Synapsin 2a tetramerisation selectively controls the presynaptic nanoscale organisation of reserve synaptic vesicles.
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Neurotransmitter release relies on the regulated fusion of synaptic vesicles (SVs) that are tightly packed within the presynaptic bouton of neurons. The mechanism by which SVs are clustered at the presynapse, while preserving their ability to dynamically recycle to support neuronal communication, remains unknown. Synapsin 2a (Syn2a) tetramerization has been suggested as a potential clustering mechanism. Here, we used Dual-pulse sub-diffractional Tracking of Internalised Molecules (DsdTIM) to simultaneously track single SVs from the recycling and the reserve pools, in live hippocampal neurons. The reserve pool displays a lower presynaptic mobility compared to the recycling pool and is also present in the axons. Triple knockout of Synapsin 1-3 genes (SynTKO) increased the mobility of reserve pool SVs. Re-expression of wild-type Syn2a (Syn2aWT), but not the tetramerization-deficient mutant K337Q (Syn2aK337Q), fully rescued these effects. Single-particle tracking revealed that Syn2aK337QmEos3.1 exhibited altered activity-dependent presynaptic translocation and nanoclustering. Therefore, Syn2a tetramerization controls its own presynaptic nanoclustering and thereby contributes to the dynamic immobilisation of the SV reserve pool.
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Acknowledgements: The super-resolution imaging was carried out at the Queensland Brain Institute’s (QBI’s) Advanced Microscopy Facility, led by Dr. Rumelo Amor and his team. We thank the QBI Information technology (IT) facility members and the entire QBI University of Queensland’s Biological Resources (UQBR) animal team for their ongoing technical assistance with our projects. We thank Dr. Alex McCann for critically appraising and editing the manuscript. We acknowledge Prof. Volker Haucke for providing the Synaptotagmin1-pHluorin plasmid, Prof. Vladislav Verkhusha for providing the pmTagBFP-N1 plasmid, Dr Sang-Ho Song for providing the Synapsin 2aWT-mEos3.1 and Synapsin 2aK337Q-mEos3.1 plasmids, Karen Chung for providing synapsin TKO mice and Melissa Yeow (Nanyang Technical University, Singapore) for dissecting the SynTKO hippocampi. This work was supported by an Australian Research Council Discovery Project grant (ARC) (DP230102278), a National Institute On Aging of the National Institutes of Health (NIH) grant R21AG080435, an ARC Linkage Infrastructure, Equipment, and Facilities grant (LE130100078), and a National Health and Medical Research Council (NHMRC) Fellowship (1155794) awarded to F.A.M., as well as grant OFIRG/MOH-000225-00 from the Singapore National Medical Research Council to G.J.A. R.M.M. was supported by a Clem Jones Foundation Fellowship, the University of Queensland (UQ) Research Stimulus Allocation 2 fellowship and the NHMRC Boosting Dementia Research Initiative. S.F.L. was supported by a Research Training Program (RTP) Scholarship. M.J. was supported by a UQ Amplify Fellowship, UQ Early Career Research Grant (2057309) and the Australian Research Council Discovery Early Career Researcher Award (DE190100565). D.H. was funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No 882673), and ANR AstroXcite.
Funder: ARC Linkage Infrastructure, Equipment, and Facilities grant (LE130100078) National Health and Medical Research Council (NHMRC) Fellowship (1155794)
Funder: European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No 882673) and ANR AstroXcite.
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2041-1723
