Abstract
Granzyme A (GzmA) induces caspase-independent cell death with morphological features of apoptosis. Here, we show that GzmA at nanomolar concentrations cleaves Ku70, a key double-strand break repair (DSBR) protein, in target cells. Ku70 is cut after Arg(301), disrupting Ku complex binding to DNA. Cleaving Ku70 facilitates GzmA-mediated cell death, as silencing Ku70 by RNA interference increases DNA damage and cell death by GzmB cluster-deficient cytotoxic T lymphocytes or by GzmA and perforin, whereas Ku70 overexpression has the opposite effect. Ku70 has two known antiapoptotic effects-facilitating DSBR and sequestering bax to prevent its translocation to mitochondria. However, GzmA triggers single-stranded, not double-stranded, DNA damage, and GzmA-induced cell death does not involve bax. Therefore, Ku70 has other antiapoptotic functions in GzmA-induced cell death, which are blocked when GzmA proteolyses Ku70.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Animals
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Antigens, Nuclear / genetics
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Antigens, Nuclear / metabolism*
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Arginine / genetics
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Arginine / metabolism
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Cell Nucleus / metabolism
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Cells, Cultured
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DNA / genetics
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DNA / metabolism*
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DNA Damage* / drug effects
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DNA Repair*
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DNA-Binding Proteins / deficiency
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Gene Expression Regulation
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Granzymes
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Humans
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Ku Autoantigen
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Membrane Glycoproteins / pharmacology
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Mice
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Perforin
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Pore Forming Cytotoxic Proteins
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Protease Inhibitors / pharmacology
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Protein Binding
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Serine Endopeptidases / metabolism*
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Serine Endopeptidases / pharmacology
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T-Lymphocytes, Cytotoxic / metabolism
Substances
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Antigens, Nuclear
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DNA-Binding Proteins
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Membrane Glycoproteins
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Pore Forming Cytotoxic Proteins
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Protease Inhibitors
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Perforin
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DNA
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Arginine
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Granzymes
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Serine Endopeptidases
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GZMA protein, human
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Xrcc6 protein, human
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Xrcc6 protein, mouse
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Ku Autoantigen