Cell volume regulation - the search for a volume sensor

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Animal cell volume is a critical factor for normal cell function and survival. Cells change their volume in many physiological and pathological conditions, such as brain injuries, diabetic complications and other disorders. Cell volume is tightly regulated via accumulation or loss of intracellular ions and other osmotically active substances. However, a major gap exists in our knowledge of how cells detect volume perturbations and how they trigger volume compensatory mechanisms. The long term objective of the proposed research program is to elucidate volume-sensing mechanism(s) in animal cells. To achieve this goal we will use novel method previously developed in our laboratory which allows imaging single, live cells in 3 dimensions and simultaneous measurements of cell volume and intracellular calcium. In the proposed research program we will further improve cell imaging system to allow simultaneous measurements of volume-dependent release of adenosine triphosphate (ATP). Extracellular ATP acts as an important molecule for inter-cellular signaling and we will determine its role in triggering volume regulatory mechanisms. Using molecular viscometers (so called molecular rotors) we will also examine role of volume-dependent viscosity changes of cytoplasm in cell volume regulation. For these experiments, we have already developed in collaboration with our colleagues at the University of North Texas suitable prototype fluorescent molecular viscometers and obtained encouraging results. Based on the data we are confident to accomplish the proposed research goals. This research program will provide both innovation in single-cell imaging techniques and notable advancement of our understanding of cell volume sensing, but also will provide opportunity for training of graduate and undergraduate students. Exploration of the volume-sensing mechanisms is essential for full understanding of a broad range of related cellular processes in normal and pathological conditions. Thus, the outcomes of this program will benefit not only research community in the field of cell volume regulation but also those interested in cell physiology and biology in general. The nature of this research program encompassing cell physiology and electrophysiology, hydrogel biophysics, microscopy imaging, chemistry, mechanical design and software development, will allow us to train students in a multidisciplinary manner.