  Many biological, physical, and social interactions have a particular
dependence on where they take place. In living cells, protein movement between
the nucleus and cytoplasm affects cellular response (i.e., proteins must be
present in the nucleus to regulate their target genes). Here we use recent
developments from dynamical systems and chemical reaction network theory to
identify and characterize the key-role of the spatial organization of
eukaryotic cells in cellular information processing. In particular the
existence of distinct compartments plays a pivotal role in whether a system is
capable of multistationarity (multiple response states), and is thus directly
linked to the amount of information that the signaling molecules can represent
in the nucleus. Multistationarity provides a mechanism for switching between
different response states in cell signaling systems and enables multiple
outcomes for cellular-decision making. We find that introducing species
localization can alter the capacity for multistationarity and mathematically
demonstrate that shuttling confers flexibility for and greater control of the
emergence of an all-or-none response.
