Caspases cleave the amino-terminal calpain inhibitory unit of calpastatin during apoptosis in human Jurkat T cells.
We have previously reported the activation of procalpain mu (precursor for low-calcium-requiring calpain) in apoptotic cells using a cleavage-site-directed antibody specific to active calpain [Kikuchi, H. and Imajoh-Ohmi, S. (1995) Cell Death Differ. 2, 195-199]. In this study, calpastatin, the endogenous inhibitor protein for calpain, was cleaved to a 90-kDa polypeptide during apoptosis in human Jurkat T cells. The limited proteolysis of calpastatin preceded the autolytic activation of procalpain. Inhibitors for caspases rescued the cells from apoptosis and simultaneously inhibited the cleavage of calpastatin. The full-length recombinant calpastatin was also cleaved by caspase-3 or caspase-7 at Asp-233 into the same size fragment. Cys-241 was also targeted by these caspases in vitro but not in apoptotic cells. Caspase-digested calpastatin lost its amino-terminal inhibitory unit, and inhibited three moles of calpain per mole. Our findings suggest that caspases trigger the decontrol of calpain activity suppression by degrading calpastatin.
Kato
M
M
Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.
Nonaka
T
T
Maki
M
M
Kikuchi
H
H
Imajoh-Ohmi
S
S
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006801:Humans; D019169:Jurkat Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D007976:Leupeptins / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000187:drug effects / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism
D000590:Amino Acid Chloromethyl Ketones; D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; C098738:N-acetyl-tyrosyl-valyl-alanyl-aspartyl chloromethyl ketone; D009842:Oligopeptides; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; C408403:acetyl-leucyl-leucyl-normethional; C093260:benzyloxycarbonyl-Asp-CH2OC(O)-2,6-dichlorobenzene; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; C063261:acetylleucyl-leucyl-norleucinal; D001224:Aspartic Acid; C033668:calpastatin; D011065:Poly(ADP-ribose) Polymerases; D002154:Calpain; D020169:Caspases