( had made similar observations with oth...)Gene discovery sheds light on causes of rare disease, cancer

had made similar observations with other bacteria. Cossart and Veiga investigated the underlying machinery behind this uncommon invasion strategy, which they knew depended on an interaction between a protein on the surface of the bacteria, known as InlB, and a protein called Met on the surface of the cell it was invading.

They discovered that when InlB interacts with Met, the cell responds by adding a chemical tag to Met that flags it for protein recycling or degradation. Since Met is on the outside surface of the cell and the recycling and degradation machineries are inside, the cell must bring Met inside through endocytosis in order to dispose of it. As the cell creates the vesicle that will transport tagged Met, Listeria stows away and invades the cell.

By manipulating the gene expression of the cells Listeria was invading, the researchers showed that specific molecules known to be involved in endocytosis were essential for successful invasion by Listeria. Similarly, they found that an enzyme that tags proteins for recycling was also required.

Listeria's use of receptor-mediated endocytosis to infect hosts, according to Cossart, suggests that other bacteria may exploit the same mechanism to gain entry into non-phagocytic cells. "This mechanism of cell entry may be used by several different kinds of bacteria, which is a major deviation from the belief that endocytosis is strictly for importing small molecules into cells," she says.

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Source:NIH/National Institute on Aging


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