Molecular Mechanisms of Excitotoxic Neurodegeneration: Novel Death Pathways in C. Elegans - Stroke / brain ischemia is a leading cause of death, and survivors require extensive long-term rehabilitation and care. Stroke is also a major source of medical disparity. The study of the mechanism neuronal damage in brain ischemia has seen many setbacks, since some critical events typically happen before admission to the emergency department. At the molecular level, key events include synaptic accumulation of glutamate, hyper-stimulation of postsynaptic receptors, Ca2+ influx, functional mitochondrial collapse, and cellular disintegration in a process called excitotoxicity. In spite of extensive efforts to develop intervention strategies, identified canonical events take place too early to be treated in the clinic, while subsequent proposed events remain highly controversial and scenario-specific. We now study these later steps in the C. elegans animal model system, under the premise that events that are conserved through large evolutionary distances are likely to be key steps in the essential core of the degenerative process. We take advantage of the particularly powerful set of technologies available in this model system. We hypothesize that while a number of signaling cascades converge on the mitochondria to produce excitotoxic necrosis, two novel effects are particularly important: 1) we identify a scantly studied mechanism where the Ca2+ sensitive kinase DAPK cooperates with p53 to cause necrosis by translocation of p53 into the mitochondrial matrix, interaction with CypD, and opening of the mitochondrial inner membrane’s mPTP. 2) we suggest that overstimulation of the mitochondria (following the excessive depolarization of the postsynaptic neurons) causes buildup of mitochondrial lipid peroxides, leading to membrane damage and cellular necrosis by ferroptosis. Finally, we suggest that additional novel mechanisms could be identified by an unbiased screen designed to detect new, previously unappreciated mechanisms in excitotoxic necrosis. We aim to study the DAPK/mitochondrial p53/CypD/mPTP axis by combining imaging, genetic KOs, and conditional expression. We will use similar approaches to study mitochondrial ferroptosis in excitotoxicity. Depending on progress in the previous aims, we will characterize novel mutants that show suppressed or enhanced excitotoxic necrosis. We will illuminate conserved, novel, and non-immediate mechanisms of neuronal damage in excitotoxicity. We hope these insights can later be used to develop new intervention strategies in stroke, a major cause of medical disparity. Relevance to human health: This project addressed stroke, a critical unmet need in healthcare with particular significance of minority populations. The life-threatening initial condition, and the devastating effects on quality of life for stroke survivors, call for a concerted effort to find new intervention strategies. We illuminate novel non-immediate mechanisms in stroke-related excitotoxicity and address core processes likely to be conserved across many forms of this neurodegenerative process. Stroke remains a leading cause of death and disability, pressing the need to find novel intervention strategies in a clinically feasible time-frame.
