Metabolic Mechanisms of Copper-Dependent Neurodegeneration and Excitability in Menkes Disease

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PROJECT SUMMARY Menkes disease is a rare genetic condition in which the disruption of copper homeostasis induces neurodegeneration and other neurological symptoms soon after birth. The underlying mechanisms of Menkes neuropathology remain unclear, but the metabolic changes observed in Menkes disease and the crucial role of mitochondria in neurons point to dysregulation of cellular bioenergetics as a possible factor. Preliminary data in human cells indicates that copper depletion decreases expression of genes regulated by hypoxia induced factor 1 alpha (HIF-1α). HIF-1α is a transcription factor sensitive to metals and oxygen that regulates cellular bioenergetics by switching metabolism from mitochondrial oxidative phosphorylation to glycolysis. Further, these copper depleted cells exhibit increased mitochondrial respiration. Resolving the newly identified role of HIF-1α in regulating mitochondrial function is central to understanding how copper dyshomeostasis elicits neurodegeneration in Menkes disease. Thus, the overall objective of this F31 NRSA application is to test how copper depletion influences the HIF-1α pathway in neurons to regulate cellular metabolism and influence cell excitability and survival. The central hypothesis that will be tested in this proposal is that neuronal copper depletion selectively downregulates transcriptional activity of the HIF-1α pathway to redirect nutrients through mitochondrial respiration rather than glycolysis, rendering cells hyperexcitable due to production of reactive oxygen species by mitochondria and thus susceptible to cell death. In Aim 1, the HIF-1α pathway will be stimulated in copper depleted and control neuroblastoma cells or primary cultured neurons in order to comprehensively assess gene expression, determine binding of HIF-1α to target genes, and quantify mitochondrial respiration and glycolysis in the context of HIF-1α activity. In Aim 2, genetically encoded calcium indicators will be used in primary neuronal cultures from wildtype or neuronal-specific copper depleted mice while stimulating the HIF-1α pathway to assess how copper depletion affects cell excitability and determine the effect of HIF-1α on these phenotypes. Completion of these aims will clarify the metabolic pathways responsive to copper and their effects on neuronal function. The application of this knowledge will inform our understanding, research, and treatment of neuropathology of diseases known to be associated with dysregulated metals and/or metabolism for which there are currently limited therapeutics.