Figure 6
From: Coordinated trafficking of synaptic vesicle and active zone proteins prior to synapse formation
A direct interaction between STVs and PTVs cannot account for the attraction of STVs to pause sites that contain PTVs. (A) PTV transport was inhibited using dominant-negative syntabulin (syntaxin binding domain, SBD) fused to GFP. (B) Expression of syntabulin-SBD-GFP decreases the density of PTV puncta in axons when compared to axons expressing GFP alone. PTVs were identified by immunofluorescent labeling for endogenous piccolo. (C) Images and kymograph (bottom) showing that STVs (magenta) move and pause in SBD-expressing axons (green). (D) The frequency of STV pausing was unchanged in the presence of SBD-GFP. (E) STV pause durations are shorter when PTV localization in the axon is disrupted. The change in pausing upon expression of SBD-GFP is not sufficient to account for the coordinated pausing of STVs and PTVs. In B, D and E, error bars correspond to the standard error. *, difference is significant. P-values are from Wilcoxon rank-sum test and are indicated in the figure. (F) The instantaneous velocities of STVs are increased in SBD-expressing axons. Black arrow, mean instantaneous velocity.