Cytosolic dopamine determines hypersensitivity to blunt force trauma.

The selective vulnerability of dopaminergic neurons to trauma-induced neurodegeneration is conserved across species, from nematodes to humans. However, the molecular mechanisms underlying this hypersensitivity to blunt force trauma remain elusive. We find that extravesicular dopamine, a key driver of Parkinson's disease, extends its toxic role to the acute challenges associated with injury. Ectopic dopamine synthesis in serotonergic neurons sensitizes this resilient neuronal subtype to trauma-induced degeneration. While dopaminergic neurons normally maintain dopamine in a functional and benign state, trauma-induced subcellular redox imbalances elicit dopamine-dependent cytotoxicity. Cytosolic dopamine accumulation, through perturbations to its synthesis, metabolism, or packaging, is necessary and sufficient to drive neurodegeneration upon injury and during aging. Additionally, degeneration is further exacerbated by rapid upregulation of the rate-limiting enzyme in dopamine synthesis, cat-2, via the FOS-1 transcription factor. Fundamentally, our study in C. elegans unravels the molecular intricacies rendering dopaminergic neurons uniquely prone to physical perturbation across evolutionary lines.

Loss of heat shock factor initiates intracellular lipid surveillance by actin destabilization.

Cells sense stress and initiate response pathways to maintain lipid and protein homeostasis. However, the interplay between these adaptive mechanisms is unclear. Herein, we demonstrate how imbalances in cytosolic protein homeostasis affect intracellular lipid surveillance. Independent of its ancient thermo-protective properties, the heat shock factor, HSF-1, modulates lipid metabolism and age regulation through the metazoan-specific nuclear hormone receptor, NHR-49. Reduced hsf-1 expression destabilizes the Caenorhabditis elegans enteric actin network, subsequently disrupting Rab GTPase-mediated trafficking and cell-surface residency of nutrient transporters. The ensuing malabsorption limits lipid availability, thereby activating the intracellular lipid surveillance response through vesicular release and nuclear translocation of NHR-49 to both increase nutrient absorption and restore lipid homeostasis. Overall, cooperation between these regulators of cytosolic protein homeostasis and lipid surveillance ensures metabolic health and age progression through actin integrity, endocytic recycling, and lipid sensing.

CRISPR/Cas9-engineered Drosophila knock-in models to study VCP diseases.

Mutations in Valosin Containing Protein (VCP) are associated with several degenerative diseases, including multisystem proteinopathy (MSP-1) and amyotrophic lateral sclerosis. However, patients with VCP mutations vary widely in their pathology and clinical penetrance, making it difficult to devise effective treatment strategies. A deeper understanding of how each mutation affects VCP function could enhance the prediction of clinical outcomes and design of personalized treatment options. The power of a genetically tractable model organism coupled with well-established in vivo assays and a relatively short life cycle make Drosophila an attractive system to study VCP disease pathogenesis. Using CRISPR/Cas9, we have generated individual Drosophila knock-in mutants that include nine hereditary VCP disease mutations. Our models display many hallmarks of VCP-mediated degeneration, including progressive decline in mobility, protein aggregate accumulation and defects in lysosomal and mitochondrial function. We also made some novel and unexpected findings, including nuclear morphology defects and sex-specific phenotypic differences in several mutants. Taken together, the Drosophila VCP disease models generated in this study will be useful for studying the etiology of individual VCP patient mutations and testing potential genetic and/or pharmacological therapies.