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C-terminal phosphorylation of NaV1.5 impairs FGF13-dependent regulation of channel inactivation.

ABSTRACT: Voltage-gated Na+ (NaV) channels are key regulators of myocardial excitability, and Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent alterations in NaV1.5 channel inactivation are emerging as a critical determinant of arrhythmias in heart failure. However, the global native phosphorylation pattern of NaV1.5 subunits associated with these arrhythmogenic disorders and the associated channel regulatory defects remain unknown. Here, we undertook phosphoproteomic analyses to identify and quantify in situ the phosphorylation sites in the NaV1.5 proteins purified from adult WT and failing CaMKII?c-overexpressing (CaMKII?c-Tg) mouse ventricles. Of 19 native NaV1.5 phosphorylation sites identified, two C-terminal phosphoserines at positions 1938 and 1989 showed increased phosphorylation in the CaMKII?c-Tg compared with the WT ventricles. We then tested the hypothesis that phosphorylation at these two sites impairs fibroblast growth factor 13 (FGF13)-dependent regulation of NaV1.5 channel inactivation. Whole-cell voltage-clamp analyses in HEK293 cells demonstrated that FGF13 increases NaV1.5 channel availability and decreases late Na+ current, two effects that were abrogated with NaV1.5 mutants mimicking phosphorylation at both sites. Additional co-immunoprecipitation experiments revealed that FGF13 potentiates the binding of calmodulin to NaV1.5 and that phosphomimetic mutations at both sites decrease the interaction of FGF13 and, consequently, of calmodulin with NaV1.5. Together, we have identified two novel native phosphorylation sites in the C terminus of NaV1.5 that impair FGF13-dependent regulation of channel inactivation and may contribute to CaMKII?c-dependent arrhythmogenic disorders in failing hearts.

SUBMITTER: Burel S

PROVIDER: S-EPMC5655519 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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C-terminal phosphorylation of NaV1.5 impairs FGF13-dependent regulation of channel inactivation.

Burel Sophie S Coyan Fabien C FC Lorenzini Maxime M Meyer Matthew R MR Lichti Cheryl F CF Brown Joan H JH Loussouarn Gildas G Charpentier Flavien F Nerbonne Jeanne M JM Townsend R Reid RR Maier Lars S LS Marionneau Céline C

The Journal of biological chemistry 20170907 42

Voltage-gated Na+ (NaV) channels are key regulators of myocardial excitability, and Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent alterations in NaV1.5 channel inactivation are emerging as a critical determinant of arrhythmias in heart failure. However, the global native phosphorylation pattern of NaV1.5 subunits associated with these arrhythmogenic disorders and the associated channel regulatory defects remain unknown. Here ...[more]

PMID: 28882890

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Project description:Infarcted myocardium is predisposed to cause lethal ventricular arrhythmias that remain the main cause of death in patients suffering myocardial ischemia. Liver-derived fibroblast growth factor 21 (FGF21) is an endocrine regulator, which exerts metabolic actions by favoring glucose and lipids metabolism. Emerging evidence has shown a beneficial effect of FGF21 on cardiovascular diseases, but the role of FGF21 on ventricular arrhythmias following myocardial infarction (MI) in humans has never been addressed. This study was conducted to investigate the pharmacological effects of FGF21 on cardiomyocytes after MI in humans. Patients with arrhythmia in acute MI and healthy volunteers were enrolled in this study. Serum samples were collected from these subjects on day 1 and days 7-10 after the onset of MI for measuring FGF21 levels using ELISA. Here, we found that the serum level of FGF21 was significantly increased on day 1 after the onset of MI and it returned to normal on days 7-10, relative to the Control samples. In order to clarify the regulation of FGF21 on arrhythmia, two kinds of arrhythmia animal models were established in this study, including ischemic arrhythmia model (MI rat model) and nonischemic arrhythmia model (ouabain-induced guinea pig arrhythmia model). The results showed that the incidence and duration time of ischemic arrhythmias in rhbFGF21-treated MI rats were significantly reduced at different time point after MI compared with normal saline-treated MI rats. Moreover, the onset of the first ventricular arrhythmias was delayed and the numbers of VF and maintenance were attenuated by FGF21 compared to the rhbFGF21-untreated group in the ouabain model. Consistently, in vitro study also demonstrated that FGF21 administration was able to shorten action potential duration (APD) in hydrogen peroxide-treated AC16 cells. Mechanically, FGF21 can ameliorate the electrophysiological function of AC16 cells, which is characterized by rescuing the expression and dysfunction of cardiac sodium current (I Na) and inward rectifier potassium (I k1) in AC16 cells induced by hydrogen peroxide. Moreover, the restorative effect of FGF21 on NaV1.5 and Kir2.1 was eliminated when FGF receptors were inhibited. Collectively, FGF21 has the potential role of ameliorating transmembrane ion channels remodeling through the NaV1.5/Kir2.1 pathway by FGF receptors and thus reducing life-threatening postinfarcted arrhythmias, which provides new strategies for antiarrhythmic therapy in clinics.

Dataset Information

C-terminal phosphorylation of NaV1.5 impairs FGF13-dependent regulation of channel inactivation.

Publications

C-terminal phosphorylation of Na<sub>V</sub>1.5 impairs FGF13-dependent regulation of channel inactivation.

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