title: Abnormal interactions of calsequestrin with the ryanodine receptor calcium release channel complex linked to exercise-induced sudden cardiac death.
abstract: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a familial arrhythmogenic disorder associated with mutations in the cardiac ryanodine receptor (RyR2) and cardiac calsequestrin (CASQ2) genes. Previous in vitro studies suggested that RyR2 and CASQ2 interact as parts of a multimolecular Ca(2+)-signaling complex; however, direct evidence for such interactions and their potential significance to myocardial function remain to be determined. We identified a novel CASQ2 mutation in a young female with a structurally normal heart and unexplained syncopal episodes. This mutation results in the nonconservative substitution of glutamine for arginine at amino acid 33 of CASQ2 (R33Q). Adenoviral-mediated expression of CASQ2(R33Q) in adult rat myocytes led to an increase in excitation-contraction coupling gain and to more frequent occurrences of spontaneous propagating (Ca2+ waves) and local Ca2+ signals (sparks) with respect to control cells expressing wild-type CASQ2 (CASQ2WT). As revealed by a Ca2+ indicator entrapped inside the sarcoplasmic reticulum (SR) of permeabilized myocytes, the increased occurrence of spontaneous Ca2+ sparks and waves was associated with a dramatic decrease in intra-SR [Ca2+]. Recombinant CASQ2WT and CASQ2R33Q exhibited similar Ca(2+)-binding capacities in vitro; however, the mutant protein lacked the ability of its WT counterpart to inhibit RyR2 activity at low luminal [Ca2+] in planar lipid bilayers. We conclude that the R33Q mutation disrupts interactions of CASQ2 with the RyR2 channel complex and impairs regulation of RyR2 by luminal Ca2+. These results show that intracellular Ca2+ cycling in normal heart relies on an intricate interplay of CASQ2 with the proteins of the RyR2 channel complex and that disruption of these interactions can lead to cardiac arrhythmia.
authors.affiliation: Department of Physiology and Cell Biology, Heart and Lung Research Institute, Ohio State University, Columbus, OH 43210, USA.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Terentyev
authors.forename: Alessandra
authors.initials: A
authors.lastname: Nori
authors.forename: Massimo
authors.initials: M
authors.lastname: Santoro
authors.forename: Serge
authors.initials: S
authors.lastname: Viatchenko-Karpinski
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Kubalova
authors.forename: Inna
authors.initials: I
authors.lastname: Gyorke
authors.forename: Radmila
authors.initials: R
authors.lastname: Terentyeva
authors.forename: Srikanth
authors.initials: S
authors.lastname: Vedamoorthyrao
authors.forename: Nico A
authors.initials: NA
authors.lastname: Blom
authors.forename: Giorgia
authors.initials: G
authors.lastname: Valle
authors.forename: Carlo
authors.initials: C
authors.lastname: Napolitano
authors.forename: Simon C
authors.initials: SC
authors.lastname: Williams
authors.forename: Pompeo
authors.initials: P
authors.lastname: Volpe
authors.forename: Silvia G
authors.initials: SG
authors.lastname: Priori
authors.forename: Sandor
authors.initials: S
authors.lastname: Gyorke
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001120:Arginine; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002155:Calsequestrin / Q000235:genetics / Q000378:metabolism*; D002304:Cardiac Pacing, Artificial / Q000379:methods; D002395:Catecholamines / Q000378:metabolism; D016757:Death, Sudden, Cardiac / Q000209:etiology*; D015444:Exercise; D005260:Female; D005973:Glutamine; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D009154:Mutation; D032383:Myocytes, Cardiac / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013575:Syncope / Q000235:genetics; D017180:Tachycardia, Ventricular / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology
chemical_list: C443109:CASQ2 protein, human; D002155:Calsequestrin; D002395:Catecholamines; D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D005973:Glutamine; D001120:Arginine; D002118:Calcium