title: Caveolin-1 regulates the functional localization of N-acetylglucosaminyltransferase III within the golgi apparatus.
abstract: In an investigation of the mechanism underlying the functional sublocalization of glycosyltransferases within the Golgi apparatus, caveolin-1 was identified as a possible cellular factor. Caveolin-1 appears to regulate the localization of N-acetylglucosaminyltransferase III (GnT-III) in the intra-Golgi subcompartment. Structural analyses of total cellular N-glycans indicated that the overexpression of GnT-III in human hepatoma cells, in which caveolin-1 is not expressed, failed to reduce branch formation, whereas expression of caveolin-1 led to a dramatic decrease in the extent of branching with no enhancement in GnT-III activity. Because the addition of a bisecting GlcNAc by GnT-III to the core beta-Man in N-glycans prevents the action of GnT-IV and GnT-V, both of which are involved in branch formation, this result suggests that caveolin-1 facilitates the prior action of GnT-III, relative to the other GnTs, on the nascent sugar chains in the Golgi apparatus and that GnT-III is redistributed in the earlier Golgi subcompartment by caveolin-1. Indeed, when caveolin-1 was expressed in human hepatoma cells, it was found to be co-localized with GnT-III, as evidenced by the fractionation of Triton X-100-insoluble cellular membranes by density gradient ultracentrifugation. Caveolin-1 may modify the biosynthetic pathway of sugar chains via the regulation of the intra-Golgi subcompartment localization of this key glycosyltransferase.
authors.affiliation: Department of Biochemistry, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Sasai
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Ihara
authors.forename: Koichi
authors.initials: K
authors.lastname: Honke
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Taniguchi
mesh_terms: D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism* / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003902:Detergents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D016695:Glycosyltransferases / Q000378:metabolism; D006056:Golgi Apparatus / Q000201:enzymology* / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D037102:Lectins / Q000378:metabolism; D017351:N-Acetylglucosaminyltransferases / Q000096:biosynthesis* / Q000737:chemistry*; D017830:Octoxynol / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D013347:Subcellular Fractions; D013997:Time Factors; D014162:Transfection; D014461:Ultracentrifugation
chemical_list: C495540:CAV1 protein, human; D051242:Caveolin 1; D022461:Caveolins; D003902:Detergents; D037102:Lectins; D011134:Polysaccharides; D017830:Octoxynol; D016695:Glycosyltransferases; D017351:N-Acetylglucosaminyltransferases; C054599:beta-1,4-mannosyl-glycoprotein beta-1,4-N-acetylglucosaminyltransferase