Dataset Information
A KCNQ1 mutation contributes to the concealed type 1 long QT phenotype by limiting the Kv7.1 channel conformational changes associated with protein kinase A phosphorylation.
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ABSTRACT: Background
Type 1 long QT syndrome (LQT1) is caused by loss-of-function mutations in the KCNQ1-encoded Kv7.1 channel that conducts the slowly activating component of the delayed rectifier K(+) current (IKs). Clinically, the diagnosis of LQT1 is complicated by variable phenotypic expressivity, whereby approximately 25% of genotype-positive individuals present with concealed LQT1 (resting corrected QT [QTc] interval ≤460 ms).Objective
To determine whether a specific molecular mechanism contributes to concealed LQT1.Methods
We identified a multigenerational LQT1 family whereby 79% of the patients genotype-positive for p.Ile235Asn-KCNQ1 (I235N-Kv7.1) have concealed LQT1. We assessed the effect I235N-Kv7.1 has on IKs and the ventricular action potential (AP) by using in vitro analysis and computational simulations.Results
Clinical data showed that all 10 patients with I235N-Kv7.1 have normal resting QTc intervals but abnormal QTc interval prolongation during the recovery phase of an electrocardiographic treadmill stress test. Voltage-clamping HEK293 cells coexpressing wild-type Kv7.1 and I235N-Kv7.1 (to mimic the patients' genotypes) showed that I235N-Kv7.1 generated relatively normal functioning Kv7.1 channels but were insensitive to protein kinase A (PKA) activation. Phosphomimetic and quinidine sensitivity studies suggest that I235N-Kv7.1 limits the conformational changes in Kv7.1 channels, which are necessary to upregulate IKs after PKA phosphorylation. Computational ventricular AP simulations predicted that the PKA insensitivity of I235N-Kv7.1 is primarily responsible for prolonging the AP with β-adrenergic stimulation, especially at slower cycle lengths.Conclusions
KCNQ1 mutations that generate relatively normal Kv7.1 channels, but limit the upregulation of IKs by PKA activation, likely contribute to concealed LQT1.
SUBMITTER: Bartos DC
PROVIDER: S-EPMC4333640 | biostudies-literature | 2014 Mar
REPOSITORIES: biostudies-literature
Publications
A KCNQ1 mutation contributes to the concealed type 1 long QT phenotype by limiting the Kv7.1 channel conformational changes associated with protein kinase A phosphorylation.
Heart rhythm 20131121 3
<h4>Background</h4>Type 1 long QT syndrome (LQT1) is caused by loss-of-function mutations in the KCNQ1-encoded Kv7.1 channel that conducts the slowly activating component of the delayed rectifier K(+) current (IKs). Clinically, the diagnosis of LQT1 is complicated by variable phenotypic expressivity, whereby approximately 25% of genotype-positive individuals present with concealed LQT1 (resting corrected QT [QTc] interval ≤460 ms).<h4>Objective</h4>To determine whether a specific molecular mecha ...[more]