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Access Type

WSU Access

Date of Award

January 2021

Degree Type


Degree Name




First Advisor

Prof. Young-Hoon Ahn


Ubiquitin proteasomal system (UPS) plays a vital role in maintaining protein homeostasis by eliminating misfolded and damaged proteins in a eukaryotic cell. Target proteins to be degraded are modified by poly-ubiquitination, which leads to degradation by 26S proteasome. Before entering the 20S catalytic subunit, the 19S regulatory particle is responsible for binding, unfolding, and deubiquitinating the target protein. Based on the nature of the polyubiquitin tag, removal of the ubiquitin is performed by the deubiquitinases (DUBs) associated with the proteasome.Ubiquitin carboxyl-terminal hydrolase isozyme L5 (UCHL5) is one of the three DUBs in the proteasome. UCHL5 regulates many cellular functions and act as a key player in modulating cancer cell survival. Despite the therapeutic potential of UCHL5 in treating cancer, there are few inhibitors, and all of them suffer from poor selectivity. Therefore, we have performed a virtual screening with an FDA-approved drug library against the active site of UCHL5 and identified tiaprofenic (TA) acid as a potential inhibitor of UCHL5. We then designed and synthesized derivatives of TA guided by computational docking analyses. Our in-vitro evaluation revealed TAB2 as one candidate compound, which inhibits UCHL5 activity with improved potency. TAB derivatives have two carboxylic groups, which would impede its cell permeability. Therefore, cell-permeable acetoxymethyl derivatives of TAB compounds were synthesized, namely TAB-AM. We further demonstrated that TAB-AM derivatives retained their potency in inhibiting cancer cell viability and migration in MDA-MB-231 and MM.1S cells. Furthermore, we have extended our structure-based high throughput virtual screening approach to identify novel lead compounds as potential inhibitors targeting UCHL5 and successfully characterized the compounds. The inhibitory potential of these lead compounds could be further improved by the design and synthesis of their derivatives in the future.

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