Carbon monoxide inhibition of Cav3.2 T-type Ca2+ channels reveals tonic modulation by thioredoxin

FASEB J. 2013 Aug;27(8):3395-407. doi: 10.1096/fj.13-227249. Epub 2013 May 13.

Abstract

T-type Ca(2+) channels play diverse roles in tissues such as sensory neurons, vascular smooth muscle, and cancers, where increased expression of the cytoprotective enzyme, heme oxygenase-1 (HO-1) is often found. Here, we report regulation of T-type Ca(2+) channels by carbon monoxide (CO) a HO-1 by-product. CO (applied as CORM-2) caused a concentration-dependent, poorly reversible inhibition of all T-type channel isoforms (Cav3.1-3.3, IC50 ∼3 μM) expressed in HEK293 cells, and native T-type channels in NG108-15 cells and primary rat sensory neurons. No recognized CO-sensitive signaling pathway could account for the CO inhibition of Cav3.2. Instead, CO sensitivity was mediated by an extracellular redox-sensitive site, which was also highly sensitive to thioredoxin (Trx). Trx depletion (using auranofin, 2-5 μM) reduced Cav3.2 currents and their CO sensitivity by >50% but increased sensitivity to dithiothreitol ∼3-fold. By contrast, Cav3.1 and Cav3.3 channels, and their sensitivity to CO, were unaffected in identical experiments. Our data propose a novel signaling pathway in which Trx acts as a tonic, endogenous regulator of Cav3.2 channels, while HO-1-derived CO disrupts this regulation, causing channel inhibition. CO modulation of T-type channels has widespread implications for diverse physiological and pathophysiological mechanisms, such as excitability, contractility, and proliferation.

Keywords: gasotransmitter; heme oxygenase 1; patch clamp; redox modulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Auranofin / pharmacology
  • Blotting, Western
  • Calcium Channels, T-Type / genetics
  • Calcium Channels, T-Type / metabolism
  • Calcium Channels, T-Type / physiology*
  • Carbon Dioxide / metabolism*
  • Cell Line, Tumor
  • Cells, Cultured
  • Dithiothreitol / pharmacology
  • HEK293 Cells
  • Heme Oxygenase-1 / metabolism
  • Humans
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / genetics
  • Ion Channel Gating / physiology*
  • Membrane Potentials / drug effects
  • Neurons / cytology
  • Neurons / metabolism
  • Neurons / physiology
  • Organometallic Compounds / metabolism
  • Organometallic Compounds / pharmacology
  • Oxidation-Reduction / drug effects
  • Patch-Clamp Techniques
  • Rats
  • Rats, Wistar
  • Thioredoxin-Disulfide Reductase / antagonists & inhibitors
  • Thioredoxin-Disulfide Reductase / metabolism
  • Thioredoxins / metabolism*

Substances

  • CACNA1H protein, human
  • Calcium Channels, T-Type
  • Organometallic Compounds
  • tricarbonyldichlororuthenium (II) dimer
  • Carbon Dioxide
  • Auranofin
  • Thioredoxins
  • HMOX1 protein, human
  • Heme Oxygenase-1
  • Thioredoxin-Disulfide Reductase
  • Dithiothreitol