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To whom correspondence should be addressed. E-mail: richard.kitsis@einstein.yu.edu

Edited* by Andrew R. Marks, Columbia University College of Physicians and Surgeons, New York, NY, and approved March 9, 2012

Author contributions: R.S.W., K.K., J.W.C., T.L., C.B.T., M.T.C., E.G., G.W.D., B.O., and R.N.K. designed research;

R.S.W., K.K., A.-C.W., Y.C., D.E.R., S.J., Y.Y., J.W.C., and E.G. performed research;

T.L., C.B.T., M.T.C., and E.G. contributed new reagents/analytic tools;

R.S.W., K.K., A.-C.W., Y.C., Y.Y., J.W.C., G.W.D., B.O., and R.N.K. analyzed data;

and R.S.W., K.K., and R.N.K. wrote the paper.

We thank Drs. Emily H.-Y. Cheng and Xu Luo for constructs and cell lines, Drs. Nina Kaludercic and Fabio DiLisa for advice regarding mitochondrial assays, Drs. Charles J. Steenbergen and Stephen M. Factor for advice regarding cardiac pathology, and Chad K. Nicholson for technical assistance.

We also thank the Wilf family for their ongoing generosity and support.

The authors declare no conflict of interest.

Subjects:

Research Funding:

This work was supported by Grants 5R01HL60665-13 (to R.N.K.), 5P30CA013330-39 (to R.N.K. and E.G.), 5P60DK020541-34 (to R.N.K.), 5R37HL054598-16 (to B.O.), 5R01HL059888-12 (to G.W.D.), 4R00HL095929-02 (to E.G.), American Heart Association Grant GRNT2290168 (to M.T.C.), 5T32AG023475-08 (to R.S.W.), and the A. G. Leventis Foundation (K.K.).

R.N.K. is supported by The Dr. Gerald and Myra Dorros Chair in Cardiovascular Disease.

Keywords:

  • Science & Technology
  • Multidisciplinary Sciences
  • Science & Technology - Other Topics
  • MULTIDISCIPLINARY SCIENCES
  • ISCHEMIA-REPERFUSION INJURY
  • CYTOCHROME-C RELEASE
  • CELL-DEATH
  • PERMEABILITY TRANSITION
  • CYCLOPHILIN-D
  • TRANSGENIC MICE
  • APOPTOSIS
  • PROTECTS
  • ACTIVATION
  • REVEALS

Bax regulates primary necrosis through mitochondrial dynamics

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Journal Title:

Proceedings of the National Academy of Sciences

Volume:

Volume 109, Number 17

Publisher:

, Pages 6566-6571

Type of Work:

Article | Final Publisher PDF

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.

Copyright information:

© Whelan et al.

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