In project A07 the SH3 domain containing scaffolding proteins intersectin 1, endophilin A1 and SNX9 and their interaction partners are studied in molecular detail. These proteins are critical for endocytosis and/or synaptic vesicle clustering and the goal here is to understand the mechanistic prerequisites of the compositional dynamics that accompanies synaptic vesicle cycling. Since proline-rich sequence (PRS) recognition by SH3 domains is characterized by interactions with high off-rates, dynamic changes in macromolecular complex associations can be rapidly tuned by the abundance, the localization and the post-translational modifications of the SH3 domains or their interaction partners. We could show that intersectin 1 and endophilin directly interact by an unusual SH3-SH3 domain interaction, still allowing proline-rich sequences, for example from dynamin, to bind to the canonical endophilin-SH3 binding site (Fig. 1).
In the current funding period we plan to further investigate SH3 domain mediated interactions in the larger complex and in the context of lipid membranes. Furthermore we will investigate the interplay between intra- and intermolecular interactions by structural biology and biophysical methods.
Pechstein, A., Shupliakov, O. & Haucke, V. Intersectin 1: a versatile actor in the synaptic vesicle cycle. Biochem. Soc. Trans. 38, 181-186 (2010).
Saheki, Y. & De Camilli, P. Synaptic vesicle endocytosis. Cold Spring Harbor Perspec Biol 4, a005645-a005645 (2012).
Posor, Y. et al. Spatiotemporal control of endocytosis by phosphatidylinositol-3, 4-bisphosphate. Nature 499, 233-237 (2013).
Pechstein, A.., Gerth, F., Milosevic, I., Jäpel, M., Eichhorn-Grünig, M., Vorontsova, O., Bacetic, J., Maritzen, T., Shupliakov, O., Freund, C. & Haucke, V. (2015) Vesicle uncoating regulated by SH3-SH3 domain-mediated complex formation between endophilin and intersectin at synapses, EMBO Rep.16, 232-239