DIFFERENTIAL ASSEMBLY OF COEXPRESSED GLUTAMATE-RECEPTOR SUBUNITS IN NEURONS OF RAT CEREBRAL-CORTEX

In the rat, subunits of the glutamate receptor family fall into three pharmacologically distinct groups: alpha-amino-3-hydroxy-5-methyl-4-is oxazole propionic acid preferring receptors (Glu R1-4), kainate prefer ring receptors (Glu R5-7, KA 1, KA 2), and N-methyl-D-aspartate prefer ring receptors (NMDA R1, NMDA R2A-2D). In the present study, we demons trate immunocytochemically that the majority of neurons in rat cerebra l cortex coexpress members of all three groups of glutamate receptor s ubunits, Glu R2/3, Glu R5/6/7, and NMDA R1. Using immunoaffinity purif ied or immunoprecipitated alpha-amino-3-hydroxy-5-methyl-4-isoxazole p ropionic acid, kainate and N-methyl-D-aspartate receptors, we show tha t alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors containing Glu R1-4, kainate receptors containing Glu R6, Glu R7, and KA 2 and N-methyl-D-aspartate receptors containing NMDA R1 each form d istinct protein complexes that do not share subunits. Our data indicat e that a mechanism exists which allows for the specific assembly of se lected glutamate receptor subunits into functionally and structurally distinct heteromeric receptors.