Proximity Dependent Biotin Labelling in Zebrafish for Proteome and Interactome Profiling.

Identification of protein interaction networks is key for understanding intricate biological processes, but mapping such networks is challenging with conventional biochemical methods, especially for weak or transient interactions. Proximity-dependent biotin labelling (BioID) using promiscuous biotin ligases and mass spectrometry (MS)-based proteomics has emerged in the past decade as a powerful method for probing local proteomes and protein interactors. Here, we describe the application of an engineered biotin ligase, TurboID, for proteomic mapping and interactor screening in vivo in zebrafish. We generated novel transgenic zebrafish lines that express TurboID fused to a conditionally stabilised GFP-binding nanobody, dGBP, which targets TurboID to the GFP-tagged proteins of interest. The TurboID-dGBP zebrafish lines enable proximity-dependent biotin labelling in live zebrafish simply through outcrossing with existing GFP-tagged lines. Here, we outline a detailed protocol of the BLITZ method (Biotin Labelling In Tagged Zebrafish) for utilising TurboID-dGBP fish lines to map local proteomes and screen novel interactors. Graphic abstract: Schematic overview of the BLITZ method. TurboID-dGBP fish are crossed with GFP-tagged lines to obtain embryos co-expressing TurboID-dGBP (indicated by mKate2) and the GFP-POI (protein of interest). Embryos expressing only TurboID are used as a negative control. Embryos (2 to 7 dpf) are incubated overnight with a 500 μM biotin-supplemented embryo medium. This biotin incubation step allows TurboID to catalyse proximity-dependent biotinylation in live zebrafish embryos. After biotin incubation, embryos are solubilised in lysis buffer, and free biotin is removed using a PD-10 desalting column. The biotinylated proteins are captured by streptavidin affinity purification, and captured proteins are analysed by MS sequencing.