Purified unitary kainate/alpha-amino-3-hydroxy-5-methylisooxazole-propionate (AMPA) and kainate/AMPA/N-methyl-D-aspartate receptors with interchangeable subunits.
We have purified and characterized two vertebrate excitatory amino acid ionotropic receptors from the Xenopus central nervous system. Each is a unitary receptor (i.e., having more than one class of excitatory amino acid agonist specificity within one protein oligomer). The first is a unitary non-N-methyl-D-aspartate (non-NMDA) receptor and the second is a unitary NMDA/non-NMDA receptor. The specific agonist-activated channel activity and pharmacology of each type were recognized by patch-clamping lipid bilayers in which the isolated protein was reconstituted. In the second case, the NMDA and the non-NMDA sites could not be physically separated and exhibited functional interaction. Parallel evidence for this was obtained when poly(A) RNA from Xenopus brain was translated in oocytes: a noncompetitive inhibition of the response to L-kainate is produced by NMDA to a maximum depression of 30% at 1 mM NMDA. Each isolated oligomer contains 42-kDa subunits of the non-NMDA ligand binding type, but the second type has an additional NMDA-receptor-specific 100-kDa subunit. Thus, a subunit-exchange hypothesis can account for the known multiplicity of excitatory amino acid receptor types.
Henley
J M
JM
Medical Research Council Molecular Neurobiology Unit, Medical Research Council Centre, Cambridge, United Kingdom.
Ambrosini
A
A
Rodriguez-Ithurralde
D
D
Sudan
H
H
Brackley
P
P
Kerry
C
C
Mellor
I
I
Abutidze
K
K
Usherwood
P N
PN
Barnard
E A
EA
D000818:Animals; D007051:Ibotenic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D007608:Kainic Acid / Q000378:metabolism; D008024:Ligands; D046911:Macromolecular Substances; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D017981:Receptors, Neurotransmitter / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D014982:Xenopus laevis; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
D007051:Ibotenic Acid; D007608:Kainic Acid; D008024:Ligands; D046911:Macromolecular Substances; D009419:Nerve Tissue Proteins; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid