title: Arrhythmogenic Calmodulin Mutations Affect the Activation and Termination of Cardiac Ryanodine Receptor-mediated Ca2+ Release.
abstract: The intracellular Ca(2+) sensor calmodulin (CaM) regulates the cardiac Ca(2+) release channel/ryanodine receptor 2 (RyR2), and mutations in CaM cause arrhythmias such as catecholaminergic polymorphic ventricular tachycardia (CPVT) and long QT syndrome. Here, we investigated the effect of CaM mutations causing CPVT (N53I), long QT syndrome (D95V and D129G), or both (CaM N97S) on RyR2-mediated Ca(2+) release. All mutations increased Ca(2+) release and rendered RyR2 more susceptible to store overload-induced Ca(2+) release (SOICR) by lowering the threshold of store Ca(2+) content at which SOICR occurred and the threshold at which SOICR terminated. To obtain mechanistic insights, we investigated the Ca(2+) binding of the N- and C-terminal domains (N- and C-domain) of CaM in the presence of a peptide corresponding to the CaM-binding domain of RyR2. The N53I mutation decreased the affinity of Ca(2+) binding to the N-domain of CaM, relative to CaM WT, but did not affect the C-domain. Conversely, mutations N97S, D95V, and D129G had little or no effect on Ca(2+) binding to the N-domain but markedly decreased the affinity of the C-domain for Ca(2+). These results suggest that mutations D95V, N97S, and D129G alter the interaction between CaM and the CaMBD and thus RyR2 regulation. Because the N53I mutation minimally affected Ca(2+) binding to the C-domain, it must cause aberrant regulation via a different mechanism. These results support aberrant RyR2 regulation as the disease mechanism for CPVT associated with CaM mutations and shows that CaM mutations not associated with CPVT can also affect RyR2. A model for the CaM-RyR2 interaction, where the Ca(2+)-saturated C-domain is constitutively bound to RyR2 and the N-domain senses increases in Ca(2+) concentration, is proposed.
authors: From the Department of Chemistry and Bioscience, Aalborg University, 9220 Aalborg, Denmark, the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 1N4, Canada, and.
authors: Mads T
authors: http://orcid.org/0000-0001-6779-5109
authors: MT
authors: Søndergaard
authors: the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 1N4, Canada, and.
authors: Xixi
authors: X
authors: Tian
authors: the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 1N4, Canada, and.
authors: Yingjie
authors: Y
authors: Liu
authors: the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 1N4, Canada, and.
authors: Ruiwu
authors: R
authors: Wang
authors: the Departments of Biochemistry and Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235.
authors: Walter J
authors: WJ
authors: Chazin
authors: the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology and Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 1N4, Canada, and.
authors: S R Wayne
authors: SR
authors: Chen
authors: From the Department of Chemistry and Bioscience, Aalborg University, 9220 Aalborg, Denmark, mto@bio.aau.dk.
authors: Michael T
authors: MT
authors: Overgaard
mesh_terms: D001145:Arrhythmias, Cardiac / Q000235:genetics* / Q000503:physiopathology; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000235:genetics*; D057809:HEK293 Cells; D006801:Humans; D009154:Mutation; D009206:Myocardium / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium
keywords: arrhythmia; calcium intracellular release; calmodulin (CaM); excitation-contraction coupling (E-C coupling); protein-protein interaction; receptor regulation; ryanodine receptor