Controlling protein–protein interactions is critical for dissecting signaling pathways, especially those initiated by ligand-receptor interactions, which alter receptor oligomerization and drive downstream signaling cascades. Traditional methods for driving protein–protein complexes use antibodies that face limitations in terms of stoichiometry, geometric rigidity, and antibody specificity. Chemical inducers of dimerization (CIDs) for fusion proteins such as HaloTag (Halo) and SNAP-Tags (SNAP) offer precise and covalent control of protein proximities, overcoming limitations of antibody-dependent methods. In this study, we expand the toolkit of Halo and SNAP CIDs with (1) benzylguanine (BG) and HaloTag ligand (HTL) crosslinkers featuring varying polyethylene glycol linker lengths and update this kit with (2) a FRET-based dimerizing sensor to induce and verify protein proximity. Here we establish our CIDs on extracellularly Halo- and SNAP-tagged TGFβ, BMP, neurotrophic factor, and metabotropic glutamate receptors, thereby elucidating the signaling potential of ligand-independent dimerization in a heteromeric fashion.
