FIGURE 2.

AMPA receptors containing GluA2 are Ca²⁺-impermeable due to editing at the Q/R site. (A) Current understanding of the quaternary structure of AMPA receptors, thought to be tetrameric assemblies of four AMPA receptor subunits form the ion channel pore. The assembled receptor can comprise any combination of GluA1–GluA4 subunits but usually contains GluA2. Reprinted from Sobolevsky et al. (2009), with permission. (B) AMPA receptors generally contain GluA2 (red) with combinations of GluA1, GluA3, and GluA4 (blue). AMPA receptors containing edited GluA2 are impermeable to Ca²⁺ (left). AMPA receptors containing unedited GluA2 and AMPA receptors lacking GluA2 are Ca²⁺-permeable (right).