title: Cytosolic O-glycosylation is abundant in nerve terminals.
abstract: Phosphorylation plays a key role in regulating growth cone migration and protein trafficking in nerve terminals. Here we show that nerve terminal proteins contain another abundant post-translational modification: beta-N-acetylglucosamine linked to hydroxyls of serines or threonines (O-GlcNAc(1)). O-GlcNAc modifications are essential for embryogenesis and mounting evidence suggests that O-GlcNAc is a regulatory modification that affects many phosphorylated proteins. We show that the activity and expression of O-GlcNAc transferase (OGT) and N-acetyl-beta-D-glucosaminidase (O-GlcNAcase), the two enzymes regulating O-GlcNAc modifications, are present in nerve terminal structures (synaptosomes) and are particularily abundant in the cytosol of synaptosomes. Numerous synaptosome proteins are highly modified with O-GlcNAc. Although most of these proteins are present in low abundance, we identified by proteomic analysis three neuron-specific O-GlcNAc modified proteins: collapsin response mediator protein-2 (CRMP-2), ubiquitin carboxyl hydrolase-L1 (UCH-L1) and beta-synuclein. CRMP-2, which is involved in growth cone collapse, is a major O-GlcNAc modified protein in synaptosomes. All three proteins are implicated in regulatory cascades that mediate intracellular signaling or neurodegenerative diseases. We propose that O-GlcNAc modifications in the nerve terminal help regulate the functions of these and other synaptosome proteins, and that O-GlcNAc may play a role in neurodegenerative disease.
authors.affiliation: Department of Biological Chemistry, School of Medicine, The Johns Hopkins University, Baltimore, Maryland 21205-2185, USA.
authors.forename: R N
authors.initials: RN
authors.lastname: Cole
authors.forename: G W
authors.initials: GW
authors.lastname: Hart
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001923:Brain Chemistry; D050260:Carbohydrate Metabolism; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism*; D005700:Galactosyltransferases / Q000378:metabolism; D006031:Glycosylation; D006868:Hydrolysis; D066298:In Vitro Techniques; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009411:Nerve Endings / Q000201:enzymology / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000737:chemistry; D009474:Neurons / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D012694:Serine / Q000031:analogs & derivatives* / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013347:Subcellular Fractions / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism; D014357:Trypsin
chemical_list: D009419:Nerve Tissue Proteins; D012694:Serine; D005700:Galactosyltransferases; D014357:Trypsin; D000117:Acetylglucosamine