Type A ?-aminobutyric acid receptors (GABA(A)), the major sites of fast
synaptic inhibition in the brain, are believed to be predominantly
composed of a, ß, and ? subunits. To examine the membrane trafficking of
GABA(A) receptors we have produced ?2L subunit chimeras with green
fluorescent protein (GFP). Addition of GFP to the N-terminus of the ?2
subunit (?2L-GFPN) was functionally silent for a1ß2?2L-GFPN receptors
expressed in A293 cells. Furthermore, this chimera allowed the
visualization of receptor membrane targeting and endocytosis in live
cells. In contrast, incorporation of GFP at the C-terminus reduced
subunit stability, impairing assembly with receptor a and ß subunits.
Using ?2L-GFPN we were able to demonstrate that targeting of the ?2
subunit to GABAergic synapses in hippocampal neurons was dependent upon
coassembly with receptor a and subunits. Together our results
demonstrate that the assembly and membrane targeting of GABA(A)
receptors composed of a1ß2?2L-GFPN subunits follow similar itineraries
in heterologous systems and neurons.