Detecting Native Protein-Protein Interactions by APEX2 Proximity Labeling in Drosophila Tissues.

Enzyme-catalyzed proximity labeling is a potent technique for the discernment of subtle molecular interactions and subcellular localization, furnishing contextual insights into the protein of interest within cells. Although ascorbate peroxidase2 (APEX2) has proven effective in this approach when overexpressed, its compatibility with endogenous proteins remains untested. We improved this technique for studying native protein-protein interactions in live Drosophila ovary tissue. Through CRISPR/Cas9 genome editing, APEX2 was fused with the endogenous dysfusion gene. By pre-treating the tissue with Triton X-100 to enhance biotin-phenol penetration, we successfully identified multiple proteins interacting with the native Dysfusion proteins that reside on the inner nuclear membrane. Our protocol offers a comprehensive workflow for delineating the interactome networks of ovarian components in Drosophila, aiding future studies on endogenous protein-protein interactions in various tissues of other animals. Key features • Elucidating Protein-protein interactions provides deeper insights into the regulation of gene expression in molecular network and complex signaling pathways, advancing protein engineering and drug design. • This protocol utilizes CRISPR/Cas9 knock-in technology to tag endogenous proteins with the APEX2 to label nearby proteins within a 20 nm radius in Drosophila melanogaster. • We optimize APEX2-proximity labeling by using Triton X-100 pre-treatment to enhance biotin-phenol penetration into Drosophila ovaries, enabling endogenous proteins enrichment under native conditions.