Dual ablation of the RyR2-Ser2808 and RyR2-Ser2814 sites increases propensity for pro-arrhythmic spontaneous Ca 2+ releases.

Autor: Janicek R; Department of Physiology, University of Bern, Bern, Switzerland., Camors EM; Department of Pediatrics, Division of Cardiology, University of Tennessee Health Science Center, Le Bonheur Children's Hospital Research Center, Memphis, TN, USA., Potenza DM; Department of Physiology, University of Bern, Bern, Switzerland., Fernandez-Tenorio M; Department of Physiology, University of Bern, Bern, Switzerland., Zhao Y; Cardiovascular Research Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA., Dooge HC; Cardiovascular Research Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA., Loaiza R; Cardiovascular Research Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA., Alvarado FJ; Cardiovascular Research Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA., Egger M; Department of Physiology, University of Bern, Bern, Switzerland., Valdivia HH; Cardiovascular Research Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA., Niggli E; Department of Physiology, University of Bern, Bern, Switzerland.
Jazyk: angličtina
Zdroj: The Journal of physiology [J Physiol] 2024 Oct; Vol. 602 (20), pp. 5179-5201. Date of Electronic Publication: 2024 Sep 24.
DOI: 10.1113/JP286453
Abstrakt: During exercise or stress, the sympathetic system stimulates cardiac contractility via β-adrenergic receptor (β-AR) activation, resulting in phosphorylation of the cardiac ryanodine receptor (RyR2). Three RyR2 phosphorylation sites have taken prominence in excitation-contraction coupling: S2808 and S2030 are described as protein kinase A specific and S2814 as a Ca 2+ /calmodulin kinase type-2-specific site. To examine the contribution of these phosphosites to Ca 2+ signalling, we generated double knock-in (DKI) mice in which Ser2808 and Ser2814 phosphorylation sites have both been replaced by alanine (RyR2-S2808A/S2814A). These mice did not exhibit an overt phenotype. Heart morphology and haemodynamic parameters were not altered. However, they had a higher susceptibility to arrhythmias. We performed confocal Ca 2+  imaging and electrophysiology experiments. Isoprenaline was used to stimulate β-ARs. Measurements of Ca 2+ waves and latencies in myocytes revealed an increased propensity for spontaneous Ca 2+ releases in DKI myocytes, both in control conditions and during β-AR stimulation. In DKI cells, waves were initiated from a lower threshold concentration of Ca 2+ inside the sarcoplasmic reticulum, suggesting higher Ca 2+ sensitivity of the RyRs. The refractoriness of Ca 2+ spark triggering depends on the Ca 2+ sensitivity of the RyR2. We found that RyR2-S2808A/S2814A channels were more Ca 2+ sensitive in control conditions. Isoprenaline further shortened RyR refractoriness in DKI cardiomyocytes. Together, our results suggest that ablation of both the RyR2-Ser2808 and RyR2-S2814 sites increases the propensity for pro-arrhythmic spontaneous Ca 2+ releases, as previously suggested for hyperphosphorylated RyRs. Given that the DKI cells present a full response to isoprenaline, the data suggest that phosphorylation of Ser2030 might be sufficient for β-AR-mediated sensitization of RyRs. KEY POINTS: Phosphorylation of cardiac sarcoplasmic reticulum Ca 2+ -release channels (ryanodine receptors, RyRs) is involved in the regulation of cardiac function. Ablation of both the RyR2-Ser2808 and RyR2-Ser2814 sites increases the propensity for pro-arrhythmic spontaneous Ca 2+ releases, as previously suggested for hyperphosphorylated RyRs. The intra-sarcoplasmic reticulum Ca 2+ threshold for spontaneous Ca 2+ wave generation is lower in RyR2-double-knock-in cells. The RyR2 from double-knock-in cells exhibits increased Ca 2+ sensitivity. Phosphorylation of Ser2808 and Ser2814 might be important for basal activity of the channel. Phosphorylation of Ser2030 might be sufficient for a β-adrenergic response.
(© 2024 The Author(s). The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)
Databáze: MEDLINE
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