ИСТИНА

Membrane trafficking requires the coordination of hundreds of interacting proteins, which act in concert to drive cargo sorting, membrane tubulation, fission, and fusion. While well characterized individually, it is not understood how their activities are regulated and targeted in vivo to fulfill diverse roles within cells. Nervous Wreck (NWK) encodes an F-BAR/SH3 protein that regulates the traffic and signaling output of synaptic growth receptors at the Drosophila neuromuscular junction (NMJ) through its interactions with the membrane, actin nucleation machinery, and other endocytic proteins including dynamin and Dap160/Intersectin. Here, we find that the membrane binding and remodeling activities of the Nwk F-BAR domain are autoinhibited through direct interaction with its two C-terminal SH3 domains, and that this autoinhibition is important for Nwk localization and function in vivo. Unlike the isolated F-BAR domain, autoinhibited Nwk strictly requires self-assembly in order to stably interact with and remodel membranes. Previous models for autoregulation of BAR family proteins proposed that SH3 domains directly compete for membrane binding, controlling exchange of the protein between the cytosol and the membrane. We found that the Nwk auto-regulatory mechanism specifically limits promiscuous membrane binding and promotes higher order assembly. Further, we find that the endocytic scaffold Dap160, which regulates Nwk localization at the NMJ, relieves autoinhibition and increases both the rate and frequency with which Nwk associates with the membrane in vitro. These results suggest a complex regulatory mechanism, dependent on separable intra-and inter-molecular interactions, by which membrane remodeling is tightly regulated, and lend insight into the mechanisms employed by the cell to specifically target membrane remodeling.