title: Carbon monoxide inhibition of Cav3.2 T-type Ca2+ channels reveals tonic modulation by thioredoxin.
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.
authors.affiliation: Leeds Institute of Genetics, Health, and Therapeutics, Faculty of Medicine and Health, University of Leeds, Leeds, UK..
authors.forename: Hannah E
authors.initials: HE
authors.lastname: Boycott
authors.forename: Mark L
authors.initials: ML
authors.lastname: Dallas
authors.forename: Jacobo
authors.initials: J
authors.lastname: Elies
authors.forename: Louisa
authors.initials: L
authors.lastname: Pettinger
authors.forename: John P
authors.initials: JP
authors.lastname: Boyle
authors.forename: Jason L
authors.initials: JL
authors.lastname: Scragg
authors.forename: Nikita
authors.initials: N
authors.lastname: Gamper
authors.forename: Chris
authors.initials: C
authors.lastname: Peers
mesh_terms: D000818:Animals; D001310:Auranofin / Q000494:pharmacology; D015153:Blotting, Western; D020747:Calcium Channels, T-Type / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004229:Dithiothreitol / Q000494:pharmacology; D057809:HEK293 Cells; D051547:Heme Oxygenase-1 / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D009942:Organometallic Compounds / Q000378:metabolism / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D013880:Thioredoxin-Disulfide Reductase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism*
chemical_list: C479952:CACNA1H protein, human; D020747:Calcium Channels, T-Type; D009942:Organometallic Compounds; C447082:tricarbonyldichlororuthenium (II) dimer; D002245:Carbon Dioxide; D001310:Auranofin; D013879:Thioredoxins; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D013880:Thioredoxin-Disulfide Reductase; D004229:Dithiothreitol
keywords: gasotransmitter; heme oxygenase 1; patch clamp; redox modulation