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Access Type
WSU Access
Date of Award
January 2024
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Chemistry
First Advisor
Hien M. Nguyen
Second Advisor
Young-Hoon Ahn
Abstract
The ubiquitin-proteasome system (UPS) plays an important role in degrading unwanted and damaged intracellular proteins. The 26S proteasome is composed of two domains, named 20S proteolytic core particle (CP), and 19S regulatory particle (RP). Proteasome identifies its targets once ubiquitin (Ub) molecules are conjugated to the substrates. The enzymes known as deubiquitinases (DUBs) are involved in the cleavage of the isopeptide bond between Ub and target proteins, which is named deubiquitination. The 19S RP of the proteasome is associated with three DUBs named regulatory particle subunit number 11 (RPN11), ubiquitin-specific protease 14 (USP14), and ubiquitin C-terminal hydrolase L5 (UCHL5). UCHL5 has two main domains. The catalytic domain is composed of a catalytic triad which acts as a cysteine protease. The C-terminal domain is involved in binding with RPN13 in the 19S RP of the proteasome. UCHL5 is known to be overexpressed in many cancers such as ovarian, and esophageal squamous cell carcinoma. It also promotes tumor cell survival, migration, and invasion in various cancers such as hepatocellular carcinoma by deubiquitinating and stabilizing proteins associated with cancer progression such as TGF-β-1. Therefore, it has emerged as a promising drug target. UCHL5 possesses protein-protein interactions (PPIs) with Ub and RPN13. We hypothesized that PPI disruption between Ub and UCHL5 might decrease UCHL5 activity. Peptoids have been used to disrupt PPIs and identified as highly proteolytic-resistant peptidomimetics. Therefore, we sought to develop a one-bead one-compound linear peptoid library using submonomer solid phase synthesis and the split-pool method. The library was used for on-bead screening with UCHL5, along with in-silico screening, to identify potential hits. Hits LP16, LP7, LP15, LP11, and LP2 were identified as hits to conduct in-vitro evaluation. LP16, LP7, LP11, and LP2 did not show inhibition of UCHL5 activity. However, LP15 showed an inhibition of UCHL5 enzyme activity. We also developed a one-bead two-compounds cyclic peptoid library to identify cyclic peptoid-based inhibitors for UCHL5. CP3 and CP6 hits were identified as candidates for in-vitro evaluation, from on-bead and in-silico screening of the library with UCHL5. However, neither compound showed inhibition of UCHL5 activity. Therefore, further optimization of the library such as peptoid chain length and primary amine building block diversity would be needed to identify the effective UCHL5 inhibitors.
Recommended Citation
Herath Mudiyanselage, Poornima Dineshika H, "Developing Peptoid-Based Inhibitors For Uchl5 Deubiquitinase" (2024). Wayne State University Dissertations. 4074.
https://digitalcommons.wayne.edu/oa_dissertations/4074