Anterograde trafficking signals in GABAA subunits are required for functional expression

• Published in: Channels (Austin, Tex.) Tex.), 2019-01, Vol.13 (1), p.440-454
• Main Authors: Nuwer, Jessica L., Fleck, Mark W.
• Format: Article
• Language: English
• Subjects: beta subunit; chimera; GABAA; Research Paper; theta subunit; trafficking
• ISSN: 1933-6950; 1933-6969
• DOI: 10.1080/19336950.2019.1676368

Pentameric GABA A receptors are composed from 19 possible subunits. The GABA A β subunit is unique because the β 1 and β 3 subunits can assemble and traffic to the cell surface as homomers, whereas most of the other subunits, including β 2 , are heteromers. The intracellular domain (ICD) of the GABA A subunits has been implicated in targeting and clustering GABA A receptors at the plasma membrane. Here, we sought to test whether and how the ICD is involved in functional expression of the β 3 subunit. Since θ is the most homologous to β but does not form homomers, we created two reciprocal chimeric subunits, swapping the ICD between the β 3 and θ subunits, and expressed them in HEK293 cells. Surface expression was detected with immunofluorescence and functional expression was quantified using whole-cell patch-clamp recording with fast perfusion. Results indicate that, unlike β 3 , neither the β 3 /θ IC nor the θ/β 3IC chimera can traffic to the plasma membrane when expressed alone; however, when expressed in combination with either wild-type α 3 or β 3 , the β 3 /θ IC chimera was functionally expressed. This suggests that the ICD of α 3 and β 3 each contain essential anterograde trafficking signals that are required to overcome ER retention of assembled GABA A homo- or heteropentamers.