Synergistic regulation of neurotransmitter release and short-term synaptic plasticity by different members of the synaptotagmin family

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It is well established that the synaptic vesicle fusion with the presynaptic membrane ismediated by the SNARE proteins that force the two membranes together. The keyplayers that synchronise vesicle fusion to neuronal spikes are presynaptic calciumsensors - synaptotagmins. The current view is that SNARE complexes on dockedvesicles are 'clamped' in a partially assembled state close to the point of triggeringfusion by synaptotagmin molecules. Calcium binding by synaptotagmins removes theclamp and allows full assembly of SNAREs that triggers fast vesicle exocytosis. Therecent crystal structure of the SNARE-synaptotagmin complex prompted severalmechanistic models that can explain how synaptotagmin isoforms with distinctmolecular properties regulate kinetics and plasticity of neurotransmitter release [3].These models are intensely debated and call for systematic testing [4]. The main goalof the current PhD project will be to capitalise on our recent methodologicalbreakthroughs [1,2] to obtain missing mechanistic insights into how differentsynaptotagmins (specifically Syt1 and Syt7) shape the timing and the plasticity ofneurotransmitter release in central synapses. (i) The student will combine geneticmanipulation of Syt1 and Syt7 with imaging of quantal glutamate release and ofpresynaptic calcium dynamics in individual synaptic terminals (K. Volynski and D.Kullmann laboratories at UCL. Critically, after imaging vesicular release, the studentwill perform a post-hoc immunofluorescence analysis of the same synapses (see therotation project above). This will allow them to relate the functional presynapticproperties to the expression levels of different synaptotagmins and the othercomponents of vesicular release machinery. (ii) In collaboration with the Departmentof Computer Science at the University of Warwick (Prof. Yulia Timoffeva) they willdevelop a computational model incorporating the presynaptic calcium dynamics andthe well-established calcium, membrane- and SNARE-binding properties ofsynaptotagmins, and relate it to the experimental data [5].