Differences in AMPA and Kainate Receptor Interactomes Facilitate Identification of AMPA Receptor Auxiliary Subunit GSG1L

SummaryAMPA receptor (AMPA-R) complexes consist of channel-forming subunits, GluA1-4, and auxiliary proteins, including TARPs, CNIHs, synDIG1, and CKAMP44, which can modulate AMPA-R function in specific ways. The combinatorial effects of four GluA subunits binding to various auxiliary subunits amplify the functional diversity of AMPA-Rs. The significance and magnitude of molecular diversity, however, remain elusive. To gain insight into the molecular complexity of AMPA and kainate receptors, we compared the proteins that copurify with each receptor type in the rat brain. This interactome study identified the majority of known interacting proteins and, more importantly, provides candidates for additional studies. We validate the claudin homolog GSG1L as a newly identified binding protein and unique modulator of AMPA-R gating, as determined by detailed molecular, cellular, electrophysiological, and biochemical experiments. GSG1L extends the functional variety of AMPA-R complexes, and further investigation of other candidates may reveal additional complexity of ionotropic glutamate receptor function.

Graphical AbstractFigure optionsDownload as PowerPoint slideHighlights
► Mass spectrometry identified proteins copurifying with AMPA and kainate receptors
► GSG1L is an AMPA-receptor-binding transmembrane protein
► GSG1L uniquely modulates AMPA receptor trafficking and channel gating
► GSG1L colocalizes with AMPA receptors at synapses