The effect of myelinating Schwann cells on axons.
Myelinating Schwann cells control the number of neurofilaments and elevate the phosphorylation state of neurofilaments in the axon, eventually leading to the typical large axon caliber. Conversely, absence of myelin leads to lower amounts of neurofilaments, reduced phosphorylation levels, and smaller axon diameters. In addition, myelinating Schwann cells mediate the spacing of Na(+) channel clusters during development of the node of Ranvier. When axons are associated with mutant Schwann cells in inherited neuropathies, their calibers are reduced and their neurofilaments are less phosphorylated and more closely spaced. Also, axonal transport is reduced and axons degenerate at the distal ends of long nerves. Myelin-associated glycoprotein may mediate some aspects of Schwann cell-axon communication, but much remains to be learned about the molecular bases of Schwann cell-axon communication.
Martini
R
R
Department of Neurology, Section of Developmental Neurobiology, University of Würzburg, Josef-Schneider-Strasse 11, D-97080 Würzburg, Germany. neuk176@mail.uni-wuerzburg.de
D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D051379:Mice; D009185:Myelin Proteins / Q000235:genetics / Q000378:metabolism; D009186:Myelin Sheath / Q000378:metabolism*; D018992:Myelin-Associated Glycoprotein / Q000235:genetics / Q000378:metabolism; D016900:Neurofilament Proteins / Q000378:metabolism; D010766:Phosphorylation; D011115:Polyneuropathies / Q000235:genetics / Q000378:metabolism; D011901:Ranvier's Nodes / Q000648:ultrastructure; D012583:Schwann Cells / Q000378:metabolism* / Q000648:ultrastructure
D009185:Myelin Proteins; D018992:Myelin-Associated Glycoprotein; D016900:Neurofilament Proteins; C073687:PMP22 protein, human; C489545:Pmp22 protein, mouse