title: Loss of electrical communication, but not plaque formation, after mutations in the cytoplasmic loop of connexin43.
abstract: OBJECTIVE
  The aim of this study was to determine if the structural integrity of a region in the cytoplasmic loop (amino acids 119-144; region "L2") of connexin43 (Cx43) is necessary to maintain normal channel function.
  
  
  BACKGROUND
  Cx43 is the most abundant gap junction protein in the heart. The ability of these channels to close under pathologic conditions such as ischemia may be a key substrate for cardiac arrhythmias. Previous studies have shown that Cx43 regulation involves the intramolecular interaction of its carboxyl terminal domain (a "gating particle") with a separate region of the molecule acting as a receptor. We recently proposed that a region in the cytoplasmic loop of Cx43 (amino acids 119-144; region "L2") might function as a receptor.
  
  
  METHODS
  Using site-directed mutagenesis and patch clamp analysis, as well as fluorescent microscopy, we examined gap junction plaque formation and channel properties of Cx43 L2 mutants.
  
  
  RESULTS
  Deletions of 5 to 6 amino acids within the L2 domain interfered with the formation of functional gap junction channels, although gap junction plaques were clearly visible. Selected point mutations in the region (including those present in patients with oculodentodigital dysplasia) caused modifications ranging from complete channel closure to changes in unitary conductance.
  
  
  CONCLUSIONS
  These results show that the L2 region is essential for maintenance of the normal architecture of the channel pore. This information is consistent with the notion that the L2 region could be a receptor for the carboxy terminal domain; the latter interaction would lead to channel closure under conditions such as myocardial ischemia and infarction.
authors.affiliation: Department of Pharmacology, SUNY Upstate Medical University, Syracuse, New York, USA.
authors.forename: Akiko
authors.initials: A
authors.lastname: Seki
authors.forename: Wanda
authors.initials: W
authors.lastname: Coombs
authors.forename: Steven M
authors.initials: SM
authors.lastname: Taffet
authors.forename: Mario
authors.initials: M
authors.lastname: Delmar
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor / Q000473:pathology; D018031:Connexin 43 / Q000737:chemistry / Q000235:genetics*; D017629:Gap Junctions / Q000235:genetics*; D049452:Green Fluorescent Proteins; D051379:Mice; D008856:Microscopy, Fluorescence; D009154:Mutation; D009447:Neuroblastoma / Q000473:pathology; D018408:Patch-Clamp Techniques; D051381:Rats
chemical_list: D018031:Connexin 43; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins