Axons cell adhesion molecules

Fig. 4.6(a) Migration of LHRH neurocrine cells prenatal transportation along the track of extra-bulbar VN axons (caudal branch). CB, cribriform plate FB, forebrain cell types, TAG-1, transient axonal surface glycoprotein and N-CAM, neural cell adhesion molecule (from Yoshida et al, 1995). 

Yoshihara Y Kawasaki M., Tamada A., Fujita H., et al. (1997). OCAM a new member of the neural cell adhesion molecule family related to zone-to-zone projection of olfactory and vomeronasal axons. J Neurosci 17, 5830-5842. 

Cell adhesion molecules influence axonal outgrowth 116... 

Cell adhesion molecules are responsible for axonal fasciculation 117... 

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 7-6 Neural cell adhesion molecule (NCAM) carries different levels of polysialic acid. (A) NCAM is depicted on a growing axon, without polysialic acid. Under these conditions, NCAM and LI molecules interact homophilically and axons fasciculate. (B) NCAM carries polysialic acid (PSA), and NCAM and LI molecules are far apart and cannot, therefore, interact. Growing axons do not fasciculate under these circumstances. 

Walsh, F. S. and Doherty, P. Neural cell adhesion molecules of the immunoglobulin superfamily role in axon growth and guidance. Annu. Rev. Cell. Dev. Biol. 13 425-456, 1997. 

Adhesion molecules such as LI, neural cell adhesion molecule (N-CAM) and N-cadherin promote axonal regeneration by homophilic interactions between axons and Schwann cell surfaces (see Ch. 7). The expression of p75 (low affinity NGF receptor, Ch. 27) is also increased at the Schwann cell surface after injury. Extracellular matrix molecules, such as tenascin and proteoglycans, increase the regenerative potential of damaged peripheral nerves by binding to integrins on the axonal surface. 

The cytoskeleton is found near the axonal membrane and consists of microfilaments linked internally to microtubules and the plasma membrane by a network of filamentous protein that includes the brain-specific protein fodrin. This protein forms attachment sites for integral membrane proteins either by means of the neuronal cell adhesion molecule (N-CAM) or indirectly by means of a specific protein called ankyrin in the case of the sodium channels. This may provide a means whereby the sodium channels are concentrated in the region of the nodes of Ranvier. Thus the cortical cytoskeleton plays a vital role in neuronal function by acting as an attachment site for various receptors and ion channels, but also for s)maptic vesicles at nerve terminals, thereby providing a mechanism for concentrating the vesicles prior to the release of the neurotransmitter. 

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). 

Neural cell adhesion molecule (NCAM) Axonal growth, cell-cell adhesion... 

Davis JQ, Lambert S, Bennett V 1996 Molecular composition of the node of Ranvier identification of ankyrin- binding cell adhesion molecules neurofascin (mucin -I- /third FNIII domain-) and NrCAM at nodal axon segments. J Cell Biol 135 1355-1367... 

---