High-throughput ligand discovery in living cells using the cellular protein stability enhancement assay

Target-based drug screening typically relies on biochemical or affinity-based assays to identify compounds that modulate or bind to purified target proteins in vitro . However, additional cellular validation is essential to confirm genuine drug-target engagements. Integrating screening and validation within a single cellular assay could greatly expedite the drug discovery process. Herein, we developed a cellular ligand discovery method called CPSEA (cellular protein stability enhancement assay), which leverages the biophysical principle of ligand-induced stabilization of target proteins containing destabilizing mutations. Using CPSEA, we identified arteannuin B and colchicine as novel ligands for FKBP12 and KRAS G12S , respectively. Importantly, we introduced both experimental and computational strategies to identify destabilizing mutations, thereby broadening the applicability of CPSEA for target proteins with and without known stabilizing ligands. Overall, CPSEA represents a powerful cell-based screening strategy with significant potential in target-based drug discovery.