title: Nedd4-2 interacts with occludin to inhibit tight junction formation and enhance paracellular conductance in collecting duct epithelia.
abstract: Nedd4-2, a E3 ubiquitin ligase, regulates epithelial sodium channel-mediated transcellular Na(+) transport in the collecting duct. We investigated the effect of Nedd4-2 on the junctional complex and paracellular conductance in mpkCCD(c14) cells, a collecting duct cell line. We demonstrate that Nedd4-2 coimmunoprecipitated with and reduced the expression of transfected occludin in HEK293 cells. This interaction was mediated via a conserved PY motif in the COOH terminus of occludin and mutation of this PY motif increased the half-life of transfected occludin in HEK293 cells from 6.4 to 11.4 h. We demonstrate that Nedd4-2 ubiquitinates occludin, which was not seen when a catalytically inactive form of Nedd4-2 was used. Overexpression of Nedd4-2 in mpkCCD(c14) cells reduced occludin at the tight junction and transiently increased paracellular conductance in a Ca(2+) switch assay consistent with a delay in the formation of tight junctions. Conversely, siRNA-mediated knockdown of Nedd4-2 increased occludin levels and reduced paracellular conductance. In summary, we demonstrate that Nedd4-2 plays a role in tight junction assembly and the regulation of paracellular conductance in the collecting duct.
authors.affiliation: Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, 52242, USA.
authors.forename: Nandita S
authors.initials: NS
authors.lastname: Raikwar
authors.forename: Alain
authors.initials: A
authors.lastname: Vandewalle
authors.forename: Christie P
authors.initials: CP
authors.lastname: Thomas
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D017097:Electric Impedance; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D000075702:Nedd4 Ubiquitin Protein Ligases; D062793:Occludin; D010539:Permeability; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D034622:RNA Interference; D019108:Tight Junctions / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; C568986:Ocln protein, mouse; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; C000618485:Nedd4L protein, human; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases; D002118:Calcium