juxtaparanode region of axon

Definition

Target type: cellularcomponent

A region of an axon near a node of Ranvier that is between the paranode and internode regions. [GOC:BHF, GOC:jl, PMID:10624965, PMID:14682359]

The juxtaparanode region of an axon is a specialized domain located at the transition zone between the myelinated and unmyelinated segments of the axon. It is characterized by a unique and complex arrangement of cellular components that play crucial roles in maintaining axonal integrity and facilitating signal propagation.

The juxtaparanode region is enriched in a variety of proteins, including:

* **Adhesion molecules:** These molecules, such as neurofascin 155 (NF155), contactin-associated protein 1 (Caspr1), and contactin, mediate the interactions between the axon and the myelinating glial cell (Schwann cell in the peripheral nervous system and oligodendrocyte in the central nervous system). They form a specialized adhesion complex at the juxtaparanode, ensuring the stability and proper alignment of the myelin sheath.
* **Ion channels:** Voltage-gated potassium channels (Kv1.1 and Kv1.2) are concentrated at the juxtaparanode. They play a critical role in regulating the propagation of action potentials along the axon by controlling the repolarization phase of the action potential.
* **Signaling molecules:** Several signaling molecules, such as the tyrosine kinase Fyn and the scaffold protein PSD-95, are also enriched in the juxtaparanode. These molecules are involved in regulating the assembly and function of the juxtaparanode complex and may also contribute to the formation of the myelin sheath.

The cytoskeleton of the juxtaparanode region is also unique, with an abundance of microtubules and actin filaments. These cytoskeletal components provide structural support for the axon and play a role in maintaining the organization of the juxtaparanode complex.

Furthermore, the juxtaparanode region contains specialized membrane domains called paranodal loops. These loops are formed by the myelinating glial cell and extend around the axon. They serve as barriers to diffusion and contribute to the formation of the high-resistance seal at the paranode, which is essential for efficient saltatory conduction of action potentials.

The juxtaparanode region is therefore a complex and dynamic structure that plays a critical role in maintaining axonal function. Its unique composition of proteins, ion channels, signaling molecules, and cytoskeletal elements allows it to regulate the propagation of action potentials, ensure the stability of the myelin sheath, and contribute to the overall health of the axon.'
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Proteins (6)

Compounds (47)