GluN1 (GRIN1) forms a tri-heterotetramer with GluN2A (GRIN2A) and GluN2C (GRIN2C). The tetramer includes two molecules of GluN1, one molecule of GluN2A and one molecule of GluN2C (Wafford et al. 1993). The tetrameric structure of the GluN1:GluN2A:GluN2C (GRIN1:GRIN2A:GRIN2C) tri-heteromer is assumed to be similar to the described structure of the Xenopus GluN1:GluN2A:GluN2B tri-heteromer (Lu et al. 2017). GluN1:GluN2A:GluN2C tri-heteromers are the predominant NMDA receptors in cerebellar granule cells (Bhattacharya et al. 2018, reviewed in Bhattacharya and Traynelis 2018).