title: On the self-association potential of transmembrane tight junction proteins.
abstract: Tight junctions seal intercellular clefts via membrane-related strands, hence, maintaining important organ functions. We investigated the self-association of strand-forming transmembrane tight junction proteins. The regulatory tight junction protein occludin was differently tagged and cotransfected in eucaryotic cells. These occludins colocalized within the plasma membrane of the same cell, coprecipitated and exhibited fluorescence resonance energy transfer. Differently tagged strand-forming claudin-5 also colocalized in the plasma membrane of the same cell and showed fluorescence resonance energy transfer. This demonstrates self-association in intact cells both of occludin and claudin-5 in one plasma membrane. In search of dimerizing regions of occludin, dimerization of its cytosolic C-terminal coiledcoil domain was identified. In claudin-5, the second extracellular loop was detected as a dimer. Since the transmembrane junctional adhesion molecule also is known to dimerize, the assumption that homodimerization of transmembrane tight junction proteins may serve as a common structural feature in tight junction assembly is supported.
authors.affiliation: Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125 Berlin, Germany. iblasig@fmp-berlin.de
authors.forename: I E
authors.initials: IE
authors.lastname: Blasig
authors.forename: L
authors.initials: L
authors.lastname: Winkler
authors.forename: B
authors.initials: B
authors.lastname: Lassowski
authors.forename: S L
authors.initials: SL
authors.lastname: Mueller
authors.forename: N
authors.initials: N
authors.lastname: Zuleger
authors.forename: E
authors.initials: E
authors.lastname: Krause
authors.forename: G
authors.initials: G
authors.lastname: Krause
authors.forename: K
authors.initials: K
authors.lastname: Gast
authors.forename: M
authors.initials: M
authors.lastname: Kolbe
authors.forename: J
authors.initials: J
authors.lastname: Piontek
mesh_terms: D000818:Animals; D001426:Bacterial Proteins; D002460:Cell Line; D002850:Chromatography, Gel; D062507:Claudin-5; D019281:Dimerization; D004285:Dogs; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D006801:Humans; D049408:Luminescent Agents; D008164:Luminescent Proteins; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D062793:Occludin; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D019108:Tight Junctions / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; C107466:CLDN5 protein, human; D062507:Claudin-5; C485182:Cyan Fluorescent Protein; D005456:Fluorescent Dyes; D049408:Luminescent Agents; D008164:Luminescent Proteins; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D011993:Recombinant Fusion Proteins; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins