Condensate Material Properties Influence Cargo Selection for Neuronal Extrusion via Large Extracellular Exopher Vesicles

Neurons can maintain proteostasis by extruding protein aggregates and damaged organelles via large extracellular vesicles called exophers. However, the biophysical rules governing exopher cargo selection remain poorly understood. Here, we discovered that biomolecular condensates can localize to exophers and investigated whether condensate material properties-ranging from liquids to dynamically arrested gels-determine their recruitment to exophers. By reprogramming interactions in a multidomain protein, we tuned condensate properties and linked them to neuronal exopher recruitment using a multidisciplinary approach combining in vivo dynamics, in vitro material properties, and molecular dynamics simulations. Our findings reveal that gel-like condensates with slower dynamics and higher viscoelasticity localize to exophers more avidly than dynamic liquid-like condensates, demonstrating a strong correlation between condensate dynamics and exopher recruitment. This work lays the framework for investigating the biophysical determinants of exopher cargo selection, providing critical insights into the influence of proteome material state on neuronal protein quality control.