Membrane receptors, such as G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs), control intracellular signaling pathways involved in many (patho-)physiological processes, making these proteins important drug targets. As the therapeutic potential of drugs depends on how they interact with their targets, it is important to assess ligand-receptor binding parameters early in the drug development process.
In their study supervised by Raimond Heukers and professor Martine Smit, Jelle van den Bor and Nick Bergkamp established a modular mix-and-measure method that uses nanobodies as fluorescent probes for real-time quantitative ligand-receptor binding studies. Nanobodies, also known as single domain antibodies or VHH, are the antigen-binding domains of a special class of antibodies (heavy chain-only) found in camels and are ideal ligands for targeting GPCRs. Binding of fluorescently labeled nanobodies or antibodies to either the intracellular- or extracellular sides of NanoLuciferase-tagged receptors results in close proximity between the luciferase and the fluorophore, leading to bioluminescence resonance energy transfer (BRET) that can be readily quantified. Furthermore, this setup can be used to determine the binding sites and affinities of unlabeled drugs and could aid the identification of novel (endogenous) ligands for orphan receptors or targets considered to be non-druggable.
Reference: https://www.sciencedirect.com/science/article/pii/S2667237523000334?via%3Dihub