Dynamics of the cellular interactome: Abstract; Through natural selection, protein conformations, interactions and their dynamics inside cells have been shaped through time to give rise to function needed to sustain life. The set of these intra- and inter-molecular protein interactions constitute the interactome which defines fundamental functional landscapes that exists inside living cells. Because selection processes operate within the crowded intra-cellular environment, these highly evolved interactome networks and the ability to map and visualize them do not exist outside cells. To overcome barriers and gain insight on cellular interactomes, our lab is developing novel in vivo chemical cross- linking molecules referred to as Protein Interaction Reporter (PIR) technologies and new mass spectrometry methods. These developments have provided the initial quantitative in vivo insights on interactomes in live cells. In this project, we propose to further advance and apply Protein Interaction Reporter (PIR) technologies together with improvements in accurate mass measurement capabilities that are possible with mass spectrometry array technologies to gain deeper insight on the cellular interactome. The primary goal driving our technology advancement is to better understand how interactome dynamics shape functional landscapes inside cells. Questions we will address include: how are interactome changes among multiple related cellular phenotypes associated; how do cellular treatments with drugs cause interactome dynamics that affect pharmacological outcome. Finally, based on our discoveries of interactome changes with Hsp90 inhibitors that induce heat shock response, we will investigate interactome dynamics during heat and other applied stresses to reveal which if any inhibitor-induced interactome charges are common to cellular heat shock response signaling. These efforts may reveal interactome changes that are critical to heat shock response that currently limit utility of many potent Hsp90 inhibitors.