The AMPAR subunit GluR2: still front and center-stage

Area of Science:

• Neuroscience
• Molecular Biology
• Pathology

Background:

• Abnormal calcium (Ca2+) influx through AMPA-type glutamate receptors (AMPARs) is implicated in neuronal death in various brain disorders.
• AMPARs' Ca2+ permeability is determined by their subunit composition, with the GluR2 subunit rendering them Ca2+-impermeable.
• Dysregulation of GluR2 expression and function is observed in conditions like ischemia and epilepsy.

Purpose of the Study:

• To investigate the role of GluR2 subunit downregulation in AMPAR-mediated Ca2+ influx and neuronal death.
• To determine if acute GluR2 downregulation, independent of other neurological insults, can induce neuronal cell death.
• To explore the contribution of Ca2+-permeable AMPARs to ischemia-induced neuronal death.

Main Methods:

• Utilized animal models of transient forebrain ischemia and epilepsy.
• Performed Ca2+ imaging and electrical recordings in hippocampal slices from post-ischemia animals.
• Conducted knockdown experiments using antisense oligonucleotides targeting GluR2 mRNA in rats and gerbils.

Main Results:

• Post-ischemia neurons exhibited enhanced AMPA-elicited intracellular Ca2+ rises, indicating increased Ca2+ permeability.
• Enhanced Ca2+-dependent component in excitatory postsynaptic currents was observed in post-ischemic neurons, mediated by Ca2+-permeable AMPARs.
• GluR2 antisense oligonucleotide treatment induced pyramidal neuron death and worsened ischemic episode pathogenicity.

Conclusions:

• Ca2+ influx through AMPARs contributes to neuronal death in pathological conditions.
• Ca2+-permeable AMPARs play a significant role in the pathogenesis of ischemia-induced neuronal death.
• Targeting GluR2 expression or function may offer therapeutic strategies for neuroprotection.