IMAGING THE DYNAMICS OF THE PROTEOME FOLLOWING VIRAL INFECTION

Individual cells in a population can show different responses to stress stimuli. This is partly due to the stochastic variation in protein expression: even genetically identical cells on the same microscope slide show differences in the expression of most proteins on the order of tens of percent. Here we explore, for the first time, how viral infection of human cells is affected by cell-to-cell variations in protein level and localization over time. To address this, we use a unique assay developed in our lab to follow ~1,000 different proteins, fluorescently tagged at their endogenous chromosomal locus. We determine the proteomic response of the cells to Herpes Simplex Virus 1 infection, a well-studied viral system and a major human pathogen. We follow the dynamics of proteins localization and level in each individual cell over time by time-lapse microscopy, under conditions where some of the cells become successfully infected while others are able to resist the infection. This allows us to identify proteins whose differential dynamics at early times correlates with eventual infection success or failure. This study provides the first global view on how initial cell-to-cell variability correlates with the outcome of infection, allowing us to move from a "virus-centric" view, where each cell is equally likely to become infected, to a more complex "virus-host" view, where the probability of infection also depends on the cell state.