A novel role of presynaptic periactive zone proteins in extracellular vesicle trafficking
Cassandra R Blanchette1, Amy L Scalera1, Zechuan Zhao1, Kathryn Harris2,3, Kate Koles1, Anna Yeh1, Julia K Apiki1, Bryan A Stewart2,3 and Avital A Rodal1
1Brandeis University, USA
2University of Toronto Mississauga, Biology, Mississauga, Canada
3University of Toronto, Cell and Systems Biology, Toronto, Canada
Extracellular vesicles (EVs) are small, endosomally-derived, membrane bound vesicles that mediate cell-cell communication in the healthy nervous system, as well as propagation of pathological proteins in neurodegenerative disease. However, it remains unclear how specific endosomal cargoes are sorted for release through the EV pathway. We identified an unexpected role for presynaptic periactive zone (PAZ) membrane remodeling proteins, which have canonical roles in clathrin-mediated endocytosis, in regulating the traffic of EV cargoes at presynaptic nerve terminals of Drosophila motor neurons. PAZ mutants, including those lacking synaptojanin, dynamin, endophilin, and the F-BAR/SH3 protein Nervous Wreck (Nwk) exhibit a local and dramatic decrease in the levels of the EV cargoes Synaptotagmin-4 (Syt4) and Amyloid Precursor Protein (APP) at presynaptic terminals. Further, this decrease is sufficient to abolish Syt4 function and reduce APP toxicity in the nervous system, suggesting that loss of specific EV cargoes may play unrecognized roles in canonical phenotypes of PAZ mutants. Interestingly, this novel EV cargo traffic defect is genetically separable from the well-established functions of these proteins in synaptic vesicle recycling and synaptic growth. Our data suggests a novel clathrin-dependent molecular mechanism that protects EV cargoes from local degradation at synapses, and promotes their release and function in EVs.