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Proteasome-mediated degradation of Smac during apoptosis: XIAP promotes Smac ubiquitination in vitro.
J Biol Chem 2002; 277(39):36611-6JB

Abstract

During apoptosis, Smac (second mitochondria-derived activator of caspases)/DIABLO, an IAP (inhibitor of apoptosis protein)-binding protein, is released from mitochondria and potentiates apoptosis by relieving IAP inhibition of caspases. We demonstrate that exposure of MCF-7 cells to the death-inducing ligand, TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), results in rapid Smac release from mitochondria, which occurs before or in parallel with loss of cytochrome c. Smac release is inhibited by Bcl-2/Bcl-xL or by a pan-caspase inhibitor demonstrating that this event is caspase-dependent and modulated by Bcl-2 family members. Following release, Smac is rapidly degraded by the proteasome, an effect suppressed by co-treatment with a proteasome inhibitor. As the RING finger domain of XIAP possesses ubiquitin-protein ligase activity and XIAP binds tightly to mature Smac, an in vitro ubiquitination assay was performed which revealed that XIAP functions as a ubiquitin-protein ligase (E3) in the ubiquitination of Smac. Both the association of XIAP with Smac and the RING finger domain of XIAP are essential for ubiquitination, suggesting that the ubiquitin-protein ligase activity of XIAP may promote the rapid degradation of mitochondrial-released Smac. Thus, in addition to its well characterized role in inhibiting caspase activity, XIAP may also protect cells from inadvertent mitochondrial damage by targeting pro-apoptotic molecules for proteasomal degradation.

Authors+Show Affiliations

Medical Research Council Toxicology Unit, Hodgkin Building, University of Leicester, P. O. Box 138, Lancaster Road, Leicester LE1 9HN, United Kingdom.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

12121969

Citation

MacFarlane, Marion, et al. "Proteasome-mediated Degradation of Smac During Apoptosis: XIAP Promotes Smac Ubiquitination in Vitro." The Journal of Biological Chemistry, vol. 277, no. 39, 2002, pp. 36611-6.
MacFarlane M, Merrison W, Bratton SB, et al. Proteasome-mediated degradation of Smac during apoptosis: XIAP promotes Smac ubiquitination in vitro. J Biol Chem. 2002;277(39):36611-6.
MacFarlane, M., Merrison, W., Bratton, S. B., & Cohen, G. M. (2002). Proteasome-mediated degradation of Smac during apoptosis: XIAP promotes Smac ubiquitination in vitro. The Journal of Biological Chemistry, 277(39), pp. 36611-6.
MacFarlane M, et al. Proteasome-mediated Degradation of Smac During Apoptosis: XIAP Promotes Smac Ubiquitination in Vitro. J Biol Chem. 2002 Sep 27;277(39):36611-6. PubMed PMID: 12121969.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Proteasome-mediated degradation of Smac during apoptosis: XIAP promotes Smac ubiquitination in vitro. AU - MacFarlane,Marion, AU - Merrison,Wendy, AU - Bratton,Shawn B, AU - Cohen,Gerald M, Y1 - 2002/07/16/ PY - 2002/7/18/pubmed PY - 2002/11/26/medline PY - 2002/7/18/entrez SP - 36611 EP - 6 JF - The Journal of biological chemistry JO - J. Biol. Chem. VL - 277 IS - 39 N2 - During apoptosis, Smac (second mitochondria-derived activator of caspases)/DIABLO, an IAP (inhibitor of apoptosis protein)-binding protein, is released from mitochondria and potentiates apoptosis by relieving IAP inhibition of caspases. We demonstrate that exposure of MCF-7 cells to the death-inducing ligand, TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), results in rapid Smac release from mitochondria, which occurs before or in parallel with loss of cytochrome c. Smac release is inhibited by Bcl-2/Bcl-xL or by a pan-caspase inhibitor demonstrating that this event is caspase-dependent and modulated by Bcl-2 family members. Following release, Smac is rapidly degraded by the proteasome, an effect suppressed by co-treatment with a proteasome inhibitor. As the RING finger domain of XIAP possesses ubiquitin-protein ligase activity and XIAP binds tightly to mature Smac, an in vitro ubiquitination assay was performed which revealed that XIAP functions as a ubiquitin-protein ligase (E3) in the ubiquitination of Smac. Both the association of XIAP with Smac and the RING finger domain of XIAP are essential for ubiquitination, suggesting that the ubiquitin-protein ligase activity of XIAP may promote the rapid degradation of mitochondrial-released Smac. Thus, in addition to its well characterized role in inhibiting caspase activity, XIAP may also protect cells from inadvertent mitochondrial damage by targeting pro-apoptotic molecules for proteasomal degradation. SN - 0021-9258 UR - https://www.unboundmedicine.com/medline/citation/12121969/Proteasome_mediated_degradation_of_Smac_during_apoptosis:_XIAP_promotes_Smac_ubiquitination_in_vitro_ L2 - http://www.jbc.org/cgi/pmidlookup?view=long&pmid=12121969 DB - PRIME DP - Unbound Medicine ER -