Abstract
The molecular events involved in apoptosis induced by ionizing radiation remain unresolved. In this paper we show that the cleavage of fodrin to a 150 kDa fragment is an early proteolytic event in radiation-induced apoptosis in the Burkitts' Lymphoma cell line BL30A and requires 100 microM zVAD-fmk for inhibition. Caspases-1, -3, -6 and -7 were shown to cleave fodrin to the 150 kDa fragment in vitro and all were inhibited by 10 microM zVAD-fmk. We also show that the in vitro cleavage of fodrin by calpain is inhibited by 100 microM zVAD-fmk as was the calpain-mediated hydrolysis of casein. We demonstrate that calpain is activated within 15 min after radiation exposure, concomitant with the cleavage of fodrin to the 150 kDa fragment whereas caspase-3 is activated at 2 h correlating with the cleavage of fodrin to the 120 kDa fragment. These results support a role for calpain in the early phases of the radiation-induced apoptosis pathway, upstream of the caspases.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Chloromethyl Ketones / pharmacology
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Amino Acid Sequence
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Apoptosis / drug effects
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Apoptosis / physiology*
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Apoptosis / radiation effects
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Burkitt Lymphoma
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Calpain / antagonists & inhibitors
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Calpain / metabolism*
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Carrier Proteins / genetics
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Carrier Proteins / metabolism
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Caspase 1 / metabolism
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Caspase 3
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Caspase 6
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Caspase 7
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Caspase Inhibitors
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Caspases / metabolism*
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Cysteine Proteinase Inhibitors / pharmacology
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Dose-Response Relationship, Drug
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Enzyme Activation
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Humans
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Microfilament Proteins / genetics
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Microfilament Proteins / metabolism
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Molecular Sequence Data
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Peptide Fragments / metabolism
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Tumor Cells, Cultured / cytology
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Tumor Cells, Cultured / enzymology
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Tumor Cells, Cultured / radiation effects
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fas Receptor
Substances
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Amino Acid Chloromethyl Ketones
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Carrier Proteins
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Caspase Inhibitors
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Cysteine Proteinase Inhibitors
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Membrane Proteins
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Microfilament Proteins
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Peptide Fragments
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benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
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fas Receptor
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fodrin
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CASP3 protein, human
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CASP6 protein, human
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CASP7 protein, human
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Calpain
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Caspase 3
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Caspase 6
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Caspase 7
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Caspases
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Caspase 1