Christie S B, Li R-W, Miralles C P, Yang B -Y, De Blas A L
Department of Physiology and Neurobiology, University of Connecticut, 3107 Horsebarn Hill Rd., U-4156, Storrs, CT 06269, USA.
Mol Cell Neurosci. 2006 Jan;31(1):1-14. doi: 10.1016/j.mcn.2005.08.014. Epub 2005 Sep 21.
In cultured hippocampal neurons, gamma2 subunit-containing GABA(A) Rs form large postsynaptic clusters at GABAergic synapses and small clusters outside GABAergic synapses. We now show that a pool of non-clustered gamma2 subunit-containing GABA(A) Rs are also present at the cell surface. We also demonstrate that myc- or EGFP-tagged gamma2, alpha2, beta3 or alpha1 subunits expressed in these neurons assemble with endogenous subunits, forming GABA(A) Rs that target large postsynaptic clusters, small clusters outside GABAergic synapses or a pool of non-clustered surface GABA(A) Rs. In contrast, myc- or EGFP-tagged delta subunits only form non-clustered GABA(A) Rs, which can be induced to form clusters by antibody capping. A myc-tagged chimeric gamma2 subunit possessing the large intracellular loop (IL) of the delta-subunit IL (myc gamma2S/delta-IL) assembled into GABA(A) Rs, but it did not form clusters, therefore behaving like the delta subunit. Thus, the large intracellular loops of gamma2 and delta play an important role in determining the synaptic clustering/non-clustering capacity of the GABA(A) Rs.
在培养的海马神经元中，含γ2亚基的GABA(A)受体在GABA能突触处形成大的突触后簇，在GABA能突触外形成小簇。我们现在表明，细胞表面也存在一组非簇状的含γ2亚基的GABA(A)受体。我们还证明，在这些神经元中表达的myc或EGFP标记的γ2、α2、β3或α1亚基与内源性亚基组装在一起，形成靶向大突触后簇、GABA能突触外小簇或一组非簇状表面GABA(A)受体的GABA(A)受体。相比之下，myc或EGFP标记的δ亚基仅形成非簇状的GABA(A)受体，可通过抗体封端诱导形成簇。具有δ亚基大细胞内环（IL）的myc标记嵌合γ2亚基（myc γ2S/δ-IL）组装到GABA(A)受体中，但不形成簇，因此表现得像δ亚基。因此，γ2和δ的大细胞内环在决定GABA(A)受体的突触簇集/非簇集能力方面起着重要作用。
