Cargo-Loading of Misfolded Proteins into Extracellular Vesicles: The CSPα-EV Export Pathway

Abstract

Extracellular vesicles (EVs) are a collection of secreted vesicles of diverse size and cargo that are implicated in the physiological removal of nonfunctional proteins as well as the cell-tocell transmission of disease-causing-proteins in several neurodegenerative diseases. We have shown that the molecular chaperone, cysteine string protein (CSPα; DnaJC5), is responsible for the export of disease-causing-misfolded proteins from neurons via EVs. We show here that CSPα-EVs efficiently deliver GFP-tagged 72Q huntingtin exon1 to naive neurons. When we analyzed the heterogeneous EV pool, we found that the misfolded GFP-tagged 72Q huntingtin exon1 cargo was primarily found in EVs between 180-240nm. We further determined that cargo-loading of GFP-tagged 72Q huntingtin exon1 into EVs was impaired by resveratrol. Importantly, in addition to CSPα, we identified two other J protein co-chaperones, DnaJB2 and DnaJB6, that facilitate EV export of GFP-tagged 72Q huntingtin exon1 . While human mutations in CSPα cause the neurodegenerative disorder, adult neuronal ceroid lipofuscinosis, mutations in DnaJB6 cause limb-girdle muscular dystrophy and mutations in DnaJB2 are linked to the neurodegenerative disorders, Charcot Marie Tooth disease, distal hereditary motor neuropathy, spinal muscular atrophy and juvenile Parkinsonism. Our data provides new insights into the parallels between proteostasis and EV export, as three J proteins linked to disease in humans are the same as those that mediate EV genesis and export of misfolded proteins.CSPα (DnaJC5) 1-198 DnaJB2 1-324-long DnaJB6 1-365-long J J CCC J CAAX box UIM UIM NLS

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