Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing*
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Amino Acid Sequence
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Apoptosis*
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Arabidopsis Proteins*
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CASP8 and FADD-Like Apoptosis Regulating Protein
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Carrier Proteins / metabolism
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Caspase 1
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Catalysis
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Cloning, Molecular
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Cysteine Endopeptidases / metabolism*
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DNA, Complementary
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Fas-Associated Death Domain Protein
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Fatty Acid Desaturases / metabolism
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Humans
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Intracellular Signaling Peptides and Proteins*
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Molecular Sequence Data
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Plant Proteins / metabolism
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Protein Binding
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Proteins / chemistry
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Proteins / genetics
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Proteins / metabolism*
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Receptors, Tumor Necrosis Factor / metabolism
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Receptors, Tumor Necrosis Factor, Member 25
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Sequence Homology, Amino Acid
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Signal Transduction
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Tumor Cells, Cultured
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fas Receptor / metabolism
Substances
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Adaptor Proteins, Signal Transducing
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Arabidopsis Proteins
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CASP8 and FADD-Like Apoptosis Regulating Protein
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CFLAR protein, human
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Carrier Proteins
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DNA, Complementary
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FADD protein, human
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Fas-Associated Death Domain Protein
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Intracellular Signaling Peptides and Proteins
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Plant Proteins
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Proteins
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Receptors, Tumor Necrosis Factor
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Receptors, Tumor Necrosis Factor, Member 25
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TNFRSF25 protein, human
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fas Receptor
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Fatty Acid Desaturases
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Fad7 protein, Arabidopsis
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Cysteine Endopeptidases
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Caspase 1
Associated data
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GENBANK/AF005774
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GENBANK/AF005775
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GENBANK/AF031652