title: A novel desmocollin-2 mutation reveals insights into the molecular link between desmosomes and gap junctions.
abstract: BACKGROUND
  Cellular adhesion mediated by cardiac desmosomes is a prerequisite for proper electric propagation mediated by gap junctions in the myocardium. However, the molecular principles underlying this interdependence are not fully understood.
  
  
  OBJECTIVE
  The purpose of this study was to determine potential causes of right ventricular conduction abnormalities in a patient with borderline diagnosis of arrhythmogenic right ventricular cardiomyopathy.
  
  
  METHODS
  To assess molecular changes, the patient's myocardial tissue was analyzed for altered desmosomal and gap junction (connexin43) protein levels and localization. In vitro functional studies were performed to characterize the consequences of the desmosomal mutations.
  
  
  RESULTS
  Loss of plakoglobin signal was evident at the cell junctions despite expression of the protein at control levels. Although the distribution of connexin43 was not altered, total protein levels were reduced and changes in phosphorylation were observed. The truncation mutant in desmocollin-2a is deficient in binding plakoglobin. Moreover, the ability of desmocollin-2a to directly interact with connexin43 was abolished by the mutation. No pathogenic potential of the desmoglein-2 missense change was identified.
  
  
  CONCLUSIONS
  The observed abnormalities in gap junction protein expression and phosphorylation, which precede an overt cardiac phenotype, likely are responsible for slow myocardial conduction in this patient. At the molecular level, altered binding properties of the desmocollin-2a mutant may contribute to the changes in connexin43. In particular, the newly identified interaction between the desmocollin-2a isoform and connexin43 provides novel insights into the molecular link between desmosomes and gap junctions.
authors.affiliation: Institute of Cardiovascular Science, University College London, and The Heart Hospital, London, United Kingdom. katja.gehmlich@cardiov.ox.ac.uk
authors.forename: Katja
authors.initials: K
authors.lastname: Gehmlich
authors.forename: Pier D
authors.initials: PD
authors.lastname: Lambiase
authors.forename: Angeliki
authors.initials: A
authors.lastname: Asimaki
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Ciaccio
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Ehler
authors.forename: Petros
authors.initials: P
authors.lastname: Syrris
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Saffitz
authors.forename: William J
authors.initials: WJ
authors.lastname: McKenna
mesh_terms: D019571:Arrhythmogenic Right Ventricular Dysplasia / Q000235:genetics* / Q000378:metabolism; D018031:Connexin 43 / Q000378:metabolism; D051187:Desmocollins / Q000235:genetics*; D003896:Desmosomes / Q000235:genetics* / Q000378:metabolism; D017629:Gap Junctions / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D006329:Heart Conduction System / Q000378:metabolism; D006801:Humans
chemical_list: D018031:Connexin 43; C081561:DSC2 protein, human; D051187:Desmocollins