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J Biol Chem. 2017 Oct 20;292(42):17431-17448. doi: 10.1074/jbc.M117.787788. Epub 2017 Sep 7.

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

Author information

1
From the l'Institut du Thorax, INSERM, CNRS, UNIV Nantes, Nantes 44007, France.
2
the Departments of Medicine.
3
the Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555.
4
the Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0636, and.
5
Developmental Biology.
6
Internal Medicine, and.
7
Cell Biology and Physiology, Washington University Medical School, St. Louis, Missouri 63110.
8
the Department of Internal Medicine II, University Heart Center, University Hospital Regensburg, D-93042 Regensburg, Germany.
9
From the l'Institut du Thorax, INSERM, CNRS, UNIV Nantes, Nantes 44007, France, celine.marionneau@univ-nantes.fr.

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 CaMKIIδc-overexpressing (CaMKIIδc-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 CaMKIIδc-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 CaMKIIδc-dependent arrhythmogenic disorders in failing hearts.

KEYWORDS:

Ca2+/calmodulin-dependent protein kinase II (CaMKII); FGF13; Nav1.5; calmodulin (CaM); channel inactivation; heart; phosphoproteomics; phosphorylation; sodium channel

PMID:
28882890
PMCID:
PMC5655519
[Available on 2018-10-20]
DOI:
10.1074/jbc.M117.787788
[Indexed for MEDLINE]

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