title: Evidence for redox sensing by a human cardiac calcium channel.
abstract: Ion channels are critical to life and respond rapidly to stimuli to evoke physiological responses. Calcium influx into heart muscle occurs through the ion conducting α1C subunit (Cav1.2) of the L-type Ca(2+) channel. Glutathionylation of Cav1.2 results in increased calcium influx and is evident in ischemic human heart. However controversy exists as to whether direct modification of Cav1.2 is responsible for altered function. We directly assessed the function of purified human Cav1.2 in proteoliposomes. Truncation of the C terminus and mutation of cysteines in the N terminal region and cytoplasmic loop III-IV linker did not alter the effects of thiol modifying agents on open probability of the channel. However mutation of cysteines in cytoplasmic loop I-II linker altered open probability and protein folding assessed by thermal shift assay. We find that C543 confers sensitivity of Cav1.2 to oxidative stress and is sufficient to modify channel function and posttranslational folding. Our data provide direct evidence for the calcium channel as a redox sensor that facilitates rapid physiological responses.
authors.affiliation: School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, WA, Australia.
authors.forename: Padmapriya
authors.initials: P
authors.lastname: Muralidharan
authors.affiliation: School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, WA, Australia.
authors.forename: Henrietta
authors.initials: H
authors.lastname: Cserne Szappanos
authors.affiliation: Harry Perkins Institute of Medical Research, QEII Medical Centre, Nedlands and Centre for Medical Research, The University of Western Australia, Crawley, WA, Australia.
authors.forename: Evan
authors.initials: E
authors.lastname: Ingley
authors.affiliation: School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, WA, Australia.|Victor Chang Cardiac Research Institute, Sydney, NSW, Australia.
authors.forename: Livia
authors.initials: L
authors.lastname: Hool
mesh_terms: D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000235:genetics; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D006801:Humans; D009154:Mutation / Q000235:genetics; D009206:Myocardium / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D017510:Protein Folding / Q000187:drug effects; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); D016877:Oxidants; D020033:Protein Isoforms; D013438:Sulfhydryl Compounds; D004228:Dithionitrobenzoic Acid; D003545:Cysteine; D004229:Dithiothreitol