Neurosteroids and GABA-A receptors and their roles in neuropsychiatric disorders

Lead Research Organisation: University College London
Department Name: Neuroscience Physiology and Pharmacology

Abstract

The brain receives and sorts information by individual nerve cells communicating with each other using a process known as chemical neurotransmission. This involves networks of cells becoming broadly excited or inhibited to control key aspects of mental function such as memory and the overall behaviour of individuals. The basis for this is the release of chemicals (neurotransmitters) from one nerve cell that binds to specific protein receptors on another, to cause excitation or inhibition. One major neurotransmitter in the brain is GABA. It is responsible for dampening nerve cell excitation by causing inhibition - it does this by interacting with a class of receptors known as GABA-A receptors (GABA-ARs). Most nerve cells in the brain will possess GABAARs underlining the pivotal role that they play in fundamental aspects of brain function including the following examples of - cognition, memory, sleep, sensation, control of muscle movement and response to stress. Indeed, so important are these receptors that their dysfunction is directly implicated in numerous and serious neurological and mental health disorders, such as anxiety and depression, epilepsy, schizophrenia, pain, substance addiction, autism, Down's and Fragile-X syndromes, to name only a few. As a consequence, GABAARs are widely recognised as molecular targets for therapeutic drug classes that include the benzodiazepines (BDZs) and general anaesthetics.

Of equal significance, GABA-ARs are also subject to regulation by a number of endogenous agents in the brain. Prime amongst these are the neurosteroids, which are released from cells and can potentiate GABA-AR function at very low concentrations. Dysfunctional neurosteroid production is also implicated in neurological diseases, such as anxiety and depression, pain and catamenial epilepsy, and this is thought to involve altered GABA-AR function. It is therefore critical to understand how neurosteroids regulate GABA-ARs, what neural circuits are involved, how this contributes to disease, and how neurosteroids may be used as therapeutic agents. Our recent breakthrough in identifying the molecular basis for neurosteroid binding sites on GABA-ARs enables us to address these questions and determine precisely which types of GABA-ARs are involved in particular actions of the neurosteroids.

Our aims are to use a combination of techniques, some involving genetic engineering, to determine how neurosteroids regulate selected GABA-ARs and to broaden our understanding of neuropsychiatric disease when neurosteroid regulation becomes dysfunctional. We will use the neurosteroid modulatory site on GABA-ARs to facilitate the development of novel therapeutics for the treatment of neurological disorders. Our aim is to improve understanding of mechanisms that may precipitate mental illness and to provide new approaches to its prevention and treatment.

Specifically, we have four goals - (i) to examine what actions of the neurosteroids are mediated by a specific isoform of the GABA-AR that is involved in mediating anxiety and pain; (ii) to understand how modification of GABA-ARs by naturally-occurring enzymes in the brain affects neurosteroid modulation; (iii) to probe these interactions with neurosteroids at another important GABA-AR that is involved in dampening excitation and is implicated in substance addiction; and (iv) to examine how we can develop new neurosteroid agents for therapeutic benefit.

The outcomes from our programme of work will have many implications. Chiefly, it will provide much needed information on the basis by which neurosteroids work in the brain, how they regulate GABA-ARs under physiological conditions and what happens during dysfunction to precipitate disease. By exploring the neurosteroid binding site, we now have for the first time, an opportunity to provide new impetus for the treatment of neurological diseases.

Technical Summary

We will examine how neurosteroids exert their effects via specific GABA-AR isoforms and the consequences for neuropsychiatric disease when this becomes dysfunctional. Our aim is to better understand some of the mechanisms that precipitate mental illness and to provide new approaches for its prevention and treatment by exploiting our knowledge of the neurosteroid modulatory site on GABA-ARs. A combination of cellular, molecular and genetic techniques will examine the roles of neurosteroids using recombinant GABA-ARs in expression systems and native GABA-ARs in cell cultures or brain slices.

Whole-cell patch clamp recording methods will measure GABA synaptic and tonic inhibition and associated kinetic parameters. Biochemical (Western blots, phosphorylation) and immunocytochemical techniques (antibody labelling, phosphorylation-specific antibodies, Tirf microscopy) will measure changes to GABA-AR composition, and single particle tracking with quantum dots and the bungarotoxin binding site will monitor GABA-AR mobility. New transgenic animals will help to explore the interactions between GABA-AR phosphorylation and neurosteroid modulation with regard to synaptic and tonic inhibition.

Behavioural techniques will examine how neurosteroids affect intact brain function and the consequences that follow when this becomes dysfunctional. We will use structure-function approaches to probe the neurosteroid binding site and transplant it into other receptors to gain valuable information on key structural determinants. We will design (collab. with UCL Chemistry and Industry) new neurosteroid molecules that could be therapeutically beneficial by targeting specific isoforms of the GABA-AR.

Our research programme will contribute to our understanding of brain function. It will help us to understand how neurological diseases can be precipitated by dysfunctional neurosteroid signalling, as well as providing new insight into novel therapeutic strategies for mental health.

Planned Impact

For Academic, Economic and Societal Impact, our proposed programme is likely to have broad-ranging effects on several groups. These include academics, and in the longer-term, healthcare professionals associated with mental health. We also expect the general/lay public who are directly or indirectly affected by poor mental health to benefit, as well as pharmaceutical companies concerned with drug development for mental health disorders.

Academics will gain valuable insight into precisely how neurosteroids function in the brain as well as achieving a better understanding of their role in mental illness. We will engender Capacity Building Impact by training new generations of scientists to use innovative technologies and methods, as well as providing clinicians with potentially new therapeutic targets for treating mental illness. Our previous collaborative studies of inhibitory synaptic transmission provide direct evidence of translation relevant to inherited neurological disorders by providing molecular diagnostics and potential therapeutic remedies (Rees et al 2006, Nature Genet 38, 801-806). In the longer term, we predict our programme has the potential to lead to improved quality of life for patients, family members, carers and indeed medical staff.

Our research programme is designed to enable a greater understanding of brain function by providing new knowledge regarding GABA-mediated synaptic and tonic inhibition and how modulation by neurosteroids can cause and affect neuropsychiatric disease. These findings are expected to be at least partly-translated across scientific disciplines during the time-course of the programme. We will ensure promulgation of our findings by presentations at major international conferences, by engaging in invited lectures in the UK and abroad to scientific and lay audiences, by publishing in internationally-recognised high quality scientific journals, and by engaging with national/international press, television and radio as appropriate.

If patentable results arise from our research programme, and this is potentially likely, UCL has excellent support structures to enable us to proceed and exploit our discoveries. Indeed, with regard to the discovery of neurosteroid binding sites, a patent has been issued with a view to encouraging interactions with the pharmaceutical industry.

In the longer term, understanding how neurosteroids and GABA receptors contribute to neurological disease could improve our identification of new components involved in disease pathology. This is particularly relevant for an ageing population where the prevalence of neural diseases is projected to increase and is in urgent need of new therapeutic initiatives.

Publications

10 25 50
 
Description Dept of Health - future of mental health over the next 10 years
Geographic Reach Europe 
Policy Influence Type Participation in a advisory committee
Impact Committee set out the problems in mental health and how best to address them over the next 10 years. Report sent to Dept of Health
 
Description Psychoactive drugs
Geographic Reach National 
Policy Influence Type Implementation circular/rapid advice/letter to e.g. Ministry of Health
 
Description ALERT grant
Amount £500,000 (GBP)
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 04/2015 
End 03/2018
 
Description PhD studentship
Amount £60,000 (GBP)
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2015 
End 09/2018
 
Description Project grant
Amount £300,000 (GBP)
Organisation The Leverhulme Trust 
Sector Academic/University
Country United Kingdom
Start 03/2014 
End 02/2017
 
Title Azobenzene GABA receptor ligands 
Description New GABA receptor antagonists made incorporating an azobenzene moiety to enable light control of activity 
Type Of Material Technology assay or reagent 
Provided To Others? No  
Impact We are able to inhibit selected GABA receptors using light alone in conjunction with the new chemical compounds 
 
Title New GABA receptor chimera 
Description Designed and created a novel form of GABA receptor chimera composed of the extracellular domain of the GLIC channel and the transmembrane domains of the alpha1 subunit from a GABA-A receptor. 
Type Of Material Biological samples 
Year Produced 2017 
Provided To Others? Yes  
Impact Enabled us to succeed in crystallising part of the GABA-A receptor 
 
Description Down's syndrome and cognition 
Organisation University College London
Department Institute of Neurology
Country United Kingdom 
Sector Academic/University 
PI Contribution Advising on the use of GABA atnagonists to improve cognition
Collaborator Contribution Access to chemical leads and clinical trials design
Impact Analysing the strategy of treating Down's syndrome patients with GABA antagonists
Start Year 2013
 
Description Homology modelling of ligand-gated ion channels 
Organisation Birkbeck, University of London
Country United Kingdom 
Sector Academic/University 
PI Contribution Provision of parts of GABA receptor structure, including information on those components necessarily deleted from the structure to improve the probability of crystallisation.
Collaborator Contribution Used homology modelling methods to compete the receptor structure, by including those parts of the structure previously deleted
Impact Fedele et al 2018 Nature Communications, in press
Start Year 2015
 
Description Light-modulated nanotweezers for activating ligand-gated ion channels 
Organisation University College London
Department Department of Chemistry
Country United Kingdom 
Sector Academic/University 
PI Contribution Designed a new chemical entity that when bound to two cysteine residues at a critical part of a receptor protein, is capable of activating the receptor by changing the conformation of the chemical using light.
Collaborator Contribution Synthesis of the new chemical entity based on an azobenezene light sensitive module
Impact Mortensen et al 2014 Photoantagonism of the GABA-A receptor Nature communications DOI: 10.1038/ncomms5454 Mortensen & Smart 2016 Neuronal inhibition in the spotlight. Neuron 88, 845-847
Start Year 2014
 
Description Molecular dynamics simulations 
Organisation University of Oxford
Country United Kingdom 
Sector Academic/University 
PI Contribution We provided structures of GABA receptors using x-ray crystallographic procedures of novel GABA receptor chimeras,
Collaborator Contribution Our partners provided expertise in molecular dynamics simulations enabling the docking of modulatory ligands, eg neurosteroids, into the newly discovered binding sites resulting from our structural studies.
Impact Laverty,Duncan; Thomas,Philip; Field,Martin; Andersen,Ole J.; Gold,Matthew G.; Biggin,Philip C.; Gielen,Marc & Smart,Trevor G. 2017 Crystal structures of a GABAA-receptor chimera reveal new endogenous neurosteroid-binding sites Nature Structural & Molecular Biology 24, 977-985.
Start Year 2016
 
Description Photo-chemical labelling of the GABA receptor 
Organisation University College London
Department Department of Chemistry
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaboration with UCL Chmiestry in the design of photo-active ligands for the GABA-A receptor
Collaborator Contribution Design of novel photochemical ligands
Impact Paper submitted
Start Year 2013
 
Description Variable new antigen receptors for delivering drugs 
Organisation Ossianix
Country United Kingdom 
Sector Private 
PI Contribution We have provided the IP, the idea for targeting drugs to specific GABAA receptors using single strand antibodies.
Collaborator Contribution Ossianix will help us to immunise sharks for producing variable new antigen receptors (VNARS) and in the process of selecting those VNARS that target our specified GABA-A receptors. UCL Chemistry - colleagues here are assisting us in linking drug molecules to the VNARs.
Impact None so far
Start Year 2016
 
Title Partial agonist for absence epilepsy 
Description MRC funded work, currently trying to devise a method for enabling this drug to pass through the blood brain barrier 
Type Therapeutic Intervention - Drug
Current Stage Of Development Refinement. Non-clinical
Year Development Stage Completed 2015
Development Status Actively seeking support
Impact Development process clearly indicates this is a potentially viable route for the treatment of absence epilepsy. 
 
Title Photoactive chemical probes 
Description Photoactive compounds capable of irreversibly modifying the function of GABA receptors 
Type Therapeutic Intervention - Drug
Current Stage Of Development Initial development
Year Development Stage Completed 2015
Development Status Under active development/distribution
Impact Potential appication in epilepsy and cognition. Compounds allow tracking of natvie GABA receptors in real time. 
 
Description 24th Neuropharmacology conference on GABAergic signalling in health and disease 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Major international conference on GABA signalling in the brain. Report to a scientific international conference at Washington DC.
Year(s) Of Engagement Activity 2014
 
Description A mechanism for desensitisation 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact MAC 2015 Conference, Bonn. Role of GABAA receptors in anaesthetic action.
Year(s) Of Engagement Activity 2015
 
Description Allo- and Orthosteric modulation of GABA receptors 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Seminar to Univ. Copenhagen. Faculty of Health and Medical Sciences
Year(s) Of Engagement Activity 2013
 
Description Allo- and genetic modulation of GABAA receptors 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact National University of Singapore. Plenary lecture. Allosteric and Genetic modulation of GABAA receptors.
Year(s) Of Engagement Activity 2015
 
Description Allosteric and Genetic modulation of GABAA receptors 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Kings College London. Wolfson Centre for Age-Related Diseases.
Year(s) Of Engagement Activity 2015
 
Description Allosteric and genetic modulation of GABA receptors 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Foster Club Cambridge. Dept of Physiology seminar
Year(s) Of Engagement Activity 2014
 
Description Bordeaux Neuroscience Federation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Lecture on plasticity of inhibitory synaptic neurotransmission.
Year(s) Of Engagement Activity 2015
 
Description British Pharmacological Society Winter meeting 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Symposium on glycinergic transmission: physiological, developmental and pathological implications
Year(s) Of Engagement Activity 2014
 
Description European Congress of Pharmacology 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Research seminar to the European Congress of Pharmacology
Year(s) Of Engagement Activity 2012
 
Description Exploring the neurosteroid binding site on GABAA receptors 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presentation to SAGE therapeutics in Boston MA
Year(s) Of Engagement Activity 2018
 
Description GABA receptors underlying tonic inhibition 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact MAC 2015 Conference, Bonn. Extrasynaptic GABAA receptors and general anaesthesia.
Year(s) Of Engagement Activity 2015
 
Description Gordon Researcjh Conference on Inhibtion in the Brain 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation of research to leading peers from around the world
Year(s) Of Engagement Activity 2015,2017
 
Description Humphrey Rang BPS 80th Symposium 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Lecture - Humphrey 50 yrs of drug use - receptors then and now.
Year(s) Of Engagement Activity 2016
 
Description Kings College London. Wolfson Centre for Age-Related Diseases. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Other audiences
Results and Impact Lecture - Allosteric and Genetic modulation of GABAA receptors
Year(s) Of Engagement Activity 2015
 
Description MAC 2015 Conference 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Role of GABAA receptors in anaesthetic action: A mechanism for GABA receptor desensitization
Year(s) Of Engagement Activity 2015
 
Description MAC 2015 Conference, Bonn 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Lecture - Extrasynaptic GABAA receptors and general anaesthesia. Which receptors produce tonic neuronal chloride currents?
Year(s) Of Engagement Activity 2015
 
Description Max Delbruck Centrum fur Molekulare Medizin - Lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Lecture on allosteric and genetic modulation of GABA-A receptors
Year(s) Of Engagement Activity 2014
 
Description Modulating GABA inhibition 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Research seminar to Center for Brain Research, Medical University Vienna, Austria
Year(s) Of Engagement Activity 2012
 
Description Molecular mechanisms of glycine receptor function 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact British Pharmacological Society Winter meeting, London. Symposium on Glycinergic transmission: Physiological, developmental and pathological implications.
Year(s) Of Engagement Activity 2014
 
Description National University of Singapore 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Lecture - Allosteric and Genetic modulation of GABAA receptors.
Year(s) Of Engagement Activity 2015
 
Description Neurological disease 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Demonstrating to school pupils the power of modern science techniques ion deciphering disease in the nervous system
Year(s) Of Engagement Activity 2018
 
Description Neurosteroids and GABAA receptors 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Research presentation at international meeting - Schaffhausen Switzerland
Year(s) Of Engagement Activity 2018
 
Description Probing regulatory mechanisms for GABA-A receptors 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact 24th. Neuropharmacology conference on GABAergic Signaling in Health and Disease, Washington DC.
Year(s) Of Engagement Activity 2014
 
Description Research presentation at Ion Channel Symposium, Cambridge University 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Discussion of recent research findings with peers in the field
Year(s) Of Engagement Activity 2017
 
Description Research seminar to University of Sussex 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Talking to a broad audience about inhibition in the brain, discussing concepts and ways to affect inhibition in the brain.
Year(s) Of Engagement Activity 2017
 
Description Revising the logic of GABA receptor modulation. Symposium. Royal Danish Academy of Science and Letters, Copenhagen. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Lecture - Regulating GABA inhibition: A role for post-translational modification.
Year(s) Of Engagement Activity 2016
 
Description School lecture on neurological disorders 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Debate in neurological disorders focused on epilepsy as a result of gene mutations
Year(s) Of Engagement Activity 2015,2018
 
Description Schools outreach lecture 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Lecture to 5th and 6th formers about neuroscience research, current methods and the big questions that need to be addressed.
Year(s) Of Engagement Activity 2018
 
Description Sunburst Brain Camp National University of Singapore. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Lay lecture - Feeling inhibited - is it good for our brains?
Year(s) Of Engagement Activity 2015