Figure 4: Syntabulin facilitates the axonal distribution of PICK1.

(A) Distribution of GFP-PICK1 and myc-Syntabulin full-length and N-terminal proteins in neurons when transfected alone. The enlarged pictures show clusters in axons in contact with another neuron. Arrowheads indicate the axons. (B) Neurons were doubly transfected with PICK1 and syntabulin and stained with the myc antibody. The merged images show almost complete colocalization of PICK1 clusters with syntabulin in axons. The enlarged pictures show clusters in axons in contact with another neuron. Scale bar = 50 μm for the original image, 10 μm for the insets in both (A,B). Arrowheads indicate the axons. (C) Quantification of PICK1 axonal targeting. A/D ratio, axon/dendrite ratio. The result shows that when coexpressed with syntabulin, PICK1 axonal targeting was increased significantly. **P = 0.003 and P = 0.007 for GFP-PICK1 expressed together with Syntabulin-FL and Syntabulin-Nt, as compared with GFP-PICK1 expressed alone; one-way ANOVA and Sidak test, n = 3–8 independent experiments. (D) Quantification of PICK1 axonal clustering. Coexpression with syntabulin significantly increased PICK1 axonal clustering. **P = 0.003 and *P = 0.018 compared to GFP-PICK1; one-way ANOVA and Sidak test, n = 4 independent experiments. Error bars represent the SEM.