title: A secretory Golgi bypass route to the apical surface domain of epithelial MDCK cells.
abstract: Proteins leave the endoplasmic reticulum (ER) for the plasma membrane via the classical secretory pathway, but routes bypassing the Golgi apparatus have also been observed. Apical and basolateral protein secretion in epithelial Madin-Darby canine kidney (MDCK) cells display differential sensitivity to Brefeldin A (BFA), where low concentrations retard apical transport, while basolateral transport still proceeds through intact Golgi cisternae. We now describe that BFA-mediated retardation of glycoprotein and proteoglycan transport through the Golgi apparatus induces surface transport of molecules lacking Golgi modifications, possessing those acquired in the ER. Low concentrations of BFA induces apical Golgi bypass, while higher concentrations were required to induce basolateral Golgi bypass. Addition of the KDEL ER-retrieval sequence to model protein cores allowed observation of apical Golgi bypass in untreated MDCK cells. Basolateral Golgi bypass was only observed after the addition of BFA or upon cholesterol depletion. Thus, in MDCK cells, an apical Golgi bypass route can transport cargo from pre-Golgi organelles in untreated cells, while the basolateral bypass route is inducible.
authors.affiliation: Department of Molecular Biosciences, University of Oslo, Oslo, Norway.
authors.forename: Heidi
authors.initials: H
authors.lastname: Tveit
authors.forename: Linn Kristin Aa
authors.initials: LK
authors.lastname: Akslen
authors.forename: Gro Live
authors.initials: GL
authors.lastname: Fagereng
authors.forename: Michael A
authors.initials: MA
authors.lastname: Tranulis
authors.forename: Kristian
authors.initials: K
authors.lastname: Prydz
mesh_terms: D000818:Animals; D001692:Biological Transport; D020126:Brefeldin A / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D016764:Cell Polarity; D016895:Culture Media, Serum-Free; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008954:Models, Biological; D021381:Protein Transport / Q000187:drug effects; D011509:Proteoglycans / Q000378:metabolism; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D016895:Culture Media, Serum-Free; D006023:Glycoproteins; D011509:Proteoglycans; D033921:Vesicular Transport Proteins; C075430:serglycin; D049452:Green Fluorescent Proteins; D020126:Brefeldin A