Arrhythmogenic calmodulin E105A mutation alters cardiac RyR2 regulation leading to cardiac dysfunction in zebrafish
Sahar I Da'as1,2, Angelos Thanassoulas3, Brian L Calver4
1Translational Medicine, Sidra Medicine, Doha, Qatar.
Abstract:
Calmodulin (CaM) is a universal calcium (Ca2+ )-binding messenger that regulates many vital cellular events. In cardiac muscle, CaM associates with ryanodine receptor 2 (RyR2) and regulates excitation-contraction coupling. Mutations in human genes CALM1, CALM2, and CALM3 have been associated with life-threatening heart disorders, such as long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia. A novel de novo LQTS-associated missense CaM mutation (E105A) was recently identified in a 6-year-old boy, who experienced an aborted first episode of cardiac arrest. Herein, we report the first molecular characterization of the CaM E105A mutation. Expression of the CaM E105A mutant in zebrafish embryos resulted in cardiac arrhythmia and increased heart rate, suggestive of ventricular tachycardia. In vitro biophysical and biochemical analysis revealed that E105A confers a deleterious effect on protein stability and a reduced Ca2+ -binding affinity due to loss of cooperativity. Finally, the CaM E105A mutation resulted in reduced CaM-RyR2 interaction and defective modulation of ryanodine binding. Our findings suggest that the CaM E105A mutation dysregulates normal cardiac function by a complex mechanism involving alterations in both CaM-Ca2+ and CaM-RyR2 interactions.
Insights
A novel calmodulin (CaM) mutation (E105A) causes heart rhythm disorders by disrupting calcium binding and interaction with RyR2. This molecular insight explains its role in life-threatening cardiac conditions like long QT syndrome.
Area of Science:
- Molecular biology
- Cardiovascular physiology
- Genetics
Background:
- Calmodulin (CaM) is a crucial calcium-binding protein regulating cellular functions.
- CaM interacts with ryanodine receptor 2 (RyR2) to control cardiac excitation-contraction coupling.
- Mutations in CALM genes are linked to severe heart rhythm disorders like LQTS.
Purpose of the Study:
- To perform the first molecular characterization of the novel CaM E105A mutation.
- To investigate the functional consequences of the CaM E105A mutation on cardiac function.
- To elucidate the underlying mechanisms of CaM E105A-associated cardiac disorders.
Main Methods:
- Zebrafish embryo expression of CaM E105A mutant.
- In vitro biophysical and biochemical analyses.
- Assessment of CaM-RyR2 interaction and ryanodine binding.
Main Results:
- CaM E105A expression in zebrafish caused cardiac arrhythmia and increased heart rate.
- E105A mutation reduced protein stability and calcium-binding affinity.
- CaM E105A mutation impaired CaM-RyR2 interaction and ryanodine binding modulation.
Conclusions:
- The CaM E105A mutation leads to cardiac dysfunction through impaired Ca2+ and RyR2 interactions.
- This mutation contributes to cardiac arrhythmias and potentially life-threatening heart conditions.
- Understanding these molecular mechanisms is vital for diagnosing and treating CaM-related heart disorders.
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