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Is myelin a mitochondrion?

Julia J Harris1, David Attwell

  • 1Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK. j.j.harris@ucl.ac.uk

Journal of Cerebral Blood Flow and Metabolism : Official Journal of the International Society of Cerebral Blood Flow and Metabolism
|October 18, 2012
PubMed

Insights

Myelin does not generate ATP. Calculations show proton flow across the myelin sheath generates insufficient energy for ATP synthesis, questioning its proposed energy-producing role.

Area of Science:

  • Neuroscience
  • Cellular Biology
  • Bioenergetics

Background:

  • The myelin sheath, formed by oligodendrocytes, is crucial for rapid nerve impulse conduction in the central nervous system.
  • A hypothesis proposed that myelin functions analogously to mitochondria, generating adenosine triphosphate (ATP) via its membrane.
  • Investigating the bioenergetic capabilities of myelin is essential for understanding oligodendrocyte function and CNS energy metabolism.

Purpose of the Study:

  • To evaluate the bioenergetic feasibility of ATP synthesis within the myelin sheath.
  • To determine if proton motive force across the myelin membrane can support ATP production.
  • To assess the potential role of the myelin sheath in cellular energy generation.

Main Methods:

  • Calculation of the proton motive force (PMF) across the myelin membrane.
  • Utilizing established values for oligodendrocyte pH and membrane potential.
  • Thermodynamic analysis of potential ATP synthesis based on PMF.

Main Results:

  • The calculated proton motive force across the myelin membrane is insufficient to drive ATP synthesis.
  • If respiratory chain components were present, ATP synthase would likely operate in reverse, consuming ATP.
  • The energy potential within the myelin sheath does not support a mitochondrion-like function.

Conclusions:

  • The hypothesis that myelin acts as an energy-generating organelle is not supported by bioenergetic calculations.
  • Myelin's role is unlikely to involve ATP synthesis through proton flow.
  • These findings cast significant doubt on the proposed energy-producing function of the myelin sheath.

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