Cloning and Characterization of a GABAA Receptor γ2 Subunit Variant

• Published in: The Journal of biological chemistry Vol. 279; no. 2; p. 1408
• Main Authors: Pei Jin, Juan Zhang, Courtney Rowe-Teeter, Junming Yang, Laura L. Stuve, Glenn K. Fu
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 09.01.2004
• DOI: 10.1074/jbc.M308656200
• ISSN: 0021-9258

We have cloned a novel γ-aminobutyric acid type A (GABA A ) receptor γ 2 subunit variant named γ 2 XL. γ 2 XL contains an alternatively spliced exon, resulting in the addition of 40 amino acids to the N-terminal extracellular domain between Ser 171 and Tyr 172 . We show that γ 2 XL failed to localize to the cell surface when it was coexpressed with the α 2 and β 1 subunits in human embryonic kidney 293 cells. Expression of γ 2 XL in 293 cells suppressed GABA A receptor binding in a dose-dependent manner by preventing GABA A receptor cell-surface localization. We also generated a γ 2 mutant with Ser 171 and Tyr 172 converted to glycine and threonine, respectively. We demonstrate that this mutant has a significantly lower affinity for the α 2 and β 1 subunits and failed to reach the cell surface when coexpressed with these subunits. Together, our results indicate that Ser 171 and Tyr 172 in the γ 2 subunit constitute a critical motif. When this motif is disrupted by insertion of the alternative exon, access of the γ 2 subunit to the cell surface is prevented.