title: Distinctive malfunctions of calmodulin mutations associated with heart RyR2-mediated arrhythmic disease.
abstract: Calmodulin (CaM) is a cytoplasmic calcium sensor that interacts with the cardiac ryanodine receptor (RyR2), a large Ca(2+) channel complex that mediates Ca(2+) efflux from the sarcoplasmic reticulum (SR) to activate cardiac muscle contraction. Direct CaM association with RyR2 is an important physiological regulator of cardiac muscle excitation-contraction coupling and defective CaM-RyR2 protein interaction has been reported in cases of heart failure. Recent genetic studies have identified CaM missense mutations in patients with a history of severe cardiac arrhythmogenic disorders that present divergent clinical features, including catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT syndrome (LQTS) and idiopathic ventricular fibrillation (IVF). Herein, we describe how two CPVT- (N54I & N98S) and three LQTS-associated (D96V, D130G & F142L) CaM mutations result in alteration of their biochemical and biophysical properties. Ca(2+)-binding studies indicate that the CPVT-associated CaM mutations, N54I & N98S, exhibit the same or a 3-fold reduced Ca(2+)-binding affinity, respectively, versus wild-type CaM, whereas the LQTS-associated CaM mutants, D96V, D130G & F142L, display more profoundly reduced Ca(2+)-binding affinity. In contrast, all five CaM mutations confer a disparate RyR2 interaction and modulation of [(3)H]ryanodine binding to RyR2, regardless of CPVT or LQTS association. Our findings suggest that the clinical presentation of CPVT or LQTS associated with these five CaM mutations may involve both altered intrinsic Ca(2+)-binding as well as defective interaction with RyR2.
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK; National Center for Scientific Research "Demokritos", 15310 Aghia Paraskevi, Greece.
authors.forename: Vyronia
authors.initials: V
authors.lastname: Vassilakopoulou
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Calver
authors.affiliation: National Center for Scientific Research "Demokritos", 15310 Aghia Paraskevi, Greece.
authors.forename: Angelos
authors.initials: A
authors.lastname: Thanassoulas
authors.affiliation: School of Dentistry, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XY, UK.
authors.forename: Konrad
authors.initials: K
authors.lastname: Beck
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: Handan
authors.initials: H
authors.lastname: Hu
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: Luke
authors.initials: L
authors.lastname: Buntwal
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: Adrian
authors.initials: A
authors.lastname: Smith
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: Maria
authors.initials: M
authors.lastname: Theodoridou
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: Junaid
authors.initials: J
authors.lastname: Kashir
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: Lynda
authors.initials: L
authors.lastname: Blayney
authors.affiliation: National Center for Scientific Research "Demokritos", 15310 Aghia Paraskevi, Greece.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Livaniou
authors.affiliation: National Center for Scientific Research "Demokritos", 15310 Aghia Paraskevi, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Nounesis
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK. Electronic address: LaiT@cardiff.ac.uk.
authors.forename: F Anthony
authors.initials: FA
authors.lastname: Lai
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, College of Biomedical & Life Sciences, Cardiff University, Cardiff CF14 4XN, UK. Electronic address: mixosn@yahoo.com.
authors.forename: Michail
authors.initials: M
authors.lastname: Nomikos
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000235:genetics*; D008133:Long QT Syndrome / Q000209:etiology*; D009154:Mutation; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology*; D013552:Swine; D017180:Tachycardia, Ventricular / Q000209:etiology*; D000098850:Polymorphic Catecholaminergic Ventricular Tachycardia
chemical_list: D002147:Calmodulin; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium
keywords: Calcium; Calmodulin; Cardiac disease; RyR2 calcium release channel; Ryanodine receptor