The A343D mutation impairs HA-KCNQ3/KCNQ2 trafficking from the ER to the axon.

<p>(A–B) Pulse-chase assay of wild-type (WT) or mutant (A343D and R353G) HA-KCNQ3/KCNQ2 channels after BFA washout. Permeabilized immunostaining was performed to visualize total (surface and intracellular) expression of HA-KCNQ3/KCNQ2 channels in the soma and AIS (A) as well as in the distal axons and dendrites (B) at indicated time points post-BFA removal (inverted images). The axon was identified by the AIS marker phospho IκBα Ser32 (14D4), whereas neuronal soma and dendrites were visualized by MAP2 immunostaining. Arrows indicate the AIS. Scale bars: 10 µm. (C) Background subtracted, mean intensity of total HA fluorescence in the AIS, distal axon, and major dendrites. Upon BFA removal, the A343D mutation but not the R353G mutation markedly reduced the appearance of HA-KCNQ3/KCNQ2 at the AIS and distal axon for the duration of the 8 hr BFA washout. The sample numbers were (n = 8–22) per time point for each construct. AU, arbitrary unit. Ave ± SEM (*p<0.05, **p<0.01, ***p<0.001).