MBP-tag

MBP-tag

The classic group of MBP isoforms (isoform 4-isoform 14) are with PLP the most abundant protein components of the myelin membrane in the CNS. They have a role in both its formation and stabilization. The smaller isoforms might have an important role in remyelination of denuded axons in multiple sclerosis. The non-classic group of MBP isoforms (isoform 1-isoform 3/Golli-MBPs) may preferentially have a role in the early developing brain long before myelination, maybe as components of transcriptional complexes, and may also be involved in signaling pathways in T-cells and neural cells. Differential splicing events combined with optional post-translational modifications give a wide spectrum of isomers, with each of them potentially having a specialized function. Induces T-cell proliferation.

Aging Source: Ensembl
Axon ensheathment Source: ProtInc
Central nervous system development Source: ProtInc
Chemical synaptic transmission Source: ProtInc
Immune response Source: ProtInc
Maintenance of blood-brain barrier Source: CAFA
MAPK cascade Source: CAFA
Membrane organization Source: Ensembl
Myelination Source: GO_Central
Negative regulation of axonogenesis Source: Ensembl
Negative regulation of heterotypic cell-cell adhesion Source: CAFA
Positive regulation of chemokine (C-X-C motif) ligand 2 production Source: CAFA
Positive regulation of interleukin-6 production Source: CAFA
Positive regulation of metalloendopeptidase activity Source: CAFA
Response to fatty acid Source: Ensembl
Response to mercury ion Source: Ensembl
Response to progesterone Source: Ensembl
Response to toxic substance Source: Ensembl
Response to tumor necrosis factor Source: Ensembl
Sensory perception of sound Source: Ensembl
Substantia nigra development Source: UniProtKB

Plasma membrane
Myelin membrane
Note: Cytoplasmic side of myelin.
Isoform 3:
Nucleus
Note: Targeted to nucleus in oligodendrocytes.

The reduction in the surface charge of citrullinated and/or methylated MBP could result in a weakened attachment to the myelin membrane. This mechanism could be operative in demyelinating diseases such as chronical multiple sclerosis (MS), and fulminating MS (Marburg disease).

Several charge isomers of MBP; C1 (the most cationic, least modified, and most abundant form), C2, C3, C4, C5, C6, C7, C8-A and C8-B (the least cationic form); are produced as a result of optional PTM, such as phosphorylation, deamidation of glutamine or asparagine, arginine citrullination and methylation. C8-A and C8-B contain each two mass isoforms termed C8-A(H), C8-A(L), C8-B(H) and C8-B(L), (H) standing for higher and (L) for lower molecular weight. C3, C4 and C5 are phosphorylated. The ratio of methylated arginine residues decreases during aging, making the protein more cationic.
The N-terminal alanine is acetylated (isoform 3, isoform 4, isoform 5 and isoform 6).
Arg-241 was found to be 6% monomethylated and 60% symmetrically dimethylated.
Proteolytically cleaved in B cell lysosomes by cathepsin CTSG which degrades the major immunogenic MBP epitope and prevents the activation of MBP-specific autoreactive T cells.
Phosphorylated by TAOK2, VRK2, MAPK11, MAPK12, MAPK14 and MINK1.