Divergent regulation of KCNQ1/E1 by targeted recruitment of protein kinase A to distinct sites on the channel complex

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Abstract

The slow delayed rectifier potassium current, I_Ks, conducted through pore-forming Q1 and auxiliary E1 ion channel complexes is important for human cardiac action potential repolarization. During exercise or fright, I_Ks is up-regulated by protein kinase A (PKA)-mediated Q1 phosphorylation to maintain heart rhythm and optimum cardiac performance. Sympathetic upregulation of I_Ks requires recruitment of PKA holoenzyme (two regulatory- RI or RII- and two catalytic Cα subunits) to Q1 C-terminus by an A kinase anchoring protein (AKAP9). Mutations in Q1 or AKAP9 that abolish their functional interaction result in long QT syndrome type 1 and 11, respectively, which increases the risk of sudden cardiac death during exercise. Here, we investigated the utility of a targeted protein phosphorylation (TPP) approach to reconstitute PKA regulation of I_Ks in the absence of AKAP9. Targeted recruitment of endogenous Cα to E1-YFP using a GFP/YFP nanobody (nano) fused to RIIα enabled acute cAMP-mediated enhancement of I_Ks, reconstituting physiological regulation of the channel complex. By contrast, nano-mediated tethering of RIIα or Cα to Q1-YFP constitutively inhibited I_Ks by retaining the channel intracellularly in the endoplasmic reticulum and Golgi. Proteomic analysis revealed distinct phosphorylation sites are modified by Cα targeted to Q1-YFP compared to free Cα. Thus, functional outcomes of synthetically recruited PKA on I_Ks regulation is critically dependent on the site of recruitment within the channel complex. The results reveal insights into divergent regulation of I_Ks by phosphorylation across different spatial and time scales, and suggest a TPP approach to develop new drugs to prevent exercise-induced sudden cardiac death.

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All data generated or analyzed during this study are included in the manuscript and supporting supplemental data file. Source data files have been provided.

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Xinle Zou

Department of Molecular Pharmacology and Therapeutics, Columbia University, New York, United States

Competing interests
No competing interests declared.
Sri Karthika Shanmugam

Department of Physiology and Cellular Biophysics, Columbia University, New York, United States

Competing interests
No competing interests declared.
Scott A Kanner

Doctoral Program in Neurobiology and Behavior, Columbia University, New York, United States

Competing interests
No competing interests declared.
Kevin J Sampson

Department of Molecular Pharmacology and Therapeutics, Columbia University, New York, United States

Competing interests
No competing interests declared.
Robert S Kass

Department of Molecular Pharmacology and Therapeutics, Columbia University, New York, United States

Competing interests
No competing interests declared.
Henry M Colecraft

Department of Molecular Pharmacology and Therapeutics, Columbia University, New York, United States

For correspondence
hc2405@cumc.columbia.edu

Competing interests
Henry M Colecraft, Reviewing editor, eLife.

"This ORCID iD identifies the author of this article:" 0000-0002-2340-8899

Funding

National Heart, Lung, and Blood Institute (R01 HL142111)

Henry M Colecraft

National Heart, Lung, and Blood Institute (R01 HL122421)

Henry M Colecraft

National Institutes of Health (R01 GM109763)

Robert S Kass

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.