Interactions between ρ and γ2 subunits of the GABA receptor

Abstract

The γ-aminobutyric acid type C (GABAC) receptor is a ligand-gated chloride channel with distinct physiological and pharmacological properties. Although the exact subunit composition of native GABAC receptors has yet to be firmly established, there is general agreement that GABA ρ subunits participate in their formation. Recent studies on white perch suggest that certain GABA ρ subunits can co-assemble with the GABA A receptor γ2 subunit to form a heteromeric receptor with electrophysiological properties that correspond more closely to the native GABAC receptor on retinal neurons than any of the homomeric ρ receptors. In the present study we examined the interactions among various perch GABA ρ and γ2 subunits. When co-expressed in Xenopus oocytes, the γ2 subunit co-immunoprecipitated with Flag-tagged perch ρ1A, ρ1B, and ρ2B subunits, but not with the Flag-tagged perch ρ2A subunit. Immunocytochemical studies indicated that the membrane surface expression of the γ2 subunit was detected only when it was co-expressed with perch ρ1A, ρ1B, or ρ2B subunit, but not with the perch ρ2A subunit or when expressed alone. In addition, co-immunoprecipitation of perch ρ1B and γ2 subunits was also detected in protein samples of the teleost retina. Taken together, these findings suggest that a heteromeric ργ2 receptor could represent one form of GABAC receptor on retinal neurons. © 2005 International Society for Neurochemistry.