Myelination cell adhesion molecules

MYELIN FORMATION, STRUCTURE AND BIOCHEMISTRY 51 MEMBRANE TRANSPORT 73 ELECTRICAL EXCITABILITY AND ION CHANNELS 95 CELL ADHESION MOLECULES 111 THE CYTOSKELETON OF NEURONS AND GLIA 123... 

Cell adhesion molecules (CAMs) play critical roles in all facets of nervous system development and maintenance. Important phenomena in which CAMs are involved include initial formation of the neural tube and the neural crest, migration of all neurons and glial cells, axonal outgrowth and guidance, target selection, synaptic stabilization and plasticity, myelination and nerve regeneration after injury (see Chs 4,24,28-30 and 53). Adhesion molecules interact with each other and with nonadhesive cell-surface and/or cytoplasmic molecules, and, in the two... 

FIGURE 7-1 The immunoglobulin (Ig) gene family of molecules. Several varieties of Ig domain-containing molecules are contained within the Ig gene superfamily. Most are type I membrane proteins some have only Ig domains or other moieties that may convey function (see text). V, variable Ig domain C, constant Ig domain MAG, myelin-associated glycoprotein NCAM, neural cell adhesion molecule GPI, glycosylphosphatidyl-inositol EC, extracellular domain FN, fibronectin. 

Epithelial cadherin (E-cadherin) has a molecular weight of 130 kDa and is found in PNS myelin. E-cadherin is a protein of the superfamily of calcium-dependent cell adhesion molecules that can usually form adherent junctions. This protein has an N-terminal extracellular domain, a short transmembrane domain and a C-terminal intracellular domain. 

Adhesion molecules. The downregulation of the polysialylated neuronal cell adhesion molecule (PSA-NCAM) from the axonal surface (Charles et al 2000) is a necessary prerequisite to render the axon permissive to myelination (Charles et al., 2002 Coman et al., 2005). LI, another adhesion molecule expressed at the axonal surface, promotes myelination (Coman et al., 2005). 

In demyelination such as MS, PSA-NCAM is expressed on denuded axons and might act as an inhibitor of remyelination, whereas the myelinated part outside the plaque is PSA-NCAM negative (Charles et al., 2000 Coman et al., 2005). On the other hand, in MS a two- to threefold increase in OPC density and proliferation was found in the subventricular zone (SVZ), which correlated with enhanced numbers of PSA-NCAM(-i-) cells (Nait-Oumesmar et al., 2007). EAE in rodents is another important example of the activation of the SVZ and the involvement of progenitor cells expressing the polysialylated form of neural cell adhesion molecule (PSA-NCAM) in the repair process (Picard-Riera et al., 2002). 

Martini R, Schachner M. 1988. Immunoelectron microscopic localization of neural cell adhesion molecules (LI, N-CAM, and myelin-associated glycoprotein) in regenerating adult mouse sciatic nerve. J CeU Biol 106 1735-1746. 

Kruse, J., Mailhammer. R., Wernecke, H., Faissner, A., Sommer, 1., Goridis, C. and Sehachner. M. (1984) Neural cell adhesion molecules and myelin-associated glycoprotein share a common carbohydrate moiety recognized by monoclonal antibodies L2 and HNK-1. Nature 311 153-155. 

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