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Advanced Neurology

REVIEW ARTICLE
An update on axon initial segment structure and

function

1,2
Zhiya Chen , Takahiko Mochizuki , and Yan Zhang *
1
1
1 State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing
100871, China
2 Yiwu Boya Rehabilitation Hospital, Yiwu City, Zhejiang Province, 322000, China

Abstract

The axon initial segment (AIS) is a specialized subcellular region located at the
proximal end of the axon and serves as the action potential initiation site due to the
high density of ion channels. The AIS plays a critical role in maintaining neuronal
polarity by regulating the trafficking and distribution of proteins that function in
the dendritic or axonal compartment of the neuron. Due to the adaptive nature
of AIS location and length, the excitability of neurons can be altered in response
to activity. In this review, we briefly introduce the structure and function of AIS
as well as discuss the recent progress in our understanding of AIS ion channel
distribution and plasticity in different types of neurons. These would contribute
to a better understanding of the AIS and give us a new perspective on AIS-related
diseases.

Keywords: Axon initial segment; Ankyrin G; Ion channels; Plasticity
*Corresponding author:
Yan Zhang
(yanzhang@pku.edu.cn)
Citation: Chen Z, Mochizuki T, 1. Introduction
Zhang Y, 2023, An update on
axon initial segment structure and There are approximately 100 billion neurons in our brains. Neurons, as the most basic
function. Adv Neuro, 2(1): 274. structural and functional units of the nervous system, are responsible for receiving
https://doi.org/10.36922/an.v2i1.274 and transmitting electrochemical signals in the nervous system and are involved
Received: November 24, 2022 in perception, calculation, learning, and memory. Signals exist in the form of action
Accepted: January 10, 2023 potentials (APs), which contain information encoded either in the firing time of the APs
[1]
Published Online: February 1, 2023 or in certain shape characteristics, such as the amplitude of APs . Almost all neurons
are composed of three parts: the soma, axon, and dendrite.
Copyright: © 2023 Author(s).
This is an Open Access article The axon initial segment (AIS) is a highly specialized region in the axon of
distributed under the terms of the
Creative Commons Attribution neurons [1-5] . The AIS, which starts right after the axon hillock, is located approximately
License, permitting distribution, 20–60 μm from the proximal end of the axon and is distinguished from the axon by
and reproduction in any medium,
provided the original work is the dense framework of ion channels and other linker proteins. The most important
properly cited. function of the AIS is AP initiation, which could trigger the release of neurotransmitters
Publisher’s Note: AccScience in the synapses at the end of the axon. In vivo axons are usually tightly wrapped by
Publishing remains neutral with lipid layers called the myelin sheath. The myelin sheath insulates axons from the outside
regard to jurisdictional claims in
published maps and institutional environment, and as a result, there is no loss of current, thus ensuring the efficiency and
affiliations. fidelity of AP conduction.

Volume 2 Issue 1 (2023) 1 https://doi.org/10.36922/an.v2i1.274