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

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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.