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Bax assembles into large ring-like structures remodeling the mitochondrial outer membrane in apoptosis

Lena Große1, Christian A Wurm2, Christian Brüser2

  • 1Department of Neurology, University Medical Center of Göttingen, Göttingen, Germany Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.

The EMBO Journal
|January 20, 2016
PubMed

Insights

Researchers found that Bax proteins form ring-like structures in the mitochondrial outer membrane, creating pores essential for apoptosis. These Bax assemblies are crucial for mitochondrial outer membrane permeabilization (MOMP) during programmed cell death.

Area of Science:

  • Cell biology
  • Molecular biology
  • Biophysics

Background:

  • Bcl-2 family proteins, Bax and Bak, are key regulators of apoptosis.
  • Bax translocation to mitochondria initiates outer membrane permeabilization (MOMP).
  • The precise mechanism of Bax-mediated MOMP remains unclear.

Purpose of the Study:

  • To elucidate the structural mechanisms of Bax-mediated mitochondrial outer membrane permeabilization (MOMP).
  • To visualize Bax assembly dynamics during apoptosis using super-resolution microscopy.

Main Methods:

  • STED (Stimulated Emission Depletion) nanoscopy to visualize protein structures.
  • Analysis of Bax and Bak protein assemblies in the mitochondrial outer membrane.
  • Investigation of protein distribution within Bax structures.

Main Results:

  • Activated Bax forms ring-like structures in the mitochondrial outer membrane, potentially with Bak.
  • These Bax rings surround openings devoid of mitochondrial outer membrane proteins (e.g., Tom20, Tom22, Sam50).
  • Bax assemblies are necessary but not sufficient for full cytochrome c release in Drp1 knockdown cells.

Conclusions:

  • Bax rings delineate pores crucial for Bax-mediated MOMP.
  • Super-resolution data provide direct evidence for large Bax-delineated pores in MOMP.
  • The formation of Bax assemblies is a critical step in initiating programmed cell death.
Keywords:
Bcl‐2MICOScell deathmembrane curvaturesuperresolution microscopy

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