Investigating CaMKII regulation of extracellular vesicle trafficking to promote synaptic plasticity

项目总结

PROJECT SUMMARY Extracellular vesicles (EVs) are small membrane-bound compartments that exchange materials between cells, and play an important role in cell communication in the nervous system. Neuronal EVs mediate activity- dependent synaptic plasticity, as well as the spread and clearance of toxic protein aggregates associated with neurodegenerative disorders such as Alzheimer’s Disease and Parkinson’s Disease. EV biogenesis and secretion occurs via endosomal trafficking, but the mechanisms by which neuronal activity regulates these cell biological processes have not been well characterized. By identifying activity-dependent mechanisms influencing neuronal EV dynamics, we will gain greater insight into basic and pathological processes in the nervous system. The majority of EV research utilizes in vitro non-neuronal cell models to isolate heterogenous EV populations, making direct measurements of neuronal EV biogenesis and trafficking mechanisms challenging. The Drosophila neuromuscular junction (NMJ) serves as a powerful in vivo model that is highly amenable to manipulating and visualizing EV cargo. My preliminary findings in this system suggest that Calcium/calmodulin-dependent protein kinase II (CaMKII), a key synaptic protein involved in structural and functional forms of synaptic plasticity, plays a role in EV trafficking. Specifically, CaMKII null mutants showed significantly decreased levels of the EV cargo Syt4 in both EV precursors in the presynaptic neuron and postsynaptically secreted EVs. Syt4 modulates NMJ synaptic growth and neurotransmitter release in an activity-dependent manner, leading to my hypothesis that CaMKII regulates Syt4 EV signaling to promote structural and functional plasticity. In Aim 1, I will ask if CaMKII controls EV cargo levels in an endocytic trafficking pathway that we previously identified to mediate EV cargo trafficking. In the second aim, I will elucidate the relationship between CaMKII and Syt4 and test if they act in a shared pathway to promote structural and functional plasticity. In Aim 3, I will isolate the specific CaMKII function(s) involved in EV cargo and trafficking regulation. These aims will provide training in advanced imaging, quantitative image analysis, Drosophila genetics, and electrophysiology. The information obtained from this project will provide new insight into how CaMKII regulates EV trafficking to facilitate synaptic plasticity, and identify new activity-dependent mechanisms regulating EVs in the nervous system.