Enzyme-Activated Sugar-Coated Bifunctional Degraders.

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• Targeted protein degradation utilizes proteolysis targeting chimeras (PROTACs) to direct proteins to the ubiquitin-proteasome system.
• Commonly used E3 ligases like cereblon (CRBN) are broadly expressed, limiting PROTAC selectivity.
• Developing strategies for metabolic gating of PROTAC activity is crucial for enhancing therapeutic specificity.

Purpose of the Study:

• To develop a novel enzymatic activation strategy for PROTACs using O-GlcNAc modification.
• To create sugar-coated PROTACs (SCPs) that are activated by enzymatic removal of the O-GlcNAc moiety.
• To investigate the impact of O-GlcNAc modification on CRBN binding and target protein degradation.

Main Methods:

• Structural analyses of cyclimid degraders complexed with CRBN and BRD4.
• Synthesis of O-GlcNAc-modified cyclimids (SCPs).
• In vitro biochemical binding assays, cellular degradation assays, and cell viability assays.

Main Results:

• Glycosylation of cyclimids reduced CRBN binding and complex formation with BRD4.
• Enzymatic removal of the O-GlcNAc moiety by O-GlcNAcase (OGA) restored CRBN binding and induced target protein degradation.
• Demonstrated requirement for enzymatic activation in engineered and native cell lines.

Conclusions:

• O-GlcNAc modification serves as an effective mechanism for metabolically gating targeted protein degradation.
• Enzymatic activation strategies can enhance the selectivity of PROTACs.
• This approach motivates the development of similar strategies using other protein modifications for improved selectivity.