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Monitoring of caspase-8/FLICE processing and activation upon Fas stimulation with novel antibodies directed against a cleavage site for caspase-8 and its substrate, FLICE-like inhibitory protein (FLIP).

Abstract：

:We generated and characterized novel antibodies specific for a cleavage site of human caspase-8/FLICE and its substrate, FLICE-like inhibitory protein (FLIP). The synthetic peptides used as immunogens were CQGDNYQKGIPVETD (#791) and VSEGQLEDSSLLEVD (#1342), which corresponded to cleaved regions of N-terminal fragments of caspase-8 and FLIP generated by active caspase-8, respectively. Each antibody purified from rabbit antiserum reacted specifically with the immunogen but not with the peptide corresponding to the unproteolyzed form, as assessed by ELISA. In vitro cleavage of GST-FLIP by active caspase-8 generated an N-terminal fragment (GST-p43) and a C-terminal one (p12). Consistent with other in vivo data, the FLIP cleavage site follows the Asp residue, LEVD(376)GPAMKNVEF, identified on N-terminal sequencing of the p12 fragment. #1342-antibody (#1342-Ab) recognized the GST-p43 fragment but not the uncleaved protein, thus confirming its specificity. When the antibodies were used for immunoblotting, flow cytometry, and confocal laser microscopy, the proteolysis of caspase-8 and FLIP, and the subcellular localization of their digests could be monitored in apoptotic U937 cells. Interestingly, a significant increase in the percentage of cells exhibiting caspase-8 and FLIP cleavage was observed upon Fas stimulation in interferon-gamma-treated U937 cells, in which the susceptibility to Fas is extremely enhanced. In contrast, U937 cells treated with vitamin D(3) or all-trans retinoic acid showed Fas-resistance, and caspase-8 processing and FLIP cleavage were strongly inhibited. In conclusion, we established a system based on the cleavage site-directed antibodies to monitor the dynamics of caspase-8 processing and activation during apoptosis. Using this system, we found that Fas-susceptibility changes during U937 differentiation occur upstream of caspase-8 processing/activation.

journal_name

J Biochem

journal_title

Journal of biochemistry

authors

Niikura Y,Nonaka T,Imajoh-Ohmi S

doi

10.1093/oxfordjournals.jbchem.a003198

keywords:

subject

Has Abstract

pub_date

2002-07-01 00:00:00

pages

53-62

issue

eissn

0021-924X

issn

1756-2651

journal_volume

132

pub_type

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Monitoring of caspase-8/FLICE processing and activation upon Fas stimulation with novel antibodies directed against a cleavage site for caspase-8 and its substrate, FLICE-like inhibitory protein (FLIP).