title: Rab13 mediates the continuous endocytic recycling of occludin to the cell surface.
abstract: During epithelial morphogenesis, adherens junctions (AJs) and tight junctions (TJs) undergo dynamic reorganization, whereas epithelial polarity is transiently lost and reestablished. Although ARF6-mediated endocytic recycling of E-cadherin has been characterized and implicated in the rapid remodeling of AJs, the molecular basis for the dynamic rearrangement of TJs remains elusive. Occludin and claudins are integral membrane proteins comprising TJ strands and are thought to be responsible for establishing and maintaining epithelial polarity. Here we investigated the intracellular transport of occludin and claudins to and from the cell surface. Using cell surface biotinylation and immunofluorescence, we found that a pool of occludin was continuously endocytosed and recycled back to the cell surface in both fibroblastic baby hamster kidney cells and epithelial MTD-1A cells. Biochemical endocytosis and recycling assays revealed that a Rab13 dominant active mutant (Rab13 Q67L) inhibited the postendocytic recycling of occludin, but not that of transferrin receptor and polymeric immunoglobulin receptor in MTD-1A cells. Double immunolabelings showed that a fraction of endocytosed occludin was colocalized with Rab13 in MTD-1A cells. These results suggest that Rab13 specifically mediates the continuous endocytic recycling of occludin to the cell surface in both fibroblastic and epithelial cells.
authors.affiliation: Department of Biochemistry, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Morimoto
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nishimura
authors.forename: Tomoya
authors.initials: T
authors.lastname: Terai
authors.forename: Shinji
authors.initials: S
authors.lastname: Manabe
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Wakako
authors.initials: W
authors.lastname: Shinahara
authors.forename: Hidenori
authors.initials: H
authors.lastname: Miyake
authors.forename: Seiki
authors.initials: S
authors.lastname: Tashiro
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Shimada
authors.forename: Takuya
authors.initials: T
authors.lastname: Sasaki
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D001710:Biotin / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D002460:Cell Line; D004705:Endocytosis / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D062793:Occludin; D019108:Tight Junctions / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000502:physiology*
chemical_list: D015820:Cadherins; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D001710:Biotin; C085485:RAB13 protein, human; D020691:rab GTP-Binding Proteins