title: Co-assembly of GABA rho subunits with the GABA(A) receptor gamma(2) subunit cloned from white perch retina.
abstract: 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.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA. hquian@uic.edu
authors.forename: Haohua
authors.initials: H
authors.lastname: Qian
authors.forename: Yi
authors.initials: Y
authors.lastname: Pan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D018757:GABA Modulators / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D010424:Pentobarbital / Q000494:pharmacology; D010471:Perches; D017434:Protein Structure, Tertiary; D011963:Receptors, GABA-A / Q000235:genetics* / Q000378:metabolism*; D018080:Receptors, GABA-B / Q000235:genetics* / Q000378:metabolism*; D012160:Retina / Q000502:physiology*; D014981:Xenopus
chemical_list: D018757:GABA Modulators; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; D010424:Pentobarbital