Voltage-gated sodium channel modulation by sigma-receptors in cardiac myocytes and heterologous systems

Am J Physiol Cell Physiol. 2009 May;296(5):C1049-57. doi: 10.1152/ajpcell.00431.2008. Epub 2009 Mar 11.

Abstract

The sigma-receptor, a broadly distributed integral membrane protein with a novel structure, is known to modulate various voltage-gated K(+) and Ca(2+) channels through a mechanism that involves neither G proteins nor phosphorylation. The present study investigated the modulation of the heart voltage-gated Na(+) channel (Na(v)1.5) by sigma-receptors. The sigma(1)-receptor ligands [SKF-10047 and (+)-pentazocine] and sigma(1)/sigma(2)-receptor ligands (haloperidol and ditolylguanidine) all reversibly inhibited Na(v)1.5 channels to varying degrees in human embryonic kidney 293 (HEK-293) cells and COS-7 cells, but the sigma(1)-receptor ligands were less effective in COS-7 cells. The same four ligands also inhibited Na(+) current in neonatal mouse cardiac myocytes. In sigma(1)-receptor knockout myocytes, the sigma(1)-receptor-specific ligands were far less effective in modulating Na(+) current, but the sigma(1)/sigma(2)-receptor ligands modulated Na(+) channels as well as in wild type. Photolabeling with the sigma(1)-receptor photoprobe [(125)I]-iodoazidococaine demonstrated that sigma(1)-receptors were abundant in heart and HEK-293 cells, but scarce in COS-7 cells. This difference was consistent with the greater efficacy of sigma(1)-receptor-specific ligands in HEK-293 cells than in COS-7 cells. sigma-Receptors modulated Na(+) channels despite the omission of GTP and ATP from the patch pipette solution. sigma-Receptor-mediated inhibition of Na(+) current had little if any voltage dependence and produced no change in channel kinetics. Na(+) channels represent a new addition to the large number of voltage-gated ion channels modulated by sigma-receptors. The modulation of Na(v)1.5 channels by sigma-receptors in the heart suggests an important pathway by which drugs can alter cardiac excitability and rhythmicity.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Animals
  • Antipsychotic Agents / pharmacology
  • COS Cells
  • Cell Line
  • Chlorocebus aethiops
  • Guanosine Triphosphate / metabolism
  • Haloperidol / pharmacology
  • Humans
  • Kidney / cytology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Muscle Proteins / genetics
  • Muscle Proteins / metabolism*
  • Myocytes, Cardiac / cytology
  • Myocytes, Cardiac / physiology*
  • NAV1.5 Voltage-Gated Sodium Channel
  • Narcotics / pharmacology
  • Patch-Clamp Techniques
  • Pentazocine / pharmacology
  • Phenazocine / analogs & derivatives
  • Phenazocine / pharmacology
  • RNA, Small Interfering
  • Receptors, sigma / genetics
  • Receptors, sigma / metabolism*
  • Sodium / metabolism*
  • Sodium Channels / genetics
  • Sodium Channels / metabolism*

Substances

  • Antipsychotic Agents
  • Muscle Proteins
  • NAV1.5 Voltage-Gated Sodium Channel
  • Narcotics
  • RNA, Small Interfering
  • Receptors, sigma
  • SCN5A protein, human
  • Scn5a protein, mouse
  • Sodium Channels
  • SK&F 10047
  • Guanosine Triphosphate
  • Adenosine Triphosphate
  • Sodium
  • Phenazocine
  • Haloperidol
  • Pentazocine