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bioRxiv · 10.1101/2021.02.18.431828

Intracellular NASPM allows an unambiguous functional measure of GluA2-lacking calcium-permeable AMPA receptor prevalence

Coombs, I. D.·Bats, C.·Sexton, C. A.·Cull-Candy, S. G.·Farrant, M.
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Abstract

Calcium-permeable AMPA-type glutamate receptors (CP-AMPARs) contribute to many forms of synaptic plasticity and pathology. They can be distinguished from GluA2-containing calcium-impermeable AMPARs by the inward rectification of their currents, which reflects voltage-dependent block by intracellular spermine. However, the efficacy of this weakly permeant blocker is differentially altered by the presence of AMPAR auxiliary subunits - including transmembrane AMPAR regulatory proteins, cornichons and GSG1L - that are widely expressed in neurons and glia. This complicates the interpretation of rectification as a measure of CP-AMPAR expression. Here we show that inclusion of the spider toxin analogue 1-naphthylacetyl spermine (NASPM) in the intracellular recording solution results in complete block of GluA1-mediated outward currents irrespective of the type of associated auxiliary subunit. In neurons from GluA2-knockout mice expressing only CP-AMPARs, intracellular NASPM, unlike spermine, blocks all outward synaptic current. Thus, our results identify an unambiguous functional measure, sensitive solely to changes in CP-AMPAR prevalence.

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Coombs, I. D., Bats, C., Sexton, C. A., Cull-Candy, S. G., Farrant, M.. 2021-02-19. Intracellular NASPM allows an unambiguous functional measure of GluA2-lacking calcium-permeable AMPA receptor prevalence. https://doi.org/10.1101/2021.02.18.431828

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