hERG1a N-terminal eag domain–containing polypeptides regulate homomeric hERG1b and heteromeric hERG1a/hERG1b channels: A possible mechanism for long QT syndrome

Trudeau, Matthew C.; Leung, Lisa M.; Roti, Elon Roti; Robertson, Gail A.

doi:10.1085/jgp.201110683

Cited by 34 publications

(51 citation statements)

References 36 publications

(79 reference statements)

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“…Consistent with the corresponding experiment on hERG 1a/1b channels expressed in HEK293 cells, native I Kr was transformed into a 1a homomeric-like current (15). Expression of the PAS fragment in iPSC-CMs significantly slowed deactivation compared with that in controls (P < 0.0001) and comparable with that in iPSC-CMs exogenously expressing hERG 1a (Fig.…”

Section: Significancesupporting

confidence: 86%

“…Control cells were either mock-transfected in the absence of an expressing vector or transfected with a nontargeting shRNA pLKO.1-NEO-CMVTurboGFP control vector. For all AP recordings, IPSC-CMs were transformed with an adenoviral vector encoding K ir 2.1 in frame with GFP and/or an adenoviral PAS construct encoding the first 135 aa of the hERG 1a N terminus in frame with CFP to enable detection (15).…”

Section: Methodsmentioning

confidence: 99%

“…Heteromeric 1a/1b currents can be converted to 1a-like currents by coexpressing a fragment representing the PAS domain (15). The PAS domain interacts directly with the heteromeric channel, presumably occupying an empty PAS domain receptor site left available by the abbreviated hERG 1b N terminus (15,16).…”

mentioning

confidence: 99%

“…The PAS domain interacts directly with the heteromeric channel, presumably occupying an empty PAS domain receptor site left available by the abbreviated hERG 1b N terminus (15,16). The resulting currents are smaller in amplitude owing to decreased rates of activation and recovery from inactivation characteristic of 1a currents, and they deactivate more slowly (15).…”

mentioning

confidence: 99%

“…Homomeric 1a currents are unaffected by the PAS fragments, as expected if all PAS receptor sites are occupied. Thus, these differences in gating kinetics arise because the 1b N terminus lacks the PAS domain and not because of an effect conferred by the unique N-terminal sequence of 1b (15).…”

mentioning

confidence: 99%

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hERG 1b is critical for human cardiac repolarization

Jones¹,

Liu²,

Vaidyanathan

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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108

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The human ether-à-go-go-related gene (hERG; or KCNH2) encodes the voltage-gated potassium channel underlying I Kr , a repolarizing current in the heart. Mutations in KCNH2 or pharmacological agents that reduce I Kr slow action potential (AP) repolarization and can trigger cardiac arrhythmias associated with long QT syndrome. Two channel-forming subunits encoded by KCNH2 (hERG 1a and 1b) are expressed in cardiac tissue. In heterologous expression systems, these subunits avidly coassemble and exhibit biophysical and pharmacological properties distinct from those of homomeric hERG 1a channels. Despite these findings, adoption of hERG 1a/1b heteromeric channels as a model for cardiac I Kr has been hampered by the lack of evidence for a direct functional role for the 1b subunit in native tissue. In this study, we measured I Kr and APs at physiological temperature in cardiomyocytes derived from human induced pluripotent stem cells (iPSC-CMs). We found that specific knockdown of the 1b subunit using shRNA caused reductions in 1b mRNA, 1b protein levels, and I Kr magnitude by roughly one-half. AP duration was increased and AP variability was enhanced relative to controls. Early afterdepolarizations, considered cellular substrates for arrhythmia, were also observed in cells with reduced 1b expression. Similar behavior was elicited when channels were effectively converted from heteromers to 1a homomers by expressing a fragment corresponding to the 1a-specific N-terminal Per-Arnt-Sim domain, which is omitted from hERG 1b by alternate transcription. These findings establish that hERG 1b is critical for normal repolarization and that loss of 1b is proarrhythmic in human cardiac cells.T he human ether-à-go-go-related gene (hERG; or KCNH2) encodes the voltage-gated potassium channel underlying a native cardiac current known as I Kr (1, 2). Mutations in the gene or drugs that block the channel can diminish I Kr and slow ventricular repolarization, thus prolonging the QT interval on the surface electrocardiogram and causing long QT syndrome (LQTS) (1-3). Individuals with LQTS have an increased risk for torsades de pointes arrhythmia, syncope, and sudden cardiac death. Since 2005, a cell-based assay expressing the hERG 1a isoform as a proxy for I Kr has been the cornerstone of drug safety screening for new drug development (4). Thus, whether current drug safety assays accurately represent the native channel is of paramount importance.The first studies of heterologously expressed hERG channels described biophysical (1, 2) and pharmacological (2, 5) properties uniquely characteristic of cardiac I Kr . Subsequently, alternate transcripts of KCNH2 in mouse and human heart were shown to encode two subunits: 1a (the original isolate) and 1b (6, 7). In the hERG 1b transcript, an alternate 5′ exon replaces 1a exons 1-5, resulting in a shorter, unique N terminus that lacks a Per-Arnt-Sim (PAS) domain (also known as the ether-à-go-go domain) (8, 9). In heterologous systems, hERG 1b subunits avidly associate with hERG 1a but fail as homomer...

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Section: Significancesupporting

confidence: 86%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

hERG 1b is critical for human cardiac repolarization

Jones¹,

Liu²,

Vaidyanathan

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

108

View full text Add to dashboard Cite

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Nonsense-Mediated mRNA Decay of hERG Mutations in Long QT Syndrome

Gong

Zhou

2017

Methods in Molecular Biology

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Long QT syndrome type 2 (LQT2) is caused by mutations in the human ether-à-go-go related gene (hERG), which encodes the Kv11.1 potassium channel in the heart. Over 30% of identified LQT2 mutations are nonsense or frameshift mutations that introduce premature termination codons (PTCs). Contrary to intuition, the predominant consequence of LQT2 nonsense and frameshift mutations is not the production of truncated proteins, but rather the degradation of mutant mRNA by nonsense-mediated mRNA decay (NMD), an RNA surveillance mechanism that selectively eliminates the mRNA transcripts that contain PTCs. In this chapter, we describe methods to study NMD of hERG nonsense and frameshift mutations in long QT syndrome.

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