Cellular signalling is commonly mediated through dynamic protein–
protein interactions (PPIs). When pivotal PPIs are deregulated, cellular
signalling can be altered; it is therefore attractive to monitor regulated PPIs
to understand their role in health and disease. Genetically encoded
biosensors that rely on protein fragment complementation have made it
feasible to monitor PPIs in living cells precisely and robustly. In particular,
split protein biosensors using fluorescent proteins or luciferases are
frequently applied. Further, split TEV and split ubiquitin biosensor
platforms flexibly allow using readouts of choice, including
transcriptional barcode reporters that are amenable to multiplexed highthroughput
formats and next-generation sequencing. Combining these
technologies will enable assessing drug target activities and cellular
response profiles in parallel, thereby opening up new avenues in drug
discovery.