CLUSTERING OF GABA(A) RECEPTORS BY RAPSYN 43KD PROTEIN IN-VITRO/

Rapsyn, a 43-kDa protein on the cytoplasmic face of the postsynaptic m embrane, is essential for clustering acetylcholine receptors (AChR) at the neuromuscular junction. When transfected into nonmuscle cells (QT -6), rapsyn forms discrete membrane domains and can cluster AChR into these same domains. Here we examined whether rapsyn can cluster other ion channels as well, When expressed in QT-6 cells, the GABA(A) recept or (human alpha 1, beta 1, and gamma 2 subunits) and the skeletal musc le sodium channel were each diffusely scattered across the cell surfac e. Rapsyn, when co-expressed, clustered the GABAA receptor as effectiv ely as it clustered AChR in previous studies. Rapsyn did not cluster c o-transfected sodium channel, confirming that it does not cluster ion channels indiscriminately. Rapsyn mRNA was detected at low levels in t he brain by polymerase chain reaction amplification of reverse-transcr ibed RNA, raising the possibility of a broader role for rapsyn.