Activation of Transcriptional Neuroprotective Programs in Nematode Excitotoxicity

City College Of New York, New York NY

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Abstract

Abstract: Activation of Transcriptional Neuroprotective Programs in Nematode Excitotoxicity Excitotoxicity is a leading mechanism of necrotic neurodegeneration in stroke/brain ischemia, triggered by the exaggerated activation of Glutamate Receptors (GluRs). The complex labyrinth of signaling cascades that are suggested to lead from GluR over-activation to neurodegeneration prevents full understanding of the significance of core mechanisms. Surprisingly, GluRs also act to subdue toxic events by activating signaling cascades that lead to the transcription of pro-survival genes. Though these cascades offer an escape route from excitotoxic neurodegeneration, their identity is also shrouded in doubt and controversy. A few transcription factors (TFs) such as CREB & FoxO were suggested to be involved, but the study of their role needs to be re-examined more carefully: recent data suggests CREB?s & FoxO?s mechanisms of activation might be very different than previously proposed, and each one on its own might be too widely used to offer sufficient specificity. Accurate information on the mode of CREB and FoxO activation or their ability to mount a concerted transcriptional neuroprotective program in excitotoxic necrosis is missing, partially due to the confusion caused by the extensive crosstalk and redundancy in mammalian signaling cascades. We address these gaps by studying how both CREB and FoxO are regulated during excitotoxic necrosis and how they mitigate Glu overstimulation. We use C. elegans, a powerful, genetically accessible model where signaling cascades are simplified, but their core is conserved. We make novel observations on both cascades, suggesting that the insulin/FoxO signaling cascade is a novel conduit for GluR regulation of neuroprotective transcription, and that activation of CREB in excitotoxic necrosis is non-canonical. We aim to determine if GluRs connect through Tamalin & Cytohesin to Insulin/FoxO signaling as a novel conduit to induce neuroprotection. We will use fluorescent tags and co-IP in transgenic animals to test for colocalization & interaction. We will over-express interaction domains to disrupt exiting interactions and test the effect on excitotoxicity; We further aim to determine if CREB activation in excitotoxicity is non-canonical. We will study the involvement of candidate components by KO, express phosphorylation-site mutants in transgenic animals, and monitor the effect on neurodegeneration ; Lastly, we aim to identify transcriptional targets co-regulated by FoxO & CREB that protect from excitotoxicity. We will perform a transcriptome analysis specifically in cells at risk of degeneration, compare excitotoxic to neuroprotective conditions, and select candidate targets for future research using evaluation by a well-defined set of criteria. Put together, we will illuminate the pathways used to trigger neuroprotection in response to Glu overstimulation, and detect mediators of neuroprotection in excitotoxic necrosis. Understanding the concerted neuroprotective signaling cascades and identifying conserved mediators of neuroprotection in the nematode can provide novel insights into similar processes in mammals, ultimately inspiring new therapeutic interventions in stroke / brain ischemia.