Negative allosteric modulation of GluN1/GluN3 NMDA receptors

Area of Science:

• Neuroscience
• Molecular Biology
• Pharmacology

Background:

• NMDA receptors are crucial for excitatory neurotransmission.
• Native NMDA receptors typically consist of GluN1 and GluN2 subunits.
• GluN1/GluN3 receptors, activated by glycine, have distinct properties but their function is poorly understood due to a lack of specific tools.

Purpose of the Study:

• To identify selective pharmacological tools for investigating GluN1/GluN3 receptors.
• To characterize the properties and selectivity of a novel modulator, EU1180-438.
• To explore the potential roles of GluN1/GluN3 receptors in neuronal function.

Main Methods:

• High-throughput screening to identify selective modulators.
• Electrophysiological recordings (e.g., non-stationary fluctuation analysis) in native neurons.
• Site-directed mutagenesis to probe ligand-binding sites.

Main Results:

• Identification of EU1180-438, a selective negative allosteric modulator for GluN1/GluN3 receptors.
• EU1180-438 demonstrated selectivity over GluN1/GluN2 NMDA, AMPA, kainate, GABA, glycine, and P2X receptors.
• EU1180-438 inhibited native GluN1/GluN3A receptor currents in hippocampal neurons in a voltage-independent manner.
• Unitary conductance of GluN1/GluN3A channels was estimated at 6.1 pS, unaffected by EU1180-438.
• Mutagenesis studies localized the binding site near the pre-M1 helix.

Conclusions:

• EU1180-438 is a valuable, selective tool for studying GluN1/GluN3 receptors.
• Structural differences in GluN3 subunits can be targeted for subunit-selective ligand development.
• This research opens avenues for exploring the physiological roles of GluN1/GluN3 receptors in the brain.