In:
Circulation Research, Ovid Technologies (Wolters Kluwer Health), Vol. 88, No. 7 ( 2001-04-13), p. 740-745
Abstract:
Abstract —Variant 3 of the congenital long-QT syndrome (LQTS-3) is caused by mutations in the gene encoding the α subunit of the cardiac Na + channel. In the present study, we report a novel LQTS-3 mutation, E1295K (EK), and describe its functional consequences when expressed in HEK293 cells. The clinical phenotype of the proband indicated QT interval prolongation in the absence of T-wave morphological abnormalities and a steep QT/R-R relationship, consistent with an LQTS-3 lesion. However, biophysical analysis of mutant channels indicates that the EK mutation changes channel activity in a manner that is distinct from previously investigated LQTS-3 mutations. The EK mutation causes significant positive shifts in the half-maximal voltage (V 1/2 ) of steady-state inactivation and activation (+5.2 and +3.4 mV, respectively). These gating changes shift the window of voltages over which Na + channels do not completely inactivate without altering the magnitude of these currents. The change in voltage dependence of window currents suggests that this alteration in the voltage dependence of Na + channel gating may cause marked changes in action potential duration because of the unique voltage-dependent rectifying properties of cardiac K + channels that underlie the plateau and terminal repolarization phases of the action potential. Na + channel window current is likely to have a greater effect on net membrane current at more positive potentials (EK channels) where total K + channel conductance is low than at more negative potentials (wild-type channels), where total K + channel conductance is high. These findings suggest a fundamentally distinct mechanism of arrhythmogenesis for congenital LQTS-3.
Type of Medium:
Online Resource
ISSN:
0009-7330
,
1524-4571
DOI:
10.1161/hh0701.089668
Language:
English
Publisher:
Ovid Technologies (Wolters Kluwer Health)
Publication Date:
2001
detail.hit.zdb_id:
1467838-X
