Carbon monoxide inhibits L-type Ca2+ channels via redox modulation of key cysteine residues by mitochondrial reactive oxygen species.
Conditions of stress, such as myocardial infarction, stimulate up-regulation of heme oxygenase (HO-1) to provide cardioprotection. Here, we show that CO, a product of heme catabolism by HO-1, directly inhibits native rat cardiomyocyte L-type Ca2+ currents and the recombinant alpha1C subunit of the human cardiac L-type Ca2+ channel. CO (applied via a recognized CO donor molecule or as the dissolved gas) caused reversible, voltage-independent channel inhibition, which was dependent on the presence of a spliced insert in the cytoplasmic C-terminal region of the channel. Sequential molecular dissection and point mutagenesis identified three key cysteine residues within the proximal 31 amino acids of the splice insert required for CO sensitivity. CO-mediated inhibition was independent of nitric oxide and protein kinase G but was prevented by antioxidants and the reducing agent, dithiothreitol. Inhibition of NADPH oxidase and xanthine oxidase did not affect the inhibitory actions of CO. Instead, inhibitors of complex III (but not complex I) of the mitochondrial electron transport chain and a mitochondrially targeted antioxidant (Mito Q) fully prevented the effects of CO. Our data indicate that the cardioprotective effects of HO-1 activity may be attributable to an inhibitory action of CO on cardiac L-type Ca2+ channels. Inhibition arises from the ability of CO to promote generation of reactive oxygen species from complex III of mitochondria. This in turn leads to redox modulation of any or all of three critical cysteine residues in the channel's cytoplasmic C-terminal tail, resulting in channel inhibition.
Scragg
Jason L
JL
Division of Cardiovascular and Neuronal Remodelling, Leeds Institute of Genetics, Health, and Therapeutics, Level 10, Worsley Bldg., University of Leeds, Leeds LS2 9JT, United Kingdom. J.Scragg@leeds.ac.uk
Dallas
Mark L
ML
Wilkinson
Jenny A
JA
Varadi
Gyula
G
Peers
Chris
C
D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002248:Carbon Monoxide / Q000378:metabolism*; D002460:Cell Line; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism*; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008929:Mitochondria, Heart / Q000201:enzymology* / Q000235:genetics; D009203:Myocardial Infarction / Q000201:enzymology / Q000235:genetics; D032383:Myocytes, Cardiac / Q000201:enzymology; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000235:genetics / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000494:pharmacology; D017354:Point Mutation; D017434:Protein Structure, Tertiary / Q000235:genetics; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000235:genetics / Q000378:metabolism
D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); D009943:Organophosphorus Compounds; D017382:Reactive Oxygen Species; D014451:Ubiquinone; D009569:Nitric Oxide; C429014:mitoquinone; D002248:Carbon Monoxide; C496541:HMOX1 protein, human; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C491523:Hmox1 protein, rat; D014969:Xanthine Oxidase; D019255:NADPH Oxidases; D017869:Cyclic GMP-Dependent Protein Kinases; D014450:Electron Transport Complex III