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

• Published in: The FASEB journal 2013-08, Vol.27 (8), p.3395-3407
• Main Authors: Boycott, Hannah E., Dallas, Mark L., Elies, Jacobo, Pettinger, Louisa, Boyle, John P., Scragg, Jason L., Gamper, Nikita, Peers, Chris
• Format: Article
• Language: English
• Subjects: 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; gasotransmitter; HEK293 Cells; heme oxygenase 1; 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; Patch-Clamp Techniques; Rats; Rats, Wistar; redox modulation; Thioredoxin-Disulfide Reductase - antagonists & inhibitors; Thioredoxin-Disulfide Reductase - metabolism; Thioredoxins - metabolism
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fj.13-227249

T‐type Ca2+ 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 Ca2+ channels by carbon monoxide (CO) a HO‐1 by‐product. CO (applied as CORM‐2) caused a concentrationdependent, 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.—Boycott, H. E., Dallas, M. L., Elies, J., Pettinger, L., Boyle, J. P., Scragg, J. L., Gamper, N., Peers, C., Carbon monoxide inhibition of Cav3.2 T‐type Ca2+ channels reveals tonic modulation by thioredoxin. FASEBJ. 27, 3395‐3407 (2013). www.fasebj.org