Modulation of apoptosis by procaspase-2 short isoform: selective inhibition of chromatin condensation, apoptotic body formation and phosphatidylserine externalization.
Procaspase-2 is one of the cysteine aspartate proteases involved in apoptotic cell death. Alternative splicing of CASP-2 messenger RNA generates a long isoform, procaspase-2L, whose overexpression induces cell death and a truncated isoform, procaspase-2S, whose function remains poorly defined. The present study explored the consequences of procaspase-2S overexpression in U937 human leukemic cells exposed to the topoisomerase II inhibitor etoposide as an apoptotic stimulus. Overexpression of procaspase-2S in U937 cells partially prevented nuclear changes associated with etoposide-induced cell death, as determined by Hoechst 33342 staining of nuclear chromatin and electron microscopy studies. Procaspase-2S also prevented the maturation of apoptotic bodies, delayed phosphatidylserine externalization on the plasma membrane and prevented the cleavage and activation of procaspase-2L. These effects were not observed when the cysteine 289 in the consensus QACRG motif was mutated into a serine. Wild-type procaspase-2S overexpression did not influence the cleavage of procaspase-3, procaspase-7 and poly(ADP-ribose)polymerase nor the fragmentation of nuclear DNA into nucleosome-sized fragments. Altogether, these results indicate that the short isoform of procaspase-2 negatively interferes with selective features of apoptosis, an activity that is suppressed by mutation of the cysteine 289.
Droin
N
N
INSERM U517, Faculties of Medicine & Pharmacy, 7 boulevard Jeanne d'Arc, 21033 Dijon, France.
Rébé
C
C
Bichat
F
F
Hammann
A
A
Bertrand
R
R
Solary
E
E
D020816:Amino Acid Motifs; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001483:Base Sequence; D053143:Caspase 2; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D002843:Chromatin / Q000648:ultrastructure*; D003545:Cysteine; D053938:DNA Fragmentation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes; D007938:Leukemia; D008969:Molecular Sequence Data; D009154:Mutation; D010718:Phosphatidylserines / Q000378:metabolism*; D059005:Topoisomerase II Inhibitors; D014162:Transfection; D014407:Tumor Cells, Cultured
D002843:Chromatin; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D007527:Isoenzymes; D010718:Phosphatidylserines; D059005:Topoisomerase II Inhibitors; D005047:Etoposide; D053143:Caspase 2; D020169:Caspases; D003545:Cysteine