Bax regulates primary necrosis through mitochondrial dynamics

Russell S. Whelan, Klitos Konstantinidis, An Chi Wei, Yun Chen, Denis E. Reyna, Saurabh Jha, Ying Yang, John W. Calvert, Tullia Lindsten, Craig B. Thompson, Michael T. Crow, Evripidis Gavathiotis, Gerald W. Dorn, Brian O'Rourke, Richard N. Kitsis

Research output: Contribution to journalArticle

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Abstract

The defining event in apoptosis is mitochondrial outer membrane permeabilization (MOMP), allowing apoptogen release. In contrast, the triggering event in primary necrosis is early opening of the inner membrane mitochondrial permeability transition pore (mPTP), precipitating mitochondrial dysfunction and cessation of ATP synthesis. Bcl-2 proteins Bax and Bak are the principal activators of MOMP and apoptosis. Unexpectedly, we find that deletion of Bax and Bak dramatically reduces necrotic injury during myocardial infarction in vivo. Triple knockout mice lacking Bax/Bak and cyclophilin D, a key regulator of necrosis, fail to show further reduction in infarct size over those deficient in Bax/Bak. Absence of Bax/Bak renders cells resistant to mPTP opening and necrosis, effects confirmed in isolated mitochondria. Reconstitution of these cells or mitochondria with wild-type Bax, or an oligomerization-deficient mutant that cannot support MOMP and apoptosis, restores mPTP opening and necrosis, implicating distinct mechanisms for Bax-regulated necrosis and apoptosis. Both forms of Bax restore mitochondrial fusion in Bax/Bak-null cells, which otherwise exhibit fragmented mitochondria. Cells lacking mitofusin 2 (Mfn2), which exhibit similar fusion defects, are protected to the same extent as Bax/Bak-null cells. Conversely, restoration of fused mitochondria through inhibition of fission potentiates mPTP opening in the absence of Bax/Bak or Mfn2, indicating that the fused state itself is critical. These data demonstrate that Bax-driven fusion lowers the threshold for mPTP opening and necrosis. Thus, Bax and Bak play wider roles in cell death than previously appreciated and may be optimal therapeutic targets for diseases that involve both forms of cell death.

Original languageEnglish (US)
Pages (from-to)6566-6571
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue number17
DOIs
StatePublished - Apr 24 2012

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Mitochondrial Dynamics
Necrosis
Mitochondria
Mitochondrial Membranes
Apoptosis
Null Lymphocytes
bcl-2 Homologous Antagonist-Killer Protein
Cell Death
bcl-2-Associated X Protein
Knockout Mice
Adenosine Triphosphate
Myocardial Infarction
mitochondrial permeability transition pore
Membranes
Wounds and Injuries

ASJC Scopus subject areas

  • General

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Bax regulates primary necrosis through mitochondrial dynamics. / Whelan, Russell S.; Konstantinidis, Klitos; Wei, An Chi; Chen, Yun; Reyna, Denis E.; Jha, Saurabh; Yang, Ying; Calvert, John W.; Lindsten, Tullia; Thompson, Craig B.; Crow, Michael T.; Gavathiotis, Evripidis; Dorn, Gerald W.; O'Rourke, Brian; Kitsis, Richard N.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 109, No. 17, 24.04.2012, p. 6566-6571.

Research output: Contribution to journalArticle

Whelan, RS, Konstantinidis, K, Wei, AC, Chen, Y, Reyna, DE, Jha, S, Yang, Y, Calvert, JW, Lindsten, T, Thompson, CB, Crow, MT, Gavathiotis, E, Dorn, GW, O'Rourke, B & Kitsis, RN 2012, 'Bax regulates primary necrosis through mitochondrial dynamics', Proceedings of the National Academy of Sciences of the United States of America, vol. 109, no. 17, pp. 6566-6571. https://doi.org/10.1073/pnas.1201608109
Whelan, Russell S. ; Konstantinidis, Klitos ; Wei, An Chi ; Chen, Yun ; Reyna, Denis E. ; Jha, Saurabh ; Yang, Ying ; Calvert, John W. ; Lindsten, Tullia ; Thompson, Craig B. ; Crow, Michael T. ; Gavathiotis, Evripidis ; Dorn, Gerald W. ; O'Rourke, Brian ; Kitsis, Richard N. / Bax regulates primary necrosis through mitochondrial dynamics. In: Proceedings of the National Academy of Sciences of the United States of America. 2012 ; Vol. 109, No. 17. pp. 6566-6571.
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AU - Whelan, Russell S.

AU - Konstantinidis, Klitos

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AU - Jha, Saurabh

AU - Yang, Ying

AU - Calvert, John W.

AU - Lindsten, Tullia

AU - Thompson, Craig B.

AU - Crow, Michael T.

AU - Gavathiotis, Evripidis

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AU - O'Rourke, Brian

AU - Kitsis, Richard N.

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N2 - The defining event in apoptosis is mitochondrial outer membrane permeabilization (MOMP), allowing apoptogen release. In contrast, the triggering event in primary necrosis is early opening of the inner membrane mitochondrial permeability transition pore (mPTP), precipitating mitochondrial dysfunction and cessation of ATP synthesis. Bcl-2 proteins Bax and Bak are the principal activators of MOMP and apoptosis. Unexpectedly, we find that deletion of Bax and Bak dramatically reduces necrotic injury during myocardial infarction in vivo. Triple knockout mice lacking Bax/Bak and cyclophilin D, a key regulator of necrosis, fail to show further reduction in infarct size over those deficient in Bax/Bak. Absence of Bax/Bak renders cells resistant to mPTP opening and necrosis, effects confirmed in isolated mitochondria. Reconstitution of these cells or mitochondria with wild-type Bax, or an oligomerization-deficient mutant that cannot support MOMP and apoptosis, restores mPTP opening and necrosis, implicating distinct mechanisms for Bax-regulated necrosis and apoptosis. Both forms of Bax restore mitochondrial fusion in Bax/Bak-null cells, which otherwise exhibit fragmented mitochondria. Cells lacking mitofusin 2 (Mfn2), which exhibit similar fusion defects, are protected to the same extent as Bax/Bak-null cells. Conversely, restoration of fused mitochondria through inhibition of fission potentiates mPTP opening in the absence of Bax/Bak or Mfn2, indicating that the fused state itself is critical. These data demonstrate that Bax-driven fusion lowers the threshold for mPTP opening and necrosis. Thus, Bax and Bak play wider roles in cell death than previously appreciated and may be optimal therapeutic targets for diseases that involve both forms of cell death.

AB - The defining event in apoptosis is mitochondrial outer membrane permeabilization (MOMP), allowing apoptogen release. In contrast, the triggering event in primary necrosis is early opening of the inner membrane mitochondrial permeability transition pore (mPTP), precipitating mitochondrial dysfunction and cessation of ATP synthesis. Bcl-2 proteins Bax and Bak are the principal activators of MOMP and apoptosis. Unexpectedly, we find that deletion of Bax and Bak dramatically reduces necrotic injury during myocardial infarction in vivo. Triple knockout mice lacking Bax/Bak and cyclophilin D, a key regulator of necrosis, fail to show further reduction in infarct size over those deficient in Bax/Bak. Absence of Bax/Bak renders cells resistant to mPTP opening and necrosis, effects confirmed in isolated mitochondria. Reconstitution of these cells or mitochondria with wild-type Bax, or an oligomerization-deficient mutant that cannot support MOMP and apoptosis, restores mPTP opening and necrosis, implicating distinct mechanisms for Bax-regulated necrosis and apoptosis. Both forms of Bax restore mitochondrial fusion in Bax/Bak-null cells, which otherwise exhibit fragmented mitochondria. Cells lacking mitofusin 2 (Mfn2), which exhibit similar fusion defects, are protected to the same extent as Bax/Bak-null cells. Conversely, restoration of fused mitochondria through inhibition of fission potentiates mPTP opening in the absence of Bax/Bak or Mfn2, indicating that the fused state itself is critical. These data demonstrate that Bax-driven fusion lowers the threshold for mPTP opening and necrosis. Thus, Bax and Bak play wider roles in cell death than previously appreciated and may be optimal therapeutic targets for diseases that involve both forms of cell death.

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