AMPA receptor endosomal sorting during ischaemia . (360G-Wellcome-087407_Z_08_Z)

Transient global ischaemia induces delayed cell death in hippocampal CA1 neurons, via Ca2+/Zn2+-permeable, GluR2-lacking AMPARs. Following ischaemia, synaptic AMPAR currents in hippocampal neurons show marked inward rectification and increased sensitivity to channel blockers selective for GluR2-lacking AMPARs. This occurs via two mechanisms: a delayed downregulation of GluR2 mRNA expression, and a rapid endocytosis during the OGD insult of GluR2-containing AMPARs, which are replaced by GluR2-lac king receptors. Our preliminary data indicate that ion flux through these early GluR2-lacking receptors contributes to delayed neuronal death, so an investigation into the molecular mechanisms that underlie rapid, OGD-induced AMPAR subunit-switching is crucial to our understanding of the processes involved in ischaemia. Using a combination of confocal imaging, biochemistry and electrophysiology, we will study the endosomal trafficking pathways followed by specific AMPAR subunits in response to O GD and the AMPAR-accessory protein interactions involved. We have preliminary data implicating PICK1 as a regulator of GluR2 internalisation during OGD. In addition, we will use an in vivo transient global ischaemia model and investigate the effects of perturbing the specific trafficking events that we define in vitro, on ischaemia-induced hippocampal neuronal death in vivo.