Identification of a Site in Glutamate Receptor Subunits That Controls Calcium Permeability

TLDR

Glutamate drives excitatory synaptic transmission, and non‑NMDA receptor subunits vary in calcium permeability depending on their gene‑encoded combinations. The study aimed to identify structural determinants of ion permeation in non‑NMDA glutamate receptors. The authors engineered single‑amino‑acid mutants of non‑NMDA receptor subunits to probe ion permeation. A single amino‑acid site that changes charge was found to modulate current‑voltage characteristics and calcium permeability, establishing a key regulatory locus in non‑NMDA receptors.

Abstract

The neurotransmitter glutamate mediates excitatory synaptic transmission throughout the brain. A family of genes encoding subunits of the non- N -methyl-D-aspartate (non-NMDA) type of glutamate receptor has been cloned. Some combinations of these subunits assemble into receptors with a substantial permeability to calcium, whereas others do not. To investigate the structural features that control ion permeation through these ligand-gated channels, mutant receptor subunits with single-amino acid changes were constructed. Mutation of a certain amino acid that results in a net charge change (from glutamine to arginine or vice versa) alters both the current-voltage relation and the calcium permeability of non-NMDA receptors. A site has thus been identified that regulates the permeation properties of these glutamate receptors.