Functional characterization of the common amino acid 897 polymorphism of the cardiac potassium channel KCNH2 (HERG).

OBJECTIVE

To determine whether the amino acid 897 threonine (T) to lysine (K) polymorphism of the KCNH2 (HERG) potassium channel influences channel performance or patient phenotype.

METHODS

The phenotypic effects of this polymorphism were investigated in vitro by electrophysiological experiments in HEK-293 cells and in vivo by exercise electrocardiography in a group of LQTS patients carrying the same genetically proven KCNQ1 mutation.

RESULTS

When expressed in HEK-293 cells, the 897T isoform of the KCNH2 channel exhibited changes in inactivation and deactivation properties, and a smaller current density than the more common 897K isoform. Western blot experiments indicated that the decreased current density associated with 897T was caused by reduced channel expression. During a maximal exercise test in 39 LQT1 patients carrying an identical KCNQ1 mutation (G589D) and showing a prolonged QT interval (>440 ms), QT intervals were longer in patients carrying the 897T allele than in those homozygous for the 897K allele.

CONCLUSIONS

The K897T variation has an effect on channel function and clinical phenotype. Our data warrant further investigations into the significance of this polymorphism in drug-induced and inherited LQTS.