Early LQT2 nonsense mutation generates N-terminally truncated hERG channels with altered gating properties by the reinitiation of translation

Matthew R. Stump, Qiuming Gong, Jonathan D. Packer, Zhengfeng Zhou

    Research output: Contribution to journalArticlepeer-review

    17 Scopus citations

    Abstract

    Mutations in the human ether-a-go-go-related gene (hERG) result in long QT syndrome type 2 (LQT2). The hERG gene encodes a K+ channel that contributes to the repolarization of the cardiac action potential. We have previously shown that hERG mRNA transcripts that contain premature termination codon mutations are rapidly degraded by nonsense-mediated mRNA decay (NMD). In this study, we identified a LQT2 nonsense mutation, Q81X, which escapes degradation by the reinitiation of translation and generates N-terminally truncated channels. RNA analysis of hERG minigenes revealed equivalent levels of wild-type and Q81X mRNA while the mRNA expressed from minigenes containing the LQT2 frameshift mutation, P141fs+2X, was significantly reduced by NMD. Western blot analysis revealed that Q81X minigenes expressed truncated channels. Q81X channels exhibited decreased tail current levels and increased deactivation kinetics compared to wild-type channels. These results are consistent with the disruption of the N-terminus, which is known to regulate hERG deactivation. Site-specific mutagenesis studies showed that translation of the Q81X transcript is reinitiated at Met124 following premature termination. Q81X co-assembled with hERG to form heteromeric channels that exhibited increased deactivation rates compared to wild-type channels. Mutant channels also generated less outward current and transferred less charge at late phases of repolarization during ventricular action potential clamp. These results provide new mechanistic insight into the prolongation of the QT interval in LQT2 patients. Our findings indicate that the reinitiation of translation may be an important pathogenic mechanism in patients with nonsense and frameshift LQT2 mutations near the 5' end of the hERG gene.

    Original languageEnglish (US)
    Pages (from-to)725-733
    Number of pages9
    JournalJournal of molecular and cellular cardiology
    Volume53
    Issue number5
    DOIs
    StatePublished - Nov 2012

    Keywords

    • Cardiac arrhythmias
    • Ion channels
    • Long QT syndrome
    • Patch clamp

    ASJC Scopus subject areas

    • Molecular Biology
    • Cardiology and Cardiovascular Medicine

    Fingerprint Dive into the research topics of 'Early LQT2 nonsense mutation generates N-terminally truncated hERG channels with altered gating properties by the reinitiation of translation'. Together they form a unique fingerprint.

    Cite this