Shisa7-Dependent Regulation of GABA Receptor Single-Channel Gating Kinetics.

GABA receptors (GABARs) mediate the majority of fast inhibitory transmission throughout the brain. Although it is widely known that pore-forming subunits critically determine receptor function, it is unclear whether their single-channel properties are modulated by GABAR-associated transmembrane proteins. We previously identified Shisa7 as a GABAR auxiliary subunit that modulates the trafficking, pharmacology, and deactivation properties of these receptors. However, whether Shisa7 also regulates GABAR single-channel properties has yet to be determined. Here, we performed single-channel recordings of α2β3γ2L GABARs cotransfected with Shisa7 in HEK293T cells and found that while Shisa7 does not change channel slope conductance, it reduced the frequency of receptor openings. Importantly, Shisa7 modulates GABAR gating by decreasing the duration and open probability within bursts. Through kinetic analysis of individual dwell time components, activation modeling, and macroscopic simulations, we demonstrate that Shisa7 accelerates GABAR deactivation by governing the time spent between close and open states during gating. Together, our data provide a mechanistic basis for how Shisa7 controls GABAR gating and reveal for the first time that GABAR single-channel properties can be modulated by an auxiliary subunit. These findings shed light on processes that shape the temporal dynamics of GABAergic transmission. Although GABA receptor (GABAR) single-channel properties are largely determined by pore-forming subunits, it remains unknown whether they are also controlled by GABAR-associated transmembrane proteins. Here, we show that Shisa7, a recently identified GABAR auxiliary subunit, modulates GABAR activation by altering single-channel burst kinetics. These results reveal that Shisa7 primarily decreases the duration and open probability of receptor burst activity during gating, leading to accelerated GABAR deactivation. These experiments are the first to assess the gating properties of GABARs in the presence of an auxiliary subunit and provides a kinetic basis for how Shisa7 modifies temporal attributes of GABAergic transmission at the single-channel level.