An LQT mutant minK alters KvLQT1 trafficking

Andrew K. Krumerman, Xiaohong Gao, Jin Song Bian, Yonathan F. Melman, Anna Kagan, Thomas V. McDonald

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

Cardiac IKs, the slowly activated delayed-rectifier K + current, is produced by the protein complex composed of α- and β-subunits: KvLQT1 and minK. Mutations of genes encoding KvLQT1 and minK are responsible for the hereditary long QT syndrome (loci LQT1 and LQT5, respectively). MinK-L51H fails to traffic to the cell surface, thereby failing to produce effective IKs. We examined the effects that minK-L51H and an endoplasmic reticulum (ER)-targeted minK (minK-ER) exerted over the electrophysiology and biosynthesis of coexpressed KvLQT1. Both minK-L51H and minK-ER were sequestered primarily in the ER as confirmed by lack of plasma membrane expression. Glycosylation and immunofluorescence patterns of minK-L51H were qualitatively different for minK-ER, suggesting differences in trafficking. Cotransfection with the minK mutants resulted in reduced surface expression of KvLQT1 as assayed by whole cell voltage clamp and immunofluorescence. MinK-L51H reduced current amplitude by 91% compared with wild-type (WT) minK/KvLQT1, and the residual current was identical to KvLQT1 without minK. The phenotype of minK-L51H on IKs was not dominant because coexpressed WT minK rescued the current and surface expression. Collectively, our data suggest that ER quality control prevents minK-L51H/KvLQT1 complexes from trafficking to the plasma membrane, resulting in decreased IKs. This is the first demonstration that a minK LQT mutation is capable of conferring trafficking defects onto its associated α-subunit.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume286
Issue number6 55-6
DOIs
StatePublished - Jun 2004

Fingerprint

Mink
Cell membranes
Electrophysiology
Glycosylation
Gene encoding
Biosynthesis
Clamping devices
Endoplasmic Reticulum
Quality control
Demonstrations
Defects
Electric potential
Proteins
Fluorescent Antibody Technique
Cell Membrane
Long QT Syndrome
Mutation

Keywords

  • Electrophysiology
  • Hereditary arrhythmia
  • Potassium channel
  • Protein interaction

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Cell Biology
  • Physiology

Cite this

An LQT mutant minK alters KvLQT1 trafficking. / Krumerman, Andrew K.; Gao, Xiaohong; Bian, Jin Song; Melman, Yonathan F.; Kagan, Anna; McDonald, Thomas V.

In: American Journal of Physiology - Cell Physiology, Vol. 286, No. 6 55-6, 06.2004.

Research output: Contribution to journalArticle

Krumerman, Andrew K. ; Gao, Xiaohong ; Bian, Jin Song ; Melman, Yonathan F. ; Kagan, Anna ; McDonald, Thomas V. / An LQT mutant minK alters KvLQT1 trafficking. In: American Journal of Physiology - Cell Physiology. 2004 ; Vol. 286, No. 6 55-6.
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AB - Cardiac IKs, the slowly activated delayed-rectifier K + current, is produced by the protein complex composed of α- and β-subunits: KvLQT1 and minK. Mutations of genes encoding KvLQT1 and minK are responsible for the hereditary long QT syndrome (loci LQT1 and LQT5, respectively). MinK-L51H fails to traffic to the cell surface, thereby failing to produce effective IKs. We examined the effects that minK-L51H and an endoplasmic reticulum (ER)-targeted minK (minK-ER) exerted over the electrophysiology and biosynthesis of coexpressed KvLQT1. Both minK-L51H and minK-ER were sequestered primarily in the ER as confirmed by lack of plasma membrane expression. Glycosylation and immunofluorescence patterns of minK-L51H were qualitatively different for minK-ER, suggesting differences in trafficking. Cotransfection with the minK mutants resulted in reduced surface expression of KvLQT1 as assayed by whole cell voltage clamp and immunofluorescence. MinK-L51H reduced current amplitude by 91% compared with wild-type (WT) minK/KvLQT1, and the residual current was identical to KvLQT1 without minK. The phenotype of minK-L51H on IKs was not dominant because coexpressed WT minK rescued the current and surface expression. Collectively, our data suggest that ER quality control prevents minK-L51H/KvLQT1 complexes from trafficking to the plasma membrane, resulting in decreased IKs. This is the first demonstration that a minK LQT mutation is capable of conferring trafficking defects onto its associated α-subunit.

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