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The dynamics of Bax channel formation: influence of ionic strength

Vidyaramanan Ganesan1, Timothy Walsh1, Kai-Ti Chang1

  • 1University of Maryland, College Park, Maryland.

Biophysical Journal
|September 6, 2012
PubMed

Insights

Ionic strength controls the rate of Bax-mediated mitochondrial outer membrane permeabilization (MOMP). Higher ionic strength impedes Bax channel expansion, revealing its role in regulating MOMP dynamics.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Biophysics

Background:

  • Mitochondrial outer membrane permeabilization (MOMP) is crucial for apoptosis but difficult to study in vivo due to cell variability.
  • In vitro models offer insights, but controlling MOMP dynamics remains a challenge.

Purpose of the Study:

  • To investigate the dynamics of Bax-mediated MOMP in isolated mitochondria.
  • To utilize ionic strength as a biophysical tool to control and study MOMP.

Main Methods:

  • Isolated mitochondria were used to study Bax-mediated MOMP.
  • Ionic strength was manipulated to control the rate of MOMP and Bax channel formation.
  • Protein release and cytochrome c oxidation rates were measured to assess permeabilization.

Main Results:

  • Bax induces both transient and long-lasting mitochondrial outer membrane permeabilization.
  • Higher ionic strength impedes Bax channel expansion, independent of tBid.
  • Increased ionic strength enhances Bcl-xL inhibition of Bax-mediated MOMP.
  • Ionic strength affects Bax assembly into channels but not its insertion into the membrane.

Conclusions:

  • Ionic strength is an effective tool for controlling Bax-mediated MOMP dynamics in vitro.
  • Ionic strength influences the assembly of Bax into functional channels, modulating permeabilization.
  • These findings provide a novel approach to studying the biophysics of MOMP.

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