Development of a live cell assay for real-time monitoring the interactions between the Hippo pathway components 14-3-3 and TAZ

The Hippo pathway plays an important role in organ size control and tissue homeostasis. Dysregulation is involved in many pathologies, including cancer, which has attracted interest in targeting the Hippo pathway. Since the upstream components are bona fide tumor suppressors, it is feasible to target oncogenic downstream targets such as TAZ, a key downstream effector in the Hippo pathway. Its activity is regulated by phosphorylation on multiple sites, with Ser89 playing a critical role in regulation of TAZ activity. Phosphorylation of TAZ at Ser89 promotes binding to 14-3-3 scaffolding proteins, preventing nuclear translocation and abolishing target gene transcription. Here we describe the development of a cell-based assay suitable for high-throughput screening, based on a split NanoLuc luciferase, for monitoring interactions between 14 3-3 and TAZ in living cells. We have validated the assay by screening of a kinase-biased library. The assay can be quickly adapted for higher throughput and thus offers a valuable tool to study new signal inputs involved in regulation of TAZ activity as well as for identification of molecules that modulate the Hippo pathway.