The structure of a calsequestrin filament reveals mechanisms of familial arrhythmia

Titus, Erron W.; Deiter, Fred; Shi, Chenxu; Wojciak, Julianne; Scheinman, Melvin M.; Jura, Natalia; Deo, Rahul C.

doi:10.1038/s41594-020-0510-9

Cited by 13 publications

(24 citation statements)

References 51 publications

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“…The study investigated potential autosomal dominant variants in CASQ2 that have been linked to families with CPVT. 31 Based on the results of in vitro turbidity assays, the authors concluded that K180R and the other autosomal dominant CASQ2 variants decreased the ability of Casq2 to polymerize. Further investigation of the crystallized polymer mapped the K180 amino acid onto a potential interdimerization site of Casq2.…”

Section: Discussionmentioning

confidence: 99%

“…Recent in vitro studies suggested that the K180R variant may affect the ability of Casq2 to form polymers. 10,31 Based on the Casq2 polymers visible on Western blot, polymer levels were not significantly decreased in K180R heterozygous and homozygous mouse lysates (Figure 3B). Other CRU (calcium release unit) protein levels (RyR2, triadin, and junctin) were also not significantly different in the K180R heterozygous and homozygous mouse cardiomyocytes (Figure 3C).…”

Section: K180r Does Not Affect Expression Levels Of Casq2 and Other J...mentioning

confidence: 95%

“…24 Given that all previously reported CASQ2 variants cause either a complete loss or a severe reduction of Casq2 protein, autosomal dominant CPVT2 variants are proposed to have a dominant-negative effect that would lead to a reduction in Casq2 levels and thus cause CPVT. 9 Supported by a novel crystal structure of a polymer filament of Casq2, 25 it was hypothesized that autosomal dominant Casq2 variants affect the ability of Casq2 to polymerize. Using the new filament, the authors mapped 2 autosomal dominant variants (K180R, and S173I) to understand how they would affect Casq2 function.…”

Section: • Autosomal Recessive Mutations In Casq2 Decreasementioning

confidence: 99%

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Impaired Dynamic Sarcoplasmic Reticulum Ca Buffering in Autosomal Dominant CPVT2

Wleklinski

Kryshtal

Kim

et al. 2022

Circulation Research

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Background: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a potentially lethal cardiac arrhythmia syndrome triggered by catecholamines released during exercise, stress, or sudden emotion. Variants in the calsequestrin-2 gene ( CASQ2 ), encoding the major calcium (Ca) binding protein in the sarcoplasmic reticulum (SR), are the second most common cause of CPVT. Recently, several CASQ2 gene variants, such as CASQ2 -K180R, have been linked to an autosomal dominant form of Casq2-linked CPVT (CPVT2), but the underlying mechanism is not known. Methods: A K180R mouse model was generated using CRIPSR/Cas9. Heterozygous and homozygous K180R mice were studied using telemetry ECG recordings in vivo. Ventricular cardiomyocytes were isolated and studied using fluorescent Ca indicators and patch clamp. Expression levels and localization of SR Ca-handling proteins were evaluated using Western blotting and immunostaining. Intra-SR Ca kinetics were quantified using low-affinity Ca indicators. Results: K180R mice exhibit an autosomal dominant CPVT phenotype following exercise or catecholamine stress. Upon catecholamine stress, K180R ventricular cardiomyocytes exhibit increased spontaneous SR Ca release events, triggering delayed afterdepolarizations and spontaneous beats. K180R had no effect on levels of Casq2, Casq2 polymers, or other SR Ca-handling proteins. Intra-SR Ca measurements revealed that K180R impaired dynamic intra-SR Ca buffering, resulting in a more rapid rise of free Ca in the SR during diastole. Steady-state SR Ca buffering and total SR Ca content were not changed. Consistent with the reduced dynamic intra-SR buffering, K180R causes reduced SR Ca release refractoriness. Conclusions: CASQ2-K180R causes CPVT2 via a heretofore unknown mechanism that differs from CASQ2 variants associated with autosomal recessive CPVT2. Unlike autosomal recessive CASQ2 variants, K180R impairs the dynamic buffering of Ca within the SR without affecting total SR Ca content or Casq2 protein levels. Our data provide insight into the molecular mechanism underlying autosomal dominant CPVT2.

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Section: Discussionmentioning

confidence: 99%

Section: K180r Does Not Affect Expression Levels Of Casq2 and Other J...mentioning

confidence: 95%

Section: • Autosomal Recessive Mutations In Casq2 Decreasementioning

confidence: 99%

See 1 more Smart Citation

Impaired Dynamic Sarcoplasmic Reticulum Ca Buffering in Autosomal Dominant CPVT2

Wleklinski

Kryshtal

Kim

et al. 2022

Circulation Research

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“…Because ESEs/ESSs in mammals and other vertebrates are conserved ( 17 ), we included human sequences that were orthologous to solved mammalian structures, both with and without evidence for metal identity in the crystal. Rare structures solved using yttrium and ytterbium ( 24 , 25 ) were also included. All retrieved sequences were cross-checked against UniprotID ( 21 ) and matched to nucleotide (nt) sequences of Ensembl (v. 104) transcripts ( 26 ).…”

Section: Methodsmentioning

confidence: 99%

Exonic splicing code and protein binding sites for calcium

Pengelly

Bakhtiar

Borovská

et al. 2022

Nucleic Acids Research

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Auxilliary splicing sequences in exons, known as enhancers (ESEs) and silencers (ESSs), have been subject to strong selection pressures at the RNA and protein level. The protein component of this splicing code is substantial, recently estimated at ∼50% of the total information within ESEs, but remains poorly understood. The ESE/ESS profiles were previously associated with the Irving-Williams (I-W) stability series for divalent metals, suggesting that the ESE/ESS evolution was shaped by metal binding sites. Here, we have examined splicing activities of exonic sequences that encode protein binding sites for Ca2+, a weak binder in the I-W affinity order. We found that predicted exon inclusion levels for the EF-hand motifs and for Ca2+-binding residues in nonEF-hand proteins were higher than for average exons. For canonical EF-hands, the increase was centred on the EF-hand chelation loop and, in particular, on Ca2+-coordinating residues, with a 1>12>3∼5>9 hierarchy in the 12-codon loop consensus and usage bias at codons 1 and 12. The same hierarchy but a lower increase was observed for noncanonical EF-hands, except for S100 proteins. EF-hand loops preferentially accumulated exon splits in two clusters, one located in their N-terminal halves and the other around codon 12. Using splicing assays and published crosslinking and immunoprecipitation data, we identify candidate trans-acting factors that preferentially bind conserved GA-rich motifs encoding negatively charged amino acids in the loops. Together, these data provide evidence for the high capacity of codons for Ca2+-coordinating residues to be retained in mature transcripts, facilitating their exon-level expansion during eukaryotic evolution.

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“…Indeed, CASQ2 is the second most mutated gene in CPVT accounting for ~5% of cases [ 41 ]. Initially described as the recessive form of CPVT (CPVT2), autosomal dominant mutations have also been reported [ 47 , 48 , 49 ]. CPVT-linked CSQ2 mutations may result in impaired Ca 2+ buffering, multimer formation and/or RyR2 regulation [ 41 , 44 , 50 ].…”

Section: Physiological Ryr2 Regulatorsmentioning

confidence: 99%

Molecular, Subcellular, and Arrhythmogenic Mechanisms in Genetic RyR2 Disease

Fowler

Zissimopoulos

2022

Biomolecules

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The ryanodine receptor (RyR2) has a critical role in controlling Ca2+ release from the sarcoplasmic reticulum (SR) throughout the cardiac cycle. RyR2 protein has multiple functional domains with specific roles, and four of these RyR2 protomers are required to form the quaternary structure that comprises the functional channel. Numerous mutations in the gene encoding RyR2 protein have been identified and many are linked to a wide spectrum of arrhythmic heart disease. Gain of function mutations (GoF) result in a hyperactive channel that causes excessive spontaneous SR Ca2+ release. This is the predominant cause of the inherited syndrome catecholaminergic polymorphic ventricular tachycardia (CPVT). Recently, rare hypoactive loss of function (LoF) mutations have been identified that produce atypical effects on cardiac Ca2+ handling that has been termed calcium release deficiency syndrome (CRDS). Aberrant Ca2+ release resulting from both GoF and LoF mutations can result in arrhythmias through the Na+/Ca2+ exchange mechanism. This mini-review discusses recent findings regarding the role of RyR2 domains and endogenous regulators that influence RyR2 gating normally and with GoF/LoF mutations. The arrhythmogenic consequences of GoF/LoF mutations will then be discussed at the macromolecular and cellular level.

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The structure of a calsequestrin filament reveals mechanisms of familial arrhythmia

Cited by 13 publications

References 51 publications

Impaired Dynamic Sarcoplasmic Reticulum Ca Buffering in Autosomal Dominant CPVT2

Impaired Dynamic Sarcoplasmic Reticulum Ca Buffering in Autosomal Dominant CPVT2

Exonic splicing code and protein binding sites for calcium

Molecular, Subcellular, and Arrhythmogenic Mechanisms in Genetic RyR2 Disease

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