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Calmodulin mutations causing catecholaminergic polymorphic ventricular tachycardia confer opposing functional and biophysical molecular changes
Author(s) -
Søndergaard Mads T.,
Sorensen Anders B.,
Skov Louise L.,
KjaerSorensen Kasper,
Bauer Mikael C.,
Nyegaard Mette,
Linse Sara,
Oxvig Claus,
Overgaard Michael T.
Publication year - 2015
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13184
Subject(s) - catecholaminergic polymorphic ventricular tachycardia , calmodulin , ryanodine receptor 2 , biology , zebrafish , microbiology and biotechnology , mutation , mutant , intracellular , genetics , medicine , gene , biochemistry , ryanodine receptor , enzyme
Calmodulin (CaM) is the central mediator of intracellular Ca 2+ signalling in cardiomyocytes, where it conveys the intricate Ca 2+ transients to the proteins controlling cardiac contraction. We recently linked two separate mutations in CaM (N53I and N97S) to dominantly inherited catecholaminergic polymorphic ventricular tachycardia ( CPVT ), an arrhythmic disorder in which exercise or acute emotion can lead to syncope and sudden cardiac death. Given the ubiquitous presence of CaM in all eukaryote cells, it is particular intriguing that carriers of either mutation show no additional symptoms. Here, we investigated the effects of the CaM CPVT mutations in a zebrafish animal model. Three‐day‐old embryos injected with either CaM m RNA showed no detectable pathologies or developmental abnormalities. However, embryos injected with CPVT CaM m RNA displayed increased heart rate compared to wild‐type CaM m RNA under β‐adrenergic stimulation, demonstrating a conserved dominant cardiac specific effect between zebrafish and human carriers of these mutations. Motivated by the highly similar physiological phenotypes, we compared the effects of the N53I and N97S mutations on the biophysical and functional properties of CaM. Surprisingly, the mutations have opposing effects on CaM C‐lobe Ca 2+ binding affinity and kinetics, and changes to the CaM N‐lobe Ca 2+ binding are minor and specific to the N53I mutation. Furthermore, both mutations induce differential perturbations to structure and stability towards unfolding. Our results suggest different molecular disease mechanisms for the CPVT (N53I and N97S mutations) and strongly support that cardiac contraction is the physiological process most sensitive to CaM integrity.