title: Enhancement of hERG channel activity by scFv antibody fragments targeted to the PAS domain.
abstract: The human human ether-à-go-go-related gene (hERG) potassium channel plays a critical role in the repolarization of the cardiac action potential. Changes in hERG channel function underlie long QT syndrome (LQTS) and are associated with cardiac arrhythmias and sudden death. A striking feature of this channel and KCNH channels in general is the presence of an N-terminal Per-Arnt-Sim (PAS) domain. In other proteins, PAS domains bind ligands and modulate effector domains. However, the PAS domains of KCNH channels are orphan receptors. We have uncovered a family of positive modulators of hERG that specifically bind to the PAS domain. We generated two single-chain variable fragments (scFvs) that recognize different epitopes on the PAS domain. Both antibodies increase the rate of deactivation but have different effects on channel activation and inactivation. Importantly, we show that both antibodies, on binding to the PAS domain, increase the total amount of current that permeates the channel during a ventricular action potential and significantly reduce the action potential duration recorded in human cardiomyocytes. Overall, these molecules constitute a previously unidentified class of positive modulators and establish that allosteric modulation of hERG channel function through ligand binding to the PAS domain can be attained.
authors: Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal;
authors: Carol A
authors: CA
authors: Harley
authors: Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705.
authors: Greg
authors: G
authors: Starek
authors: Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705.
authors: David K
authors: DK
authors: Jones
authors: Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal;
authors: Andreia S
authors: AS
authors: Fernandes
authors: Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705 garobert@wisc.edu jcabral@ibmc.up.pt.
authors: Gail A
authors: GA
authors: Robertson
authors: Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal; garobert@wisc.edu jcabral@ibmc.up.pt.
authors: João H
authors: JH
authors: Morais-Cabral
mesh_terms: D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D002645:Chickens; D004558:Electric Stimulation / Q000379:methods; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D057127:Single-Chain Antibodies / Q000276:immunology / Q000494:pharmacology*
chemical_list: D000939:Epitopes; D051638:Ether-A-Go-Go Potassium Channels; D057127:Single-Chain Antibodies
keywords: KCNH; PAS domain; hERG; potassium channel; scFv