Nav1.3 sodium channels: Rapid repriming and slow closed-state inactivation display quantitative differences after expression in a mammalian cell line and in spinal sensory neurons

Theodore R. Cummins, Fabio Aglieco, Mathurkrisnan Renganathan, Raimund I. Herzog, Sulayman D. Dib-Hajj, Stephen G. Waxman

Research output: Contribution to journalArticlepeer-review

237 Scopus citations

Abstract

Although rat brain Nav1.3 voltage-gated sodium channels have been expressed and studied in Xenopus oocytes, these channels have not been studied after their expression in mammalian cells. We characterized the properties of the rat brain Nav1.3 sodium channels expressed in human embryonic kidney (HEK) 293 cells. Nav1.3 channels generated fast-activating and fast-inactivating currents. Recovery from inactivation was relatively rapid at negative potentials (< -80 mV) but was slow at more positive potentials. Development of closed-state inactivation was slow, and, as predicted on this basis, Nav1.3 channels generated large ramp currents in response to slow depolarizations. Coexpression of β3 subunits had small but significant effects on the kinetic and voltage-dependent properties of Nav1.3 currents in HEK 293 cells, but coexpression of β1 and β2 subunits had little or no effect on Nav1.3 properties. Nav1.3 channels, mutated to be tetrodotoxin-resistant (TTX-R), were expressed in SNS-null dorsal root ganglion (DRG) neurons via biolistics and were compared with the same construct expressed in HEK 293 cells. The voltage dependence of steady-state inactivation was ∼7 mV more depolarized in SNS-null DRG neurons, demonstrating the importance of background cell type in determining physiological properties. Moreover, consistent with the idea that cellular factors can modulate the properties of Nav1.3, the repriming kinetics were twofold faster in the neurons than in the HEK 293 cells. The rapid repriming of Nav1.3 suggests that it contributes to the acceleration of repriming of TTX-sensitive (TTX-S) sodium currents that are seen after peripheral axotomy of DRG neurons. The relatively rapid recovery from inactivation and the slow closed-state inactivation kinetics of Nav1.3 channels suggest that neurons expressing Nav1.3 may exhibit a reduced threshold and/or a relatively high frequency of firing.

Original languageEnglish (US)
Pages (from-to)5952-5961
Number of pages10
JournalJournal of Neuroscience
Volume21
Issue number16
DOIs
StatePublished - Aug 15 2001

Keywords

  • Biolistics
  • Ion channel
  • Nerve injury
  • Ramp current
  • Spinal sensory neurons
  • β-subunits

ASJC Scopus subject areas

  • Neuroscience(all)

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