Bax-induced cytochrome c release from mitochondria depends on alpha-helices-5 and -6

Heimlich, Gerd; McKinnon, Alastair D.; Bernardo, Katussevani; Brdiczka, Dieter; Reed, John C.; Kain, Renate; Krönke, Martin; Jürgensmeier, Juliane M.

doi:10.1042/bj20031152

Cited by 92 publications

(62 citation statements)

References 67 publications

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“…Of note, these two sequences have been shown to be implicated in the addressing and the insertion of Bax into mitochondrial membrane. 4,5 Interestingly, a weaker interaction was observed with the hydrophobic Ha9 and the two regions flanking the BH3 domain of Bax (Figure 2a). The interaction of VDAC with Bax has been suggested 26 but only a faint association of Bax peptides with VDAC was observed under our conditions (Figure 2a), suggesting that the Bax/VDAC association does not occur through 'linear' primary sequences.…”

Section: Resultsmentioning

confidence: 98%

“…Our previous results suggested that Ha1 was involved in the addressing of Bax to mitochondria but that the membrane insertion domain of Bax was carried out by Ha5 and Ha6, 5 as previously shown by others. 4,32 Quite remarkably, TOM22 can also bind to a region linking the Ha5 and Ha6, suggesting that it might also be involved in the insertion of Bax in the outer mitochondrial membrane (Figure 2). Of course, we cannot eliminate the possibility that other proteins whose mitochondrial targeting is dependent on Tom22 specifically affect Bax translocation and apoptosis.…”

Section: Discussionmentioning

confidence: 99%

“…4,5 Bax resides in an inactive state in the cytosol in many resting cells and is translocated to the mitochondria at the onset of apoptosis. 6 This translocation is associated with major conformational changes in Bax as both the amino-terminal end (N-T) and carboxy terminal end (C-T) become exposed facilitating its mitochondrial addressing and membrane insertion.…”

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confidence: 99%

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TOM22, a core component of the mitochondria outer membrane protein translocation pore, is a mitochondrial receptor for the proapoptotic protein Bax

et al. 2006

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The association of Bax with mitochondria is an essential step in the implementation of apoptosis. By using a bacterial two-hybrid assay and crosslinking strategies, we have identified TOM22, a component of the translocase of the outer mitochondrial membrane (TOM), as a mitochondrial receptor of Bax. Peptide mapping showed that the interaction of Bax with TOM22 involved the first alpha helix of Bax and possibly two central alpha helices, which are homologous to the pore forming domains of some toxins. Antibodies directed against TOM22 or an antisense knockdown of the expression of TOM22 specifically inhibited the association of Bax with mitochondria and prevented Bax-dependent apoptosis. In yeast, a haploid strain for TOM22 exhibited a decreased expression of TOM22 and mitochondrial association of ectopically expressed human Bax. Our data provide a new perspective on the mechanism of association of Bax with mitochondria as it involves a classical import pathway. Apoptosis is a cell death program, which is central in many aspects to metazoan cell physiology and pathology. 1 Proteins of the Bcl-2 family are key players in the execution phase of apoptosis and their main functions is to control the release of apoptogenic proteins, such as cytochrome c (cyt c) and apoptosis inducing factor (AIF) from the mitochondria. 2 The Bcl-2 family is composed of antiapoptotic members such as Bcl-2 and proapoptotic proteins such as Bax or Bak, which share several domains of homology called BH. 1 In addition to these proteins, a third Bcl-2-related family of proteins have been identified as major amplifiers and/inducers of apoptosis. 2 The latter family has a homology to Bcl-2 limited to the BH3 domain and thus is called the BH3 only proteins. 2 The double knockout of Bax and Bak renders cells completely resistant to cell death 2 highlighting the essential role of these proteins during apoptosis.The determination of the solution structure of Bax showed its organization around nine a-helices (Ha1 to Ha9) 3 of which Ha2 contained most of the BH3 domain and Ha5 and Ha6, a putative pore forming domain that has been shown to be involved in the integration of Bax into the membrane. 4,5 Bax resides in an inactive state in the cytosol in many resting cells and is translocated to the mitochondria at the onset of apoptosis. 6 This translocation is associated with major conformational changes in Bax as both the amino-terminal end (N-T) and carboxy terminal end (C-T) become exposed facilitating its mitochondrial addressing and membrane insertion. 5,7 Bax mitochondrial membrane insertion and oligomerization is closely associated with the release into the cytosol of several intermembrane space proteins such as cyt c, second mitochondrial apoptotic factor (Smac) and AIF. 2 The nature of the different stimuli involved in the activation or in the inhibition of Bax is still largely unknown although this step remains one of the most critical points of control of the apoptotic program during which therapeutic interventions can be envisaged. 2 The mit...

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Section: Resultsmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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TOM22, a core component of the mitochondria outer membrane protein translocation pore, is a mitochondrial receptor for the proapoptotic protein Bax

et al. 2006

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“…This domain has been shown to be required for mitochondrial targeting of Bax protein (Wolter et al, 1997;Goping et al, 1998). However, these conclusions have been challenged by data showing that deletion of Da9 did not abolish mitochondrial targeting and cytochrome c release (Tremblais et al, 1999;Heimlich et al, 2004). Nevertheless, we successfully obtained reliable transfectants stably expressing BaxDa9, in contrast with expression of wild-type Bax (see below).…”

Section: Expression Of the Transgenes In Cho Cellsmentioning

confidence: 97%

Bax and Bid, two proapoptotic Bcl-2 family members, inhibit homologous recombination, independently of apoptosis regulation

et al. 2006

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In order to analyse the relationships between regulation of apoptosis and homologous recombination (HR), we overexpressed proapoptotic Bax or only-BH3 Bid proteins or antiapoptotic Bcl-2 or Bcl-XL, in hamster CHO cells or in SV40-transformed human fibroblasts. We measured HR induced by c-rays, UVC or a specific double-strand cleavage targeted in the recombination substrate by the meganuclease I-SceI. We show here that the induction of both recombinant cells and recombinant colonies was impaired when expressing Bcl-2 family members, in hamster as well as in human cells. Moreover, the pro-as well as antiapoptotic Bcl-2 family members inhibited HR, independently of degradation of the RAD51 recombination protein and of their impact on apoptosis. These data reveal a mechanism of HR downregulation by potentially proapoptotic proteins, distinct from and parallel to degradation of recombination proteins, a situation that should also optimize the efficiency of programmed cell death.

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“…72 This structural analogy led to experimental confirmation that BCL-2 family members can mediate pore formation in liposomal and mitochondrial systems, [73][74][75][76] an activity that is dependent upon core helices 5 and 6. [76][77][78] Another critical architectural feature of BCL-X L was identified on its protein surface, a hydrophobic groove formed at the apex by the confluence of BH1, 2, and 3 domains and at the base by a-helices 3 and 4. The structure of a BAK BH3 peptide in complex with BCL-X L revealed that the hydrophobic groove was indeed the contact site for proapoptotic binding 53 ( Figure 4b).…”

Section: Bcl-2 Family Form and Functionmentioning

confidence: 99%

BCL-2 in the crosshairs: tipping the balance of life and death

Walensky¹

2006

Cell Death Differ

225

175

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The discovery of B-cell lymphoma-2 (BCL-2) over 20 years ago revealed a new paradigm in cancer biology: the development and persistence of cancer can be driven by molecular roadblocks along the natural pathway to cell death. The subsequent identification of an expansive family of BCL-2 proteins provoked an intensive investigation of the interplay among these critical regulators of cell death. What emerged was a compelling tale of guardians and executioners, each participating in a molecular choreography that dictates cell fate. Ten years into the BCL-2 era, structural details defined how certain BCL-2 family proteins interact, and molecular targeting of the BCL-2 family has since become a pharmacological quest. Although many facets of BCL-2 family death signaling remain a mechanistic mystery, small molecules and peptides that effectively target BCL-2 are eliminating the roadblock to cell death, raising hopes for a medical breakthrough in cancer and other diseases of deregulated apoptosis.

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Bax-induced cytochrome c release from mitochondria depends on alpha-helices-5 and -6

Cited by 92 publications

References 67 publications

TOM22, a core component of the mitochondria outer membrane protein translocation pore, is a mitochondrial receptor for the proapoptotic protein Bax

TOM22, a core component of the mitochondria outer membrane protein translocation pore, is a mitochondrial receptor for the proapoptotic protein Bax

Bax and Bid, two proapoptotic Bcl-2 family members, inhibit homologous recombination, independently of apoptosis regulation

BCL-2 in the crosshairs: tipping the balance of life and death

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