Identification of subunits mediating clustering of GABAA 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 gamma-aminobutyric acid(A) receptors on the cell surface that could be clustered 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 surface 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), beta(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) subunits are able to form sites mediating clustering by rapsyn. These results demonstrate that rapsyn has the potential to cluster the majority of GABAA receptor subtypes via beta or gamma(2) subunits. Further experiments will have to clarify the physiological importance of this observation. (C) 1999 Elsevier Science Ltd. All rights reserved.