Thursday, November 21, 2024
11/21/2024
PROJECT SUMMARY Over the past two decades, the role of astrocytes in brain physiology has become clearer. Astrocytes control neuronal function by modulating synaptic transmission, ion gradients, and more. They sense and rapidly respond to synaptic activity. Glutamate, the primary excitatory neurotransmitter in the central nervous system, is essential for normal brain function. In the healthy brain, once released from neurons, glutamate is transported into astrocytes by the excitatory amino acid transporters (EAATs) GLT-1 and GLAST. Previously, using iGluSnFR-based glutamate imaging and electrophysiology in the healthy adult mouse cortex, our lab has shown that glutamate uptake is slowed up to threefold following bursts of neuronal activity. We suspected that this occurs because neuronal activity generates action potentials, causing focal increases in extracellular potassium ([K+]e). We showed that increases in [K+]e drives local astrocyte depolarization, causing voltage-dependent inhibition of EAATs and prolonging extracellular glutamate transients. Our model suggests that dysregulation of both EAATs and astrocytic K+ uptake, mediated by the K+ channel Kir4.1, can both contribute to disrupted glutamate dynamics, but the exact role these channels and transporters play is unknown. We hypothesize that EAATs, like GLT-1, drive uptake while Kir4.1 shapes activity-dependent slowing of glutamate. This F99/K00 D-SPAN proposal encompasses 2 Aims detailing my goals and objectives. In Aim 1, I describe my progress thus far as well as my proposed research to complete my Ph.D. Key preliminary data using the controlled cortical impact (CCI) model of traumatic brain injury (TBI) in mice show 3 days after injury (1) glutamate decay time constants are slowed, (2) peak glutamate response is increased, (3) GLT-1 expression is decreased, and (4) Kir4.1 expression is not altered. To better understand Kir4.1’s importance to glutamate clearance, we will utilize a Kir4.1fl/fl mouse line and AAVs to conditionally and focally knockout Kir4.1 in astrocytes. When completed, this study will provide novel insight into how glutamate dynamics are altered by TBI, the role of Kir4.1 in shaping glutamate uptake, and how these molecular changes in astrocytes drive synaptic activity. In Aim 2, I outline my post-doctoral aspirations of studying glial function and how glia contribute to neurological disease. I will identify a strong post-doctoral laboratory and institution that promotes innovative scientific research, collaboration, diversity, professional growth, and pushes forward the biomedical field. With the support of my sponsor, Dr. Chris Dulla, I have grown as a scientist by attending multiple conferences and workshops, published in high impact journals, and grown in my confidence. I have identified my strengths and areas for growth as a scientist, mentor, and member of the scientific community. Ultimately, I believe I am at a perfect juncture to appreciate and benefit from such a fantastic opportunity to be a part of the D-SPAN community and this award will propel me in my academic and professional pursuits of being an independent research scientist.
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