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Modulation of repulsive forces between neurofilaments by sidearm phosphorylation
1Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Biochemical and Biophysical Research Communications
|October 12, 2004
Summary
Neurofilament (NF) organization in axons relies on sidearm repulsion. Phosphorylation levels of NF sidearms modulate these forces, influencing NF spacing and axonal structure.
Area of Science:
- Neuroscience
- Cell Biology
- Biophysics
Background:
- Axonal organization of neurofilaments (NFs) is crucial for neuronal function.
- Previous theories proposed steric repulsion between NF sidearms governs NF spacing.
Purpose of the Study:
- To investigate the role of neurofilament sidearm phosphorylation in regulating interfilamentous forces.
- To provide experimental evidence for the modulation of NF organization by phosphorylation.
Main Methods:
- Sedimentation assays of neurofilaments under varying ionic strengths and dephosphorylation conditions.
- Atomic force microscopy (AFM) imaging of isolated mammalian neurofilaments.
- Analysis of colloidal particle exclusion from neurofilament backbones.
Main Results:
- Pellet volume decreased with increased ionic strength and enzymatic dephosphorylation.
- Divalent cations significantly reduced pellet volume of phosphorylated NFs.
- AFM revealed reduced particle exclusion from NF backbones at high ionic strength and after dephosphorylation.
- Evidence suggests graded modulation of NF excluded volume by phosphate-dependent repulsion.
Conclusions:
- Neurofilament sidearm phosphorylation is a key regulator of interfilamentous forces.
- Modulation of NF excluded volume by phosphorylation influences axonal neurofilament organization.
- These findings offer a mechanistic understanding of how neurofilaments are organized within axons.