title: The CPVT-associated RyR2 mutation G230C enhances store overload-induced Ca2+ release and destabilizes the N-terminal domains.
abstract: CPVT (catecholaminergic polymorphic ventricular tachycardia) is an inherited life-threatening arrhythmogenic disorder. CPVT is caused by DADs (delayed after-depolarizations) that are induced by spontaneous Ca2+ release during SR (sarcoplasmic reticulum) Ca2+ overload, a process also known as SOICR (store-overload-induced Ca2+ release). A number of mutations in the cardiac ryanodine receptor RyR2 are linked to CPVT. Many of these CPVT-associated RyR2 mutations enhance the propensity for SOICR and DADs by sensitizing RyR2 to luminal or luminal/cytosolic Ca2+ activation. Recently, a novel CPVT RyR2 mutation, G230C, was found to increase the cytosolic, but not the luminal, Ca2+ sensitivity of single RyR2 channels in lipid bilayers. This observation led to the suggestion of a SOICR-independent disease mechanism for the G230C mutation. However, the cellular impact of this mutation on SOICR is yet to be determined. To this end, we generated stable inducible HEK (human embryonic kidney)-293 cell lines expressing the RyR2 WT (wild-type) and the G230C mutant. Using single-cell Ca2+ imaging, we found that the G230C mutation markedly enhanced the propensity for SOICR and reduced the SOICR threshold. Furthermore, the G230C mutation increased the sensitivity of single RyR2 channels to both luminal and cytosolic Ca2+ activation and the Ca2+-dependent activation of [3H]ryanodine binding. In addition, the G230C mutation decreased the thermal stability of the N-terminal region (amino acids 1-547) of RyR2. These data suggest that the G230C mutation enhances the propensity for SOICR by sensitizing the channel to luminal and cytosolic Ca2+ activation, and that G230C has an intrinsic structural impact on the N-terminal domains of RyR2.
authors.affiliation: Department of Physiology and Pharmacology, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Liu
authors.forename: Lynn
authors.initials: L
authors.lastname: Kimlicka
authors.forename: Florian
authors.initials: F
authors.lastname: Hiess
authors.forename: Xixi
authors.initials: X
authors.lastname: Tian
authors.forename: Ruiwu
authors.initials: R
authors.lastname: Wang
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.forename: Peter P
authors.initials: PP
authors.lastname: Jones
authors.forename: Filip
authors.initials: F
authors.lastname: Van Petegem
authors.forename: S R Wayne
authors.initials: SR
authors.lastname: Chen
mesh_terms: D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D017354:Point Mutation / Q000235:genetics*; D017434:Protein Structure, Tertiary / Q000235:genetics; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D017180:Tachycardia, Ventricular / Q000235:genetics* / Q000378:metabolism*; D015854:Up-Regulation / Q000235:genetics*; D000098850:Polymorphic Catecholaminergic Ventricular Tachycardia
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium