Ankyrin-G mediates targeting of both Na+ and KATP channels to the rat cardiac intercalated disc.

Hua-Qian Yang,Eli Rothenberg,Andriy Shevchuk,Julia Gorelik,Jose Sanchez-Alonso,Mario Delmar,William A Coetzee,Marta Pérez-Hernández

doi:10.7554/elife.52373

Abstract

We investigated targeting mechanisms of Na+ and KATP channels to the intercalated disk (ICD) of cardiomyocytes. Patch clamp and surface biotinylation data show reciprocal downregulation of each other's surface density. Mutagenesis of the Kir6.2 ankyrin binding site disrupts this functional coupling. Duplex patch clamping and Angle SICM recordings show that INa and IKATP functionally co-localize at the rat ICD, but not at the lateral membrane. Quantitative STORM imaging show that Na+ and KATP channels are localized close to each other and to AnkG, but not to AnkB, at the ICD. Peptides corresponding to Nav1.5 and Kir6.2 ankyrin binding sites dysregulate targeting of both Na+ and KATP channels to the ICD, but not to lateral membranes. Finally, a clinically relevant gene variant that disrupts KATP channel trafficking also regulates Na+ channel surface expression. The functional coupling between these two channels need to be considered when assessing clinical variants and therapeutics.

Highlights

Voltage-gated Na+ channels are responsible for the initiation and propagation of action potentials in many excitable cell types, including neurons, skeletal muscle and cardiac myocytes
Distinct subpopulations of Na+ channels and KATP channels exist in a cardiomyocyte, but the relevance of this observation has been unclear
We examined whether Ankyrin binding promotes trafficking of Na+ channels and KATP channels to the intercalated disk (ICD) of cardiac myocytes

Summary

Introduction

Voltage-gated Na+ channels are responsible for the initiation and propagation of action potentials in many excitable cell types, including neurons, skeletal muscle and cardiac myocytes. As with Na+ channels, KATP channels are enriched at the ICD of cardiac myocytes where they morphologically cluster with desmosomal proteins such as PKP2 (Hong et al, 2012), suggesting that KATP channels form part of an ICD channel/transporter complex that is gaining increasing recognition for roles in cell-cell communication and cell adhesion It is a common theme in cardiac electrophysiology that ion channels in the same subdomain have the potential to interact with each other, as well as with other channels and transporters. We provide evidence that Na+ channels and KATP channels are morphologically clustered ( at the ICD) and that they interact functionally, most likely due to the fact that they are targeted to a common subcellular location by AnkG These studies provide a new paradigm when considering pharmacological and genetic aspects of arrhythmogenesis

Results

Discussion

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Materials and methods

Funding Funder National Institutes of Health