The Structural Mechanism of K2P Channel Gating

Lead Research Organisation: University of Kent
Department Name: Medway School of Pharmacy

Abstract

Almost every single process in the human body is controlled at some level by electrical signals, from the way our hearts beat, the way our muscles move, to the way we think. These electrical signals are generated and controlled by ion channels which act as electrical 'switches' to control the selective movement of charged ions like potassium (K+) and sodium (Na+) into and out of the cell. They therefore play a fundamentally important role in normal cellular function and their dysfunction is known to result in a wide variety of disease states. The 'Two-Pore' or 'K2P' channels are a major subfamily of potassium channels found in many different tissues throughout the human body and are involved in many important physiological processes, in particular the control of electrical activity in nerve cells. However, in marked contrast to many other types of K+ ion channel, the molecular mechanisms which control K2P channel function and their 3D structure are still poorly understood. In an attempt to tackle this problem we have recently identified a range of high-affinity drugs which can be used as molecular tools to probe the structure of the K2P channel and the mechanisms by which they open and close. We have also identified an important difference between two particular K2P channels (TREK and TRESK) which now provides us with a fresh insight into how these channels function and why their gating mechanism is different to other types of K+ channel. In the proposed study we aim to exploit these exciting new findings and to use these molecular tools to investigate the structural mechanism of K2P channel gating. The proposed industrial partnership with Pfizer also provides us with access to a variety of chemical tools, expertise and resources that are not normally available in an academic environment and which place us in a unique position to be able to pursue these goals.

Technical Summary

Two-pore-domain potassium (K2P) channels comprise a major and structurally distinct subset of the mammalian K+ channel superfamily, and underlie the background, or leak, currents that regulate the resting membrane potential and excitability of many mammalian cells. However, in contrast to many other classes of K+ channel, relatively little is known about the structural mechanisms of K2P channel gating. In particular it is unclear how different regulatory stimuli open the channel pore - do they open the channel at the helix bundle crossing or modify the proposed 'inactivation gate' at the selectivity filter? Also, it is unknown how these two gates are affected by the binding of different activatory ligands. We have recently identified a range of pharmacological tools which can be used to probe the structure and gating mechanism of the K2P channel pore. Using these tools our initial studies of TREK-1 indicate that the primary gating mechanism resides close to or within the selectivity filter and does not involve closure of the channel at the helix bundle crossing. We have also obtained evidence which indicates that a structural and functional asymmetry exists within the K2P channel pore, and that fundamental differences between the role of the pore-lining helices in TREK-1 and TRESK gating will provide an important insight into how the binding of regulatory ligands affects channel activity. This proposal aims to exploit these recent advances in order to probe the fundamental molecular mechanisms of K2P channel gating. To help with achieving these objectives the project involves an industrial partnership with Pfizer which provides unique access to a wide range of resources, expertise and new molecular tools.

Planned Impact

The proposed study aims to enhance our basic knowledge of how an important class of ion channels function at the molecular level, and although the project is science-led and driven by a curiosity to understand the structural basis of K+ channel gating, the long-term potential impact of this work is significant. K2P channels are involved in many important physiological process and the future design of any novel therapeutic strategies to target these channels ultimately relies upon a fundamental understanding of the intimate relationship between their structure and their functional properties. In particular the TREK and TRESK K2P channels are now known to be involved in a variety of pain sensation pathways. They therefore represent potentially important and novel therapeutic targets for the treatment of pain. The social and economic impact of potential new developments in this area is therefore wide-ranging and will have obvious and long-lasting implications. In addition, the proposed study will not only help to raise the overall profile of industrially-sponsored basic academic research in the UK, but also establish a new academic collaboration between the two principal applicants. Other potential stakeholders include academic and industrial research groups who will benefit from the tools and reagents developed as part of this study. Closer to home, the PDRAs employed on this grant will also receive training in new areas to enhance their career development, and the project will provide an excellent training environment for research students at the University of Oxford and the Medway School of Pharmacy. This project would therefore represent a strategic investment in UK bioscience.

Publications

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Mathie A (2015) Two-pore domain potassium channels: potential therapeutic targets for the treatment of pain. in Pflugers Archiv : European journal of physiology

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Mondejar-Parreño G (2018) HIV transgene expression impairs K channel function in the pulmonary vasculature. in American journal of physiology. Lung cellular and molecular physiology

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Olschewski A (2017) TASK-1 (KCNK3) channels in the lung: from cell biology to clinical implications. in The European respiratory journal

 
Description 1. We have shown that pharmacological enhancement of mutated TASK3 channel current during development may provide a potentially useful therapeutic strategy in the treatment of KCNK9 imprinting syndrome.

2. We have provided insight into the mechanism of TREK1 channel activation by fenamates, and, given the role of TREK1 channels in pain, these results suggest a novel analgesic mechanism for these compounds.

3. We have shown that the Aristolochic acid (AristA), the active ingredient in a number of herbal remedies causes enhancement of TREK1 and TREK2 potassium channels and inhibition of TRESK. This may contribute to therapeutically useful effects of this compound in pain.

4. Whilst AristA is unlikely to interact directly with TASK2 channels in Balkan Endemic Neuropathy, loss of functional TASK2 channels may indirectly increase susceptibility to AristA toxicity.
Exploitation Route Potential new therapies for the treatment of neuropathic pain and KCNK9 imprinting syndrome
Sectors Healthcare,Pharmaceuticals and Medical Biotechnology

 
Description Our work on the identification of novel potassium channel activators and description of their mechanism of action (e.g. Veale et al 2014a,b) has influenced the research direction of two different pharmaceutical companies (Pfizer and MRC Technology) seeking to identify novel therapeutic agents for the treatment of pain. Both have invested resources in their research as a direct result of this work. Also as a direct result of this work, one activator has been adopted in a trial in the USA for use in the treatment of "KCNK9 imprinting syndrome", a disease resulting from the mutation of the potassium channel, TASK3.
First Year Of Impact 2015
Sector Healthcare,Pharmaceuticals and Medical Biotechnology
Impact Types Societal

 
Description Royal Society Industry Fellowship
Amount £158,000 (GBP)
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom
Start 11/2009 
End 10/2013
 
Title Mutations of ion channels which alter function 
Description As above! 
Type Of Material Model of mechanisms or symptoms - in vitro 
Year Produced 2006 
Provided To Others? Yes  
Impact Research outputs from other groups. Formation of collaborative links 
 
Description Kent Giessen Collaboration 
Organisation Justus Liebig University Giessen
Country Germany 
Sector Academic/University 
PI Contribution A collaborative agreement between colleagues at the University of Kent, United Kingdom (Professor Ghazwan Butrous, Professor Alistair Mathie) and at the University of Giessen, Germany (Professor Ralph Schermuly, Professor Norbert Weissmann) and their associated research groups, in order to achieve the four aims listed below. This will be a long-term strategic collaboration between colleagues at the University of Giessen and the University of Kent. The initial agreement will be for three years, from 1st October 2014, after which it will be reviewed and renewed according to need and value. Aims of the proposed collaboration 1) Foster scientific collaboration and promote collaborative projects which are mutually beneficial to the participants. 2) Promote joint research conferences and/or workshops 3) Facilitate joint applications to research and enterprise funding opportunities 4) Provide opportunities for exchange of personnel, scientific and technical information, equipment and software.
Collaborator Contribution Professors Schermuly and Weissmann in Giessen are part of the "Excellence Cluster Cardio-Pulmonary System", a world leading research group working on the cardio-pulmonary system funded by the German Federal Ministry of Education and Research. In Kent, Professor Butrous is a world expert in pulmonary hypertension and Professor Mathie's group brings internationally recognized expertise in the study of ion channels and their regulation. Collaborators from both Giessen and UOK are founders of the pulmonary vascular research institute which has world-wide links (www.pvri.info/). The combined and complementary expertise of the two groups should afford the collaboration a unique opportunity to address a range of important questions in cardiopulmonary medicine and related fields. Together, we have already established an experimental laboratory located at the Medway campus (Medway School of Pharmacy) of the University of Kent with financial support from the University of Giessen. This has already led to research outputs arising from the collaboration (Kolosionek et al 2013, Pulm Circ 3, 356-362; Pullamsetti et al 2012, Arterioscler Thromb Vasc Biol 32, 1354-1365). Initial Collaboration Initial collaborative plans will be based around joint research activities. Three potential initial areas of collaboration are identified. Arrangements for future initiatives around joint research conferences, funding applications and PhD studentships will be put in place by the end of 2014.
Impact None as yet.
Start Year 2014
 
Description Pfizer Pain collaboration 
Organisation Pfizer Ltd
Department Neusentis Pfizer
Country United Kingdom 
Sector Private 
PI Contribution Collaborative project to develop novel compounds useful in the treatment of pain that target ion channels.
Collaborator Contribution Provision of compounds and intellectual property around research
Impact Publications in 2014.
Start Year 2009