Superoxide dismutase impacts extracellular vesicle shedding and uptake

Abstract

Extracellular vesicles (EVs), which transfer bioactive macromolecules between cells, play a critical role in the pathogenesis of multiple neurodegenerative diseases. Focus has centered on how altered EV contents propagate disease and on the potential for EVs as diagnostic biomarkers, while the effects of pathogenic factors on EV release are poorly understood. Using a functional endogenous reporter, we showed that the key antioxidant enzyme superoxide dismutase 1 (SOD-1) is expressed in C. elegans EV-releasing neurons, localizes to the cytoplasm, and reduces levels of reactive oxygen species (ROS). We then defined how sod-1 mutations affect EV shedding from sensory neuron primary cilia into the environment, ciliary enrichment of proteins packaged into EVs, and glial uptake of EVs in vivo, by imaging C. elegans expressing fluorescent protein-tagged EV cargoes. Deletion of SOD-1, as well as the SOD-1(G85R) amyotrophic lateral sclerosis (ALS) pathogenic variant, increased EV shedding from the cilium distal tip, and this was associated with greater abundance of EV cargo in this ciliary compartment. In contrast, loss of SOD-1 reduced the glial uptake of a different EV subpopulation that is shed from the ciliary base, without affecting release into the environment. These results demonstrate that SOD-1 has a subtype-specific effect on the release of EVs with distinct signaling potentials. Intriguingly, we discovered that exposure to paraquat, which increases mitochondrial ROS, reduced the shedding of both distal tip and ciliary base-derived EVs. These opposing effects of the sod-1 mutations and paraquat treatment on EV release suggest that ROS in distinct subcellular compartments may differentially impact ciliary EV shedding.