In:
Circulation Research, Ovid Technologies (Wolters Kluwer Health), Vol. 119, No. 4 ( 2016-08-05), p. 544-556
Kurzfassung:
Mechanisms underlying membrane protein localization are crucial in the proper function of cardiac myocytes. The main cardiac sodium channel, Na V 1.5, carries the sodium current ( I Na ) that provides a rapid depolarizing current during the upstroke of the action potential. Although enriched in the intercalated disc, Na V 1.5 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 Na V 1.5 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 I Na in vitro. In vivo CASK knockdown similarly increased I Na recorded in freshly isolated myocytes. Pull-down experiments revealed that CASK directly interacts with the C-terminus of Na V 1.5. CASK silencing reduces syntrophin expression without affecting Na V 1.5 and dystrophin expression levels. Total Internal Reflection Fluorescence microscopy and biotinylation assays showed that CASK silencing increased the surface expression of Na V 1.5 without changing mRNA levels. Quantification of Na V 1.5 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 I Na 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 Na V 1.5 channel and controls its surface expression at the lateral membrane by regulating ion channel trafficking.
Materialart:
Online-Ressource
ISSN:
0009-7330
,
1524-4571
DOI:
10.1161/CIRCRESAHA.116.309254
Sprache:
Englisch
Verlag:
Ovid Technologies (Wolters Kluwer Health)
Publikationsdatum:
2016
ZDB Id:
1467838-X
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