Cell-Based Biosensors Based on Intein-Mediated Protein Engineering for Detection of Biologically Active Signaling...

Live-cell-based biosensors have emerged as a useful tool for biotechnology and chemical biology. Genetically encoded sensor cells often use bimolecular fluorescence complementation or fluorescence resonance energy transfer to build a reporter unit that suffers from nonspecific signal activation at high concentrations. Here, we designed genetically encoded sensor cells that can report the presence of biologically active molecules via fluorescence-translocation based on split intein-mediated conditional protein trans-splicing (PTS) and conditional protein trans-cleavage (PTC) reactions. In this work, the target molecules or the external stimuli activated intein-mediated reactions, which resulted in activation of the fluorophore-conjugated signal peptide. This approach fully valued the bond-making and bond-breaking features of intein-mediated reactions in sensor construction and thus eliminated the interference of false-positive signals resulting from the mere binding of fragmented reporters. We could also avoid the necessity of designing split reporters to refold into active structures upon reconstitution. These live-cell-based sensors were able to detect biologically active signaling molecules, such as Ca²⁺ and cortisol, as well as relevant biological stimuli, such as histamine-induced Ca²⁺ stimuli and the glucocorticoid receptor agonist, dexamethasone. These live-cell-based sensing systems hold large potential for applications such as drug screening and toxicology studies, which require functional information about targets.