L539 fs/47, a truncated mutation of human ether‐a‐go‐go‐related gene (hERG), decreases hERG ion channel currents in HEK 293 cells

Abstract

Mutations in the human ether-a-go-go-related gene (hERG) are responsible for congenital Type 2 long QT syndrome (LQT2). Previously, we reported a truncated mutation of hERG in a Chinese family with LQT2, namely L539 fs/47, which is composed of a 19 bp deletion mutation and an A1692G polymorphism. This mutation was found to cause an LQT2 phenotype. The aim of the present study was to investigate the functional role of L539 fs/47 at the cellular level and its potential contribution to the loss of function of hERG channels. The function of the truncated mutation L539 fs/47 was evaluated by constructing a mutated plasmid, transfection of the mutated cDNA into HEK 293 cells and subsequent patch-clamp, western blotting and immunostaining experiments. Homologous expression of L539 fs/47 in HEK 293 cells produced a non-functional protein that was detected in cell membranes. When L539 fs/47 was expressed simultaneously with wild-type hERG, it suppressed wild-type hERG currents in a dose-dependent manner and changed the gating properties of the channel. Although L539 fs/47 hERG proteins were detected on plasma membranes, they failed to generate hERG currents. In general, L539 fs/47 dose-dependently decreases hERG ion channel currents and suppresses the function of wild-type channels function. This may explain, in part, the clinical manifestations of LQT2 in the family with this mutation.

F463L increases the potential of dofetilide on human ether‐a‐go‐go‐related gene (hERG) channels

“…Long QT syndrome (LQTS) is an inherited or acquired heart disease characterized by a prolonged QT interval on 12‐lead ECG. Individuals with LQTS are at high risk of syncope, seizures and torsade de pointes (TdP), which is a special form of irregular heartbeat that originates from the ventricles and is responsible for sudden cardiac death (Ackerman et al, ; Priori et al, ; Zhang et al, ). Mutations in the human ether‐a‐go‐go‐related gene (hERG) can reduce the delayed rectifier potassium current ( I Kr ), leading to type 2 LQTS (LQT2) (Branch, ; Li & Liu, ; Li et al, ).…”

Allitridin Reduces <b><i>I</i></b>_Kr Current by Disrupting the Trafficking of Human Ether-à-Go-Go-Related Gene Channels

“…I Kr was elicited by the protocol shown in the inset of figure 1a, which is a standard protocol used to study I Kr in our laboratory [17]. The holding potential was maintained at -90 mV, and tail currents ( I tail ) were recorded at a level of -40 mV for 4 s after depolarizing pulses from -60 mV to +60 mV in 10-mV increments for 2 s.…”

“…The normalized I tail of hERG channels was plotted as a function of the test potential and then fitted to a Boltzmann function, as in our previous study [17]. As shown in figure 1d, the voltage to achieve V 1/2 for the hERG channels with 3.0 μ M allitridin was 11.63 ± 0.58 mV (n = 10), which was statistically indistinguishable from the corresponding value of 6.21 ± 0.47 mV under control conditions (p > 0.05; n = 10).…”

“…The course of inactivation of hERG currents over time was measured as previously described [17]. Briefly, we used a 3-pulse protocol (fig.…”

“…Recovery from inactivation was analyzed as previously described [17]. Briefly, the holding potential was -80 mV, and then depolarization occurred from 50 mV for 1.5 s to activate and inactivate the channel.…”