paranodal junction assembly

Definition

Target type: biologicalprocess

Formation of the junction between an axon and the glial cell that forms the myelin sheath. Paranodal junctions form at each paranode, i.e. at the ends of the unmyelinated nodes of Ranvier. [PMID:14715942]

The paranodal junction is a specialized structure that forms between the axon and the myelinating glial cell (Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system). This junction is crucial for proper saltatory conduction, ensuring efficient and rapid nerve impulse transmission. Its assembly is a complex process involving multiple molecular interactions and cellular signaling pathways.

The process begins with the initial contact between the axon and the glial cell. This contact triggers the formation of the paranodal loop, a specialized structure formed by the wrapping of the glial cell membrane around the axon. The paranodal loop is characterized by the presence of specialized adhesion molecules that anchor the glial cell to the axon, including contactin-associated protein (Caspr) and neurofascin 155 (NF155). These molecules interact with their respective counter-receptors on the axon, such as contactin and neurofascin 186.

Simultaneously, the glial cell starts to produce and transport myelin proteins, such as myelin basic protein (MBP) and proteolipid protein (PLP), which are crucial for myelin sheath formation. These proteins are transported along the glial cell membrane and accumulate at the paranodal region.

The formation of the paranodal junction is also influenced by the presence of cytoskeletal elements, including microtubules and actin filaments. Microtubules provide structural support for the glial cell and facilitate the transport of myelin proteins. Actin filaments are involved in the formation and maintenance of the paranodal loop and the clustering of adhesion molecules.

As the paranodal junction matures, the glial cell membrane folds around the axon, forming the compact myelin sheath. The paranodal junction is further stabilized by the formation of specialized domains called the juxtaparanodal region and the paranodal region. The juxtaparanodal region is enriched in voltage-gated potassium channels (Kv1.1 and Kv1.2), which are essential for maintaining the resting membrane potential of the axon. The paranodal region is enriched in the adhesion molecules mentioned earlier, which are crucial for the stable interaction between the axon and the glial cell.

In conclusion, paranodal junction assembly is a complex and tightly regulated process involving multiple molecular interactions and cellular signaling pathways. This assembly is essential for the proper functioning of the nervous system, ensuring efficient and rapid nerve impulse transmission.'
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Proteins (1)

Compounds (3)