Table 1.

Glutamate Receptor Protein Subunit Composition and Properties

Glutamate Receptor	Protein Subunits	Receptor Properties
Ionotropic receptors
NMDAR	NR1, NR2A,a NR2B,a NR2C, NR2D, NR3A, and NR3B	Heterotetrameric; calcium permeability high; long channel open time
AMPAR	GluR1,a GluR2, edited GluR2, GluR3,a and GluR4a	Heterotetrameric; calcium permeability low if edited GluR2, otherwise moderate; short channel open time
Kainate receptor	GluR5,a GluR6, GluR7, KA1, and KA2	Homotetrameric or heterotetrameric; calcium permeability low; short channel open time
Metabotropic receptors
Group 1	mGluR1a and mGluR5	Homodimeric; signals via phospholipase C
Group 2	mGluR2 and mGluR3	Homodimeric; signals via adenylyl cyclase
Group 3	mGluR4, mGluR6, mGluR7, and mGluR8	Homodimeric; signals via adenylyl cyclase

Abbreviations: AMPAR, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor; NMDAR, N-methyl-D-aspartate receptor.

^aGlutamate receptor protein subunits for which human autoantibodies have been reported.