MAP1B

Official Full Name

microtubule associated protein 1B

Organism

Homo sapiens

GeneID

4131

Background

This gene encodes a protein that belongs to the microtubule-associated protein family. The proteins of this family are thought to be involved in microtubule assembly, which is an essential step in neurogenesis. The product of this gene is a precursor polypeptide that presumably undergoes proteolytic processing to generate the final MAP1B heavy chain and LC1 light chain. Gene knockout studies of the mouse microtubule-associated protein 1B gene suggested an important role in development and function of the nervous system. [provided by RefSeq, Jul 2008]

Synonyms

MAP5; PVNH9; DFNA83; FUTSCH; PPP1R102;

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Detailed Information

Microtubule associated proteins 1B (MAP1B) are important components of neurocytoskeletal proteins and are widely expressed in the central and peripheral nervous systems. They are distributed in neuronal cell bodies, axons, dendrites and synapses. The dynamic state of the tube and the promotion of microtubule polymerization into bundles play an important role in axon guidance, elongation and sudden triggering. MAP1B is a high-molecular-weight microtubule-associated protein (MAPs) expressed early in the development of the nervous system. It is abundantly expressed in the growing neurites and is required for axon growth.

Phosphorylation Regulation of MAP1B

MAP1B and its phosphorylated subtype (PMAP1B) are widely distributed in the central nervous system (CNS) and the peripheral nervous system (PNS). MAP1B is mainly distributed in neuronal cell bodies and dendrites, while P-MAP1B is mainly present in growing axons and concentrated at the ends of axons close to the growth cone. MAP1B and P-MAP1B are highly expressed in the early developmental stage of the nervous system. With the developmental maturation, the expression of MAP1B and P-MAP1B is gradually decreased in most areas of CNS. However, in adult PNS, the expression of MAP1B and P-MAP1B remains relatively high. The study also found that P-MAP1B has two forms, I and II, which are denoted as P I-MAP1B and P II-MAP1B, respectively.They are related to the formation and remodeling of mature neural systems.

The phosphorylation of MAP1B is positively regulated by JNK 1 (c-Jun NH2 -terminal protein kinase). When the gene encoding JNK 1 is knocked out, the phosphorylation of MAP1B occurs, and dendrites and axonal microtubules are progressively deleted. This indicates that JNK 1 is a key regulator of microtubule-associated protein activity and microtubule assembly. P35 promotes the in vitro regulation of the biological function of MAP1B by cyclin-dependent protein kinase (CDK5).

Figure 1. Model of regulation of EBs localization by MAP1B during neurite/axon outgrowth. （Tortosa, et al. 2013）

The Role of MAP1B in Neurodevelopment

MAP1B induces neurotubule bundle reorganization, which regulates the dynamic state of microtubules and affects the development of axons. Studies have confirmed that nerve regeneration in brain trauma, epilepsy, and ischemic cerebrovascular disease is accompanied by up-regulation of MAP1B. Moreover, studies have shown that the number of myelinated fibers in the peri-nural nerve of MAP1B-deficient mice is significantly reduced, and the myelin sheath becomes thinner.

The study found that MAP1B is involved in the regulation of the growth direction of the axon growth cone. There are two forms of MAP1B and P-MAP1B in the body. It is found that these two forms regulate the growth of axons by mutual transformation, MAP1B stabilizes the polymerization of microtubules, and PMAP1B reverses. Moreover, P-MAP1B has been shown to be the most highly expressed in the axon near growth cone, thus making the microtubule system in axon regeneration a dynamic unstable state. Goold et al. believe that this unstable state was a necessary state for axon growth cone microtubules to extend and rotate during axon growth.

Schwann cells are the main glial components of the peripheral nerves. The myelin sheath of the peripheral nerve-derived fibers is formed by the morphological changes of Schwann cells and the laminarization of the plasma membrane to axons. According to the phenomenon that MAP1B and its mRNA are highly expressed in Schwann cells during sciatic nerve injury and regeneration, and MAP1B is also expressed in neonatal mouse Schwann cells cultured in vitro, studies have shown that MAP1B expressed in Schwann cells affects axonal regeneration and remyelination by supporting the morphological changes of Schwann cells during axonal regeneration and remyelination in the early stage after peripheral nerve injury.

References:

Tortosa, E. , Galjart, N. , Avila, Jesús, & Sayas, C. L. . (2013). Map1b regulates microtubule dynamics by sequestering eb1/3 in the cytosol of developing neuronal cells. The EMBO Journal,32(9), 1293-1306.
Villarroel-Campos, D. , & Gonzalez-Billault, C. . (2014). The map1b case: an old map that is new again. Developmental Neurobiology, 74(10), 953-971.
Palenzuela, Rocío, Gutiérrez, Yolanda, Draffin, J. E. , Lario, A. , Benoist, M. , & Esteban, José A. (2017). Map1b light chain modulates synaptic transmission via ampa receptor intracellular trapping. The Journal of Neuroscience, 0505-17.

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