title: Phosphorylation of neuroglycan C, a brain-specific transmembrane chondroitin sulfate proteoglycan, and its localization in the lipid rafts.
abstract: Neuroglycan C (NGC) is a brain-specific transmembrane chondroitin sulfate proteoglycan. In the present study, we examined whether NGC could be phosphorylated in neural cells. On metabolic labeling of cultured cerebral cortical cells from the rat fetus with (32)P(i), serine residues in NGC were radiolabeled. Some NGC became detectable in the raft fraction from the rat cerebrum, a signaling microdomain of the plasma membrane, with cerebral development. NGC from the non-raft fraction, not the raft fraction, could be phosphorylated by an in vitro kinase reaction. The phosphorylation of NGC was inhibited by adding to the reaction mixture a recombinant peptide representing the ectodomain of NGC, but not by adding a peptide representing its cytoplasmic domain. NGC could be labeled by an in vitro kinase reaction using [gamma-(32)P]GTP as well as [gamma-(32)P]ATP, and this kinase activity was partially inhibited by 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole, a selective inhibitor of casein kinase II. In addition to the intracellular phosphorylation, NGC was also phosphorylated at the cell surface by an ectoprotein kinase. This is the first report to demonstrate that NGC can be phosphorylated both intracellularly and pericellularly, and our findings suggest that a kinase with a specificity similar to that of casein kinase II is responsible for the NGC ectodomain phosphorylation.
authors.affiliation: Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi 480-0392, Japan.
authors.forename: Shinobu
authors.initials: S
authors.lastname: Yamauchi
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Tokita
authors.forename: Sachiko
authors.initials: S
authors.lastname: Aono
authors.forename: Fumiko
authors.initials: F
authors.lastname: Matsui
authors.forename: Takuya
authors.initials: T
authors.lastname: Shuo
authors.forename: Hidenori
authors.initials: H
authors.lastname: Ito
authors.forename: Kanefusa
authors.initials: K
authors.lastname: Kato
authors.forename: Kohji
authors.initials: K
authors.lastname: Kasahara
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Oohira
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D011508:Chondroitin Sulfate Proteoglycans / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D010766:Phosphorylation; D011509:Proteoglycans / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D011508:Chondroitin Sulfate Proteoglycans; C485738:Cspg5 protein, rat; D008565:Membrane Proteins; D011509:Proteoglycans; D011994:Recombinant Proteins