David Ochoa, Mindaugas Jonikas, Robert T Lawrence, Bachir El Debs, Joel Selkrig, Athanasios Typas, Judit Villén, Silvia DM Santos, Pedro Beltrao
Cells need to constantly adapt to internal and external conditions in order to maintain homoeostasis. During cellular decision-making, signal-transduction networks dynamically change in response to cues, triggering cellular state-defining responses. Multiple mechanisms exist to transfer this information from sensors to the corresponding molecular responses, one of the fastest being the reversible post-translational modification of proteins (PTMs). Through these targeted modifications, such as phosphorylation, the cell can quickly alter enzymatic activities, protein interactions or sub-cellular localization in order to produce a coordinated response to a given stimulus (Pawson 2004). Protein phospho-regulation constitutes a highly conserved regulatory mechanism relevant for a broad set of biological functions and diseases (Beltrao 2012).
Over the past decades, our view of cellular signaling has advanced from an idea of isolated and linear cascades to highly complex and cooperative regulatory networks (Jordan 2000, Gibson 2009). Different perturbations in cellular conditions often activate different sets of interconnected kinases, ultimately triggering appropriate cellular responses. The complete understanding of such cell-fate decisions would require the systematic measurement of changes in kinase activities under multiple perturbations, but the small number of quantified regulatory events (i.e. tens) that were possible to date has limited our knowledge of cellular decision making and its molecular consequences (Kim 2011, Bendall 2011, Niepel 2013,