CD14 and TLRs in Abeta-Induced Microglial Signaling

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DESCRIPTION (provided by applicant): This research proposal is designed to elucidate the mechanisms by which microglia recognize fibrillar beta amyloid (fAbeta) to induce a pro-inflammatory response. This is critical as inflammation has been shown to be intimately involved in the disease pathology of Alzheimer's disease (AD). Interactions of microglia with Ab plaques results in pro-inflammatory signaling cascades and the secretion of neurotoxic secretory products. Previous studies have demonstrated a multi-component receptor complex on the surface of microglia that that mediates the binding of fAb and subsequent activation of intracellular signaling pathways leading to a pro-inflammatory response and an induction of phagocytosis. Moreover, CD14, a protein found on the surface of monocytes and neutrophils that serves as a microbe-detecting receptor to activates immune cells to eliminate pathogens, has been implicated in binding fAb. We hypothesize that CD14 acts as a member of the fAb cell surface receptor complex to bind fAbeta and elicit a pro-inflammatory response. This proposal seeks to determine whether CD14 is required for fAb-induced signaling to intracellular effectors, and whether it associates with the receptor components to do so. It also seeks to identify the signaling cascades downstream of CD14 that produce an inflammatory response. To achieve these goals, she will use a combination of approaches, including function blocking antibodies and RNAi vectors to inhibit protein function, immunoprecipitation and FRET to detect association of fAb receptor complex molecules, Western blot analysis, real-time PCR, and ELISA to detect expression levels of signaling proteins, inflammatory molecules, and Ab peptides, and mice deficient in CD14, TLR4, TLR2, and MyD88, as well as those that model AD to examine the importance of CD14 in microglial activation by fAb and plaque development in a mouse model of AD. This application proposes to better understand the ways in which the immune cells of the brain work to trigger an immune response to the fibrillar Abeta deposits that form in the Alzheimer's disease brain. It will inform development of new therapeutic approaches and a better understanding these processes.