title: Glycosyltransferase-specific Golgi-targeting mechanisms.
abstract: Glycosylation of secreted and membrane-bound mucins is carried out by glycosyltransferases localized to specific Golgi compartments according to the step in which each enzyme participates. However, the Golgi-targeting mechanisms of these enzymes are not clear. Herein, we investigate the Golgi-targeting mechanisms of core 1 β3 galactosyltransferase (C1GalT1) and core 2 β1,6-N-acetylglucosaminyltransferase-2 or mucus type (C2GnT-M), which participate in the early O-glycosylation steps. siRNAs, co-immunoprecipitation, and confocal fluorescence microscopy were employed to identify the golgins involved in the Golgi docking of vesicular complexes (VCs) that carry these two enzymes. We have found that these VCs use different golgins for docking: C2GnT-M-carrying VC (C2GnT-M-VC) utilizes Giantin, whereas C1GalT1-VC employs GM130-GRASP65 complex. However, in the absence of GRASP65, C1GalT1-VC utilizes GM130-Giantin complex. Also, we have found that these VCs are 1.1-1.2 μm in diameter, specific for each enzyme, and independent of coat protein complex II and I (COPII and COPI). These two fluorescently tagged enzymes exhibit different fluorescence recovery times in the Golgi after photobleaching. Thus, novel enzyme-specific Golgi-targeting mechanisms are employed by glycosyltransferases, and multiple Golgi docking strategies are utilized by C1GalT1.
authors.affiliation: Department of Research Service, Veterans Affairs Nebraska-Western Iowa Health Care System, Omaha, Nebraska 68105, USA.
authors.forename: Armen
authors.initials: A
authors.lastname: Petrosyan
authors.forename: Mohamed F
authors.initials: MF
authors.lastname: Ali
authors.forename: Pi-Wan
authors.initials: PW
authors.lastname: Cheng
mesh_terms: D001324:Autoantigens / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D045744:Cell Line, Tumor; D020756:Coatomer Protein / Q000235:genetics / Q000378:metabolism; D005700:Galactosyltransferases / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000201:enzymology*; D000077614:Golgi Matrix Proteins; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D034622:RNA Interference; D022161:Transport Vesicles / Q000201:enzymology*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism; D000097573:Red Fluorescent Protein
chemical_list: D001324:Autoantigens; D020756:Coatomer Protein; D005700:Galactosyltransferases; D000077614:Golgi Matrix Proteins; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D017351:N-Acetylglucosaminyltransferases; D033921:Vesicular Transport Proteins; D000097573:Red Fluorescent Protein; C108705:GORASP1 protein, human; C097741:Golgin subfamily A member 2; C087574:macrogolgin; C505293:C1GALT1 protein, human; C117361:beta-1,3-galactosyl-O-glycosyl-glycoprotein beta-1,6-N-acetylglucosaminyltransferase 3