The arrhythmogenic N53I variant subtly changes the structure and dynamics in the calmodulin N-terminal domain, altering its interaction with the cardiac ryanodine receptor

Christian Holt, Louise Hamborg, Kelvin Lau, Malene Brohus, Anders Bundgaard Sørensen, Kamilla Taunsig Larsen, Cordula Sommer, Filip Van Petegem, Michael Toft Overgaard, Reinhard Wimmer

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

20 Citationer (Scopus)

Abstract

Mutations in the genes encoding the highly conserved Ca2+-sensing protein calmodulin (CaM) cause severe cardiac arrhythmias, including catecholaminergic polymorphic ventricular tachycardia or long QT syndrome and sudden cardiac death. Most of the identified arrhythmogenic mutations reside in the C-terminal domain of CaM and mostly affect Ca2+-coordinating residues. One exception is the catecholaminergic polymorphic ventricular tachycardia-causing N53I substitution, which resides in the N-terminal domain (N-domain). It does not affect Ca2+ coordination and has only a minor impact on binding affinity toward Ca2+ and on other biophysical properties. Nevertheless, the N53I substitution dramatically affects CaM's ability to reduce the open probability of the cardiac ryanodine receptor (RyR2) while having no effect on the regulation of the plasmalemmal voltage-gated Ca2+ channel, Cav1.2. To gain more insight into the molecular disease mechanism of this mutant, we used NMR to investigate the structures and dynamics of both apo- and Ca2+-bound CaM-N53I in solution. We also solved the crystal structures of WT and N53I CaM in complex with the primary calmodulin-binding domain (CaMBD2) from RyR2 at 1.84-2.13 Å resolutions. We found that all structures of the arrhythmogenic CaM-N53I variant are highly similar to those of WT CaM. However, we noted that the N53I substitution exposes an additional hydrophobic surface and that the intramolecular dynamics of the protein are significantly altered such that they destabilize the CaM N-domain. We conclude that the N53I-induced changes alter the interaction of the CaM N-domain with RyR2 and thereby likely cause the arrhythmogenic phenotype of this mutation.

OriginalsprogEngelsk
TidsskriftJournal of Biological Chemistry
Vol/bind295
Udgave nummer22
Sider (fra-til)7620-7634
Antal sider15
ISSN0021-9258
DOI
StatusUdgivet - 29 maj 2020

Bibliografisk note

© 2020 Holt et al.

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