Fig 9. Schematic diagram shows model for Henji function at the NMJ.

At WT NMJs, Henji localizes at the SSR and binds with dPAK, preventing dPAK from localizing to the PSDs. With dPAK synaptic levels under control, the rate of GluRIIA clustering into PSDs is limited as dPAK is unavailable. At the henji mutant NMJ, unbound dPAK is activated and accumulates at PSDs to promote GluRIIA clustering and accumulation. Excess GluRIIA enhances presynaptic bouton addition, causing satellite boutons to form. Dashed arrows indicate unknown mechanisms. Curved arrows indicate localization of molecules into PSDs.