Ternary Neurexin-T178-PTPR complexes represent a pre-synaptic core-module of neuronal synapse organization

Synapses, prototypic sites for neuronal communication, are key to brain function. Their organization and properties are instructed by synaptic cell adhesion molecules (sCAMs) that may operate independently or in coordination through yet unknown linker proteins. Here, we used multi-epitope affinity-purifications combined with quantitative mass spectrometry and immuno-EM to comprehensively map synaptic protein networks in the mouse brain.

We identify a pre-synaptic core-module assembled from the major sCAMs, Neurexins1-3 and LAR-type receptor protein-tyrosine-phosphatases (PTPRs), and the previously uncharacterized tetraspanins T178A/B. These ternary Neurexin-T178-PTPR complexes form through their trans-membrane domains and assemble during biogenesis in the ER. Loss of T178B leads to module destabilization, accompanied by strong reduction of LAR-PTPRs and re-distribution of synaptic Neurexins.

At synapses, the Neurexin-T178-PTPR module recruits stable trans-synaptic protein networks thereby interlinking machineries of the pre-synaptic active zone and establishing stable associations with post-synaptic neurotransmitter receptors. This work uncovers a widely distributed core-module for synaptic adhesion and trans-synaptic signaling in the mammalian brain. We thank the Fakler and Scheiffele lab members for helpful discussions and I.

Schaber for excellent technical assistance. B.F. appreciates the interactions with T. Südhof and his efforts leading to initiation of this project.

This work was supported by grants of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) TRR152 (project-ID 239283807), FA 332/15-1, 16-1 and 21-1 (to B.F.), the Swedish Research Council (grants 2017- 03331 and 2022-00817 to F.H.S.), the Swiss National Science Foundation (project 179432, TMAG-3-209273), the European Research Council (Advanced Grant (SPLICECODE) and the AIMS-2-TRIALS (supported by the Innovative Medicines Initiatives from the European Commission, to P.S), and the Japan Society for the Promotion of Science (KAKENHI 20H05628 and 25H01011 to M.Y.). Open Access funding enabled and organized by Projekt DEAL. These authors contributed equally: Spyros Thivaios, Jochen Schwenk.

Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg, Germany Spyros Thivaios, Jochen Schwenk, Aline Brechet, Sami Boudkkazi, Nithya Sethumadhavan, Phil Henneken, Maciej K. Kocylowski, Alexander Haupt, Jean-Baptiste van den Broucke, Akos Kulik, Uwe Schulte & Bernd Fakler Department of Neurophysiology, Keio University School of Medicine, Tokyo, Japan Eriko Miura, Ayumi Hayashi & Michisuke Yuzaki Department of Laboratory Medicine, Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden Department of Clinical Chemistry, Sahlgrenska University Hospital, Gothenburg, Sweden Biozentrum of the University of Basel, Basel, Switzerland Dietmar Schreiner, Agata Nowacka & Peter Scheiffele Logopharm GmbH, Schlossstr. 14, March-Buchheim, Germany Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Gothenburg, Sweden Signalling Research Centres BIOSS and CIBSS, Schänzlestr. 18, Freiburg, Germany Center for Basics in NeuroModulation, Breisacherstr. 4, Freiburg, Germany Correspondence to Jochen Schwenk or Bernd Fakler. The authors declare no competing interests.