Quality Control of Damaged Proteins at Synapses

forthcoming

SYNDAM investigates how the brain detects and clears damaged proteins at the primary loci for information transfer and storage— synapses. The synapse expresses many proteins that are mutated or dysregulated in major brain disorders. The information transfer rate at synapses is high and, as a result, synapses are continuously exposed to oxidative challenges that arise from local mitochondrial respiration and oxidase activity. This puts synaptic proteins at risk. This risk is exacerbated by the long lifetimes of neuronal proteins, which prolong their exposure to environmental assaults. It is unclear how this apparent risk is mitigated by protein quality control at synapses— a vital process for brain waste clearance and synaptic homeostasis e.g. during sleep. In this context, we face a fundamental knowledge gap: we do not even know which synaptic proteins are targets of oxidative damage, let alone how such damage may trigger protein clearance via key cellular degradation signals such as ubiquitin. This elusive damage-control mechanism is critical for the restorative function of sleep. To address these knowledge gaps, SYNDAM will (1) identify the synaptic ubiquitin regulators that can detect protein oxidative damage (2) visualize the activity-dependent synaptic protein oxidative damage and ubiquitylation in situ (3) investigate sleep-regulated detection and clearance of protein oxidative damage through ubiquitin To achieve these goals, we will combine subcellular oxidized and ubiquitylated proteomics, DNA PAINT-based single-molecule localization, chemogenetic induction of synaptic oxidative damage, in situ detection of protein modifications, functional imaging, synaptic activity manipulations, electrophysiology, and sleep behaviour in mice. SYNDAM will elucidate a critical surveillance mechanism for removing damaged proteins before protein toxicity activates cellular stress responses that may lead to neuroinflammation and degeneration.