title: N-glycans mediate apical recycling of the sialomucin endolyn in polarized MDCK cells.
abstract: Apical and basolateral proteins are maintained within distinct membrane subdomains in polarized epithelial cells by biosynthetic and postendocytic sorting processes. Sorting of basolateral proteins in these processes has been well studied; however, the sorting signals and mechanisms that direct proteins to the apical surface are less well understood. We previously demonstrated that an N-glycan-dependent sorting signal directs the sialomucin endolyn to the apical surface in polarized Madin-Darby canine kidney cells. Terminal processing of a subset of endolyn's N-glycans is key for polarized biosynthetic delivery to the apical membrane. Endolyn is subsequently internalized, and via a cytoplasmic tyrosine-based sorting motif is targeted to lysosomes from where it constitutively cycles to the cell surface. Here, we examine the polarized sorting of endolyn along the postendocytic pathway in polarized cells. Our results suggest that similar N-glycan sorting determinants are required for apical delivery of endolyn along both the biosynthetic and the postendocytic pathways.
authors.affiliation: Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Potter
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Weixel
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Bruns
authors.forename: Gudrun
authors.initials: G
authors.lastname: Ihrke
authors.forename: Ora A
authors.initials: OA
authors.lastname: Weisz
mesh_terms: D000818:Animals; D002451:Cell Compartmentation; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D004285:Dogs; D004705:Endocytosis / Q000502:physiology; D051930:Endolyn / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D011134:Polysaccharides / Q000378:metabolism*; D012794:Sialic Acids / Q000737:chemistry; D015398:Signal Transduction; D021601:trans-Golgi Network / Q000378:metabolism
chemical_list: D051930:Endolyn; D008565:Membrane Proteins; D011134:Polysaccharides; D012794:Sialic Acids