Cell folds hide the mystery of “deformation”

In order to move, cells must be able to change shape quickly. American researchers have found that cells achieve this by storing extra “skin” in folds and protrusions on the surface. The study was recently published in the Journal of Biophysics.

Cell membranes are very flexible, but they can only stretch about 3% without breaking. There are additional folded surfaces that can be expanded as needed, allowing cells to move and divide while safely maintaining cell volume and membrane integrity.

“It’s a safety measure because you can’t stretch the cell membrane, and if it ruptures, the cell dissolves and dies, so the cell needs this reserve.” Maryna Kapustina, PhD, lead author of the paper and the University of North Carolina at Chapel Hill, said, “These protrusions can store large amounts of cell surfaces and are highly dynamic, meaning they can change rapidly and immediately recreate elsewhere around the cell. ”

Cell surface protrusions vary in shape and size. Some are called bubbles, small round lumps on the surface of cells with little internal structure. Bubbles form within seconds and shrink after a few minutes. Larger protrusions take longer to form, but since they have internal structures consisting of microtubules and actin, etc., they can last for more than 1 hour.

Using electron and fluorescence microscopy, the researchers looked at round, cigar-shaped, and irregularly shaped cells embedded in a three-dimensional collagen matrix, a network of collagen fibers in which cells can squeeze and migrate. Using fluorescent tags, they captured the time interval between cell surface dynamics and movement over several hours.

The team found that when cells are round, their surface is rough and complex, covered by many tiny protrusions, such as bubbles, microvilli, filamentous feet, and folds. However, as the cells continue to protrude, these extra “skin” folds unfold and their surfaces become relatively smooth, especially in the area near the protrusions.

The researchers believe that cell surface “stocks” are important in both mesenchymal cell and amoeba motility, the two main ways cells move. During mesenchymal cell movement, cells adhere to environmental surfaces and then use contractile force to push themselves between collagen fibers or crawl along two-dimensional surfaces. During amoeba locomotion (faster movement), the cells do not rely on adhesion, but are propelled by the rapid movement of smaller protrusions.

The team believes that although the exact function of microtubules is unknown, they play an important role in regulating the cellular excess surface in mesenchymal cell and amoeba movement. “Microtubules may provide mechanical support to the cell surface, or it may be associated with activating submembrane actin, creating an active site for stable protrusions.” Kapustina said, “When there is no such active site to create stable protrusions, the cells basically just form bubbles. (Source: Feng Weiwei, China Science News)

Image source: Pixabay

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