title: A novel ryanodine receptor mutation linked to sudden death increases sensitivity to cytosolic calcium.
abstract: BACKGROUND
  Mutations in the cardiac type 2 ryanodine receptor (RyR2) have been linked to catecholaminergic polymorphic ventricular tachycardia (CPVT). CPVT-associated RyR2 mutations cause fatal ventricular arrhythmias in young individuals during β-adrenergic stimulation.
  
  
  OBJECTIVE
  This study sought to determine the effects of a novel RyR2-G230C mutation and whether this mutation and RyR2-P2328S alter the sensitivity of the channel to luminal calcium (Ca(2+)).
  
  
  RESULTS
  Functional characterizations of recombinant human RyR2-G230C channels were performed under conditions mimicking stress. Human RyR2 mutant channels were generated by site-directed mutagenesis and heterologously expressed in HEK293 cells together with calstabin2. RyR2 channels were measured to examine the regulation of the channels by cytosolic versus luminal sarcoplasmic reticulum Ca(2+). A 50-year-old white man with repeated syncopal episodes after exercise had a cardiac arrest and harbored the mutation RyR2-G230C. cAMP-dependent protein kinase-phosphorylated RyR2-G230C channels exhibited a significantly higher open probability at diastolic Ca(2+) concentrations, associated with a depletion of calstabin2. The luminal Ca(2+) sensitivities of RyR2-G230C and RyR2-P2328S channels were WT-like.
  
  
  CONCLUSIONS
  The RyR2-G230C mutant exhibits similar biophysical defects compared with previously characterized CPVT mutations: decreased binding of the stabilizing subunit calstabin2 and a leftward shift in the Ca(2+) dependence for activation under conditions that simulate exercise, consistent with a "leaky" channel. Both RyR2-G230C and RyR2-P2328S channels exhibit normal luminal Ca(2+) activation. Thus, diastolic sarcoplasmic reticulum Ca(2+) leak caused by reduced calstabin2 binding and a leftward shift in the Ca(2+) dependence for activation by diastolic levels of cytosolic Ca(2+) is a common mechanism underlying CPVT.
authors.affiliation: Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, College of Physicians and Surgeons of Columbia University, New York, NY, USA.
authors.forename: Albano C
authors.initials: AC
authors.lastname: Meli
authors.forename: Marwan M
authors.initials: MM
authors.lastname: Refaat
authors.forename: Miroslav
authors.initials: M
authors.lastname: Dura
authors.forename: Steven
authors.initials: S
authors.lastname: Reiken
authors.forename: Anetta
authors.initials: A
authors.lastname: Wronska
authors.forename: Julianne
authors.initials: J
authors.lastname: Wojciak
authors.forename: Joan
authors.initials: J
authors.lastname: Carroll
authors.forename: Melvin M
authors.initials: MM
authors.lastname: Scheinman
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Marks
mesh_terms: D002118:Calcium / Q000502:physiology*; D002395:Catecholamines / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D003600:Cytosol / Q000502:physiology; D016757:Death, Sudden, Cardiac; D003971:Diastole / Q000502:physiology; D004562:Electrocardiography; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D008297:Male; D008875:Middle Aged; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D017354:Point Mutation; D011994:Recombinant Proteins / Q000235:genetics; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics* / Q000502:physiology*; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology*; D022021:Tacrolimus Binding Proteins / Q000502:physiology; D000098850:Polymorphic Catecholaminergic Ventricular Tachycardia
chemical_list: D002395:Catecholamines; D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D017868:Cyclic AMP-Dependent Protein Kinases; D022021:Tacrolimus Binding Proteins; C403484:tacrolimus binding protein 1B; D002118:Calcium