Cells are constantly on the move. They shift, grow, and migrate to new locations—for example, to heal a wound or to intercept an infectious agent as part of an immune response. But how do cells actually move?
In this image, Torsten Wittmann, an NIH-funded cell biologist at the University of California, San Francisco, reveals the usually-invisible cytoskeleton of a normal human skin cell that lends the cell its mobility. The cytoskeleton is made from protein structures called microtubules—the wispy threads surrounding the purple DNA-containing nucleus—and filaments of a protein called actin, seen here as the fine blue meshwork in the cell periphery. Both actin and microtubules are critical for growth and movement.
Unlike our own bony skeleton, which keeps the same arrangement throughout our lives, the cellular cytoskeleton is dynamic, continuously morphing in response to cellular signals. In this image, cytoskeleton remodeling of the skin cell was triggered by addition of a growth factor, which produced protrusions of the cell edge and the characteristic “fried egg” shape of this cell. These protrusions have little “feet” that help the cell move forward. The Wittmann lab recently used these skin cells to model the complex choreography by which microtubules control cell movement .
Microtubules do more than give cells mobility. They serve as an intracellular transportation system that carries proteins from one region of the cell to another. But unlike fixed, human-built roadways or train tracks, the microtubule network is constantly changing, in response to protein supply and demand. Check out this video that Andreas Ettinger, a postdoctoral researcher in the Wittmann lab, made of microtubules continuously remodeling in the cell.
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