How cells sense and react to these forces is poorly understood, he adds. The details are being filled in by their new computer model, developed with the help of Krithika Mohan and Pablo Iglesias from the Johns Hopkins University Whiting School of Engineering.
To develop it, the team worked with the proteins that feel the environment, part of a network that wraps around the inside edge of the cell, giving it shape and structure and inspiring the name "cytoskeleton." The most prevalent among the proteins is actin, which forms short rods held together in a crisscross pattern by linker proteins. There are also anchoring proteins that attach the actin rods to the cell's skin, or plasma membrane. Together, these components act as the "molecular muscles," allowing the cell to change its shape when needed for example, when it squeezes through small spaces to migrate to a different part of the body, or when it pinches itself in half to divide.
The team linked each of 37 cytoskeletal proteins to a fluorescent tag that marked its position in the cell. They then applied pressure to the cells, using a tiny glass tube to gently suck on the cells, deforming them and creating a "neck" as might occur if the hose of a vacuum cleaner sucked on a lightly inflated balloon.
As they recorded a protein's movements under the microscope, they analyzed how each protein responded to the deformation of the cell: where each protein moved, how much of it moved and how quickly it got there.
There were two types of force in play during the experiments, says Tianzhi Luo, the primary author of the report. The tip of the neck experienced dilation: The overall shape was maintained while the area expanded. The elongated portion of the neck experienced shear: The area was maintained but the shape changed, like blocks of gelatin when they shake. What the team discovered were three d
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Johns Hopkins Medicine