CLARP, a death effector domain-containing protein interacts with caspase-8 and regulates apoptosis.
We have identified and characterized CLARP, a caspase-like apoptosis-regulatory protein. Sequence analysis revealed that human CLARP contains two amino-terminal death effector domains fused to a carboxyl-terminal caspase-like domain. The structure and amino acid sequence of CLARP resemble those of caspase-8, caspase-10, and DCP2, a Drosophila melanogaster protein identified in this study. Unlike caspase-8, caspase-10, and DCP2, however, two important residues predicted to be involved in catalysis were lost in the caspase-like domain of CLARP. Analysis with fluorogenic substrates for caspase activity confirmed that CLARP is catalytically inactive. CLARP was found to interact with caspase-8 but not with FADD/MORT-1, an upstream death effector domain-containing protein of the Fas and tumor necrosis factor receptor 1 signaling pathway. Expression of CLARP induced apoptosis, which was blocked by the viral caspase inhibitor p35, dominant negative mutant caspase-8, and the synthetic caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-(OMe)-fluoromethylketone (zVAD-fmk). Moreover, CLARP augmented the killing ability of caspase-8 and FADD/MORT-1 in mammalian cells. The human clarp gene maps to 2q33. Thus, CLARP represents a regulator of the upstream caspase-8, which may play a role in apoptosis during tissue development and homeostasis.
Inohara
N
N
Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
Koseki
T
T
Hu
Y
Y
Chen
S
S
Núñez
G
G
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D017209:Apoptosis; D029681:Arabidopsis Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism; D020170:Caspase 1; D002384:Catalysis; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D018076:DNA, Complementary; D053200:Fas-Associated Death Domain Protein; D044943:Fatty Acid Desaturases / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D053219:Receptors, Tumor Necrosis Factor, Member 25; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D029681:Arabidopsis Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; D018076:DNA, Complementary; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D047908:Intracellular Signaling Peptides and Proteins; D010940:Plant Proteins; D011506:Proteins; D018124:Receptors, Tumor Necrosis Factor; D053219:Receptors, Tumor Necrosis Factor, Member 25; C506033:TNFRSF25 protein, human; D019014:fas Receptor; D044943:Fatty Acid Desaturases; C084083:Fad7 protein, Arabidopsis; D003546:Cysteine Endopeptidases; D020170:Caspase 1