Identification of subunits mediating clustering of GABA(A) receptors by rapsyn

kHuman embryonic kidney 293 cells transfected with alpha(1)beta(1)gamma(2), alpha(1)beta(2)gamma(2), alpha(1)beta(3)gamma(2), alpha(1)beta(1), alpha(1 )beta(2), alpha(1)beta(3), beta(3)gamma(2), or beta(3) subunits formed gamm a-aminobutyric acid(A) receptors on the cell surface that could be clustere d by rapsyn. In contrast, alpha(1), beta(1), beta(2), or gamma(2) Subunits, or alpha(1)gamma(2) subunit combinations could not be detected on the surf ace of transfected cells and could not be clustered by rapsyn. Experiments investigating the ability of rapsyn to cluster chimeras consisting of the N -terminus of the beta(3) subunit and the remaining part of the alpha(1), be ta(2) or gamma(2) subunits indicated that the intracellular domains of beta (1), beta(2), beta(3), or gamma(2) subunits, but not those of alpha(1) subu nits are able to form sites mediating clustering by rapsyn. These results d emonstrate that rapsyn has the potential to cluster the majority of GABAA r eceptor subtypes via beta or gamma(2) subunits. Further experiments will ha ve to clarify the physiological importance of this observation. (C) 1999 El sevier Science Ltd. All rights reserved.