Under control to the very end – how our cells kill themselves

Cell death is crucial for all organisms. Damaged cells or cells infected with viruses or bacteria eliminate themselves by starting a built-in “suicide” programme, which prevents the development of tumors and the spread of pathogens in the body.

Until recently, it was assumed that cells simply burst and die at the end of their life. Now, researchers at the Biozentrum, University of Basel, the University of Lausanne and the Department of Biosystems Science and Engineering (D-BSSE) at ETH Zurich have provided new insights into the final step of cell death. In the scientific journal Nature, they describe how a protein called ninjurin-1 assembles into filaments that work like a zipper and open the cell membrane, thus leading to the disintegration of the cell. The new insights are an important milestone in the understanding of cell death.

Protein acts as a breaking point in the cell membrane

Various signals, such as bacterial components, trigger the cell death machinery. At the final stage of this process, the cell’s protective membrane is compromised by tiny pores which allow ions to stream into the cell. “The common understanding was that the cell then swells until it finally bursts due to increasing osmotic pressure,” explains Sebastian Hiller. “We have now resolved how the cells really rupture. Instead of bursting like a balloon, the protein ninjurin-1 provides a breaking point in the cell membrane, causing rupture at specific sites.”

How the ninjurin-1 protein induces membrane rupture

Using advanced techniques such as highly sensitive microscopes and NMR spectroscopy, the scientists have been able to elucidate the mechanism by which ninjurin-1 induces membrane rupture at the level of individual atoms. Ninjurin-1 is a small protein embedded in the cell membrane.

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