The long-term challenge of proteomics as a tool for systems biology is to define the identities, quantities, structures and functions of complete complements of proteins, and to characterize how these properties vary in different cellular environments. To add a functional dimension to the dynamic TGFbeta network revealed by the LUMIER screen, a recently developed and validated high throughput technology for analysis of dynamic protein interactions in mammalian cells, I have used functional assays based on Smad transcriptional responses. Novel pathway inhibitors, including an uncharacterized protein FLJ12604, two WW domain-containing proteins WWP2, TAZ as well as PP2A regulatory subunit PPP2R2D were identified. To facilitate analysis of distinct subnetworks within the TGFbeta interactome, I have also worked towards developing a mass spectrometry (MS)-based approach to study dynamics of protein complex assembly in a quantitative manner. Taken together, LUMIER coupled with the MS technology can be used to study crucial, although previously unexplored, dimensions of signaling pathways.