A dual mechanism for I Ks current reduction by the pathogenic mutation KCNQ1-S277L

Jerri Chen, Michael Weber, Sung Yon Um, Christine A. Walsh, Yingying Tang, Thomas V. McDonald

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Background: The hereditary long QT syndrome is characterized by prolonged ventricular repolarization that can be caused by mutations to the KCNQ1 gene, which encodes the α subunits of the cardiac potassium channel complex that carries the I Ks current (the β subunits are encoded by KCNE1). In this study, we characterized a deleterious variant, KCNQ1-S277L, found in a patient who presented with sudden cardiac death in the presence of cocaine use. Methods: The KCNQ1-S277L mutation was analyzed via whole-cell patch clamp, confocal imaging, surface biotinylation assays, and computer modeling. Results: Homomeric mutant KCNQ1-S277L channels were unable to carry current, either alone or with KCNE1. When co-expressed in a 50/50 ratio with WT KCNQ1, current density was reduced in a dominant-negative manner, with the residual current predominantly wild type. There was no change in the activation rate and minimal changes to voltage-dependent activation for both KCNQ1 current and I Ks current. Immunofluorescence confocal imaging revealed reduced surface expression of mutant KCNQ1-S277L, which was biochemically confirmed by surface biotinylation showing a 44% decrease in mutant surface expression. Expression of KCNQ1-S277L with human ether-a-go-go-related gene (HERG) did not significantly affect HERG protein or current density compared to KCNQ1-WT co-expression. Conclusion: The KCNQ1-S277L mutation causes biophysical defects that result in dominant-negative reduction in KCNQ1 and I Ks current density, and a trafficking defect that results in reduced surface expression, both without affecting HERG/I Kr. KCNQ1-S277L mutation in the proband resulted in defective channels that compromised repolarization reserve, thereby enhancing the arrhythmic susceptibility to pharmacological blockage of I Kr current.

Original languageEnglish (US)
Pages (from-to)1652-1664
Number of pages13
JournalPACE - Pacing and Clinical Electrophysiology
Volume34
Issue number12
DOIs
StatePublished - Dec 2011

Fingerprint

Biotinylation
Mutation
Ether
Genes
Long QT Syndrome
Potassium Channels
Sudden Cardiac Death
Cocaine
Fluorescent Antibody Technique
Pharmacology
Proteins
human KCNH2 protein

Keywords

  • Disease mechanism
  • Genetic phenotype
  • I
  • KCNQ1
  • long QT syndrome
  • Sudden death

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

Cite this

A dual mechanism for I Ks current reduction by the pathogenic mutation KCNQ1-S277L. / Chen, Jerri; Weber, Michael; Yon Um, Sung; Walsh, Christine A.; Tang, Yingying; McDonald, Thomas V.

In: PACE - Pacing and Clinical Electrophysiology, Vol. 34, No. 12, 12.2011, p. 1652-1664.

Research output: Contribution to journalArticle

Chen, Jerri ; Weber, Michael ; Yon Um, Sung ; Walsh, Christine A. ; Tang, Yingying ; McDonald, Thomas V. / A dual mechanism for I Ks current reduction by the pathogenic mutation KCNQ1-S277L. In: PACE - Pacing and Clinical Electrophysiology. 2011 ; Vol. 34, No. 12. pp. 1652-1664.
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abstract = "Background: The hereditary long QT syndrome is characterized by prolonged ventricular repolarization that can be caused by mutations to the KCNQ1 gene, which encodes the α subunits of the cardiac potassium channel complex that carries the I Ks current (the β subunits are encoded by KCNE1). In this study, we characterized a deleterious variant, KCNQ1-S277L, found in a patient who presented with sudden cardiac death in the presence of cocaine use. Methods: The KCNQ1-S277L mutation was analyzed via whole-cell patch clamp, confocal imaging, surface biotinylation assays, and computer modeling. Results: Homomeric mutant KCNQ1-S277L channels were unable to carry current, either alone or with KCNE1. When co-expressed in a 50/50 ratio with WT KCNQ1, current density was reduced in a dominant-negative manner, with the residual current predominantly wild type. There was no change in the activation rate and minimal changes to voltage-dependent activation for both KCNQ1 current and I Ks current. Immunofluorescence confocal imaging revealed reduced surface expression of mutant KCNQ1-S277L, which was biochemically confirmed by surface biotinylation showing a 44{\%} decrease in mutant surface expression. Expression of KCNQ1-S277L with human ether-a-go-go-related gene (HERG) did not significantly affect HERG protein or current density compared to KCNQ1-WT co-expression. Conclusion: The KCNQ1-S277L mutation causes biophysical defects that result in dominant-negative reduction in KCNQ1 and I Ks current density, and a trafficking defect that results in reduced surface expression, both without affecting HERG/I Kr. KCNQ1-S277L mutation in the proband resulted in defective channels that compromised repolarization reserve, thereby enhancing the arrhythmic susceptibility to pharmacological blockage of I Kr current.",
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AU - Chen, Jerri

AU - Weber, Michael

AU - Yon Um, Sung

AU - Walsh, Christine A.

AU - Tang, Yingying

AU - McDonald, Thomas V.

PY - 2011/12

Y1 - 2011/12

N2 - Background: The hereditary long QT syndrome is characterized by prolonged ventricular repolarization that can be caused by mutations to the KCNQ1 gene, which encodes the α subunits of the cardiac potassium channel complex that carries the I Ks current (the β subunits are encoded by KCNE1). In this study, we characterized a deleterious variant, KCNQ1-S277L, found in a patient who presented with sudden cardiac death in the presence of cocaine use. Methods: The KCNQ1-S277L mutation was analyzed via whole-cell patch clamp, confocal imaging, surface biotinylation assays, and computer modeling. Results: Homomeric mutant KCNQ1-S277L channels were unable to carry current, either alone or with KCNE1. When co-expressed in a 50/50 ratio with WT KCNQ1, current density was reduced in a dominant-negative manner, with the residual current predominantly wild type. There was no change in the activation rate and minimal changes to voltage-dependent activation for both KCNQ1 current and I Ks current. Immunofluorescence confocal imaging revealed reduced surface expression of mutant KCNQ1-S277L, which was biochemically confirmed by surface biotinylation showing a 44% decrease in mutant surface expression. Expression of KCNQ1-S277L with human ether-a-go-go-related gene (HERG) did not significantly affect HERG protein or current density compared to KCNQ1-WT co-expression. Conclusion: The KCNQ1-S277L mutation causes biophysical defects that result in dominant-negative reduction in KCNQ1 and I Ks current density, and a trafficking defect that results in reduced surface expression, both without affecting HERG/I Kr. KCNQ1-S277L mutation in the proband resulted in defective channels that compromised repolarization reserve, thereby enhancing the arrhythmic susceptibility to pharmacological blockage of I Kr current.

AB - Background: The hereditary long QT syndrome is characterized by prolonged ventricular repolarization that can be caused by mutations to the KCNQ1 gene, which encodes the α subunits of the cardiac potassium channel complex that carries the I Ks current (the β subunits are encoded by KCNE1). In this study, we characterized a deleterious variant, KCNQ1-S277L, found in a patient who presented with sudden cardiac death in the presence of cocaine use. Methods: The KCNQ1-S277L mutation was analyzed via whole-cell patch clamp, confocal imaging, surface biotinylation assays, and computer modeling. Results: Homomeric mutant KCNQ1-S277L channels were unable to carry current, either alone or with KCNE1. When co-expressed in a 50/50 ratio with WT KCNQ1, current density was reduced in a dominant-negative manner, with the residual current predominantly wild type. There was no change in the activation rate and minimal changes to voltage-dependent activation for both KCNQ1 current and I Ks current. Immunofluorescence confocal imaging revealed reduced surface expression of mutant KCNQ1-S277L, which was biochemically confirmed by surface biotinylation showing a 44% decrease in mutant surface expression. Expression of KCNQ1-S277L with human ether-a-go-go-related gene (HERG) did not significantly affect HERG protein or current density compared to KCNQ1-WT co-expression. Conclusion: The KCNQ1-S277L mutation causes biophysical defects that result in dominant-negative reduction in KCNQ1 and I Ks current density, and a trafficking defect that results in reduced surface expression, both without affecting HERG/I Kr. KCNQ1-S277L mutation in the proband resulted in defective channels that compromised repolarization reserve, thereby enhancing the arrhythmic susceptibility to pharmacological blockage of I Kr current.

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KW - Genetic phenotype

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KW - long QT syndrome

KW - Sudden death

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