The γ2 subunit, tubulin-binding motif of GABARAP, and microtubules are involved in clustering of GABA_{A} receptors. (*A*) GABARAP promotes GABA_{A} receptor clustering when coexpressed in QT-6 cells. The bar graph summarizes the percentage of cells that had GABA_{A} receptor clusters. The expressed subunits and GABARAP are shown below. The bd17-positive QT-6 cells were randomly divided into about 100 cells per group, then the percentage of cells with clustered staining in each group was counted [(number of cells showing clustered stain/total of cells in the group) × 100%]. Each bar represents the mean and SD of 6–10 groups of the cells. *, *P* < 0.001 (*t* test). (*B*) Microtubule disruption prevents clustering of GABA_{A} receptors in a time-dependent manner. QT-6 cells were transfected with plasmids encoding α1, β2, γ2L-GFP GABA_{A} receptors and GABARAP. The microtubule disruption agent nocodazole (1 μg/ml) was added into culture medium at 4 h, 24 h, and 72 h after transfection. GFP-tagged receptors were examined with clustering assay described above. Each bar represents the mean and SD of 4–6 groups of the cells. *, *P* < 0.001 (*t* test).

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