Both SNX27a and SNX27b contain a single PDZ domain that is essential for its regulation of GIRK channels (Lunn et al., 2007). This PDZ interaction is mediated by a PDZ binding motif, ‘E(N/S)ESKV’, which is present on the C-terminus of GIRK2c and GIRK3 channels (Balana et al., 2011; Lunn et al., 2007). We hypothesized that the reduced GABABR-activated GIRK currents in SNX27DA KO mice occurred because endogenous PDZ-interacting GIRK2c and GIRK3 subunits required SNX27 for expression (Cruz et al., 2004). To investigate the role of the PDZ binding motif in GIRK2, we constructed an AAV to express the splice variant GIRK2a, which lacks a PDZ binding motif and does not associate with SNX27 (Balana et al., 2011; Lunn et al., 2007). In addition, GIRK2a is capable of forming homotetramers and thus functional channels (Inanobe et al., 1999). SNX27DA KO mice were injected with AAV DIO-Girk2a-eYFP or AAV DIO-eYFP, as described above, and midbrain slices were prepared for whole-cell patch-clamp recordings (Figure 6A,B). As expected, mean IBaclofen currents were smaller in SNX27DA KO mice injected with AAV DIO-eYFP, 80.2 ± 16.9
