title: The inner nuclear membrane protein Sun1 mediates the anchorage of Nesprin-2 to the nuclear envelope.
abstract: Nesprins form a novel class of nuclear envelope-anchored spectrin-repeat proteins. We show that a direct association of their highly conserved C-terminal luminal domain with the inner nuclear membrane protein Sun1 mediates their nuclear envelope localisation. In Nesprin-1 and Nesprin-2 the conserved C-terminal amino acids PPPX are essential for the interaction with a C-terminal region in Sun1. In fact, Sun1 is required for the proper nuclear envelope localisation of Nesprin-2 as shown using dominant-negative mutants and by knockdown of Sun1 expression. Sun1 itself does not require functional A-type lamins for its localisation at the inner nuclear membrane in mammalian cells. Our findings propose a conserved nuclear anchorage mechanism between Caenorhabditis elegans and mammals and suggest a model in which Sun1 serves as a ;structural bridge' connecting the nuclear interior with the actin cytoskeleton.
authors.affiliation: Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Strasse 52, 50931 Cologne, Germany.
authors.forename: V C
authors.initials: VC
authors.lastname: Padmakumar
authors.forename: Thorsten
authors.initials: T
authors.lastname: Libotte
authors.forename: Wenshu
authors.initials: W
authors.lastname: Lu
authors.forename: Hafida
authors.initials: H
authors.lastname: Zaim
authors.forename: Sabu
authors.initials: S
authors.lastname: Abraham
authors.forename: Angelika A
authors.initials: AA
authors.lastname: Noegel
authors.forename: Josef
authors.initials: J
authors.lastname: Gotzmann
authors.forename: Roland
authors.initials: R
authors.lastname: Foisner
authors.forename: Iakowos
authors.initials: I
authors.lastname: Karakesisoglou
mesh_terms: D000818:Animals; D019556:COS Cells; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D003598:Cytoskeletal Proteins; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009685:Nuclear Envelope / Q000145:classification / Q000378:metabolism* / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C506117:SUN1 protein, human; C464932:SUN1 protein, mouse; C415465:SYNE1 protein, human; C485904:SYNE2 protein, human; C485901:Syne1 protein, mouse; C485903:Syne2 protein, mouse