Residual Cx45 and its relationship to Cx43 in Murine ventricular myocardium

Mingwei Bao, Evelyn M. Kanter, Richard Y.C. Huang, Stephan Maxeiner, Marina Frank, Yan Zhang, Richard B. Schuessler, Timothy W. Smith, R. Reid Townsend, Henry W. Rohrs, Viviana M. Berthoud, Klaus Willecke, James G. Laing, Kathryn A. Yamada

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Gap junction channels in ventricular myocardium are required for electrical and metabolic coupling between cardiac myocytes and for normal cardiac pump function. Although much is known about expression patterns and remodeling of cardiac connexin (Cx)43, little is known about the less abundant Cx45, which is required for embryonic development and viability, is downregulated in adult hearts, and is pathophysiologically upregulated in human end-stage heart failure. We applied quantitative immunoblotting and immunoprecipitation to native myocardial extracts, immunogold electron microscopy to cardiac tissue and membrane sections, electrophysiological recordings to whole hearts, and high-resolution tandem mass spectrometry to Cx45 fusion protein, and developed two new tools, anti-Cx45 antisera and Cre+;Cx45 floxed mice, to facilitate characterization of Cx45 in adult mammalian hearts. We found that Cx45 represents 0.3% of total Cx protein (predominantly 200 fmol Cx43 protein/μg ventricular protein) and colocalizes with Cx43 in native ventricular gap junctions, particularly in the apex and septum. Cre +;Cx45 floxed mice express 85% less Cx45, but do not exhibit overt electrophysiologic abnormalities. Although the basal phosphorylation status of native Cx45 remains unknown, CaMKII phosphorylates eight Ser/Thr residues in Cx45 in vitro. Thus, although downregulation of Cx45 does not produce notable deficits in electrical conduction in adult, diseasefree hearts, Cx45 is a target of the multifunctional kinase CaMKII, and the phosphorylation status of Cx45 and the role of Cx43/Cx45 heteromeric gap junction channels in both normal and diseased hearts merits further investigation.

Original languageEnglish
JournalChannels
Volume5
Issue number6
DOIs
StatePublished - 2011

Keywords

  • CaMKII
  • Co-immunoprecipitation
  • Connexin45
  • Cx45 phosphorylation
  • Electron microscopy
  • Gap junctions
  • Quantitative immunoblots
  • Transgenic mice

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