A 100 amino acid region in the GABA ρ1 subunit confers robust homo- oligomeric expression

RETINAL γ-aminobutyric acid type C (GABA(C)) receptors are believed to be composed of p subunits. Although p1 and p2 are over 80% similar, the whole-cell currents generated by p1 receptors in Xenopus oocytes are significantly greater than those generated by p2 receptors. In this study, chimeric subunits containing different portions of human p1 and human p2 were created to localize sequences facilitating robust p1 expression. Our results indicate that these sequences reside in a 100 amino acid domain in the N-terminus of p1, and may involve N-linked glycosylation. Since the N- terminus also contains subunit assembly signals, p1 receptors may be formed more efficiently than p2 receptors. Therefore, this study furthers our understanding of the molecular basis of GABA-mediated inhibition in the retina.