The role of ionic fluxes in cell volume, electromechanics and cell motility

Monday, March 12, 2018 - 2:00pm - 2:50pm
Lind 305
Sean Sun (Johns Hopkins University)
Cell volume regulation is fundamentally important in phenomena such as cell growth, proliferation, tissue homeostasis and embryogenesis. How the cell size is set, maintained, and changed over a cell's lifetime is not well understood. In this work we focus on how the volume of non-excitable tissue cells is coupled to the cell membrane electrical potential and the concentration of membrane-permeable ions in the cell environment. Specifically, we demonstrate that a sudden cell depolarization using the whole cell patch clamp results in a 30 percent increase in cell volume, while hyperpolarization results in a slight volume decrease. We find that cell volume can be partially controlled by changing the chloride or the sodium/potassium concentrations in the extracellular environment while maintaining a constant external osmotic pressure. Depletion of external chloride leads to a volume decrease in suspended HN31 cells. Introducing cells to a high potassium solution causes volume increase by up to 50\%. Cell volume is also influenced by cortical tension: actin depolymerization leads to cell volume increase. We will discuss an electrophysiology model of water dynamics driven by changes in membrane potential and in the concentration of permeable ions in the cell surrounding. The model quantitatively predicts that the cell volume is determined by the total amount of intracellular ion and protein content. Moreover, the model can be extended to analyze how a polarized cell can use ionic fluxes across the cell membrane to drive directional water fluxes and cell motility. Such a model predicts that the cell is sensitive to external electric fields, and depending on the cell type, can migrate towards the cathode or the anode in an actin-independent manner.