title: Linking integrin alpha6beta4-based cell adhesion to the intermediate filament cytoskeleton: direct interaction between the beta4 subunit and plectin at multiple molecular sites.
abstract: Recent studies with patients suffering from epidermolysis bullosa simplex associated with muscular dystrophy and the targeted gene disruption in mice suggested that plectin, a versatile cytoskeletal linker and intermediate filament-binding protein, may play an essential role in hemidesmosome integrity and stabilization. To define plectin's interactions with hemidesmosomal proteins on the molecular level, we studied its interaction with the uniquely long cytoplasmic tail domain of the beta4 subunit of the basement membrane laminin receptor integrin alpha6beta4 that has been implicated in connecting the transmembrane integrin complex with hemidesmosome-anchored cytokeratin filaments. In vitro binding and in vivo cotransfection assays, using recombinant mutant forms of both proteins, revealed their direct interaction via multiple molecular domains. Furthermore, we show in vitro self-interaction of integrin beta4 cytoplasmic domains, as well as disruption of intermediate filament network arrays and dislocation of hemidesmosome-associated endogenous plectin upon ectopic overexpression of this domain in PtK2 and/or 804G cells. The close association of plectin molecules with hemidesmosomal structures and their apparent random orientation was indicated by gold immunoelectron microscopy using domain-specific antibodies. Our data support a model in which plectin stabilizes hemidesmosomes, via directly interlinking integrin beta4 subunits and cytokeratin filaments.
authors.affiliation: Institute of Biochemistry and Molecular Cell Biology, Vienna Biocenter, 1030 Vienna, Austria.
authors.forename: G A
authors.initials: GA
authors.lastname: Rezniczek
authors.forename: J M
authors.initials: JM
authors.lastname: de Pereda
authors.forename: S
authors.initials: S
authors.lastname: Reipert
authors.forename: G
authors.initials: G
authors.lastname: Wiche
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D000954:Antigens, Surface / Q000378:metabolism*; D001485:Basement Membrane / Q000502:physiology; D001665:Binding Sites; D002448:Cell Adhesion / Q000502:physiology*; D002460:Cell Line; D003599:Cytoskeleton / Q000502:physiology* / Q000648:ultrastructure; D005063:Europium; D006801:Humans; D039161:Integrin alpha6beta4; D039663:Integrin beta4; D016023:Integrins / Q000378:metabolism*; D007381:Intermediate Filament Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D007382:Intermediate Filaments / Q000502:physiology* / Q000648:ultrastructure; D007633:Keratins / Q000378:metabolism; D046911:Macromolecular Substances; D007614:Macropodidae; D051379:Mice; D051190:Plectin; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D014162:Transfection
chemical_list: D015703:Antigens, CD; D000954:Antigens, Surface; D039161:Integrin alpha6beta4; D039663:Integrin beta4; D016023:Integrins; D007381:Intermediate Filament Proteins; D046911:Macromolecular Substances; C495332:PLEC protein, human; C495333:Plec protein, mouse; D051190:Plectin; D011994:Recombinant Proteins; D005063:Europium; D007633:Keratins