Novel pharmacological modulation of dystonic phenotypes caused by a gain-of-function mutation in the Na+ leak-current channel

Behav Pharmacol. 2020 Aug;31(5):465-476. doi: 10.1097/FBP.0000000000000526.

Abstract

The Na leak-current channel (NALCN) regulates the resting membrane potential in excitable cells, thus determining the likelihood of depolarization in response to incoming signals. Gain-of-function (gf) mutations in this channel are associated with severe dystonic movement disorders in man. Currently, there are no known pharmacological antagonists or selective modulators of this important channel. A gain-of-function mutation in NALCN of C. elegans [known as unc-77(e625)] causes uncoordinated, hyperactive locomotion. We hypothesized that this hyperactive phenotype can be rescued with pharmacological modulators. Here, we summarize the results of targeted drug screening aimed at identification of drugs that corrected locomotion deficits in unc-77(e625) animals. To assay hyperactive locomotion, animals were acutely removed from food and characteristic foraging movements were quantified. Drug screening revealed that 2-aminoethoxydiphenyl borate (2-ABP), nifedipine, nimodipine, flunarizine and ethoxzolamide significantly decreased abnormal movements in unc-77(e625) animals. 2-APB also corrected egg release and coiling deficits in this strain. In addition, serotonin and dopamine both reduced hyperactive locomotion, consistent with regulatory interactions between these systems and the NALCN. 2-APB induced movement phenotypes in wild-type animals that faithfully mimicked those observed in NALCN knockout strains, which suggested that this drug may directly block the channel. Moreover, 2-APB and flunarizine showed significant structural similarities suggestive of overlap in their mode of action. Together, these studies have revealed new insights into regulation of NALCN function and led to the discovery of a potential pharmacological antagonist of the NALCN.

Publication types

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

MeSH terms

  • Animals
  • Boron Compounds
  • Caenorhabditis elegans
  • Caenorhabditis elegans Proteins / antagonists & inhibitors
  • Caenorhabditis elegans Proteins / genetics*
  • Dystonia / genetics*
  • Ethoxzolamide / pharmacology
  • Flunarizine / pharmacology
  • Gain of Function Mutation / drug effects*
  • Gene Knockout Techniques
  • Ion Channels / genetics*
  • Motor Disorders / prevention & control*
  • Nifedipine / pharmacology
  • Nimodipine / pharmacology
  • Phenotype
  • Sodium Channels

Substances

  • Boron Compounds
  • Caenorhabditis elegans Proteins
  • Ion Channels
  • NALCN protein, C elegans
  • Sodium Channels
  • unc-77 protein, C elegans
  • Nimodipine
  • 2-aminoethoxydiphenyl borate
  • Nifedipine
  • Flunarizine
  • Ethoxzolamide