Quality of cellular proteins is controlled by a sophisticated machinery - proteostasis network - including folding chaperones, disaggregates, autophagy machinery, proteasome and numerous other factors. It is estimated that more than 10% of cellular proteome is devoted to the protein quality control. What is the functional specialisation of the PN elements? At which stage of the protein's lifecycle the PN interrogates its clients? We are seeking answers to these questions by profiling in a time-resolved manner the interactions of PN with the cellular proteome using tools like quantitative mass-spectrometry and mathematical models based on proteomic data.