The APEXTAC System for Ligand-Guided Proximity Labeling.

Area of Science:

• Chemical Biology
• Molecular Biology
• Drug Discovery

Background:

• Unbiased drug-target identification is crucial for understanding drug mechanisms and off-target effects.
• Existing methods like BioTAC have limitations, including specific chemistry and labeling duration.
• The need for improved proximity labeling tools in live-cell studies is evident.

Purpose of the Study:

• To develop and validate the APEXTAC system, a novel small molecule-guided proximity labeling platform.
• To compare APEXTAC head-to-head with the BioTAC system for drug-target identification.
• To assess APEXTAC's utility in studying protein homeostasis and targeted protein degradation.

Main Methods:

• Development of the APEXTAC system utilizing the APEX2 peroxidase enzyme.
• Head-to-head comparison of APEXTAC and BioTAC using (+)-JQ1 for target identification.
• Assessment of labeling efficiency and specificity in live cells.

Main Results:

• APEXTAC successfully labeled E3-ligases via their ligands without proteasome inhibitors.
• The APEXTAC system demonstrated faster and potentially more accurate target identification compared to BioTAC.
• APEXTAC proved effective for live-cell target identification across various molecules, including protein homeostasis components.

Conclusions:

• APEXTAC is a valuable complementary tool for unbiased live-cell drug-target identification.
• The system overcomes key limitations of previous proximity labeling methods.
• APEXTAC shows significant potential for applications in targeted protein degradation research.