Requirement of a Macromolecular Signaling Complex for β Adrenergic Receptor Modulation of the KCNQ1-KCNE1 Potassium Channel

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Abstract
Sympathetic nervous system (SNS) regulation of cardiac action potential duration (APD) is mediated by β adrenergic receptor (βAR) activation, which increases the slow outward potassium ion current ( I KS ). Mutations in two human I KS channel subunits, hKCNQ1 and hKCNE1, prolong APD and cause inherited cardiac arrhythmias known as LQTS (long QT syndrome). We show that βAR modulation of I KS requires targeting of adenosine 3′,5′-monophosphate (cAMP)–dependent protein kinase (PKA) and protein phosphatase 1 (PP1) to hKCNQ1 through the targeting protein yotiao. Yotiao binds to hKCNQ1 by a leucine zipper motif, which is disrupted by an LQTS mutation (hKCNQ1-G589D). Identification of the hKCNQ1 macromolecular complex provides a mechanism for SNS modulation of cardiac APD through I KS .