Crystal Structure and Functional Analysis of the HERG Potassium Channel N Terminus

Morais-Cabral, J.H.; Lee, Alice; Cohen, Steven L.; Chait, Brian T.; Li, Min; MacKinnon, Roderick

doi:10.1016/s0092-8674(00)81635-9

Cited by 405 publications

(372 citation statements)

References 28 publications

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“…We have attempted to investigate this through computer simulation of all of the structurally characterized PAS domains, namely PYP (7), FixL (35), HERG (33), and LOV (34). The complete proteins were subjected to CONCOORD simulations (42) followed by extraction of the common C ␣ atoms as defined by a structurebased sequence alignment (Figs.…”

Section: Resultsmentioning

confidence: 99%

PAS Domains

Vreede

Horst

Hellingwerf

et al. 2003

Journal of Biological Chemistry

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PAS (PER-ARNT-SIM) domains are a family of sensor protein domains involved in signal transduction in a wide range of organisms. Recent structural studies have revealed that these domains contain a structurally conserved ␣/␤-fold, whereas almost no conservation is observed at the amino acid sequence level. The photoactive yellow protein, a bacterial light sensor, has been proposed as the PAS structural prototype yet contains an N-terminal helix-turn-helix motif not found in other PAS domains. Here we describe the atomic resolution structure of a photoactive yellow protein deletion mutant lacking this motif, revealing that the PAS domain is indeed able to fold independently and is not affected by the removal of these residues. Computer simulations of currently known PAS domain structures reveal that these domains are not only structurally conserved but are also similar in their conformational flexibilities. The observed motions point to a possible common mechanism for communicating ligand binding/activation to downstream transducer proteins.

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Section: Resultsmentioning

confidence: 99%

PAS Domains

Vreede

Horst

Hellingwerf

et al. 2003

Journal of Biological Chemistry

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“…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 homomers to traffic efficiently to the plasma membrane (10).…”

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confidence: 99%

hERG 1b is critical for human cardiac repolarization

Jones¹,

Liu²,

Vaidyanathan

et al. 2014

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

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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“…In addition to their sensory functions, PAS domains have been reported to mediate protein-protein interactions (18). The PAS superfamily is characterized structurally by three helical segments flanking a five-stranded antiparallel ␤-sheet (19)(20)(21)(22)(23) (27)(28)(29); and (iv) FMN noncovalently bound to phototropin (9,12). Three crystal structures from the PAS-domain superfamily have been reported: the bacterial blue-light photosensor PYP (19,20), the heme-binding domain of the rhizobial oxygen sensor FixL (21,22), and the N-terminal domain of the human ether-a-gogo-related gene potassium channel (HERG; ref.…”

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confidence: 99%

“…Three crystal structures from the PAS-domain superfamily have been reported: the bacterial blue-light photosensor PYP (19,20), the heme-binding domain of the rhizobial oxygen sensor FixL (21,22), and the N-terminal domain of the human ether-a-gogo-related gene potassium channel (HERG; ref. 23). Notably, HERG contains no cofactor but retains the protein fold characteristic of PAS domains.…”

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confidence: 99%