Fundamental Biology of Neuronal Extracellular Vesicles

Project Summary Extracellular vesicles carry Aβ and tau that may spread pathogenic proteins across the brain, promote Aβ aggregation and accelerate amyloid plaque formation, and may also serve as biomarkers of Alzheimer's disease. EVs from blood, cerebral spinal fluid, and cell culture contain Aβ and tau and are proposed to be central mediators in the progression of Alzheimer's disease pathology. Conversely, EVs may have benefits in Alzheimer's disease: neuron-derived EVs promote uptake of Aβ by microglia and reduce extracellular levels of Aβ in cultured cells. Up-regulation of EV secretion - induced by neutral sphingomyelinase knockdown - efficiently reduced extracellular levels of Aβ in a co-culture of neuronal and microglial cells. The role of EVs in Alzheimer's disease is currently a major mystery of the disease mechanism. We will study how neuronal EV shedding is modulated by factors relevant to Alzheimer's disease, including age, oxidative stress, and proteostasis and neuron-glia dysfunction. Virtually all cell types in the brain release EVs including stem cells, neurons, astrocytes, microglia, and oligodendrocytes. EVs may be used by cells as a form of intercellular communication and may thereby mediate a broad range of physiological and pathological processes. Cells package beneficial or toxic EV cargo to promote health or disease. In the mammalian nervous system, EVs have neuroprotective roles against oxidative stress, cellular stress, and ischemia; and may also promote myelination in aging. In the brain, EVs may carry aggregation-prone cargo and contribute to the spread of Alzheimer's diseases. Understanding the fundamental biology of an EV-based signaling in vivo is essential for elaborating their physiological and pathological functions in Alzheimer's disease. A basic molecular dissection is critical for developing novel therapeutic applications. biology has been thwarted by a A big problem, however, is that advancing mechanistic dissection of EV lack of tractable experimental animal systems. We propose to take advantage of the powerful and unparalleled cell biological and molecular approaches that can be applied in the nematode C. elegans as a springboard to study the fundamental biology of neuronal EVs in vivo. We developed the first system to study neuronal EV biogenesis, shedding, targeting and signaling in living animals, and this strategy will overcome limitations of cell-culture based studies. This innovative approach will be used to tackle major challenges in the EV field . Our goals are to: 1) Determine the impact of neuronal activity, age and stress on neuronal EV shedding and signaling; 2) Decipher molecular mechanisms that control neuronal EV shedding; and 3) Determine the functions of neuronal EVs in long- distance intercellular communication and in neuron-glia communication. Our work should inform the fundamental biology of neuronal EVs relevant to both healthy brain aging and Alzheimer's disease and identify therapeutic targets to combat diseases like Alzheimer's associated with abnormal EV signaling.