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The Arrhythmogenic Calmodulin p.Phe142Leu Mutation Impairs C-domain Ca2+ Binding but Not Calmodulin-dependent Inhibition of the Cardiac Ryanodine Receptor.


ABSTRACT: A number of point mutations in the intracellular Ca2+-sensing protein calmodulin (CaM) are arrhythmogenic, yet their underlying mechanisms are not clear. These mutations generally decrease Ca2+ binding to CaM and impair inhibition of CaM-regulated Ca2+ channels like the cardiac Ca2+ release channel (ryanodine receptor, RyR2), and it appears that attenuated CaM Ca2+ binding correlates with impaired CaM-dependent RyR2 inhibition. Here, we investigated the RyR2 inhibitory action of the CaM p.Phe142Leu mutation (F142L; numbered including the start-Met), which markedly reduces CaM Ca2+ binding. Surprisingly, CaM-F142L had little to no aberrant effect on RyR2-mediated store overload-induced Ca2+ release in HEK293 cells compared with CaM-WT. Furthermore, CaM-F142L enhanced CaM-dependent RyR2 inhibition at the single channel level compared with CaM-WT. This is in stark contrast to the actions of arrhythmogenic CaM mutations N54I, D96V, N98S, and D130G, which all diminish CaM-dependent RyR2 inhibition. Thermodynamic analysis showed that apoCaM-F142L converts an endothermal interaction between CaM and the CaM-binding domain (CaMBD) of RyR2 into an exothermal one. Moreover, NMR spectra revealed that the CaM-F142L-CaMBD interaction is structurally different from that of CaM-WT at low Ca2+ These data indicate a distinct interaction between CaM-F142L and the RyR2 CaMBD, which may explain the stronger CaM-dependent RyR2 inhibition by CaM-F142L, despite its reduced Ca2+ binding. Collectively, these results add to our understanding of CaM-dependent regulation of RyR2 as well as the mechanistic effects of arrhythmogenic CaM mutations. The unique properties of the CaM-F142L mutation may provide novel clues on how to suppress excessive RyR2 Ca2+ release by manipulating the CaM-RyR2 interaction.

SUBMITTER: Sondergaard MT 

PROVIDER: S-EPMC5270481 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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The Arrhythmogenic Calmodulin p.Phe142Leu Mutation Impairs C-domain Ca2+ Binding but Not Calmodulin-dependent Inhibition of the Cardiac Ryanodine Receptor.

Søndergaard Mads Toft MT   Liu Yingjie Y   Larsen Kamilla Taunsig KT   Nani Alma A   Tian Xixi X   Holt Christian C   Wang Ruiwu R   Wimmer Reinhard R   Van Petegem Filip F   Fill Michael M   Chen S R Wayne SR   Overgaard Michael Toft MT  

The Journal of biological chemistry 20161207 4


A number of point mutations in the intracellular Ca<sup>2+</sup>-sensing protein calmodulin (CaM) are arrhythmogenic, yet their underlying mechanisms are not clear. These mutations generally decrease Ca<sup>2+</sup> binding to CaM and impair inhibition of CaM-regulated Ca<sup>2+</sup> channels like the cardiac Ca<sup>2+</sup> release channel (ryanodine receptor, RyR2), and it appears that attenuated CaM Ca<sup>2+</sup> binding correlates with impaired CaM-dependent RyR2 inhibition. Here, we inve  ...[more]

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