title: Regulation of O-glycosylation through Golgi-to-ER relocation of initiation enzymes.
abstract: After growth factor stimulation, kinases are activated to regulate multiple aspects of cell physiology. Activated Src is present on Golgi membranes, but its function here remains unclear. We find that Src regulates mucin-type protein O-glycosylation through redistribution of the initiating enzymes, polypeptide N-acetylgalactosaminyl transferases (GalNac-Ts), from the Golgi to the ER. Redistribution occurs after stimulation with EGF or PDGF in a Src-dependent manner and in cells with constitutively elevated Src activity. All GalNac-T family enzymes tested are affected, whereas multiple other glycosylation enzymes are not displaced from the Golgi. Upon Src activation, the COP-I coat is also redistributed in punctate structures that colocalize with GalNac-Ts and a dominant-negative Arf1 isoform, Arf1(Q71L), efficiently blocks GalNac-T redistribution, indicating that Src activates a COP-I-dependent trafficking event. Finally, Src activation increases O-glycosylation initiation as seen by lectin staining and metabolic labeling. We propose that growth factor stimulation regulates O-glycosylation initiation in a Src-dependent fashion by GalNac-T redistribution to the ER.
authors.affiliation: Institute of Molecular and Cell Biology, Proteos, Singapore 138673.
authors.forename: David J
authors.initials: DJ
authors.lastname: Gill
authors.forename: Joanne
authors.initials: J
authors.lastname: Chia
authors.forename: Jamie
authors.initials: J
authors.lastname: Senewiratne
authors.forename: Frederic
authors.initials: F
authors.lastname: Bard
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000235:genetics / Q000378:metabolism; D000116:Acetylgalactosamine / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006031:Glycosylation; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008954:Models, Biological; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000097763:Polypeptide N-acetylgalactosaminyltransferase
chemical_list: D020823:ADP-Ribosylation Factor 1; D000116:Acetylgalactosamine; D004815:Epidermal Growth Factor; D017350:N-Acetylgalactosaminyltransferases; D010982:Platelet-Derived Growth Factor; D047428:Protein Kinase Inhibitors; D021122:Protein Subunits; D044767:Ubiquitin-Protein Ligases; D019061:src-Family Kinases; D000097763:Polypeptide N-acetylgalactosaminyltransferase; C471981:COP1 protein, human