“Nwk protects extracellular vesicle cargoes from degradation in the nervous system”
Sara Hamadani, Cassandra Blanchette, Amy Scalera, Avital Rodal
Cargo trafficking via extracellular vesicles (EVs) is a vital biological process for cellular communication. EVs can transport a variety of cargoes such as DNA, RNA and protein. EV trafficking is thought to be linked to neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease, and EVs traffic disease-relevant cargoes. Knowledge gathered from studying extracellular vesicle trafficking in an intact nervous system, such as the Drosophila neuromuscular junction (NMJ), can be vital to understanding the underlying disease-causing pathways.
We have identified a role for Nervous Wreck (Nwk), an F-BAR/SH3 protein, in regulating EV traffic at the Drosophila NMJ. nwk mutant animals have a reduction in EV cargoes, including Syt4, an important protein for cellular communication and plasticity, pre- and postsynaptically at the NMJ. We hypothesized that the reason for this reduction of EV cargoes in nwk mutants is that cargoes are being sent to the lysosome for degradation rather than being sent out of the cell in EVs.
We tested this hypothesis by looking at nwk;spin double mutant Drosophila and found that disruption of the lysosome via loss of spinster in the nwk mutant background restores Syt4 levels presynaptically. Here, we utilized an alternative method to disrupt the lysosome in nwk animals to provide further support for our hypothesis that Syt4 is being sent to the lysosome for degradation in nwk mutant animals. We impaired lysosomal function using the drug chloroquine which raises lysosomal pH. We used a long-term treatment method in which the wild type and nwk mutant Drosophila larvae are grown on either control food or food containing chloroquine. Ultimately, we found Syt4 levels increased presynaptically but not postsynaptically in nwk mutant animals that were grown in food containing 4.5 mM chloroquine, compared to nwk mutants grown on control food. This is consistent with our hypothesis that Syt4 is being sent to the lysosome for degradation in a nwk mutant.
Support: MRSEC REU