Identification of O-linked N-acetylglucosamine modification of ankyrinG isoforms targeted to nodes of Ranvier.
AnkyrinGs of 270 and 480 kDa are localized at nodes of Ranvier and are candidates to couple the voltage-dependent sodium channel and neurofascin to the spectrin/actin network. This study presents evidence that these ankyrins contain O-linked GlcNAc residues and identifies as the site of glycosylation a serine-rich domain that distinguishes them from other ankyrin isoforms. The 480-kDa ankyrinG, extracted from brain membranes associated with wheat germ agglutinin-affinity columns, was [3H]galactose-labeled with UDP-[3H] galactose and galactosyltransferase, and cross-reacted with an antibody against O-GlcNAc monosaccharides. AnkyrinG-associated sugars are O-linked monosaccharides based on resistance to peptide-N-glycosidase F and analysis of saccharides released by beta-elimination. The serine-rich domain is the site of glycosylation based on wheat germ agglutinin binding activity of polypeptides produced by in vitro translation in reticulocyte lysates. Immunofluorescence revealed co-localization of ankyrinG and O-GlcNAc immunoreactivity at nodes of Ranvier. These observations suggest that ankyrin at the node of Ranvier is O-GlcNAc-glycosylated and are the first demonstration of a post-translational modification that is concentrated at the node of Ranvier and not in adjacent areas of myelinated axons.
Zhang
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Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Bennett
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D000117:Acetylglucosamine; D017487:Ankyrins / Q000737:chemistry / Q000378:metabolism*; D001923:Brain Chemistry; D005690:Galactose / Q000378:metabolism; D005700:Galactosyltransferases / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D008970:Molecular Weight; D011901:Ranvier's Nodes / Q000737:chemistry*; D014018:Tissue Distribution; D014909:Wheat Germ Agglutinins / Q000378:metabolism
D017487:Ankyrins; D014909:Wheat Germ Agglutinins; D005700:Galactosyltransferases; D000117:Acetylglucosamine; D005690:Galactose