Chemical tools to define and manipulate interferon-inducible Ubl protease USP18

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• Ubiquitin-specific protease 18 (USP18) is a key enzyme in the interferon pathway, primarily cleaving the ISG15 modifier from protein substrates.
• Accurate detection of USP18 enzymatic activity is crucial for understanding its biological roles and developing targeted therapies.

Purpose of the Study:

• To design and synthesize novel activity-based probes (ABPs) for selective detection of USP18 activity.
• To utilize these probes in a chemoproteomics platform for identifying USP18 inhibitors.
• To profile USP18 activity in disease contexts, such as lung cancer.

Main Methods:

• Design and synthesis of ISG15-based activity-based probes (ABPs) incorporating unnatural amino acids.
• Application of USP18 ABPs in a chemoproteomics screening platform alongside ubiquitin-based DUB ABPs.
• Profiling of USP18 activity in lung cancer cell lines.

Main Results:

• Developed ISG15-based ABPs that selectively detect USP18 activity, distinguishing it from other deubiquitinases (DUBs) like USP5 and USP14.
• Successfully employed a chemoproteomics platform using USP18 ABPs to identify and assess DUB inhibitors, including those targeting USP18.
• Demonstrated the utility of USP18 ABPs for profiling differential USP18 activity in lung cancer cell lines.

Conclusions:

• Novel ISG15-based ABPs provide a selective tool for monitoring USP18 enzymatic activity.
• The chemoproteomics platform enables efficient screening for USP18 inhibitors.
• USP18 ABPs offer a valuable strategy for investigating USP18's role in various disease states and understanding (de)ISGylation-dependent processes.