Brain Res Mol Brain Res 2002 Jun 30;1031-2:62-70. doi: 10.1016/s0169-328x(02)00140-7.

Co-assembly of GABA rho subunits with the GABA(A) receptor gamma(2) subunit cloned from white perch retina.

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Although it is well established that GABA(C) receptors are comprised in part of GABA rho subunits, the exact subunit composition of neuronal GABA(C) receptors is yet to be determined. A detailed comparison of GABA(C)-mediated neuronal responses elicited from retinal neurons with those obtained from receptors formed by GABA rho subunits revealed a number of significant differences both in the kinetics and the pharmacology of the responses. Our previous studies indicated that the human GABA(A) receptor gamma(2) subunit could co-assemble with one (rho(1B)) of the white perch GABA rho subunits to form a heterooligomeric receptor with properties that resembled those of the GABA(C) receptors on white perch bipolar cells. In this study, we cloned the white perch gamma(2) subunit, and investigated its co-assembly with four white perch GABA rho subunits. When expressed in Xenopus oocytes, perch gamma(2) and rho(1B) subunits form heterooligomeric receptors with distinct properties: the GABA-elicited responses have fast kinetics and are sensitive to pentobarbital modulation. The enhancement of GABA-elicited responses by pentobarbital on the heterooligomeric receptors could be eliminated by a single mutation in the third transmembrane domain of the gamma(2) subunit, indicating that pentobarbital sensitivity is mediated by the incorporated gamma(2) subunit. On the other hand, co-expression of the perch gamma(2) subunit with the other perch GABA rho subunits produced no detectable changes in the kinetics of GABA-elicited response or the sensitivity to pentobarbital modulation. These results suggest that the gamma(2) subunit can co-assemble only with one (rho(1B)), but not with other white perch GABA rho subunits.

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Species referenced: Xenopus
Genes referenced: rho rho.2