c-IAP1 Is Cleaved by Caspases to Produce a Proapoptotic C-terminal Fragment

c-IAP1 Is Cleaved by Caspases to Produce a Proapoptotic C-terminal Fragment

Although human c-IAP1 and c-IAP2 have been reported to possess antiapoptotic activity against a variety of stimuli in several mammalian cell types, we observed that full-length c-IAP1 and c-IAP2 failed to protect cells from apoptosis induced by Bax overexpression, tumor necrosis factor α treatment o...

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Bibliographic Details
Published in:The Journal of biological chemistry Vol. 276; no. 10; pp. 7602 - 7608
Main Authors: Clem, Rollie J., Sheu, Ting-Ting, Richter, BettinaW.M., He, Wei-Wu, Thornberry, Nancy A., Duckett, Colin S., Hardwick, J.Marie
Format: Journal Article
Language:English
Published: United States Elsevier Inc 09-03-2001
American Society for Biochemistry and Molecular Biology
Subjects:
Animals
Apoptosis
Binding Sites
Caspase 3
Caspases - metabolism
Cell Line
CHO Cells
Cricetinae
Gene Deletion
Humans
Immunoblotting
Inhibitor of Apoptosis Proteins
Models, Genetic
Mutagenesis, Site-Directed
Plasmids - metabolism
Protein Binding
Protein Structure, Tertiary
Sindbis Virus - genetics
Transfection
Viral Proteins - chemistry
Viral Proteins - metabolism
Zinc - metabolism
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Summary:Although human c-IAP1 and c-IAP2 have been reported to possess antiapoptotic activity against a variety of stimuli in several mammalian cell types, we observed that full-length c-IAP1 and c-IAP2 failed to protect cells from apoptosis induced by Bax overexpression, tumor necrosis factor α treatment or Sindbis virus infection. However, deletion of the C-terminal RING domains of c-IAP1 and c-IAP2 restored antiapoptotic activity, indicating that this region negatively regulates the antiapoptotic function of the N-terminal BIR domain. This finding is consistent with the observation by others that the spacer region and RING domain of c-IAP1 functions as an E3 ligase, promoting autoubiquitination and degradation of c-IAP1. In addition, we found that c-IAP1 is cleaved during apoptosis to 52- and 35-kDa fragments. Both fragments contain the C-terminal end of c-IAP1 including the RING finger. In vitro cleavage of c-IAP1 with apoptotic cell extracts or with purified recombinant caspase-3 produced similar fragments. Furthermore, transfection of cells with the spacer-RING domain alone suppressed the antiapoptotic function of the N-terminal BIR domain of c-IAP1 and induced apoptosis. Optimal death-inducing activity of the spacer-RING required both the spacer region and the zinc-binding RING domain of c-IAP1 but did not require the caspase recruitment domain located within the spacer region. To the contrary, deletion of the caspase recruitment domain increased proapoptotic activity, apparently by stabilizing the C-terminal fragment.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M010259200