Abstract

Cells have a remarkable ability to rapidly adapt to environmental changes by altering their shape and volume, changing the composition of their internal solution. Decades of in vitro studies have demonstrated that biomolecular structure, activity, and interactions can be highly sensitive to solution composition changes, yet how dynamics in the cellular environment affect the cell’s components remains unclear. I will present a novel method termed Environmental Perturbation Microscopy that allows robust control of the volume and composition of live mammalian cells, and simultaneous detection of intracellular protein dynamics. I use this method to show that rapidly changing the cellular volume can alter protein structure, and perturb weak interactions between proteins. My data reveals that cellular volume changes, a common event during the cell cycle, can act as a regulatory signal in dividing cells. In a different set of experiments, I alter the intracellular concentrations of specific solutes and show that elevated levels of specific solutes can alter protein thermal stability and the structure of the unfolded state. These findings indicate that protein activity can be controlled by changing intracellular solute composition, offer a glimpse into the way proteins function in their natural environment, and highlight the importance of abundant, molecularly-small solutes to biomolecular activity in the cell.