Discovering novel subtype-selective glutamate receptor antagonists for the study of hippocampal synaptic plasticity

Lead Research Organisation: University of Bristol
Department Name: Physiology and Pharmacology

Abstract

The main aim of this work is to design and synthesize new chemical substances to be used as tools to investigate the fundamental mechanism of learning and memory. This research may lead to new treatments for disorders that involve cognitive dysfunction, such as schizophrenia, Alzheimer’s and Parkinson’s disease.
Communication between one nerve cell (neuron) and others in the brain is effected at the junctions (synapses). One of the main mechanisms by which one cell in a neuronal chain communicates with the next cell is by releasing an amino acid, glutamate from its multiple synaptic endings. We have helped establish that glutamate can interact with a family of structurally related proteins known as glutamate receptor subtypes each performing different functions in the central nervous system (CNS).
Whereas glutamate activates all the subtypes of glutamate receptor, we aim to produce tools that block the activation of only one subtype of receptor. By observing what effect specific activation or blockade of a particular glutamate receptor subtype has on the functioning of the CNS, one can deduce the particular role of that receptor subtype in the integrated pattern of nervous activity that underlies learning and memory.

Technical Summary

NMDA receptors (NMDARs) are ligand gated ion channels that belong to the glutamate receptor (GluR) family and are expressed throughout the central nervous system (CNS). NMDARS are tetrameric assemblies of NR1, NR2A-D and NR3A and NR3B subunits. NMDARs have been identified as key players in synaptic plasticity and CNS disorders. However, the roles the different NMDAR subunits play in synaptic plasticity in the hippocampus are poorly understood. A related family of GluRs, the metabotropic glutamate receptors (mGluRs), play a modulatory role in CNS function. Of particular interest are subtypes of group III mGluRs (mGluR7 and 8) as these are known to be expressed in the hippocampus and play a role in synaptic plasticity in this brain region. However, the lack of pharmacological tools that are capable of distinguishing between the various types of NMDAR subunits or the subtypes of mGluRs is hampering our understanding of the functions of NMDARs and mGluRs in synaptic plasticity in the hippocampus. We plan to develop antagonists that are selective for mGluR7, mGluR8, NR2A, NR2B and NR3A. Two interrelated approaches will be adopted to develop isoform specific antagonists, 1) rational drug design based on known structure-activity data combined with the use of X-ray crystal structures and homology models to target unique amino acid residues in the binding site of the protein of interest and 2) validation of hypotheses generated in modelling studies by testing compounds on appropriate point mutations of the protein target. Once mGluR7 and mGluR8 selective antagonists have been identified, we will use them, in conjunction with knockout mice, to elucidate the roles of mGluR7 and mGluR8 in hippocampal synaptic plasticity. The roles of NR2A and NR2B in long-term potentiation (LTP) and long-term depression (LTD) are controversial, largely due to the lack of suitably selective pharmacological tools. The NR2A and NR2B selective antagonists developed here will be used to probe the roles of these subunits in hippocampal synaptic function. Very little is known about the functions of NR3 subunits in LTP and LTD. We will therefore use selective antagonists to investigate plasticity at CA3-CA1 synapses where the NR3 subunit is expressed in young animals. We also plan to develop biotin-conjugated photoaffinity ligands and fluorescently labelled compounds based on the isoform specific antagonists identified during this project. These will be used to investigate the molecular organisation, developmental regulation, regional, cellular and subcellular distribution and trafficking of the native NMDARs and mGluRs.

Publications

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Amici M (2009) Neuronal calcium sensors and synaptic plasticity. in Biochemical Society transactions

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Collingridge GL (2013) The NMDA receptor as a target for cognitive enhancement. in Neuropharmacology

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Collingridge GL (2017) Antidepressant Actions of Ketamine Versus Hydroxynorketamine. in Biological psychiatry

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Costa BM (2010) A novel family of negative and positive allosteric modulators of NMDA receptors. in The Journal of pharmacology and experimental therapeutics

 
Description Elucidation of the role of kainate receptor subtypes in hippocampal synaptic function using novel pharmacological tools
Amount £694 (GBP)
Funding ID BB/F012519/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 03/2008 
End 02/2011
 
Description Project grant. Development and pharmacology of positive allosteric modulators of NMDA receptiors
Amount $1,821,280 (USD)
Funding ID 2R01MH060252-09A1 
Organisation National Institutes of Health (NIH) 
Department National Institute of Mental Health (NIMH)
Sector Public
Country United States
Start 04/2013 
End 12/2017
 
Description Research Grant, Responsive Mode. Development of biotin-tagged affinity ligands and fluorophore-conjugated probes for the study of native kainate receptors
Amount £638,364 (GBP)
Funding ID BB/J015938/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 03/2013 
End 02/2016
 
Description Research Grant, Responsive Mode. Identifying role of NMDA receptors in STP
Amount £637,120 (GBP)
Funding ID BB/L001977/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 02/2014 
End 02/2017
 
Title ACET a GluK1 receptor antagonist 
Description The initial work leading to the development of a range of selective GluK1 (GluR5) kainate receptor antagonists such as UBP282, UBP296, UBP302, UBP304, UBP310 and ACET was funded by an MRC programme grant. 
Type Of Material Technology assay or reagent 
Year Produced 2009 
Provided To Others? Yes  
Impact Allowed some of the physiological roles of GluK1 (GluR5) containing kainate receptors to be identified including their role in hippocampal synaptic mechanisms and object recognition memory. Led to a collaboration with Eli Lilly and company on the development of kainate receptor antagonists and a consultancy position being set up with the company to advise on the development of KAR antagonists for clinical applications such as treatment of neuropathic pain and migraine. The initial work funded by the MRC led to further funding by the BBSRC (two 3 year project grants). Sold by Tocris Bioscience 
URL http://www.tocris.com/dispprod.php?ItemId=40541#.VFyxgfmsUaw
 
Title MDCPG 
Description An mGlu8 receptor selective antagonist 
Type Of Material Technology assay or reagent 
Year Produced 2012 
Provided To Others? Yes  
Impact Collaboration with Prof David Lodge and Prof Graham Collingridge resulted in two papers in Neuropharmacology. 
 
Title Subtype selective positive and negative allosteric modulators of NMDA receptors 
Description We have recently identified a range of novel compounds that bind to allosteric sites on the NMDA receptor. Some are positive allosteric modulators that interact seelctively with particular GluN2 subtypes. We have also identified negative allosteric modulators that interact selectively with GluN2C/GluN2D subunits 
Type Of Material Technology assay or reagent 
Year Produced 2010 
Provided To Others? Yes  
Impact The new compounds have only recently been identified but given their mode of action and subtype selectivity they are likely to have a large impact on the glutamate receptor field and we have already had interest from a number of drug companies. We have published a paper in JPET. 
 
Title UBP161, a dual antagonist of GluK1 and NMDA receptors 
Description UBP161 is an antagonist that is selective for GluK1 in the kainate receptor family but also has antagonist activity at NMDA receptors. 
Type Of Material Technology assay or reagent 
Year Produced 2012 
Provided To Others? Yes  
Impact We have recently reported that UBP161 showed antinociceptive effects in an animal model of mild nerve injury. 
 
Title UBP608 
Description Negative allosteric modulator of the NMDA receptor 
Type Of Material Technology assay or reagent 
Year Produced 2012 
Provided To Others? Yes  
Impact Resulted in a publication in Neurochemistry International. Now sold by the neurochemical company Sigma Aldrich. 
URL http://www.sigmaaldrich.com/catalog/product/sigma/sml0606?lang=en®ion=GB
 
Title UBP714 
Description Positive allosteric modulator of the NMDA receptor 
Type Of Material Technology assay or reagent 
Year Produced 2012 
Provided To Others? Yes  
Impact Resulted in a publication in Neurochemistry International. UBP714 is now sold by the neurochemical company Sigma Aldrich 
URL http://www.sigmaaldrich.com/catalog/product/sigma/sml0718?lang=en®ion=GB
 
Title [3H]UBP310 new radioligand for GluK1 kainate receptors 
Description new radiolabelled form of UBP310 a selective GluK1/GluK3 kainate receptor antagonist 
Type Of Material Technology assay or reagent 
Year Produced 2009 
Provided To Others? Yes  
Impact Paper published in Molecular Pharmacology 
 
Description Discovery of novel NR2A/NR2B selective antagonists 
Organisation Eli Lilly & Company Ltd
Country United Kingdom 
Sector Private 
PI Contribution I have provided medicinal chemsitry expertise to develop targets for NR2A and NR2B antagonists. I have also co-supervised the postdoctoral chemsit at Eli Lilly. I participate in twice yearly meetings of the CCN at Eli Lilly. A postdoc is funded 50% of time to test compounds on NMDA receptor subtypes.
Collaborator Contribution Eli Lilly have appointed a postdoctoral chemist to work at their site at Erl Wood, Surrey, engaged on the synthesis of NR2A/NR2B antagonists to support the synthetic chemistry effort at Bristol. Once selective antagonists have been identified they will be fed into projects in the MRC centre of Synaptic Plasticity. I am also part of the Centre for Cognitive Neuroscience (CCN) set up by Eli Lilly and compounds generated as a result of our collaboration will also be fed into projects within the CCN.
Impact As part of a multidisciplinary project involving chemistry, pharmacology and neuroscience, Eli Lilly have contributred a postdoctoral chemist to work for 3 years on the synthesis of NR2A/NR2B selective antagonists. This will complement the synthetic effort at Bristol. Eli Lilly have funded a researcher for 50% of the time to test compounds synthesised at Lilly and will also pay for running costs for the pharmacological screening. As mentioned elsewhere Eli Lilly have appointed a postdoctoral chemist to work at their site at Erl Wood, Surrey, engaged on the synthesis of NR2A/NR2B antagonists to support the synthetic chemistry effort at Bristol. Once selective antagonists have been identified they will be fed into projects in the MRC centre of Synaptic Plasticity. I am also part of the Centre for Cognitive Neuroscience (CCN) set up by Eli Lilly and compounds generated as a result of our collaboration will also be fed into projects within the CCN.
Start Year 2007
 
Description International conference on glutamate receptors 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talked sparked lively discussion and opened up the possibility of new collaborations with scientists in the audience.

No notable impacts
Year(s) Of Engagement Activity 2014
URL http://conferences-on-aminoacidergic-transmission.eu/index.php/conference-2014
 
Description School Visit 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Type Of Presentation Workshop Facilitator
Geographic Reach Local
Primary Audience Schools
Results and Impact Two school pupils per year visited my laboratory and shadowed research workers in my laboratory to gain an insight into the research carried out in my group. This included interactive demonstrations of computer-aided drug design, how drugs are synthesised by chemists, how they are evaluated pharmacologically and then tested in a model of synaptic plasticity.

The pupils gave the visit a high rating and are now thinking of choosing a science based subject to study at university.
Year(s) Of Engagement Activity 2008,2009,2010,2011,2012
 
Description lecture and interactive tutorial 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Type Of Presentation Workshop Facilitator
Geographic Reach Local
Primary Audience Schools
Results and Impact Gave a lecture and interactive computer-based tutorial entitled "drugs as molecules" for local school children. The lecture included an explanation of my research activities and their possible implications for the treatment of neurological disorders.

Impact of visit not assessed
Year(s) Of Engagement Activity 2006,2007,2008