Human ether a go-go-related gene 1a (HERG1a, Kv11.1) K+ channels play a critical role in maintaining the fundamental cardiac rhythm. The significance of HERG1a channels is that they are the central component of the rapid delayed-rectifier K+ channel (IKr) in heart. HERG and IKr are specialized to conduct an outward K+ current that drives repolarization of the late phase of the cardiac action potential. The critical role of HERG1a in health and disease is emphasized by inherited mutations in the gene encoding HERG channels. Mutations in HERG are associated with the long QT syndrome (LQTS) a cardiac disorder that causes arrhythmia, syncope and sudden death. HERG channels are of additional significance as a side-effect of an increasing number of pharmaceuticals is to produce an acquired form of LQTS (aLQTS) by inhibiting the function of HERG channels. The opening and closing (gating) of HERG and IKr channels are critical for normal cardiac electrophysiology and the normal heartbeat. In particular, the closing rate of native IKr channels is vital for the perfect timing of the outward IKr current during repolarization. Some advances, including our previous work, have delineated key molecular components of the channel closing (deactivation) mechanism, including two critical domains within the HERG1a N-terminal region. These are the `PAS'domain and a short region upstream here termed the PAS-CAP. Diversity in the mechanism of deactivation comes from a HERG1a variant, HERG1b that lacks the key PAS and PAS-CAP domains and consequently closes much faster than HERG1a. The presence of HERG1b in heart may explain the faster kinetics of deactivation measured for IKr. Despite these advances, a mechanism for channel deactivation has remained elusive. The goals of the proposed experiments are to determine a comprehensive molecular mechanism for closing in HERG and IKr.
The Specific Aims are to 1) test the hypothesis that the PAS-CAP region determines deactivation gating via an electrostatic interaction with the channel 2) to test the hypothesis that the hydrophobic surface of the PAS domain interacts with a hydrophobic `PAS receptor site'in the channel to mediate deactivation and 3) to test the hypothesis that the HERG1b subunit is a key functional component of native IKr and that ERG1b accounts for the faster kinetics described for native IKr. To carry out the specific aims we will use a multidisciplinary approach that includes patch-clamp and voltage-clamp electrophysiology in heterologous expression systems and native cells, fluorescence spectroscopy, gene transfer to myocytes and native cell culture techniques. Our long-term objectives are to determine the fundamental molecular basis of gating and modulation in cardiac IKr channels, in an effort to better treat inherited LQTS and prevent acquired LQTS.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Electrical Signaling, Ion Transport, and Arrhythmias Study Section (ESTA)
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Krull, Holly
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University of Maryland Baltimore
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United States
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Brelidze, Tinatin I; Gianulis, Elena C; DiMaio, Frank et al. (2013) Structure of the C-terminal region of an ERG channel and functional implications. Proc Natl Acad Sci U S A 110:11648-53
Gustina, Ahleah S; Trudeau, Matthew C (2013) The eag domain regulates hERG channel inactivation gating via a direct interaction. J Gen Physiol 141:229-41
Gianulis, Elena C; Liu, Qiangni; Trudeau, Matthew C (2013) Direct interaction of eag domains and cyclic nucleotide-binding homology domains regulate deactivation gating in hERG channels. J Gen Physiol 142:351-66
Trudeau, Matthew C; Leung, Lisa M; Roti, Elon Roti et al. (2011) hERG1a N-terminal eag domain-containing polypeptides regulate homomeric hERG1b and heteromeric hERG1a/hERG1b channels: a possible mechanism for long QT syndrome. J Gen Physiol 138:581-92
Gianulis, Elena C; Trudeau, Matthew C (2011) Rescue of aberrant gating by a genetically encoded PAS (Per-Arnt-Sim) domain in several long QT syndrome mutant human ether-รก-go-go-related gene potassium channels. J Biol Chem 286:22160-9
Gustina, Ahleah S; Trudeau, Matthew C (2011) hERG potassium channel gating is mediated by N- and C-terminal region interactions. J Gen Physiol 137:315-25