title: COG complex-mediated recycling of Golgi glycosyltransferases is essential for normal protein glycosylation.
abstract: Defects in conserved oligomeric Golgi (COG) complex result in multiple deficiencies in protein glycosylation. On the other hand, acute knock-down (KD) of Cog3p (COG3 KD) causes accumulation of intra-Golgi COG complex-dependent (CCD) vesicles. Here, we analyzed cellular phenotypes at different stages of COG3 KD to uncover the molecular link between COG function and glycosylation disorders. For the first time, we demonstrated that medial-Golgi enzymes are transiently relocated into CCD vesicles in COG3 KD cells. As a result, Golgi modifications of both plasma membrane (CD44) and lysosomal (Lamp2) glycoproteins are distorted. Localization of these proteins is not altered, indicating that the COG complex is not required for anterograde trafficking and accurate sorting. COG7 KD and double COG3/COG7 KD caused similar defects with respect to both Golgi traffic and glycosylation, suggesting that the entire COG complex orchestrates recycling of medial-Golgi-resident proteins. COG complex-dependent docking of isolated CCD vesicles was reconstituted in vitro, supporting their role as functional trafficking intermediates. Altogether, the data suggest that constantly cycling medial-Golgi enzymes are transported from distal compartments in CCD vesicles. Dysfunction of COG complex leads to separation of glycosyltransferases from anterograde cargo molecules passing along secretory pathway, thus affecting normal protein glycosylation.
authors.affiliation: Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Shestakova
authors.forename: Sergey
authors.initials: S
authors.lastname: Zolov
authors.forename: Vladimir
authors.initials: V
authors.lastname: Lupashin
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D016695:Glycosyltransferases / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D046912:Multiprotein Complexes; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D010641:Phenotype; D011499:Protein Processing, Post-Translational; D050767:Qc-SNARE Proteins / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C107588:BET1L protein, human; C498528:COG3 protein, human; D008562:Membrane Glycoproteins; D046912:Multiprotein Complexes; D050767:Qc-SNARE Proteins; D034741:RNA, Small Interfering; D016695:Glycosyltransferases; D017351:N-Acetylglucosaminyltransferases; C024850:alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase I