Catecholaminergic polymorphic ventricular tachycardia is caused by mutation-linked defective conformational regulation of the ryanodine receptor.
BACKGROUND
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is caused by a single point mutation in a well-defined region of the cardiac type 2 ryanodine receptor (RyR)2. However, the underlying mechanism by which a single mutation in such a large molecule produces drastic effects on channel function remains unresolved.


OBJECTIVE
Using a knock-in (KI) mouse model with a human CPVT-associated RyR2 mutation (R2474S), we investigated the molecular mechanism by which CPVT is induced by a single point mutation within the RyR2.


RESULTS
The R2474S/+ KI mice showed no apparent structural or histological abnormalities in the heart, but they showed clear indications of other abnormalities. Bidirectional or polymorphic ventricular tachycardia was induced after exercise on a treadmill. The interaction between the N-terminal (amino acids 1 to 600) and central (amino acids 2000 to 2500) domains of the RyR2 (an intrinsic mechanism to close Ca(2+) channels) was weakened (domain unzipping). On protein kinase A-mediated phosphorylation of the RyR2, this domain unzipping further increased, resulting in a significant increase in the frequency of spontaneous Ca(2+) transients. cAMP-induced aberrant Ca(2+) release events (Ca(2+) sparks/waves) occurred at much lower sarcoplasmic reticulum Ca(2+) content as compared to the wild type. Addition of a domain-unzipping peptide, DPc10 (amino acids 2460 to 2495), to the wild type reproduced the aforementioned abnormalities that are characteristic of the R2474S/+ KI mice. Addition of DPc10 to the (cAMP-treated) KI cardiomyocytes produced no further effect.


CONCLUSIONS
A single point mutation within the RyR2 sensitizes the channel to agonists and reduces the threshold of luminal [Ca(2+)] for activation, primarily mediated by defective interdomain interaction within the RyR2.
Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan.
Hitoshi
H
Uchinoumi
Masafumi
M
Yano
Takeshi
T
Suetomi
Makoto
M
Ono
Xiaojuan
X
Xu
Hiroki
H
Tateishi
Tetsuro
T
Oda
Shinichi
S
Okuda
Masahiro
M
Doi
Shigeki
S
Kobayashi
Takeshi
T
Yamamoto
Yasuhiro
Y
Ikeda
Tomoko
T
Ohkusa
Noriaki
N
Ikemoto
Masunori
M
Matsuzaki
D000818:Animals; D002110:Caffeine; D020013:Calcium Signaling / Q000235:genetics; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004195:Disease Models, Animal; D004837:Epinephrine; D056966:Excitation Contraction Coupling; D005838:Genotype; D007545:Isoproterenol; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D005082:Physical Exertion; D017354:Point Mutation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013329:Structure-Activity Relationship; D017180:Tachycardia, Ventricular / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D013997:Time Factors
D010446:Peptide Fragments; D019837:Ryanodine Receptor Calcium Release Channel; C451409:ryanodine receptor calcium release channel (2460-2495), Ser(2474)-; D002110:Caffeine; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol; D004837:Epinephrine