title: Redistribution of connexin45 in gap junctions of connexin43-deficient hearts.
abstract: OBJECTIVE
  Adult ventricular myocytes express two gap junction channel proteins: connexin43 (Cx43) and connexin45 (Cx45). Cx43-deficient mice exhibit slow ventricular epicardial conduction, suggesting that Cx43 plays an important role in intercellular coupling in the ventricle. Cx45 is much less abundant than Cx43 in working ventricular myocytes. Its role in ventricular conduction has not been defined, nor is it known whether expression or distribution of Cx45 is altered in Cx43-deficient mice. The present study was undertaken to determine (1) whether expression of Cx45 is upregulated and (2) whether gap junction structure and distribution are altered in Cx43-deficient mice.
  
  
  METHODS
  Ventricular tissue from neonatal Cx43(+/+), Cx43(+/-) and Cx43(-/-) and adult Cx43(+/+) and Cx43(+/-) mice was analyzed by immunoblotting and confocal immunofluorescence microscopy.
  
  
  RESULTS
  Total Cx45 protein abundance measured by immunoblotting was not different in Cx43-deficient or null hearts compared to wild-type control hearts. However, the amount and distribution of Cx45 immunoreactive signal measured by quantitative confocal analysis were markedly reduced in both Cx43(+/-) and Cx43(-/-) hearts.
  
  
  CONCLUSIONS
  Although the total content of Cx45 is not upregulated in Cx43-deficient hearts, the localization of Cx45 to cardiac gap junctions depends on the expression level of Cx43 and is dramatically altered in mice that express no Cx43.
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Johnson
authors.forename: Evelyn M
authors.initials: EM
authors.lastname: Kanter
authors.forename: Karen G
authors.initials: KG
authors.lastname: Green
authors.forename: James G
authors.initials: JG
authors.lastname: Laing
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Betsuyaku
authors.forename: Eric C
authors.initials: EC
authors.lastname: Beyer
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Steinberg
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Saffitz
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Yamada
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D018031:Connexin 43 / Q000378:metabolism; D017630:Connexins / Q000172:deficiency / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009206:Myocardium / Q000378:metabolism*; D000097003:Gap Junction alpha-5 Protein
chemical_list: D018031:Connexin 43; D017630:Connexins; D000097003:Gap Junction alpha-5 Protein; C082920:connexin 45