Mutations to the kainate receptor subunit GluR6 binding pocket that selectively affect domoate binding

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Kainate receptors are ionotropic glutamate receptors with critical roles in synaptic transmission.
• Domoate is a potent kainate receptor agonist that elicits large currents and slow deactivation.
• Understanding the molecular basis of domoate action on kainate receptors is essential for elucidating receptor function.

Purpose of the Study:

• To investigate the structural determinants of domoate binding and activation in GluR6 kainate receptors.
• To characterize the functional consequences of specific residue mutations at the agonist binding site.
• To elucidate the mechanisms underlying kainate receptor responses to domoate.

Main Methods:

• Site-directed mutagenesis of GluR6 receptor subunits.
• Whole-cell electrophysiology to record receptor currents.
• Ligand application (domoate, glutamate, kainate) to assess receptor function.
• Kinetic modeling to analyze mutant phenotypes.

Main Results:

• Mutation of Met691 to alanine attenuated domoate responses, suggesting a role in domoate binding via hydrogen bonding.
• Mutation of Val685 to glutamine (V685Q) dramatically accelerated deactivation kinetics of domoate responses (>50-fold).
• The V685Q mutation reduced agonist potency and was explained by faster ligand dissociation, without affecting desensitization or gating.

Conclusions:

• Met691 and Val685 are critical residues at the mouth of the GluR6 agonist binding pocket.
• Val685 plays a key role in regulating the deactivation rate of kainate receptors upon domoate binding.
• The V685Q mutant serves as a valuable tool for dissecting ligand binding and gating mechanisms in kainate receptors.