Identification of novel 14-3-3ζ interacting proteins by quantitative immunoprecipitation combined with knockdown (QUICK).

The family of 14-3-3 proteins has emerged as critical regulators of diverse cellular responses under both physiological and pathological conditions. To gain insight into the molecular action of 14-3-3ζ in multiple myeloma (MM), we performed a systematic proteomic analysis of 14-3-3ζ-associated proteins. This analysis, recently developed by Matthias Mann, termed quantitative immunoprecipitation combined with knockdown (QUICK), integrates RNAi, SILAC, immunoprecipitation, and quantitative MS technologies. Quantitative mass spectrometry analysis allowed us to distinguish 14-3-3ζ-interacting proteins from background proteins, resulting in the identification of 292 proteins in total with 95 novel interactions. Three 14-3-3ζ-interacting proteins-BAX, HSP70, and BAG3-were further confirmed by reciprocal coimmunoprecipitations and colocalization analysis. Our results therefore not only uncover a large number of novel 14-3-3ζ-associated proteins that possess a variety of cellular functions, but also provide new research directions for the study of the functions of 14-3-3ζ. This study also demonstrated that QUICK is a useful approach to detect specific protein-protein interactions with very high confidence and may have a wide range of applications in the investigation of protein complex interaction networks.