Background: Autophagy is over activated in Alzheimer's disease (AD) brain, but still activating autophagy has received most attention, however recent evidence suggests that ubiquitin-proteasome system can clear aggregate proteins and a potential therapeutic target for AD and protein misfolding diseases.

Methods: We developed an assay using the MC65 AD cell model to screen  library of small molecule proteostasis modulators and identified IU1, a USP14 inhibitor, that improved cell survival and promoted Aβ clearance. Screening 71 novel small molecule proteostasis inhibitors revealed better neuroprotective analogues of IU1, AA10 and AA51. The effects of these compounds on autophagy, proteasome activity, and APP-C99/Aβ clearance, neurodegeneration and behavior were analyzed using fluorescence microscopy, western blotting, proteasome studies, neurodegeneration, toxicity and lifespan assay by AD cell and worm models.

Results: Our data on MC65 and C. elegans AD models have shown promising results with compounds AA10 and AA51 from the screened library of proteostasis modulators. In cell studies, these compounds alleviated AD proteostasis dysfunction, reduced protein aggregation, and regulated autophagy clearance. Cell survival improved from 40% with IU1 to 55% with AA10 and AA51. Initial studies on the worm model support these findings, showing a 55% reduction in neurodegeneration with AA10 and 53% reduction with AA51.

Conclusions: Ours, is the first report of using IU1 in AD models as USP14 inhibitor. The novel IU1 analogues AA10 and AA51 looks more promising and hold potential as candidates for pre-clinical validation in AD. The next steps involve testing therapeutic efficacy and brain bioavailability in AD mice model.