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cell volume regulation

This SWELL Protein Keeps Cells in Shape

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Human cell

Caption: A human cell expressing both the SWELL1 (red) and green fluorescent protein. The red dots reveal the location of SWELL1 on the cell surface.
Credit: Zhaozhu Qiu, The Scripps Research Institute, La Jolla, CA

Anyone who’s taken part in a water balloon fight knows what happens when you fill a balloon with too much water—it bursts. Now, consider that most of our cells are essentially water balloons: a thin membrane envelope containing a mixture that’s mostly water along with some salts, proteins, lipids, carbohydrates, and nucleic acids. Given that the average adult’s body is about 60% water, what keeps our cells from overfilling and exploding?

A few years ago, Zhaozhu Qiu, a postdoctoral fellow in Ardem Patapoutian’s lab at Scripps Research Institute in La Jolla, CA, decided to dig into the molecular details of how cells are able to sense their volume and adjust their shapes accordingly. It’s long been known that, when cells are placed in low-salt solutions, water tends to flow into them, causing them to swell—sometimes to the verge of bursting. Scientists determined, about 30 years ago, that, when this occurs, channels in the cell membrane open and the cells release chloride and other molecules, such as amino acids: a process that drives out the excess water and returns cells to their normal size [1].