Figure 6. Deficits in endocytic recycling of GABA_ARs in CAML mutant neurons.

A, The expression of CAML in 4-hydroxytamoxifen-treated CAML mutant (CAGGCre-ER™ × CAML^f/- or CAGGCre-ER™ × CAML^f/f) normalized and compared to pseudo-WT (CAML^f/f) control neuron cultures (DIV 12) was reduced to 10.4 ± 0.3% of controls (= 100%) (n = 8 experiments, p < 0.001). B, The cell surface expression of γ2 subunit-containing GABA_ARs purified using cell surface biotinylation of CAML mutant cultures was reduced to 72.6 ± 4.7% of CAML^f/- and CAML^f/f controls (n = 5, p < 0.01). C, The cell surface levels of GABA_AR β2/3 subunits in CAML mutant cultures were similarly reduced to 84.8 ± 6.1% of controls (n = 5, p < 0.05). D, E, The cell surface expression (D) and rate of endocytosis (E) of GluR2 and/or GluR3-containing AMPA receptors were unaltered in mutants compared to controls (GluR2/3 surface expression in mutants: 100.5 ± 5.1% of controls, n = 5; GluR2/3 endocytosed in mutants during 30 min: 92.0 ± 3.9% of controls, n = 3, p > 0.05). F, The rate of endocytosis of GABA_ARs in CAML mutant neuron cultures was not different from controls (CAML mutant, 102.6 ± 4.5% of controls, n = 5, p > 0.05). G, The portion of endocytosed GABA_ARs that remained intracellular after recycling for 40 min was greatly increased in CAML mutant (31.4 ± 2.8% of endocytosed receptors) compared to control cultures (17.1 ± 2.1%, n = 5, p < 0.01). Data represent means ± S.E; * p < 0.05, ** p < 0.01, *** p < 0.001, Student's t-test.