNF receptor signals cell death , 1993, Cell.

[6]  G. Natoli,et al.  Activation of SAPK/JNK by TNF Receptor 1 Through a Noncytotoxic TRAF2-Dependent Pathway , 1997, Science.

[7]  K. Mielke,et al.  JNK and p38 stresskinases — degenerative effectors of signal-transduction-cascades in the nervous system , 2000, Progress in Neurobiology.

[8]  A. Hackam,et al.  Cleavage of Atrophin-1 at Caspase Site Aspartic Acid 109 Modulates Cytotoxicity* , 1999, The Journal of Biological Chemistry.

[9]  E. Peterson,et al.  The Drosophila caspase DRONC cleaves following glutamate or aspartate and is regulated by DIAP1, HID, and GRIM. , 2000, The Journal of biological chemistry.

[10]  D. Green.  Apoptotic Pathways The Roads to Ruin , 1998, Cell.

[11]  David Baltimore,et al.  NF-κB: Ten Years After , 1996, Cell.

[12]  J C Reed,et al.  IAP family proteins--suppressors of apoptosis. , 1999, Genes & development.

[13]  M. Kelliher,et al.  The distinct roles of TRAF2 and RIP in IKK activation by TNF-R1: TRAF2 recruits IKK to TNF-R1 while RIP mediates IKK activation. , 2000, Immunity.

[14]  Hong-Bing Shu,et al.  TRADD–TRAF2 and TRADD–FADD Interactions Define Two Distinct TNF Receptor 1 Signal Transduction Pathways , 1996, Cell.

[15]  L. Williams,et al.  Tumor necrosis factor α‐induced activation of c‐jun N‐terminal kinase is mediated by TRAF2 , 1997, The EMBO journal.

[16]  Y. Lin,et al.  Cleavage of the death domain kinase RIP by caspase-8 prompts TNF-induced apoptosis. , 1999, Genes & development.

[17]  Michael Karin,et al.  Dissection of TNF Receptor 1 Effector Functions: JNK Activation Is Not Linked to Apoptosis While NF-κB Activation Prevents Cell Death , 1996, Cell.

[18]  H. Müller,et al.  The Drosophila Caspase Inhibitor DIAP1 Is Essential for Cell Survival and Is Negatively Regulated by HID , 1999, Cell.

[19]  Guy S. Salvesen,et al.  X-linked IAP is a direct inhibitor of cell-death proteases , 1997, Nature.

[20]  Junying Yuan,et al.  Human ICE/CED-3 Protease Nomenclature , 1996, Cell.

[21]  Xiaodong Wang,et al.  Smac, a Mitochondrial Protein that Promotes Cytochrome c–Dependent Caspase Activation by Eliminating IAP Inhibition , 2000, Cell.

[22]  S. Nagata.  Human autoimmune lymphoproliferative syndrome, a defect in the apoptosis-inducing Fas receptor: A lesson from the mouse model , 1998, Journal of Human Genetics.

[23]  D. Goeddel,et al.  The TNF receptor 1-associated protein TRADD signals cell death and NF-κB activation , 1995, Cell.

[24]  Robert L Moritz,et al.  Identification of DIABLO, a Mammalian Protein that Promotes Apoptosis by Binding to and Antagonizing IAP Proteins , 2000, Cell.

[25]  H. Steller,et al.  Induction of apoptosis by Drosophila reaper, hid and grim through inhibition of IAP function , 2000, The EMBO journal.

[26]  D. Green,et al.  Caspases Induce Cytochrome c Release from Mitochondria by Activating Cytosolic Factors* , 1999, The Journal of Biological Chemistry.