Lipid-binding ability of Prx2 regulates the structural and functional properties of exosomes from SW480 cells

Exosomes are nanoscale extracellular vesicles that play a critical role in intercellular communication, contributing to health maintenance and disease progression. Since Prx2 is often abundant in exosomes, this study investigated how its lipid-binding ability regulates Prx2's localization and functional state on/within exosomes. In SW480 cells, wild-type Prx2 predominantly localized on the exosomal surface via binding to phosphatidylserine (PS). In contrast, a lipid-binding-deficient mutant (MT) was enriched within the lumen, likely due to increased retention in the cytosol during exosome biogenesis. Despite this difference, high-speed atomic force microscopy (HS-AFM) observations revealed no significant difference in exosome size or stiffness between the two, suggesting preserved vesicular architecture. Importantly, PS-binding triggered a functional switch: surface-localized Prx2 lost its peroxidase activity but acquired molecular chaperone activity. Consistently, WT exosomes strongly suppressed protein aggregation in thermal assays, whereas MT exosomes exhibited weaker effects. These findings identify PS binding as a molecular switch that dictates both the localization and function of Prx2, indicating a role for exosome-associated Prx2 in extracellular protein quality control.