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 methionine), 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 to CaM-WT. Furthermore, CaM-F142L enhanced CaM-dependent RyR2 inhibition at the single channel level, compared to 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 shows that apoCaM-F142L converts an endothermal interaction between CaM and the CaM-binding domain (CaMBD) of RyR2 into an exothermal one. Moreover, NMR spectra reveals 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 RyR2s 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.


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    Title :

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



    Publication date :

    2017-01-01


    Remarks:

    Søndergaard , M T , Liu , Y , Larsen , K T , Nani , A , Tian , X , Holt , C , Wang , R , Wimmer , R , Van Petegem , F , Fill , M , Chen , S R W & Overgaard , M T 2017 , ' The Arrhythmogenic Calmodulin p.Phe142Leu Mutation Impairs C-domain Ca2+-binding but not Calmodulin-dependent Inhibition of the Cardiac Ryanodine Receptor ' , Journal of Biological Chemistry , vol. 292 , pp. 1385-1395 . https://doi.org/10.1074/jbc.M116.766253



    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English


    Classification :

    DDC:    629