title: Remodeling of mechanical junctions and of microtubule-associated proteins accompany cardiac connexin43 lateralization.
abstract: BACKGROUND
  Desmosomes and adherens junctions provide mechanical continuity between cardiac cells, whereas gap junctions allow for cell-cell electrical/metabolic coupling. These structures reside at the cardiac intercalated disc (ID). Also at the ID is the voltage-gated sodium channel (VGSC) complex. Functional interactions between desmosomes, gap junctions, and VGSC have been demonstrated. Separate studies show, under various conditions, reduced presence of gap junctions at the ID and redistribution of connexin43 (Cx43) to plaques oriented parallel to fiber direction (gap junction "lateralization").
  
  
  OBJECTIVE
  To determine the mechanisms of Cx43 lateralization, and the fate of desmosomal and sodium channel molecules in the setting of Cx43 remodeling.
  
  
  METHODS
  Adult sheep were subjected to right ventricular pressure overload (pulmonary hypertension). Tissue was analyzed by quantitative confocal microscopy and by transmission electron microscopy. Ionic currents were measured using conventional patch clamp.
  
  
  RESULTS
  Quantitative confocal microscopy demonstrated lateralization of immunoreactive junctional molecules. Desmosomes and gap junctions in lateral membranes were demonstrable by electron microscopy. Cx43/desmosomal remodeling was accompanied by lateralization of 2 microtubule-associated proteins relevant for Cx43 trafficking: EB1 and kinesin protein Kif5b. In contrast, molecules of the VGSC failed to reorganize in plaques discernable by confocal microscopy. Patch-clamp studies demonstrated change in amplitude and kinetics of sodium current and a small reduction in electrical coupling between cells.
  
  
  CONCLUSIONS
  Cx43 lateralization is part of a complex remodeling that includes mechanical and gap junctions but may exclude components of the VGSC. We speculate that lateralization results from redirectionality of microtubule-mediated forward trafficking. Remodeling of junctional complexes may preserve electrical synchrony under conditions that disrupt ID integrity.
authors.affiliation: The Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, New York, USA.
authors.forename: Halina S
authors.initials: HS
authors.lastname: Chkourko
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Guerrero-Serna
authors.forename: Xianming
authors.initials: X
authors.lastname: Lin
authors.forename: Nedal
authors.initials: N
authors.lastname: Darwish
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Pohlmann
authors.forename: Keith E
authors.initials: KE
authors.lastname: Cook
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Martens
authors.forename: Eli
authors.initials: E
authors.lastname: Rothenberg
authors.forename: Hassan
authors.initials: H
authors.lastname: Musa
authors.forename: Mario
authors.initials: M
authors.lastname: Delmar
mesh_terms: D000818:Animals; D017487:Ankyrins / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D018031:Connexin 43 / Q000502:physiology*; D003896:Desmosomes / Q000502:physiology*; D004195:Disease Models, Animal; D022062:Electrophysiologic Techniques, Cardiac; D017629:Gap Junctions / Q000502:physiology*; D006976:Hypertension, Pulmonary / Q000503:physiopathology*; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000502:physiology*; D018408:Patch-Clamp Techniques; D012756:Sheep
chemical_list: D017487:Ankyrins; D015820:Cadherins; D018031:Connexin 43; D008869:Microtubule-Associated Proteins