Figure 4.

Altered actin distribution and localization of F-actin in NSF2^E/Q boutons. (a) Images are of actin-GFP distribution in control and NSF2^E/Q nerve terminals. In controls the GFP signal shows a nonuniform punctate appearance, whereas in the NSF2^E/Q nerve terminal it is much more diffuse. (b) Single-slice confocal images of control actin-GFP–expressing nerve terminal labeled with phalloidin reveals that the actin-GFP puncta correspond to filamentous actin. Most of the phalloidin signal in this image is postsynaptic, corresponding to the subsynaptic reticulum of the muscle; however, the presynaptically expressed GFP coincides with phalloidin labeling. (c) Similar image of actin-GFP expressing NSF2^E/Q boutons. This image was selected because it shows the exclusion of phalloidin signal from the actin-GFP signal, marked by the double arrowhead, whereas there are some GFP concentrations that do coincide with phalloidin, marked by the single arrowheads. (d) Colocalization of actin-GFP with synaptotagmin. Control nerve terminals expressing actin-GFP were immunostained with an antibody against Drosophila synaptotagmin. The two signals overlap to a great extent, but there are some areas in which the GFP signal is seen in the absence of Syt labeling. Scale bars, 4 μm.