Single-Molecule Localization of the Cardiac Voltage-Gated Sodium Channel Reveals Different Modes of Reorganization at Cardiomyocyte Membrane Domains

Circ Arrhythm Electrophysiol. 2020 Jul;13(7):e008241. doi: 10.1161/CIRCEP.119.008241. Epub 2020 Jun 15.

Abstract

Background: Mutations in the gene encoding the cardiac voltage-gated sodium channel Nav1.5 cause various cardiac arrhythmias. This variety may arise from different determinants of Nav1.5 expression between cardiomyocyte domains. At the lateral membrane and T-tubules, Nav1.5 localization and function remain insufficiently characterized.

Methods: We used novel single-molecule localization microscopy and computational modeling to define nanoscale features of Nav1.5 localization and distribution at the lateral membrane, the lateral membrane groove, and T-tubules in cardiomyocytes from wild-type (N=3), dystrophin-deficient (mdx; N=3) mice, and mice expressing C-terminally truncated Nav1.5 (ΔSIV; N=3). We moreover assessed T-tubules sodium current by recording whole-cell sodium currents in control (N=5) and detubulated (N=5) wild-type cardiomyocytes.

Results: We show that Nav1.5 organizes as distinct clusters in the groove and T-tubules which density, distribution, and organization partially depend on SIV and dystrophin. We found that overall reduction in Nav1.5 expression in mdx and ΔSIV cells results in a nonuniform redistribution with Nav1.5 being specifically reduced at the groove of ΔSIV and increased in T-tubules of mdx cardiomyocytes. A T-tubules sodium current could, however, not be demonstrated.

Conclusions: Nav1.5 mutations may site-specifically affect Nav1.5 localization and distribution at the lateral membrane and T-tubules, depending on site-specific interacting proteins. Future research efforts should elucidate the functional consequences of this redistribution.

Keywords: cardiac arrhythmias; cardiomyocyte; dystrophin; electrophysiology; membranes; microscopy; sodium channel.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Membrane / metabolism*
  • Cell Membrane / ultrastructure
  • Computer Simulation
  • Dystrophin / genetics
  • Dystrophin / metabolism
  • Ion Channel Gating*
  • Membrane Potentials
  • Mice, Inbred mdx
  • Mice, Transgenic
  • Models, Cardiovascular
  • Myocytes, Cardiac / metabolism*
  • Myocytes, Cardiac / ultrastructure
  • NAV1.5 Voltage-Gated Sodium Channel / genetics
  • NAV1.5 Voltage-Gated Sodium Channel / metabolism*
  • Protein Transport
  • Single Molecule Imaging*

Substances

  • Dystrophin
  • NAV1.5 Voltage-Gated Sodium Channel
  • Scn5a protein, mouse