Splicing, RNA editing, and auxiliary subunits shaped AMPA receptor function through coordinated evolution

Post-transcriptional regulation of AMPA-type ionotropic glutamate receptors (AMPARs) emerged in early vertebrates alongside a major expansion of AMPAR auxiliary subunits. Recent work shows that two key modifications-alternative splicing of the flip/flop cassette and Q/R site RNA editing-fine-tune channel gating and Ca²⁺ permeability, respectively, through interactions with two distinct auxiliary protein families: the transmembrane AMPA receptor regulatory proteins (TARPs) and the cornichons (CNIHs). I propose that these regulatory layers did not evolve independently but instead coalesced into an integrated system in which splicing, editing, and auxiliary proteins reciprocally shaped each other. This coordinated evolution maximized excitatory signaling diversity during vertebrate brain expansion, helping to explain why perturbations in any layer contribute to neurological disease.