Distinct Rab11-associated membrane trafficking pathways bidirectionally control neuronal extracellular vesicle cargo traffic

Abstract

Neuronal extracellular vesicles (EVs) are released from synapses, and play roles in cellular communication, proteostasis, and the spread of toxic proteins in disease. The small GTPase Rab11 is required to maintain a reservoir of EV cargoes at presynaptic terminals, but how its diverse effector proteins contribute to this function and where Rab11 acts in neurons remains unclear. Using Drosophila motor neurons as a model, we show that EV cargoes redistribute from synapses to axons and cell bodies in rab11 mutants, concomitant with reduced release from synapses. We conducted a directed genetic screen of Rab11-associated factors and found that they have distinct roles in EV trafficking. Tethering and sorting factors are required to maintain levels of presynaptic EV precursors, supporting the hypothesis that Rab11 regulates EV cargo pools through recycling flux rather than by directly mediating EV release. Unexpectedly, we found that different classes of Rab11-associated proteins have opposite functions: the motor protein MyoV and the PI4KIII component Rbo sustain cargo levels at synapses, while the motor adaptor Nuf/Rab11FIP4 and the PI4KIII{beta} homolog Fwd restrict cargo levels. Together, these results indicate that Rab11 regulates multiple distinct organelle transport trajectories and PI(4)P populations to direct EV cargoes toward different cellular fates.