CELL-SURFACE EXPRESSION OF THE HUMAN N-METHYL-D-ASPARTATE RECEPTOR SUBUNIT-1A REQUIRES THE COEXPRESSION OF THE NR2A-SUBUNIT IN TRANSFECTED CELLS

Cell surface expression of the NR1a subunit has been examined in mouse L cell lines permanently transfected with the complementary DNA for h uman NR1a or with the complementary DNAs for NR1a and NR2A. The expres sion of the subunits was under the control of the murine mammary tumou r virus promoter and following induction of expression by dexamethazon e both cell lines expressed high levels of the NR1a subunit as determi ned by immunofluorescence using permeabilized cells and immunoblotting of cell membranes with subunit specific antibodies. However, cell sur face expression of the NR1a subunit was found only in the cells expres sing both the NR1a and NR2A subunits. This was confirmed by cell surfa ce biotinylation of the two cell lines and affinity isolation of the r eceptor subunits. To determine if this result was solely due to the us e of a particular cell line and or the choice of expression vector, Co s-7 cells were transiently transfected with either NR1a or NR1a plus N R2A. Here too cell surface expression was only found following co-tran sfection of both subunits.