Detecting protein–protein interactions based on kinase-mediated growth induction of mammalian cells

Detection of protein-protein interactions (PPIs) is important for understanding numerous processes in mammalian cells; however, existing PPI detection methods often give significant background signals. Here, we propose a novel PPI-detection method based on kinase-mediated growth induction of mammalian cells. In this method, target proteins are fused to the intracellular domain of c-kit (c-kit ICD) and expressed in interleukin-3-dependent mammalian cells. The PPI induces dimerization and activation of c-kit ICDs, which leads to cell growth in the absence of interleukin-3. Using this system, we successfully detected the ligand-dependent homo-interaction of FKBPF36V and hetero-interaction of FKBP and FRBT2098L, as well as the constitutive interaction between MDM2 and a known peptide inhibitor. Intriguingly, cells expressing high-affinity peptide chimeras are selected from the mixture of the cell populations dominantly expressing low-affinity peptide chimeras. These results indicate that this method can detect PPIs with low background levels and is suitable for peptide inhibitor screening.