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Pang X, Zhang J, Lopez H, Wang Y, Li W, O'Neill KL, Evans JJD, George NM, Long J, Chen Y, Luo X. The carboxyl-terminal tail of Noxa protein regulates the stability of Noxa and Mcl-1. J Biol Chem 2014; 289:17802-11. [PMID: 24811167 DOI: 10.1074/jbc.m114.548172] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The BH3-only protein Noxa is a critical mediator of apoptosis and functions primarily by sequestering/inactivating the antiapoptotic Bcl-2 family protein Mcl-1. Although Noxa is a highly labile protein, recent studies suggested that it is degraded by the proteasome in a ubiquitylation-independent manner. In the present study, we investigated the mechanism of Noxa degradation and its ability to regulate the stability of Mcl-1. We found that the ubiquitylation-independent degradation of Noxa does not require a physical association with Mcl-1. A short stretch of amino acid residues in the C-terminal tail was found to mediate the proteasome-dependent degradation of Noxa. Ectopic placement of this degron was able to render other proteins unstable. Surprisingly, mutation of this sequence not only attenuated the rapid degradation of Noxa, but also stabilized endogenous Mcl-1 through the BH3-mediated direct interaction. Together, these results suggest that the C-terminal tail of Noxa regulates the stability of both Noxa and Mcl-1.
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Affiliation(s)
- Xiaming Pang
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Jingjing Zhang
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696, the Xiangya School of Medicine, Central South University, Changsha 410013, China, and
| | - Hernando Lopez
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Yushu Wang
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696, the School of Medicine, Shandong University, Jinan 250100, China
| | - Wenyang Li
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Katelyn L O'Neill
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Jacquelynn J D Evans
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Nicholas M George
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Jianhong Long
- the Xiangya School of Medicine, Central South University, Changsha 410013, China, and
| | - Yi Chen
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Xu Luo
- From the Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696,
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Lopez H, Zhang L, George NM, Liu X, Pang X, Evans JJD, Targy NM, Luo X. Perturbation of the Bcl-2 network and an induced Noxa/Bcl-xL interaction trigger mitochondrial dysfunction after DNA damage. J Biol Chem 2010; 285:15016-15026. [PMID: 20223826 DOI: 10.1074/jbc.m109.086231] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
How most apoptotic stimuli trigger mitochondrial dysfunction remains to be resolved. We screened the entire Bcl-2 network for its involvement in DNA damage-induced apoptosis in HeLa cells. Although the anti-apoptotic member Bcl-xL served as a major suppressor, apoptosis initiated only when both Mcl-1 and Bcl-xL were eliminated. The pro-apoptotic members Bak, Bad, Bim, and Noxa were required for apoptosis induced by DNA damaging agents camptothecin and UV. We, therefore, used a His-tagged Bcl-xL expression system to capture the relevant BH3-only proteins that bind to Bcl-xL in response to DNA damage. Surprisingly, unlike Bad and Bim, which bound Bcl-xL constitutively, Noxa became "Mcl-1-free" and interacted with Bcl-xL after DNA damage but not after death receptor engagement. Similar observations were also made in A431 cells. Importantly, this induced interaction caused cytochrome c release and apoptosis and was directly inhibited by Mcl-1, a protein eliminated or inactivated after DNA damage. These results suggest that the loss/inactivation of Mcl-1 in conjunction with an induced Noxa/Bcl-xL interaction may serve as a trigger for mitochondrial dysfunction during DNA damage-induced apoptosis.
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Affiliation(s)
- Hernando Lopez
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Liqiang Zhang
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Nicholas M George
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Xiaoqiong Liu
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Xiaming Pang
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Jacquelynn J D Evans
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Natalie M Targy
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696
| | - Xu Luo
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696.
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George NM, Targy N, Evans JJD, Zhang L, Luo X. Bax contains two functional mitochondrial targeting sequences and translocates to mitochondria in a conformational change- and homo-oligomerization-driven process. J Biol Chem 2009; 285:1384-92. [PMID: 19880508 DOI: 10.1074/jbc.m109.049924] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The apoptosis gateway protein Bax normally exists in the cytosol as a globular shaped monomer composed of nine alpha-helices. During apoptosis, Bax translocates to the mitochondria, forms homo-oligomers, and subsequently induces mitochondrial damage. The mechanism of Bax mitochondrial translocation remains unclear. Among the nine alpha-helices of Bax, helices 4, 5, 6, and 9 are capable of targeting a heterologous protein to mitochondria. However, only helices 6 and 9 can independently direct the oligomerized Bax to the mitochondria. Although Bax mitochondrial translocation can still proceed with mutations in either helix 6 or helix 9, combined mutations completely abolished mitochondrial targeting in response to activating signals. Using a proline mutagenesis scanning analysis, we demonstrated that conformational changes were sufficient to cause Bax to move from the cytosol to the mitochondria. Moreover, we found that homo-oligomerization of Bax contributed to its mitochondrial translocation. These results suggest that Bax is targeted to the mitochondria through the exposure of one or both of the two functional mitochondrial targeting sequences in a conformational change-driven and homo-oligomerization-aided process.
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Affiliation(s)
- Nicholas M George
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696, USA
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