GluA1m and GluA2m formed functional heteromeric GluA1/A2 receptors. (A) Nonreducing Western blot for WT GluA1 and mutated GluA1 (GluA1m, Cys-524, -585, -811, -825, and -875 were mutated to nonreducing alanines). Note spontaneous oligomerizations formed only in WT GluA1. (B) Nonreducing Western blot for WT GluA2 and mutated GluA2 (GluA2m, Cys-436, -528, -589, and -815 were mutated to alanine residues). Note that spontaneous oligomerizations formed only in WT GluA2. (C) The glutamate-induced currents of GluA1m in HEK cells was strongly rectified (RI = 0.15 ± 0.04; n = 6). (D) I–V curve of GluA1m/GluA2m (1:1) was linear (RI = 0.71 ± 0.04; n = 17).