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bioRxiv · 10.1101/2023.09.01.555853

S100A1's single cysteine is an indispensable redox-switch for the protection against diastolic calcium leakage in cardiomyocytes

Seitz, A.·Busch, M.·Kroemer, J.·Schneider, A.·Simon, S.·Jungmann, A.·Katus, H. A.·Most, P.·Ritterhoff, J.
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Abstract

The EF-hand calcium (Ca2+) sensor protein S100A1 combines inotropic with antiarrhythmic potency in cardiomyocytes (CM). Oxidative posttranslational modification (ox-PTM) of S100A1s conserved, single cysteine residue (C85) via reactive nitrogen species (i.e. S-nitrosylation or glutathionylation) was proposed to modulate conformational flexibility of intrinsically disordered sequence fragments and to increase the molecules affinity towards Ca2+. In light of the unknown biological functional consequence, we aimed to determine the impact of the C85 moiety of S100A1 as a potential redox-switch. We first uncovered that S100A1 is endogenously glutathionylated in the adult heart in vivo. To prevent glutathionylation of S100A1, we generated S100A1 variants that were unresponsive to ox-PTMs. Overexpression of wildtype (WT) and C85-deficient S100A1 protein variants in isolated CM demonstrated equal inotropic potency, as shown by equally augmented Ca2+ transient amplitudes under basal conditions and {beta}-adrenergic receptor ({beta}AR) stimulation. However, in contrast ox-PTM defective S100A1 variants failed to protect against arrhythmogenic diastolic sarcoplasmic reticulum (SR) Ca2+ leak and ryanodine receptor (RyR2) hypernitrosylation during {beta}-AR stimulation. Despite diastolic performance failure, C85-deficient S100A1 protein variants exerted similar Ca2+-dependent interaction with the RyR2 than WT-S100A1. Dissecting S100A1s molecular structure-function relationship, our data indicate for the first time that the conserved C85 residue potentially acts as a redox-switch that is indispensable for S100A1s antiarrhythmic but not its inotropic potency in CM. We therefore propose a model where C85s ox-PTM determines S100A1s ability to beneficially control diastolic but not systolic RyR2 activity.

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Seitz, A., Busch, M., Kroemer, J., Schneider, A., Simon, S., Jungmann, A., Katus, H. A., Most, P., Ritterhoff, J.. 2023-09-01. S100A1's single cysteine is an indispensable redox-switch for the protection against diastolic calcium leakage in cardiomyocytes. https://doi.org/10.1101/2023.09.01.555853

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