title: The COG complex, Rab6 and COPI define a novel Golgi retrograde trafficking pathway that is exploited by SubAB toxin.
abstract: Toxin trafficking studies provide valuable information about endogenous pathways of intracellular transport. Subtilase cytotoxin (SubAB) is transported in a retrograde manner through the endosome to the Golgi and then to the endoplasmic reticulum (ER), where it specifically cleaves the ER chaperone BiP/GRP78 (Binding immunoglobin protein/Glucose-Regulated Protein of 78 kDa). To identify the SubAB Golgi trafficking route, we have used siRNA-mediated silencing and immunofluorescence microscopy in HeLa and Vero cells. Knockdown (KD) of subunits of the conserved oligomeric Golgi (COG) complex significantly delays SubAB cytotoxicity and blocks SubAB trafficking to the cis Golgi. Depletion of Rab6 and beta-COP proteins causes a similar delay in SubAB-mediated GRP78 cleavage and did not augment the trafficking block observed in COG KD cells, indicating that all three Golgi factors operate on the same 'fast' retrograde trafficking pathway. SubAB trafficking is completely blocked in cells deficient in the Golgi SNARE Syntaxin 5 and does not require the activity of endosomal sorting nexins SNX1 and SNX2. Surprisingly, depletion of Golgi tethers p115 and golgin-84 that regulates two previously described coat protein I (COPI) vesicle-mediated pathways did not interfere with SubAB trafficking, indicating that SubAB is exploiting a novel COG/Rab6/COPI-dependent retrograde trafficking pathway.
authors.affiliation: Department of Physiology and Biophysics, UAMS, Little Rock, AR, USA.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Smith
authors.forename: Rose
authors.initials: R
authors.lastname: Willett
authors.forename: Tetyana
authors.initials: T
authors.lastname: Kudlyk
authors.forename: Irina
authors.initials: I
authors.lastname: Pokrovskaya
authors.forename: Adrienne W
authors.initials: AW
authors.lastname: Paton
authors.forename: James C
authors.initials: JC
authors.lastname: Paton
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Lupashin
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D018929:Cell Culture Techniques; D002522:Chlorocebus aethiops; D020755:Coat Protein Complex I / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D000091342:Endoplasmic Reticulum Chaperone BiP; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D021122:Protein Subunits; D021381:Protein Transport; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013381:Subtilisins / Q000378:metabolism*; D014162:Transfection; D014709:Vero Cells; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D020755:Coat Protein Complex I; D000091342:Endoplasmic Reticulum Chaperone BiP; D029968:Escherichia coli Proteins; C000717247:HSPA5 protein, human; D021122:Protein Subunits; C094135:Rab6 protein; D013381:Subtilisins; C527234:subtilase cytotoxin, E coli; D020691:rab GTP-Binding Proteins
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