Development of a multifunctional toolkit of intrabody-based biosensors recognizing the V5 peptide tag: highlighting applications with G protein-coupled receptors

Protein-protein interactions (PPIs) form the underpinnings of any cellular signaling network. PPIs are highly dynamic processes and often, cell-based assays can be essential for their study as they closely mimic the biological intricacies of cellular environments. Since no sole platform can perform all needed experiments to gain a thoroughly comprehensive understanding into these processes, developing a versatile toolkit is much needed to address this longstanding gap. The use of small peptide tags, such as the V5-tag, has been extensively used in biological and biomedical research, including labeling the C-termini of one of the largest human genome-wide open-reading frame collections. However, these small peptide tags have been primarily used in vitro and lack the in vivo traceability and functionality of larger specialized tags. In this study, we combined structural studies and computer-aided maturation to generate an intracellular nanobody, interacting with the V5-tag. Suitable for assays commonly used to study protein-protein interactions, our nanobody has been applied herein to interrogate G protein-coupled receptor signalling. This novel serviceable intrabody is the cornerstone of a multipurpose intracellular nanobody-based biosensors toolkit, named iBodyV5, which will be available for the scientific community at large. ### Competing Interest Statement The authors have declared no competing interest.