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The Drosophila DIAP1 protein is required to prevent accumulation of a continuously generated, processed form of the apical caspase DRONC

Muro, Israel and Hay, Bruce A. and Clem, Rollie J. (2002) The Drosophila DIAP1 protein is required to prevent accumulation of a continuously generated, processed form of the apical caspase DRONC. Journal of Biological Chemistry, 277 (51). pp. 49644-49650. ISSN 0021-9258. doi:10.1074/jbc.M203464200.

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Although loss of the inhibitor of apoptosis (LAP) protein DIAP1 has been shown to result in caspase activation and spontaneous cell death in Drosophila cells and embryos, the point at which DIAP1 normally functions to inhibit caspase activation is unknown. Depletion of the DIAP1 protein in Drosophila S2 cells or the Sf-IAP protein in Spodoptera frugiperda Sf21 cells by RNA interference (RNAi) or cycloheximide treatment resulted in rapid and widespread caspase-dependent apoptosis. Co-silencing of dronc or dark largely suppressed this apoptosis, indicating that DIAP1 is normally required to inhibit an activity dependent on these proteins. Silencing of dronc also inhibited DRICE processing following stimulation of apoptosis, demonstrating that DRONC functions as an apical caspase in S2 cells. Silencing of diap1 or treatment with UV light induced DRONC processing, which occurred in two steps. The first step appeared to occur continuously even in the absence of an apoptotic signal and to be dependent on DARK because full-length DRONC accumulated when dark was silenced in non-apoptotic cells. In addition, treatment with the proteasome inhibitor MG132 resulted in accumulation of this initially processed form of DRONC, but not full-length DRONC, in non-apoptotic cells. The second step in DRONC processing was observed only in apoptotic cells. These results indicate that the initial step in DRONC processing occurs continuously via a DARK-dependent mechanism in Drosophila cells and that DIAP1 is required to prevent excess accumulation of this first form of processed DRONC, presumably through its ability to act as a ubiquitin-protein ligase.

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Additional Information:© 2002 The American Society for Biochemistry and Molecular Biology, Inc. Received for publication, April 10, 2002, and in revised form, October 20, 2002. Published, JBC Papers in Press, October 22, 2002, DOI 10.1074/jbc.M203464200. This work was supported in part by United States Public Health Service Grant CA78602 from the NCI, National Institutes of Health (to R.J.C.), and the Kansas Agricultural Experiment Station. This is Contribution Number 02-297-J from the Kansas Agricultural Experiment Station. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. [I.M.] Recipient of support from NCI Predoctoral Training Grant T32 CA09418 from the National Institutes of Health.
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Kansas Agricultural Experiment StationUNSPECIFIED
NIH Predoctoral FellowshipT32 CA09418
Issue or Number:51
Record Number:CaltechAUTHORS:MURjbc02
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4278
Deposited By: Lindsay Cleary
Deposited On:11 Aug 2006
Last Modified:08 Nov 2021 20:16

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