Format

Send to

Choose Destination
Circ Res. 2016 Aug 5;119(4):544-56. doi: 10.1161/CIRCRESAHA.116.309254. Epub 2016 Jun 30.

Lateral Membrane-Specific MAGUK CASK Down-Regulates NaV1.5 Channel in Cardiac Myocytes.

Author information

1
From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.).
2
From the Sorbonne Universités, UPMC University Paris 06, Inserm, UMR_S 1166, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, France (C.A.E., A.B., F.L., G.D., J.A., A.C., S.N.H., E.B.); Département de Cardiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, France (J.A., S.N.H.); and Department of Clinical Research, University of Bern, Switzerland (M.Y.E.C., J.-S.R., H.A.). elise.balse@upmc.fr.

Abstract

RATIONALE:

Mechanisms underlying membrane protein localization are crucial in the proper function of cardiac myocytes. The main cardiac sodium channel, NaV1.5, carries the sodium current (INa) that provides a rapid depolarizing current during the upstroke of the action potential. Although enriched in the intercalated disc, NaV1.5 is present in different membrane domains in myocytes and interacts with several partners.

OBJECTIVE:

To test the hypothesis that the MAGUK (membrane-associated guanylate kinase) protein CASK (calcium/calmodulin-dependent serine protein kinase) interacts with and regulates NaV1.5 in cardiac myocytes.

METHODS AND RESULTS:

Immunostaining experiments showed that CASK localizes at lateral membranes of cardiac myocytes, in association with dystrophin. Whole-cell patch clamp showed that CASK-silencing increases INa in vitro. In vivo CASK knockdown similarly increased INa recorded in freshly isolated myocytes. Pull-down experiments revealed that CASK directly interacts with the C-terminus of NaV1.5. CASK silencing reduces syntrophin expression without affecting NaV1.5 and dystrophin expression levels. Total Internal Reflection Fluorescence microscopy and biotinylation assays showed that CASK silencing increased the surface expression of NaV1.5 without changing mRNA levels. Quantification of NaV1.5 expression at the lateral membrane and intercalated disc revealed that the lateral membrane pool only was increased upon CASK silencing. The protein transport inhibitor brefeldin-A prevented INa increase in CASK-silenced myocytes. During atrial dilation/remodeling, CASK expression was reduced but its localization remained unchanged.

CONCLUSION:

This study constitutes the first description of an unconventional MAGUK protein, CASK, which directly interacts with NaV1.5 channel and controls its surface expression at the lateral membrane by regulating ion channel trafficking.

KEYWORDS:

calcium/calmodulin-dependent serine protein kinase; cardiac myocytes; dystrophin; ion channels; membrane-associated guanylate kinase; sodium channels; syntrophin

PMID:
27364017
DOI:
10.1161/CIRCRESAHA.116.309254
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Atypon
Loading ...
Support Center