A high affinity RIM-binding protein/Aplip1 interaction prevents the formation of ectopic axonal active zones

Elife. 2015 Aug 14;4:e06935. doi: 10.7554/eLife.06935.

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.

Keywords: AZ scaffold proteins; D. melanogaster; active zone; axonal transport; neuroscience; synapses; transport adaptor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axonal Transport*
  • Binding Sites
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • DNA Mutational Analysis
  • Drosophila / physiology*
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Optical Imaging
  • Protein Binding
  • Protein Interaction Mapping
  • Protein Transport
  • rab3 GTP-Binding Proteins / metabolism*

Substances

  • APP-like protein interacting protein 1, Drosophila
  • Carrier Proteins
  • Drosophila Proteins
  • RIM protein, Drosophila
  • rab3 GTP-Binding Proteins