Calcium-permeable AMPA receptors govern PV neuron feature selectivity.

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Brain survival relies on internal world representations, with excitatory neurons precisely tuned to stimuli.
• Inhibitory neurons, like parvalbumin-positive (PV) interneurons, typically show lower feature selectivity.
• PV interneurons express calcium-permeable AMPA receptors (CP-AMPARs) lacking the GluA2 subunit, unlike calcium-impermeable AMPARs in excitatory neurons.

Purpose of the Study:

• To investigate the causal role of CP-AMPARs in the reduced feature selectivity of PV interneurons.
• To explore the conserved molecular mechanisms underlying PV interneuron selectivity across species.
• To determine if CP-AMPARs influence selectivity in other neuron types and brain regions.

Main Methods:

• Analyzed GRIA2 mRNA expression stoichiometry in PV interneurons across species.
• Genetically modified PV interneurons to replace CP-AMPARs with calcium-impermeable AMPARs.
• Assessed orientation selectivity in visual cortex and spatial tuning in hippocampal PV interneurons.
• Utilized Gria2-knockout mice to study the effects of universal CP-AMPAR expression.

Main Results:

• Low GRIA2 mRNA expression in PV interneurons leads to abundant CP-AMPARs, conserved across species.
• Replacing CP-AMPARs in PV interneurons increased their orientation selectivity in a cell-autonomous manner.
• Excitatory neurons in Gria2-knockout mice exhibited degraded orientation selectivity, confirming CP-AMPARs' sufficiency for low selectivity.
• Hippocampal PV interneurons showed enhanced spatial selectivity upon CP-AMPAR removal.

Conclusions:

• CP-AMPARs play a crucial role in maintaining low feature selectivity in PV interneurons.
• A conserved molecular mechanism involving CP-AMPARs distinguishes PV interneurons in the neocortex.
• Modulating CP-AMPARs offers a potential strategy to alter neuronal selectivity without affecting synaptic connectivity.