HSP110 dependent HSP70 disaggregation machinery mediates prion-like propagation of amyloidogenic proteins in metazoa

The gradual accumulation and prion-like propagation of -synuclein and other amyloidogenic proteins is associated with devastating neurodegenerative diseases. The metazoan disaggregation machinery, a specific combination of HSP70 and its co-chaperones, is able to disassemble -synuclein fibrils in vitro, but the physiological consequence in vivo is unknown. To explore this, we used Caenorhabditis elegans models that exhibit pathological features of -synuclein, such as misfolding, intercellular spreading and toxicity. We inhibited the HSP70 disaggregase by depleting the crucial component HSP-110 and monitored the effect on -synuclein related phenotypes. The knockdown of HSP-110 not only impaired HSP70 disaggregation activity and prevented the resolubilization of amorphous heat shock induced firefly luciferase aggregates, but also compromised the cellular folding capacity. In stark contrast, HSP-110 depletion reduced -synuclein foci formation, cell-to-cell transmission and toxicity. Similar effects were observed for a polyQ model substrate, confirming that inhibition of HSP70 disaggregation function mitigates amyloid toxicity. These data demonstrate that the metazoan HSP70 disaggregation complex plays a critical role in the prion-like propagation of amyloid-type conformers. Therefore, the HSP70 disaggregation activity is a double-edged sword as it is essential for the maintenance of cellular proteostasis while being involved in the generation of toxic amyloid-type protein species.