Title: Activation of AMPA-type glutamate receptors in health and disease
Funder: The Academy of Medical Sciences

Abstract: Glutamate is present in ~80% of cortical synapses, and thus a key neurotransmitter shaping cognitive functions such as memory formation and learning. Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) are the first ion channels to be activated by presynaptically released glutamate and their activity shapes fast excitatory synaptic response. This project aims to identify AMPAR activation steps in health and disease. AMPARs are composed of four subunits with each harbouring one glutamate binding site. Full opening of an AMPAR includes activation of all four subunits, but their individual contributions are unknown. Intermediate steps towards full activation are physiologically relevant as they define functional states that contribute to synaptic transmission. The key limitation in understanding intermediate activation steps is the sub-millisecond activation of AMPARs. My preliminary data shows this can be overcome with a mouse mutant called Lurcher, also identified in patients diagnosed with rare and complex neurodevelopmental disorders with limited treatment options. The proposal will test the hypothesis that individual subunits differentially contribute to the AMPAR ion channel opening and also characterise the mutant via three objectives: 1) Determine the contributions of individual subunits to AMPAR activation using single-channel patch-clamp recordings in Lurcher and wild-type AMPARs. 2) Functionally characterise Lurcher AMPARs using macroscopic patch-clamp recordings. 3) Establish whether Perampanel, the only clinically approved, anti-convulsant drug targeting AMPARs, can revert Lurcher kinetics to wild-type properties. Subunit-specific model of AMPAR activation will address a fundamental question in AMPAR biology and in-depth characterisation of the mutant will open new therapeutic avenues for complex neurodevelopmental disorders.

Lay abstract: Our ability to form memories and learn relies on communication between nerve cells. Nerves contain a large number of proteins governing these processes and among the most important ones are AMPA receptors (AMPARs). If normal functioning of AMPARs is disrupted, it can cause diseases such as epilepsy and autism. Each AMPAR is composed of four parts (subunits) and although a lot is known about AMPARs, we do not yet understand what role each of these parts plays in their activation. This is because AMPARs take less than one millisecond to activate, making it technically challenging to study individual steps in this process. Here, I propose to use a mutation found in AMPARs that slows down their activation and so overcomes this technical limitation. This mutation is medically relevant because it has been found in patients diagnosed with rare neurodevelopmental disorders characterised by seizures, learning difficulties and delayed development, for which there are limited or no treatment options. Together with a team of experts I have assembled at the University of Edinburgh, I will use a technique called patch-clamp electrophysiology to answer three questions: 1) What are the steps in activation of AMPARs? 2) What characteristics of mutant AMPARs cause neurodevelopmental disorders? 3) Can a drug Perampanel, which binds AMPARs, help patients who carry the mutation? The answers will help us understand what has gone wrong in patients carrying the mutation, whether this can be reversed using current drugs and how to design better treatments for complex neurodevelopmental disorders.

Research activity codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS
Health categories: GENERIC HEALTH RELEVANCE;NEUROLOGICAL