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

It is well established that the synaptic vesicle fusion with the presynaptic membrane is
mediated by the SNARE proteins that force the two membranes together. The key
players that synchronise vesicle fusion to neuronal spikes are presynaptic calcium
sensors - synaptotagmins. The current view is that SNARE complexes on docked
vesicles are 'clamped' in a partially assembled state close to the point of triggering
fusion by synaptotagmin molecules. Calcium binding by synaptotagmins removes the
clamp and allows full assembly of SNAREs that triggers fast vesicle exocytosis. The
recent crystal structure of the SNARE-synaptotagmin complex prompted several
mechanistic models that can explain how synaptotagmin isoforms with distinct
molecular properties regulate kinetics and plasticity of neurotransmitter release [3].
These models are intensely debated and call for systematic testing [4]. The main goal
of the current PhD project will be to capitalise on our recent methodological
breakthroughs [1,2] to obtain missing mechanistic insights into how different
synaptotagmins (specifically Syt1 and Syt7) shape the timing and the plasticity of
neurotransmitter release in central synapses. (i) The student will combine genetic
manipulation of Syt1 and Syt7 with imaging of quantal glutamate release and of
presynaptic calcium dynamics in individual synaptic terminals (K. Volynski and D.
Kullmann laboratories at UCL. Critically, after imaging vesicular release, the student
will perform a post-hoc immunofluorescence analysis of the same synapses (see the
rotation project above). This will allow them to relate the functional presynaptic
properties to the expression levels of different synaptotagmins and the other
components of vesicular release machinery. (ii) In collaboration with the Department
of Computer Science at the University of Warwick (Prof. Yulia Timoffeva) they will
develop a computational model incorporating the presynaptic calcium dynamics and
the well-established calcium, membrane- and SNARE-binding properties of
synaptotagmins, and relate it to the experimental data [5].