Molecular mechanisms and synaptic functions of kainate receptor SUMOylation
Lead Research Organisation:
University of Bristol
Department Name: Anatomy
Abstract
Efficient communication between neurones at synapses is required for proper brain function. This communication uses chemical transmitters and relies on the presence of receptor proteins at the synapse surface. A key feature of this system is that the number of receptors changes depending on the activity at the synapse. We have found that for one type of receptor called the kainate receptor, binding of the transmitter leads to attachment of a small protein called SUMO and this results in the receptor being removed from the surface into the cell (where it can no longer function) by a mechanism called endocytosis. Preventing SUMO attachment to kainate receptors blocks endocytosis. We go on to demonstrate that this process regulates communication between neurones. This is significant because kainate receptors regulate the general excitability of neurones and synaptic transmission and their dysfunction has been implicated in diseases such as epilepsy and Huntington's disease. In addition, we show that in addition to the receptor we have characterised, there are many other proteins present at synapses that undergo similar addition of SUMO. The aim of this proposal is to go on to work out some of the details of how this process works. Specifically we want to find out what change in the receptor allows it to bind SUMO and what molecular changes take place once the receptor is SUMOylated. We believe these experiments will have very important implications for understanding how synapses function. Furthermore, once we shed light on how kainate receptors are handled in normal cells we can then gain insight into what happens in injured or diseased cells and try to formulate strategies to compensate for or repair the problems.
Technical Summary
Kainate receptors (KARs) play crucial roles in the regulation of both excitatory and inhibitory neurotransmission. Their dysfunction has been proposed to underlie or contribute to many conditions that have a major impact on the quality and length of human life associated with profound economic and social consequences for society as a whole. Protein SUMOylation has important roles in the regulation of nuclear function. Far less well investigated are the targets and roles of SUMO modification outside the nucleus. In a paper in press at Nature, we have shown that SUMOylation of the GluR6a KAR subunit following agonist activation evokes kainate receptor endocytosis and modulation of synaptic transmission. The specific implications of our observations are that regulation of kainate receptors by SUMOylation will be involved in synaptic plasticity and neuronal excitability. In a wider context, our findings raise the prospect that protein SUMOylation, similar to other posttranslational modifications such as phosphorylation and ubiquitination, may be of fundamental importance in controlling the interactions and functions of synaptic target proteins. The aim of this proposal is to elucidate the upstream and downstream events and processes that lead to and result from GluR6 SUMOylation. We intend to explore the roles of phosphorylation as a potential trigger for SUMOylation and the effects SUMOylation has on PDZ interactions and protein complex formation. In addition, we aim to identify proteins specifically involved in the SUMOylation-dependent endocytic pathway and investigate the role of GluR6 SUMOylation in certain types of synaptic plasticity. We believe that these are novel and important issues that we are in a unique position to address.
Organisations
Publications
Anderson DB
(2017)
Sumoylation: Implications for Neurodegenerative Diseases.
in Advances in experimental medicine and biology
Berndt A
(2012)
Regulation of Neuronal Protein Trafficking and Translocation by SUMOylation.
in Biomolecules
Berndt A
(2013)
In vivo characterization of the properties of SUMO1-specific monobodies.
in The Biochemical journal
Binda CS
(2019)
Sorting nexin 27 rescues neuroligin 2 from lysosomal degradation to control inhibitory synapse number.
in The Biochemical journal
Carmichael R
(2018)
MEF2A regulates mGluR-dependent AMPA receptor trafficking independently of Arc/Arg3.1
in Scientific Reports
Carmichael RE
(2018)
Transcriptional and post-translational regulation of Arc in synaptic plasticity.
in Seminars in cell & developmental biology
Chamberlain SE
(2012)
SUMOylation and phosphorylation of GluK2 regulate kainate receptor trafficking and synaptic plasticity.
in Nature neuroscience
Craig TJ
(2015)
Fighting polyglutamine disease by wrestling with SUMO.
in The Journal of clinical investigation
Dias RB
(2018)
Erythropoietin Induces Homeostatic Plasticity at Hippocampal Synapses.
in Cerebral cortex (New York, N.Y. : 1991)
Evans AJ
(2017)
Assembly, Secretory Pathway Trafficking, and Surface Delivery of Kainate Receptors Is Regulated by Neuronal Activity.
in Cell reports
Description | In this project we have built on our previous data demonstrating the importance of ainate receptor SUMOylation and achieved significant advances towards understanding some of the key details underlying how the number of receptors at synapses change depending on the activity at that synapse. We have characterised the role of SUMO in the regulation of one type of receptor, the kainate receptor that is critical for normal brain function. We demonstrated that for these receptors SUMOylation is downstream of phosphorylation that occurs on agonist binding, indicating the complex orchestration of protein interactions and modifications that occurs at synapses. We went on to show that this regulatory cascade is essential for kainate receptor synaptic plasticity. In addition, we made good progress in uncovering other synaptic processes and systems that are regulated by SUMO. In particular, we show that functional expression of another critical receptor in the brain, the AMPA receptor, is indirectly regulated by SUMOylation and that overexpression of SENP1, an enzyme that deSUMOylates proteins, prevents homeostatic plasticity. Overall, we feel this grant has been extremely successful and allowed us to discover and publish important new findings about how SUMO is involved in synaptic protein trafficking. Our work has shed light on how kainate receptors are handled in normal cells and we have now extended this to investigate what happens in injured or diseased cells. In particular, we are using cell culture models of stroke to study how the SUMOylation systems and receptor trafficking processes in neurones respond to severe metabolic stress caused by oxygen and glucose deprivation. Although these experiments are ongoing they have already revealed important new insights into previously unsuspected processes involved in cell death and survival pathways. We anticipate that these data together with future studies may allow us to try to formulate strategies to attempt compensate for or repair SUMO dysfunction in damaged and diseased cells. At a fundamental level the BBSRC funding enabled us to provide core, detailed information as to how synapses work under normal, activated and stressed conditions. |
Exploitation Route | A large number of new reagents were generated during the course of this grant and these have been published and, when requested, disseminated to scientists worldwide. More specifically, we have made a series of loss and gain of function point mutations in GluK2 subunit to investigate the relationship between phosphorylation and SUMOylation of kainate receptors. In addition, we have constructed Sindbis virus vectors expression fluorophore tagged versions of these constructs for their efficient expression in dispersed cortical and hippocampal cell cultures as well as cite slice cultures. As a spin off from the core aims of this project we also made tools in parallel to investigate the effects of neuronal SUMOylation on other key pre- and postsynaptic proteins. Again these comprise multiple targeted point mutants and expression constructs. We are in contact with GSK and NeuroSearch regarding likely SUMO targets and possible approaches to modulate these targets in disease. For example, with NeuroSearch we exchanged material relating to Huntingtin protein since this is a validated SUMO substrate. However, unfortunately NeuroSearch has withdrawn from all basic research to focus on clinical trials of a potential Huntington drug. |
Sectors | Pharmaceuticals and Medical Biotechnology |
Description | Provided a basis for possible therapeutic design targeting SUMOylation |
First Year Of Impact | 2014 |
Sector | Pharmaceuticals and Medical Biotechnology |
Impact Types | Societal |
Description | Alzheimer's Society studentship "Can protein SUMOylation be neuroprotective in Alzheimer's disease?" |
Amount | £80,000 (GBP) |
Funding ID | 170 |
Organisation | Alzheimer's Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 09/2013 |
End | 01/2017 |
Description | BBSRC - Mechanisms and consequences of presynaptic protein SUMOylation in the regulation of neurotransmitter release |
Amount | £398,028 (GBP) |
Funding ID | BB/K014358/1 |
Organisation | Biotechnology and Biological Sciences Research Council (BBSRC) |
Sector | Public |
Country | United Kingdom |
Start | 09/2014 |
End | 10/2017 |
Description | BRACE Studentship "Analysis of changes in protein SUMOylation in Alzheimer's and Down's syndrome brain: implications for reducing impaired AMPAR trafficking and synaptic dysfunction" |
Amount | £84,306 (GBP) |
Organisation | BRACE (Alzheimer's disease charity) |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 02/2015 |
End | 01/2018 |
Description | Can manipulating SUMOylation of PTEN correct aberrant AMPA receptor trafficking and synaptic dysfunction in Alzheimer's disease? |
Amount | £86,957 (GBP) |
Organisation | BRACE (Alzheimer's disease charity) |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 02/2017 |
End | 01/2020 |
Description | European Research Council - 'Mechanisms and consequences of synaptic SUMOylation in health and disease' |
Amount | £1,700,000 (GBP) |
Funding ID | 232881 |
Organisation | European Research Council (ERC) |
Sector | Public |
Country | Belgium |
Start | 03/2009 |
End | 02/2013 |
Description | Manipulating protein SUMOylation for neuroprotection in Parkinson's disease |
Amount | £64,711 (GBP) |
Funding ID | G-1605 |
Organisation | Parkinson's UK |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 05/2017 |
End | 05/2018 |
Description | Protective mechanisms of protein SUMOylation in the heart |
Amount | £282,650 (GBP) |
Funding ID | PG/14/60/31014 |
Organisation | British Heart Foundation (BHF) |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 06/2015 |
End | 07/2018 |
Description | Royal Society Newton Award "SUMOylation: novel neuroprotective approach for Alzheimer's disease" |
Amount | £56,500 (GBP) |
Organisation | The Royal Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 04/2015 |
End | 05/2018 |
Description | Royal Society-Wolfson Merit Award |
Amount | £75,000 (GBP) |
Funding ID | WRSA09R2/HLL |
Organisation | The Royal Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start |
Title | AMPAR subunit pHluorin cDNAs |
Description | fluorophore tagged AMPAR subunits that allow real-time live cell imaging of receptor trafficking and surface expression |
Type Of Material | Technology assay or reagent |
Year Produced | 2006 |
Provided To Others? | Yes |
Impact | Multiple papers have been published by other groups using these reagents |
Title | SEP-GluRs |
Description | flourophore tagged proteins and mutant cDNA clones |
Type Of Material | Technology assay or reagent |
Year Produced | 2008 |
Provided To Others? | Yes |
Impact | improved experimental design |