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Bax assembly into rings and arcs in apoptotic mitochondria is linked to membrane pores

Raquel Salvador-Gallego1, Markus Mund2, Katia Cosentino1

  • 1Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany Max Planck Institute for Intelligent Systems, Stuttgart, Germany.

The EMBO Journal
|January 20, 2016
PubMed

Insights

Researchers visualized the spatial organization of Bax during apoptosis. Active Bax formed ring and arc structures on mitochondria, creating pores that lead to cell death.

Area of Science:

  • Cell biology
  • Molecular biology
  • Biophysics

Background:

  • Bax protein regulates apoptosis (programmed cell death) by permeabilizing the mitochondrial outer membrane.
  • The precise mechanism of Bax-mediated membrane permeabilization and its spatial organization during apoptosis are not fully understood.

Purpose of the Study:

  • To investigate the spatial organization and supramolecular architectures of Bax during apoptosis.
  • To elucidate the role of Bax oligomeric structures in mitochondrial outer membrane permeabilization.

Main Methods:

  • Dual-color single-molecule localization-based super-resolution microscopy was employed to visualize Bax organization in apoptotic cells.
  • Atomic force microscopy was used to assess the membrane-perforating capabilities of Bax assemblies in lipid bilayers.

Main Results:

  • Active Bax proteins formed distinct oligomeric architectures, including rings, arcs, and linear assemblies, localized in foci on mitochondria.
  • Both ring and arc-shaped Bax assemblies demonstrated the ability to perforate lipid bilayers, indicating pore formation.
  • The study identified diverse supramolecular organizations of Bax during the apoptotic process.

Conclusions:

  • Bax oligomers exhibit varied spatial arrangements, such as rings and arcs, at the mitochondria during apoptosis.
  • These Bax assemblies function by delineating pores of varying sizes to permeabilize the mitochondrial outer membrane.
  • The findings provide a molecular mechanism for Bax-driven mitochondrial outer membrane permeabilization in apoptosis.
Keywords:
AFMBcl‐2apoptosispore‐forming proteinsuper‐resolution microscopy

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