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Cell Rep. 2015 Dec 29;13(12):2781-93. doi: 10.1016/j.celrep.2015.11.051. Epub 2015 Dec 17.

Nanoscale Architecture of the Axon Initial Segment Reveals an Organized and Robust Scaffold.

Author information

1
Aix Marseille Université, CNRS, CRN2M UMR7286, 13344 Cedex 15 Marseille, France. Electronic address: christophe.leterrier@univ-amu.fr.
2
Aix Marseille Université, CNRS, CRN2M UMR7286, 13344 Cedex 15 Marseille, France.

Abstract

The axon initial segment (AIS), located within the first 30 μm of the axon, has two essential roles in generating action potentials and maintaining axonal identity. AIS assembly depends on a ßIV-spectrin/ankyrin G scaffold, but its macromolecular arrangement is not well understood. Here, we quantitatively determined the AIS nanoscale architecture by using stochastic optical reconstruction microscopy (STORM). First, we directly demonstrate that the 190-nm periodicity of the AIS submembrane lattice results from longitudinal, head-to-head ßIV-spectrin molecules connecting actin rings. Using multicolor 3D-STORM, we resolve the nanoscale organization of ankyrin G: its amino terminus associates with the submembrane lattice, whereas the C terminus radially extends (∼ 32 nm on average) toward the cytosol. This AIS nano-architecture is highly resistant to cytoskeletal perturbations, indicating its role in structural stabilization. Our findings provide a comprehensive view of AIS molecular architecture and will help reveal the crucial physiological functions of this compartment.

KEYWORDS:

ankyrin G; axon initial segment; cytoskeleton; scaffold; super-resolution microscopy

PMID:
26711344
DOI:
10.1016/j.celrep.2015.11.051
[Indexed for MEDLINE]
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