Thesis (Ph.D.) - Cairo University - Faculty of Veterinary Medicine - Department of Histology and Cytology

Apoptosis is one of programmed cell death pathways, it is a physiological process through which the animal could organize the number of cells in tissues. Failure of apoptosis results in different diseases including cancer. Prostate cancer remains the second leading cause of cancer related death in men. Therefore, induction of apoptosis has become one of the most effective strategies for cancer treatment. In our study, we induced apoptosis via targeting the ubiquitin proteasome system (UPS). Inhibition of UPS was achieved by using proteasome inhibitors mainly natural 19S inhibitors as isothiocyanates (ITCs) which found abundantly in cruciferous vegetables. We hypothesize that ITCs as electrophiles could interact with the catalytic triads (CYS, HIS and ASP) of the 19S associated USP14 and UCHL5, ultimately inhibiting their activities. Docking and biochemical results suggest that ITCs are potent inhibitors of UCHL5 than USP14. Indeed, Ub-VS assay confirmed the inhibitory activity of each ITC as the ubiquitin binding activity of UCHL5 and USP14. This inhibition of USP14 and UCHL5 caused increased levels of USP14 and UCHL5 proteins but not the third 19S DUB, RPN11 suggesting feedback loop activation and further supporting that ITCs are inhibitors of proteasomal cysteine DUBs

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