This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A protein that sticks cells and tissues together has been found to have a surprising second job: helping cells that are packed into a continuous sealed layer, also known as epithelial cells, engulf nearby dead cells. The debris of dying cells is one of the main causes of inflammation, so the finding by researchers at the Centre for Genomic Regulation (CRG) in Barcelona could lead to new clues for understanding chronic inflammatory conditions.
The study, published today in Nature Communications, centers on the E-cadherin complex, which consists of E-cadherin and three other proteins. They work together to link the cells that line our skin, guts and airways, providing structural support that stops tissues from falling apart. Every cell in these epithelial tissues clasps the E-cadherin on the surface of the cell directly next to it.
Verena Ruprecht studied epithelia in live zebrafish and mouse embryos and discovered the machinery also assembles at the precise spot where a dying cell drifts into contact. The researchers asked whether the protein and its partners were gripping the dying cell as they normally grip their neighbors. They first offered the tissue dying cells that had been stripped of E-cadherin, which the tissue cleared away as efficiently as normal ones.
They then offered the cells droplets of fat containing no protein at all but harboring a signal that dying cells display on their surface. Those were swallowed too. "We were intrigued to find out that epithelial cells repurpose their molecular adhesion machinery—the 'glue' that normally holds them together—to engulf dying cells," says ICREA Research Professor Verena Ruprecht, senior author of the study.
The cells doing the swallowing are locked into a barrier that has to stay watertight, so wrapping themselves around something the size of another cell presents a real difficulty. The imaging showed cells manage this because the top and bottom surfaces of a single cell behave independently of one another. The bottom of a cell stretches and wraps around a dead cell while the opposite side, which faces the outside world or an open space like the inside of a lumen, stays still and continues to form a sealed barrier.
When the researchers measured the top surface of a cell before, during and after it had swallowed something, the area barely changed while the bottom surface deformed significantly during the 'eating' process. Ruprecht compares it to a line of dancers with their arms linked, whose upper bodies stay steady while their feet do the work, moving from a simple step to something far more energetic once a dying cell arrives. "It's the same dancer with a different choreography," she says.
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