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Published on: February 19, 2016
The Arrhythmogenic Calmodulin Mutation D129G Dysregulates Cell Growth, Calmodulin-dependent Kinase II Activity, and
Martin W Berchtold1, Triantafyllos Zacharias2, Katarzyna Kulej3
1From the Department of Biology and mabe@bio.ku.dk.
Abstract:
Calmodulin (CaM) is a Ca2+ binding protein modulating multiple targets, several of which are associated with cardiac pathophysiology. Recently, CaM mutations were linked to heart arrhythmia. CaM is crucial for cell growth and viability, yet the effect of the arrhythmogenic CaM mutations on cell viability, as well as heart rhythm, remains unknown, and only a few targets with relevance for heart physiology have been analyzed for their response to mutant CaM. We show that the arrhythmia-associated CaM mutants support growth and viability of DT40 cells in the absence of WT CaM except for the long QT syndrome mutant CaM D129G. Of the six CaM mutants tested (N53I, F89L, D95V, N97S, D129G, and F141L), three showed a decreased activation of Ca2+/CaM-dependent kinase II, most prominently the D129G CaM mutation, which was incapable of stimulating Thr286 autophosphorylation. Furthermore, the CaM D129G mutation led to bradycardia in zebrafish and an arrhythmic phenotype in a subset of the analyzed zebrafish.
Insights
Arrhythmogenic calmodulin (CaM) mutations impact cell viability and heart rhythm. The D129G CaM mutant, linked to Long QT syndrome, impairs Ca2+/CaM-dependent kinase II activation and causes zebrafish heart dysfunction.
Area of Science:
- Molecular Biology
- Cardiology
- Genetics
Background:
- Calmodulin (CaM) is a vital calcium-binding protein regulating numerous cellular targets, with implications in cardiac pathophysiology.
- Recent studies link CaM mutations to cardiac arrhythmias, but their effects on cell viability and heart rhythm remain largely unexplored.
- Understanding mutant CaM's impact is crucial for elucidating mechanisms of inherited heart conditions.
Purpose of the Study:
- To investigate the functional consequences of arrhythmia-associated CaM mutations on cell viability and Ca2+/CaM-dependent kinase II (CaMKII) activation.
- To assess the in vivo effects of specific CaM mutations on cardiac rhythm using zebrafish models.
- To identify CaM mutations that compromise cell viability or disrupt cardiac function.
Main Methods:
- Assessed growth and viability of DT40 cells lacking wild-type CaM when expressing various CaM mutants.
- Quantified CaMKII activation, specifically Thr286 autophosphorylation, in response to different CaM mutants.
- Utilized zebrafish models to analyze the cardiac phenotypes, including heart rate and rhythm, associated with CaM mutations.
Main Results:
- Most CaM mutants supported DT40 cell growth and viability, with the exception of the Long QT syndrome mutant CaM D129G.
- Three of six tested CaM mutants exhibited reduced CaMKII activation, with D129G showing a complete inability to stimulate Thr286 autophosphorylation.
- The CaM D129G mutation induced bradycardia and an arrhythmic phenotype in a subset of zebrafish.
Conclusions:
- The CaM D129G mutation, associated with Long QT syndrome, significantly impairs CaMKII signaling and disrupts cardiac function in vivo.
- This study highlights the differential impact of CaM mutations on cell viability and cardiac rhythm, identifying D129G as particularly detrimental.
- Findings provide insights into the molecular mechanisms underlying CaM-related cardiac arrhythmias and underscore the importance of CaMKII regulation.
