Siebert, M.; Böhme, M.A.; Driller, J.H.; Babikir, H.; Mampell, M.M.; Rey, U.; Ramesh, N.; Matkovic, T.; Holton, N.; Reddy-Alla, S.; Göttfert, F.; Kamin, D.; Quentin, C.; Klinedinst, S.; Andlauer, T.F.; Hell, S.W.; Collins, C.A.; Wahl, M.C.; Loll, B.; Sigrist, S.J.: A high affinity RIM-binding protein/Aplip1 interaction prevents the formation of ectopic axonal active zones. eLife 4 (2015), p. e06935/1-30
10.7554/eLife.06935
Open Access Version (externer Anbieter)
Abstract:
Synaptic vesicles (SVs) fuse at active zones (AZs) covered by a protein scaffold, at Drosophila synapses comprised of ELKS family member Bruchpilot (BRP) and RIM-binding protein (RBP). We here demonstrate axonal co-transport of BRP and RBP using intravital live imaging, with both proteins co-accumulating in axonal aggregates of several transport mutants. RBP, via its C-terminal Src-homology 3 (SH3) domains, binds Aplip1/JIP1, a transport adaptor involved in kinesin-dependent SV transport. We show in atomic detail that RBP C-terminal SH3 domains bind a proline-rich (PxxP) motif of Aplip1/JIP1 with submicromolar affinity. Pointmutating this PxxP motif provoked formation of ectopic AZ-like structures at axonal membranes. Direct interactions between AZ proteins and transport adaptors seem to provide complex avidity and shield synaptic interaction surfaces of pre-assembled scaffold protein transport complexes, thus, favouring physiological synaptic AZ assembly over premature assembly at axonal membranes.