A03 - In vivo analysis of active zone assembly

Principal Investigators

Prof. Dr. Stephan Sigrist, FU Berlin

Dr. Astrid Petzoldt, FU Berlin

Synapses exocytose synaptic vesicles (SVs) at specialized membrane sites called active zones (AZs) covered by protein scaffolds, which control SV exocytosis. Bruchpilot (BRP) is a major scaffold building block in Drosophila. Our recent work suggests that DSyd-1 orchestrates the assembly of the BRP-scaffold via trans-synaptic DNrx-DNlg1 signaling. Here we combine Drosophila genetics with in vivo imaging and super-resolution light and electron microscopy to address the role of DSyd-1 and DNrx/DNlg1 in BRP-scaffold assembly. Novel factors involved in DSyd-1- and DNrx/DNlg1-mediated BRP-scaffold assembly shall be identified and the dynamics underlying BRP-scaffold assembly and turnover will be investigated.

Model highlighting the role of Spn in controlling Nrx-1 synaptogenic activity in conjunction with Syd-1.

The intracellular interaction of Nrx-1 (binding postsynaptic Nlg1 (dark blue)) with Syd-1, via a PDZ binding motif, marks the entry of a nascent synapse into an irreversible assembly stage. To keep this process in balance, Spn takes away fractions of Nrx-1, also via PDZ binding motif, to be stalled by Syd-1. Thus, Spn mediates the higher mobility of Nrx-1, ensuring the already stalled Nrx-1/Syd-1 complex will maturate (incorporation of BRP presynaptically and maturation of PSDs postsynaptically). In the absence of Spn, Nrx-1 is less mobile and, therefore, more efficiently dragged by Syd-1, resulting in many, but not fully matured synapses.


References:

  • Owald, D. et al. Cooperation of Syd-1 with Neurexin synchronizes pre- with postsynaptic assembly. Nat Neurosci 15, 1219-1226 (2012).

  • Walter, A. M., Haucke, V. & Sigrist, S. J. Neurotransmission: spontaneous and evoked release filing for divorce. Curr Biol 24, R192-194 (2014).

  • Haucke, V., Neher, E. & Sigrist, S .J. Protein scaffolds in the coupling of synaptic exocytosis and endocytosis. Nat Rev Neurosci 12, 127-138 (2011).

  • Liu, K. S. et al. RIM-binding protein, a central part of the active zone, is essential for neurotransmitter release. Science 334, 1565-1569 (2011).

  • Kittel, R. J. et al. Bruchpilot promotes active zone assembly, Ca2+ channel clustering, and vesicle release. Science 312, 1051-1054 (2006).

  • Owald, D. et al. A Syd-1 homologue regulates pre- and postsynaptic maturation in Drosophila. J Cell Biol 188, 565-579 (2010).

  • Owald, D. & Sigrist, S. J. Assembling the presynaptic active zone. Curr Opin Neurobiol 19, 311-318 (2009).

  • Banovic, D. et al. Drosophila neuroligin 1 promotes growth and postsynaptic differentiation at glutamatergic neuromuscular junctions. Neuron 66, 724-738 (2010).

  • Podufall, J. et al. A presynaptic role for the cytomatrix protein GIT in synaptic vesicle recycling. Cell Rep 7, 1417-1425 (2014).

  • Petzoldt, A. G. et al. Gating characteristics control glutamate receptor distribution and trafficking in vivo. Curr Biol 24, 2059-2065 (2014).