title: Myelin-associated glycoprotein inhibits microtubule assembly by a Rho-kinase-dependent mechanism.
abstract: Myelin-associated glycoprotein (MAG) and Nogo are potent inhibitors of neurite outgrowth from a variety of neurons, and they have been identified as possible components of the central nervous system myelin that prevents axonal regeneration in the adult vertebrate central nervous system. The activation of RhoA and Rho-kinase is reported to be an essential part of the signaling mechanism of these proteins. Here, we report that the collapsing response mediator protein-2 (CRMP-2) is phosphorylated by a Rho-kinase-dependent mechanism downstream of MAG or Nogo-66. The overexpression of the nonphosphorylated form of CRMP-2 at threonine 555, which is the phosphorylation site for Rho-kinase, counteracts the inhibitory effect of MAG on the postnatal cerebellar neurons. Additionally, the expression of the dominant negative form of CRMP-2 or knockdown of the gene using small interference RNA (siRNA) mimics the effect of MAG in vitro. Consistent with the function of CRMP-2, which promotes microtubule assembly, microtubule levels are down-regulated in the cerebellar neurons that are stimulated with MAG in vitro. Reduction in the density of microtubules is also observed in the injured axons following the spinal cord injury, and this effect depends on the Rho-kinase activity. Our data suggest the important roles of CRMP-2 and microtubules in the inhibition of the axon regeneration by the myelin-derived inhibitors.
authors.affiliation: Department of Neurobiology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670.
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Mimura
authors.forename: Satoru
authors.initials: S
authors.lastname: Yamagishi
authors.forename: Nariko
authors.initials: N
authors.lastname: Arimura
authors.forename: Masashi
authors.initials: M
authors.lastname: Fujitani
authors.forename: Takekazu
authors.initials: T
authors.lastname: Kubo
authors.forename: Kozo
authors.initials: K
authors.lastname: Kaibuchi
authors.forename: Toshihide
authors.initials: T
authors.lastname: Yamashita
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D005455:Fluorescent Antibody Technique; D036341:Intercellular Signaling Peptides and Proteins; D008870:Microtubules / Q000502:physiology*; D009185:Myelin Proteins / Q000502:physiology; D018992:Myelin-Associated Glycoprotein / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000502:physiology; D000070798:Nogo Proteins; D010766:Phosphorylation; D051381:Rats; D020741:rho GTP-Binding Proteins / Q000502:physiology*
chemical_list: D017931:DNA Primers; D036341:Intercellular Signaling Peptides and Proteins; D009185:Myelin Proteins; D018992:Myelin-Associated Glycoprotein; D009419:Nerve Tissue Proteins; D000070798:Nogo Proteins; C000603197:Rtn4 protein, rat; C095114:collapsin response mediator protein-2; D020741:rho GTP-Binding Proteins