LQT5 masquerading as LQT2: a dominant negative effect of KCNE1-D85N rare polymorphism on KCNH2 current

Europace. 2011 Oct;13(10):1478-83. doi: 10.1093/europace/eur184. Epub 2011 Jun 28.


Aims: KCNE1 encodes an auxiliary subunit of cardiac potassium channels. Loss-of-function variations in this gene have been associated with the LQT5 form of the long QT syndrome (LQTS), secondary to reduction of I(Ks) current. We present a case in which a D85N rare polymorphism in KCNE1 is associated with an LQT2 phenotype.

Methods and results: An 11-year old competitive athlete presented with mild bradycardia and a QTc interval of 470 ms. An LQT2 phenotype, consisting of low-voltage bifid T waves, was evident in the right precordial electrocardiogram leads. During the tachycardia phase following adenosine, QTc increased to 620 ms. Genetic analysis revealed a rare heterozygous polymorphism in KCNE1 predicting the substitution of asparagine for aspartic acid at position 85 of minK (D85N). Patch clamp experiments showed that KCNE1-D85N, when co-expressed with KCNH2 in TSA201 cells, significantly reduced I(Kr). Homozygous co-expression of the mutant with KCNH2 reduced I(Kr) tail current by 85%, whereas heterozygous co-expression reduced the current by 52%, demonstrating for the first time a dominant-negative effect of D85N to reduce I(Kr). Co-expression of the mutant with KCNQ1, either homozygously or heterozygously, produced no change in I(Ks).

Conclusions: Our results suggest that a rare polymorphism KCNE1-D85N underlies the development of an LQT2 phenotype in this young athlete by interacting with KCNH2 to cause a dominant-negative effect to reduce I(Kr). Our data provide further evidence in support of the promiscuity of potassium channel β subunits in modulating the function of multiple potassium channels leading to a diversity of clinical phenotypes.

Publication types

  • Case Reports
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Athletes
  • Bradycardia / diagnosis
  • Bradycardia / etiology
  • Bradycardia / physiopathology
  • Child
  • Diagnosis, Differential
  • ERG1 Potassium Channel
  • Electrocardiography*
  • Ether-A-Go-Go Potassium Channels / genetics*
  • Female
  • Humans
  • Long QT Syndrome / classification*
  • Long QT Syndrome / diagnosis*
  • Long QT Syndrome / physiopathology
  • Phenotype
  • Polymorphism, Single Nucleotide / genetics*
  • Potassium Channels, Voltage-Gated / genetics*


  • ERG1 Potassium Channel
  • Ether-A-Go-Go Potassium Channels
  • KCNE1 protein, human
  • KCNH2 protein, human
  • Potassium Channels, Voltage-Gated