B07: Leist

This project focusses on the role of cellular metabolites in the control of neuronal death decisions. Metabolic control plays many important roles in the nervous system. However, studies on the connection of neuronal metabolism with cell death have been particularly difficult, due to the high cellular heterogeneity of brain tissue or primary cultures. Here, we use the availability of highly homogeneous cultures, of novel fully defined media, and of a well-characterized set of neurotoxicants to address metabolic control of neuronal death. The main goal is to understand how the ensemble of metabolites determines whether a toxicant leads to the demise of an entire cell by apoptosis or by a non-apoptotic death (e.g. ferroptosis) or to a selective neurite degeneration. The metabolic states in a cell are controlled on one hand by the physiological state (cell type, nutrient availability, etc.) and on the other hand by effects of the toxicant. We study here two physiological states distinguished by the main source of cellular ATP from mitochondria or glycolysis. Moreover, we generate sub-states with high or low iron availability. We have found in pilot studies that mitotoxicants with apparently similar modes of action (block of complex I of the respiratory chain) can lead to apoptosis, ferroptosis or specific neurite degeneration, depending on the cellular metabolic ground state. We hypothesize that the global (or local) ratios of ATP-depletion, NADH oxidation and formation of reactive oxygen species (ROS) control switching between the cell death modes, and we will use approaches to systematically vary and analyze these factors. In Aim A of the project, we correlate metabolic changes and the type of cell death observed. This involves system-wide studies of the metabolome and transcriptome and the incorporation of the findings into predictive models. In Aim B of this project, we study whether it is possible to switch types of neurodegeneration by controlled interventions into metabolism or signaling. For instance, the cellular oxidation status (ROS, reduced thiol levels, availability of free iron, etc.) will be modified; in another of our approaches, the NAD+ levels will be modified by metabolite supplementation or by modulation of the NADase SARM1 (a novel controller of neurite death). Altogether, we expect to define key metabolites involved in cell fate decisions, and to describe a network of interactions for such control factors.