Advertisement

Pflügers Archiv - European Journal of Physiology

, Volume 468, Issue 10, pp 1651–1661 | Cite as

Potassium channels in the Cx43 gap junction perinexus modulate ephaptic coupling: an experimental and modeling study

  • Rengasayee Veeraraghavan
  • Joyce Lin
  • James P. Keener
  • Robert Gourdie
  • Steven Poelzing
Ion channels, receptors and transporters

Abstract

It was recently demonstrated that cardiac sodium channels (Nav1.5) localized at the perinexus, an intercalated disc (ID) nanodomain associated with gap junctions (GJ), may contribute to electrical coupling between cardiac myocytes via an ephaptic mechanism. Impairment of ephaptic coupling by acute interstitial edema (AIE)-induced swelling of the perinexus was associated with arrhythmogenic, anisotropic conduction slowing. Given that Kir2.1 has also recently been reported to localize at intercalated discs, we hypothesized that Kir2.1 channels may reside within the perinexus and that inhibiting them may mitigate arrhythmogenic conduction slowing observed during AIE. Using gated stimulated emission depletion (gSTED) and stochastic optical reconstruction microscopy (STORM) super-resolution microscopy, we indeed find that a significant proportion of Kir2.1 channels resides within the perinexus. Moreover, whereas Nav1.5 inhibition during AIE exacerbated arrhythmogenic conduction slowing, inhibiting Kir2.1 channels during AIE preferentially increased transverse conduction velocity—decreasing anisotropy and ameliorating arrhythmia risk compared to AIE alone. Comparison of our results with a nanodomain computer model identified enrichment of both Nav1.5 and Kir2.1 at intercalated discs as key factors underlying the experimental observations. We demonstrate that Kir2.1 channels are localized within the perinexus alongside Nav1.5 channels. Further, targeting Kir2.1 modulates intercellular coupling between cardiac myocytes, anisotropy of conduction, and arrhythmia propensity in a manner consistent with a role for ephaptic coupling in cardiac conduction. For over half a century, electrical excitation in the heart has been thought to occur exclusively via gap junction-mediated ionic current flow between cells. Further, excitation was thought to depend almost exclusively on sodium channels with potassium channels being involved mainly in returning the cell to rest. Here, we demonstrate that sodium and potassium channels co-reside within nanoscale domains at cell-to-cell contact sites. Experimental and computer modeling results suggest a role for these channels in electrical coupling between cardiac muscle cells via an ephaptic mechanism working in tandem with gap junctions. This new insight into the mechanism of cardiac electrical excitation could pave the way for novel therapies against cardiac rhythm disturbances.

Keywords

Cardiac conduction Gap junctions Sodium channels Potassium channels Arrhythmia Ephaptic coupling 

Notes

Acknowledgments

The authors would like to thank Dr. James Smyth for the assistance with the STORM microscopy. Thanks also to Dr. Gregory Hoeker and Michael Entz for the assistance with optical mapping experiments and to Mrs. Jane Jourdan for the assistance with NRVM experiments.

Compliance with ethical standards

The investigation was conducted in conformation with the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH publication no. 85-23, revised 1996). All animal study protocols were approved by the Institutional Animal Care and Use Committee (IACUC) at the Virginia Polytechnic University.

Conflicts of interest

The authors declare that they have no conflict of interest.

Funding sources

This work was supported by an NIH R01 grant awarded to Dr. Poelzing (R01-HL102298-01A1), by an NIH R01 grant awarded to Dr. Gourdie (RO1 HL56728-14A2), and by an American Heart Association post-doctoral fellowship awarded to Dr. Veeraraghavan (2013–15, completed).

Disclosures

None

References

  1. 1.
    Agullo-Pascual E, Lin X, Leo-Macias A, Zhang M, Liang FX, Li Z, Pfenniger A, Lubkemeier I, Keegan S, Fenyo D, Willecke K, Rothenberg E, and Delmar M. Super-resolution imaging reveals that loss of the C-terminus of connexin43 limits microtubule plus-end capture and NaV1.5 localization at the intercalated disc. Cardiovascular research 2014.Google Scholar
  2. 2.
    Clausen Mathias P, Galiani S, de la Serna Jorge B, Fritzsche M, Chojnacki J, Gehmlich K, Lagerholm BC, and Eggeling C. Pathways to optical STED microscopy. In: NanoBioImaging 2013, p. 1.Google Scholar
  3. 3.
    Dhein S, Seidel T, Salameh A, Jozwiak J, Hagen A, Kostelka M, Hindricks G, Mohr FW (2014) Remodeling of cardiac passive electrical properties and susceptibility to ventricular and atrial arrhythmias. Front Physiol 5:424CrossRefPubMedPubMedCentralGoogle Scholar
  4. 4.
    Ferreira G, Yi J, Rios E, Shirokov R (1997) Ion-dependent inactivation of barium current through L-type calcium channels. J Gen Physiol 109:449–461CrossRefPubMedPubMedCentralGoogle Scholar
  5. 5.
    Geisler SB, Green KJ, Isom LL, Meshinchi S, Martens JR, Delmar M, Russell MW (2010) Ordered assembly of the adhesive and electrochemical connections within newly formed intercalated disks in primary cultures of adult rat cardiomyocytes. J Biomed Biotechnol 2010:624719CrossRefPubMedPubMedCentralGoogle Scholar
  6. 6.
    George SA, Sciuto KJ, Lin J, Salama ME, Keener JP, Gourdie RG, and Poelzing S. Extracellular sodium and potassium levels modulate cardiac conduction in mice heterozygous null for the Connexin43 gene. Pflugers Arch 2015.Google Scholar
  7. 7.
    Girouard SD, Laurita KR, Rosenbaum DS (1996) Unique properties of cardiac action potentials recorded with voltage-sensitive dyes. J Cardiovasc Electrophysiol 7:1024–1038CrossRefPubMedGoogle Scholar
  8. 8.
    Green CR, Severs NJ (1984) Gap junction connexon configuration in rapidly frozen myocardium and isolated intercalated disks. The Journal of cell biology 99:453–463CrossRefPubMedGoogle Scholar
  9. 9.
    Hong M, Bao L, Kefaloyianni E, Agullo-Pascual E, Chkourko H, Foster M, Taskin E, Zhandre M, Reid DA, Rothenberg E, Delmar M, Coetzee WA (2012) Heterogeneity of ATP-sensitive K+ channels in cardiac myocytes: enrichment at the intercalated disk. J Biol Chem 287:41258–41267CrossRefPubMedPubMedCentralGoogle Scholar
  10. 10.
    Hoyt RH, Cohen ML, Saffitz JE (1989) Distribution and three-dimensional structure of intercellular junctions in canine myocardium. Circ Res 64:563–574CrossRefPubMedGoogle Scholar
  11. 11.
    Kleber AG, Rudy Y (2004) Basic mechanisms of cardiac impulse propagation and associated arrhythmias. Physiol Rev 84:431–488CrossRefPubMedGoogle Scholar
  12. 12.
    Kucera JP, Kleber AG, Rohr S (1998) Slow conduction in cardiac tissue. II: effects of branching tissue geometry Circulation research 83:795–805PubMedGoogle Scholar
  13. 13.
    Kucera JP, Rohr S, Rudy Y (2002) Localization of sodium channels in intercalated disks modulates cardiac conduction. Circ Res 91:1176–1182CrossRefPubMedPubMedCentralGoogle Scholar
  14. 14.
    Larsen AP, Olesen SP, Grunnet M, Poelzing S (2010) Pharmacological activation of IKr impairs conduction in guinea pig hearts. J Cardiovasc Electrophysiol 21:923–929PubMedGoogle Scholar
  15. 15.
    Leo-Macias A, Liang FX, Delmar M (2015) Ultrastructure of the intercellular space in adult murine ventricle revealed by quantitative tomographic electron microscopy. Cardiovasc Res 107:442–452CrossRefPubMedPubMedCentralGoogle Scholar
  16. 16.
    Lin J, Keener JP (2013) Ephaptic coupling in cardiac myocytes. IEEE Trans Biomed Eng 60:576–582CrossRefPubMedGoogle Scholar
  17. 17.
    Lin J, Keener JP (2014) Microdomain effects on transverse cardiac propagation. Biophys J 106:925–931CrossRefPubMedPubMedCentralGoogle Scholar
  18. 18.
    Matthes S, Zhang M, Taffet S, Delmar M (2010) Desmosomes and gap junctions in epicardium-derived cells a possible role in arrhythmogenic right ventricular cardiomyopathy? Heart Rhythm 7:1715–1716CrossRefGoogle Scholar
  19. 19.
    Mays DJ, Foose JM, Philipson LH, Tamkun MM (1995) Localization of the Kv15 K+ channel protein in explanted cardiac tissue. J Clin Invest 96:282–292CrossRefPubMedPubMedCentralGoogle Scholar
  20. 20.
    Milstein ML, Musa H, Balbuena DP, Anumonwo JM, Auerbach DS, Furspan PB, Hou L, Hu B, Schumacher SM, Vaidyanathan R, Martens JR, Jalife J (2012) Dynamic reciprocity of sodium and potassium channel expression in a macromolecular complex controls cardiac excitability and arrhythmia. Proc Natl Acad Sci U S A 109:E2134–E2143CrossRefPubMedPubMedCentralGoogle Scholar
  21. 21.
    Mori Y, Fishman GI, Peskin CS (2008) Ephaptic conduction in a cardiac strand model with 3D electrodiffusion. Proc Natl Acad Sci U S A 105:6463–6468CrossRefPubMedPubMedCentralGoogle Scholar
  22. 22.
    Poelzing S, Veeraraghavan R (2007) Heterogeneous ventricular chamber response to hypokalemia and inward rectifier potassium channel blockade underlies bifurcated T wave in guinea pig. Am J Phys Heart Circ Phys 292:H3043–H3051Google Scholar
  23. 23.
    Rhett JM, Jourdan J, Gourdie RG (2011) Connexin 43 connexon to gap junction transition is regulated by zonula occludens-1. Mol Biol Cell 22:1516–1528CrossRefPubMedPubMedCentralGoogle Scholar
  24. 24.
    Rhett JM, Ongstad EL, Jourdan J, Gourdie RG (2012) Cx43 associates with Na(v)15 in the cardiomyocyte perinexus. J Membr Biol 245:411–422CrossRefPubMedPubMedCentralGoogle Scholar
  25. 25.
    Schoonderwoert V, Dijkstra R, Luckinavicius G, Kobler O, der Voort H Huygens STED v (2013) Deconvolution increases signal-to-noise and image resolution towards 22 nm. Micros Today 21:38–44CrossRefGoogle Scholar
  26. 26.
    Skibsbye L, Wang X, Axelsen LN, Bomholtz SH, Nielsen MS, Grunnet M, Bentzen BH, Jespersen T (2015) Antiarrhythmic mechanisms of SK channel inhibition in the rat atrium. J Cardiovasc Pharmacol 66:165–176CrossRefPubMedGoogle Scholar
  27. 27.
    Slawsky MT, Castle NA (1994) K+ channel blocking actions of flecainide compared with those of propafenone and quinidine in adult rat ventricular myocytes. J Pharmacol Exp Ther 269:66–74PubMedGoogle Scholar
  28. 28.
    Sperelakis N, McConnell K (2002) Electric field interactions between closely abutting excitable cells. IEEE Eng Med Biol Mag 21:77–89CrossRefPubMedGoogle Scholar
  29. 29.
    Stein M, Boulaksil M, Engelen MA, van Veen TA, Hauer RN, de Bakker JM, van Rijen HV (2006) Conduction reserve and arrhythmias. Neth Heart J 14:113–116PubMedPubMedCentralGoogle Scholar
  30. 30.
    Stein M, van Veen TA, Remme CA, Boulaksil M, Noorman M, van Stuijvenberg L, van der Nagel R, Bezzina CR, Hauer RN, de Bakker JM, van Rijen HV (2009) Combined reduction of intercellular coupling and membrane excitability differentially affects transverse and longitudinal cardiac conduction. Cardiovasc Res 83:52–60CrossRefPubMedGoogle Scholar
  31. 31.
    Tran TN, Drab K, Daszykowski M (2013) Revised DBSCAN algorithm to cluster data with dense adjacent clusters. Chemom Intell Lab Syst 120:92–96CrossRefGoogle Scholar
  32. 32.
    Veeraraghavan R, and Gourdie R Stochastic optical reconstruction microscopy-based relative localization analysis (STORM-RLA) for quantitative nanoscale assessment of spatial protein organization Mol Biol Cell 2016Google Scholar
  33. 33.
    Veeraraghavan R, Larsen AP, Torres NS, Grunnet M, Poelzing S (2013) Potassium channel activators differentially modulate the effect of sodium channel blockade on cardiac conduction. Acta Physiol (Oxf) 207:280–289CrossRefGoogle Scholar
  34. 34.
    Veeraraghavan R, Lin J, Hoeker GS, Keener JP, Gourdie RG, and Poelzing S Sodium channels in the Cx43 gap junction perinexus may constitute a cardiac ephapse: an experimental and modeling study Pflugers Arch 2015Google Scholar
  35. 35.
    Veeraraghavan R, Poelzing S (2008) Mechanisms underlying increased right ventricular conduction sensitivity to flecainide challenge. Cardiovasc Res 77:749–756CrossRefPubMedGoogle Scholar
  36. 36.
    Veeraraghavan R, Salama ME, and Poelzing S Interstitial volume modulates the conduction velocity—gap junction relationship American journal of physiology Heart and circulatory physiology 2012Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative MedicineVirginia Polytechnic UniversityRoanokeUSA
  2. 2.School of Biomedical Engineering and SciencesVirginia Polytechnic UniversityBlacksburgUSA
  3. 3.Department of MathematicsCalifornia Polytechnic State UniversitySan Luis ObispoUSA
  4. 4.Department of MathematicsUniversity of UtahSalt Lake CityUSA

Personalised recommendations