Quantitative mapping of molecules and release properties at nerve terminals

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DESCRIPTION (provided by applicant): Information flow in the brain is mediated by transduction of electrical information into chemical information and back again at chemical synapses. Synapses are made up of crucial cellular machineries that orchestrate a balance of membrane traffic to and from the plasma membrane. Our goal is to develop detailed quantitative understanding of the synapse both in terms of physiological responses to action potential stimuli as well as the molecular underpinnings of its function. One of the most important functional elements is the voltage-gated calcium channel as it converts the electrical signal into a flux of calcium that drives neurotransmitter release in a highly non-linear fashion. We recently developed sensitive approaches that allow us to characterize key properties of these channels and the electrical signal that controls them in their native environment, the nerve terminal. The goal of this project is determine the molecular basis of key mechanisms that determine VGCC function. The first aim will examine the mechanisms of a novel form of adaptive plasticity whereby changes in VGCC number at nerve terminals in turn changes the shape of the electrical signal (the action potential). These experiments make use of an emerging technology of genetically-encoded fluorescent voltage indicators that allow one to quantitatively measure the action potential waveform in the nerve terminal and how it is controlled. Our second Aim will use another new technology allowing us to determine how long VGCCs typically stay resident in the active zone, whether they can recycle through an intracellular presynaptic compartment and how these dynamics are controlled by activity, calcium influx and a number of presynaptic proteins. The third Aim will examine how different active zone proteins, in particular Munc13 and Rim1, control different functional and cell biological aspects of VGCC function at nerve terminals.