Skin is like a coat tailored from a sole piece, covering the body from head to feet, protecting against wind, being water-proof, strong but still elastic, and continuously renewing itself. It protects the body against blows, cuts, rain, wind, radiations, powerful sunlight, and germs.
A new research, published in the journal "Nature", comes with the best look ever of the interactions inside human skin cells, revealing a Velcro-like pattern that connects them and makes skin both strong and supple. The novel cryo-electron tomography delivered, for the first time, inner cell images of the proteins involved in cell-cell contacts.
"This
is a real breakthrough in two respects. Never before has it been possible to look in three dimensions at a tissue so close to its native state at such a high resolution. We can now see details at the scale of a few millionths of a millimeter. In this way we have gained a new view on the interactions of molecules that underlie cell adhesion in tissues-a mechanism that has been disputed over decades," said Achilleas Frangakis, of the European Molecular Biology Laboratory.
Till now, data on proteins' location and interactions inside the cell has been obtained through poor resolution light microscopy or by using techniques that denatured the proteins.
Normally, electron microscopy means that tissue will be treated with chemicals or coated in metal, processes that also denature the proteins. The research team managed, by using the new technique, to instantly freeze cells in their natural condition, and these samples could be investigated through electron microscopy. Cyro-electron tomography allowed the achievement of images of the untreated sample from various directions. These images could be combined into precise 3-D image by a software.
The team looked at proteins that were essential for the integrity of tissues and organs such as the skin and the heart, and at those involved in cell proliferation. The proteins conferring the skin its solidity are named cadherins; they are anchored in cell membranes and, through their interaction, the cells are interconnected and tightly brought together.
"We could see the interaction between two cadherins directly, and this revealed where the strength of human skin comes from. The trick is that each cadherin binds twice: once to a molecule from the juxtaposed cell and once to its next-door neighbor. The system works a bit like specialized Velcro and establishes very tight contacts between cells." said author Ashraf Al-Amoudi, of the European Molecular Biology Laboratory.
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