scholarly journals Axonal spectrins: All-purpose fences

2013 ◽  
Vol 203 (3) ◽  
pp. 381-383 ◽  
Author(s):  
Yael Eshed-Eisenbach ◽  
Elior Peles
Keyword(s):  
Adhesion Molecules ◽  
Diffusion Barrier ◽  
Initial Segment ◽  
Nodes Of Ranvier ◽  
Myelinated Axons ◽  
Membrane Cytoskeleton ◽  
Cell Biol ◽  
Axonal Initial Segment ◽  
Membrane Barrier

A membrane barrier important for assembly of the nodes of Ranvier is found at the paranodal junction. This junction is comprised of axonal and glial adhesion molecules linked to the axonal actin–spectrin membrane cytoskeleton through specific adaptors. In this issue, Zhang et al. (2013. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201308116) show that axonal βII spectrin maintains the diffusion barrier at the paranodal junction. Thus, βII spectrin serves to compartmentalize the membrane of myelinated axons at specific locations that are determined either intrinsically (i.e., at the axonal initial segment), or by axoglial contacts (i.e., at the paranodal junction).

scholarly journals Developmental formation of a diffusion barrier in the plasma membrane of the axonal initial segment : single lipid molecule approach

2000 ◽  
Vol 40 (supplement) ◽  
pp. S212
Author(s):  
C. Nakada ◽  
M. Nozaki ◽  
H. Yamashita ◽  
K. Yamaguchi ◽  
Ken Ritchie ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Diffusion Barrier ◽  
Initial Segment ◽  
Lipid Molecule ◽  
Axonal Initial Segment

scholarly journals Healthy attachments: Cell adhesion molecules collectively control myelin integrity

2019 ◽  
Vol 218 (9) ◽  
pp. 2824-2825
Author(s):  
Jiaxing Li ◽  
Kelly R. Monk
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecules ◽  
Cell Adhesion Molecules ◽  
Myelinated Axons ◽  
Adhesion Proteins ◽  
Functional Interactions ◽  
Cell Biol ◽  
Myelinating Glia

Many cell adhesion molecules are present along myelinated axons and in myelinating glia, but functional interactions among these proteins have not been fully elucidated. In this issue, Elazar et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201906099) report that distinct adhesion proteins act in coordination to ensure accurate myelination.

scholarly journals Developmental formation of a diffusion barrier in the axonal initial segment membrane of the neuron ; a single molecule approach.

2001 ◽  
Vol 41 (supplement) ◽  
pp. S121
Author(s):  
C. Nakada ◽  
Kenneth Ritchie ◽  
T. Fujiwara ◽  
Y. Hotta ◽  
R. Iino ◽  
...  
Keyword(s):  
Single Molecule ◽  
Diffusion Barrier ◽  
Initial Segment ◽  
Axonal Initial Segment

scholarly journals Ankyrin G restricts ion channel diffusion at the axonal initial segment before the establishment of the diffusion barrier

2010 ◽  
Vol 191 (2) ◽  
pp. 383-395 ◽  
Author(s):  
Anna Brachet ◽  
Christophe Leterrier ◽  
Marie Irondelle ◽  
Marie-Pierre Fache ◽  
Victor Racine ◽  
...  
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Diffusion Barrier ◽  
Hippocampal Neurons ◽  
Initial Segment ◽  
Specific Binding ◽  
Single Particle Tracking ◽  
Binding Motif ◽  
Ankyrin G ◽  
Axonal Initial Segment

In mammalian neurons, the precise accumulation of sodium channels at the axonal initial segment (AIS) ensures action potential initiation. This accumulation precedes the immobilization of membrane proteins and lipids by a diffusion barrier at the AIS. Using single-particle tracking, we measured the mobility of a chimeric ion channel bearing the ankyrin-binding motif of the Nav1.2 sodium channel. We found that ankyrin G (ankG) limits membrane diffusion of ion channels when coexpressed in neuroblastoma cells. Site-directed mutants with decreased affinity for ankG exhibit increased diffusion speeds. In immature hippocampal neurons, we demonstrated that ion channel immobilization by ankG is regulated by protein kinase CK2 and occurs as soon as ankG accumulates at the AIS of elongating axons. Once the diffusion barrier is formed, ankG is still required to stabilize ion channels. In conclusion, our findings indicate that specific binding to ankG constitutes the initial step for Nav channel immobilization at the AIS membrane and precedes the establishment of the diffusion barrier.

scholarly journals Nodes of Ranvier Act as Barriers to Restrict Invasion of Flanking Paranodal Domains in Myelinated Axons

Neuron ◽  
2011 ◽  
Vol 69 (2) ◽  
pp. 244-257 ◽  
Author(s):  
Courtney Thaxton ◽  
Anilkumar M. Pillai ◽  
Alaine L. Pribisko ◽  
Jeffrey L. Dupree ◽  
Manzoor A. Bhat
Keyword(s):  
Nodes Of Ranvier ◽  
Myelinated Axons

scholarly journals Ca2+ entry through NaV channels generates submillisecond axonal Ca2+ signaling

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Naomi AK Hanemaaijer ◽  
Marko A Popovic ◽  
Xante Wilders ◽  
Sara Grasman ◽  
Oriol Pavón Arocas ◽  
...  
Keyword(s):  
Calcium Channels ◽  
High Speed ◽  
Initial Segment ◽  
Hek 293 ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
293 Cells ◽  
Axonal Initial Segment ◽  
Nav Channels ◽  
Activity Dependent

Calcium ions (Ca2+) are essential for many cellular signaling mechanisms and enter the cytosol mostly through voltage-gated calcium channels. Here, using high-speed Ca2+ imaging up to 20 kHz in the rat layer five pyramidal neuron axon we found that activity-dependent intracellular calcium concentration ([Ca2+]i) in the axonal initial segment was only partially dependent on voltage-gated calcium channels. Instead, [Ca2+]i changes were sensitive to the specific voltage-gated sodium (NaV) channel blocker tetrodotoxin. Consistent with the conjecture that Ca2+ enters through the NaV channel pore, the optically resolved ICa in the axon initial segment overlapped with the activation kinetics of NaV channels and heterologous expression of NaV1.2 in HEK-293 cells revealed a tetrodotoxin-sensitive [Ca2+]i rise. Finally, computational simulations predicted that axonal [Ca2+]i transients reflect a 0.4% Ca2+ conductivity of NaV channels. The findings indicate that Ca2+ permeation through NaV channels provides a submillisecond rapid entry route in NaV-enriched domains of mammalian axons.

scholarly journals Altered action potential waveform and shorter axonal initial segment in hiPSC-derived motor neurons with mutations in VRK1

2022 ◽  
pp. 105609
Author(s):  
Rémi Bos ◽  
Khalil Rihan ◽  
Patrice Quintana ◽  
Lara El-Bazzal ◽  
Nathalie Bernard-Marissal ◽  
...  
Keyword(s):  
Action Potential ◽  
Motor Neurons ◽  
Initial Segment ◽  
Axonal Initial Segment ◽  
Action Potential Waveform ◽  
Potential Waveform

scholarly journals Minimizing the caliber of myelinated axons by means of nodal constrictions

2015 ◽  
Vol 114 (3) ◽  
pp. 1874-1884 ◽  
Author(s):  
Christopher Johnson ◽  
William R. Holmes ◽  
Anthony Brown ◽  
Peter Jung
Keyword(s):  
Ion Channels ◽  
Conduction Velocity ◽  
Myelin Sheath ◽  
Fixed Number ◽  
Evolutionary Constraint ◽  
Metabolic Efficiency ◽  
Nodes Of Ranvier ◽  
Myelinated Axons ◽  
Cross Sectional ◽  
Voltage Gated Ion Channels

In myelinated axons, most of the voltage-gated ion channels are concentrated at the nodes of Ranvier, which are short gaps in the myelin sheath. This arrangement leads to saltatory conduction and a larger conduction velocity than in nonmyelinated axons. Intriguingly, axons in the peripheral nervous system that exceed about 2 μm in diameter exhibit a characteristic narrowing of the axon at nodes that results in a local reduction of the axonal cross-sectional area. The extent of constriction increases with increasing internodal axonal caliber, reaching a threefold reduction in diameter for the largest axons. In this paper, we use computational modeling to investigate the effect of nodal constrictions on axonal conduction velocity. For a fixed number of ion channels, we find that there is an optimal extent of nodal constriction which minimizes the internodal axon caliber that is required to achieve a given target conduction velocity, and we show that this is sensitive to the precise geometry of the axon and myelin sheath in the flanking paranodal regions. Thus axonal constrictions at nodes of Ranvier appear to be a biological adaptation to minimize axonal volume, thereby maximizing the spatial and metabolic efficiency of these processes, which can be a significant evolutionary constraint. We show that the optimal nodal morphologies are relatively insensitive to changes in the number of nodal sodium channels.

scholarly journals Organization of the axon initial segment: Actin like a fence

2016 ◽  
Vol 215 (1) ◽  
pp. 9-11 ◽  
Author(s):  
Yu-Mei Huang ◽  
Matthew N. Rasband
Keyword(s):  
Particle Tracking ◽  
Single Particle ◽  
High Speed ◽  
Initial Segment ◽  
Single Particle Tracking ◽  
Axon Initial Segment ◽  
Membrane Domains ◽  
Superresolution Microscopy ◽  
Cell Biol ◽  
Actin Rings

What prevents the movement of membrane molecules between axonal and somatodendritic domains is unclear. In this issue, Albrecht et. al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201603108) demonstrate via high-speed single-particle tracking and superresolution microscopy that lipid-anchored molecules in the axon initial segment are confined to membrane domains separated by periodically spaced actin rings.

scholarly journals Formation mechanism of a diffusion barrier in the initial segment membrane of the neuron as studied by single molecule techniques

2001 ◽  
Vol 41 (supplement) ◽  
pp. S28
Author(s):  
C. Nakada ◽  
Kenneth Ritchie ◽  
T. Fujiwara ◽  
Y. Hotta ◽  
R. Iino ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Single Molecule ◽  
Diffusion Barrier ◽  
Initial Segment
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