Large glycosylated modified toxins are the main virulence factors for different types of pathogenic Clostridium. The prototype is Clostridium difficile toxins A and B, which can cause antibiotic-associated diarrhea and pseudomembranous colitis. Current models of toxin action indicate that the C-terminal domain of the bound repeat oligopeptide (CROP) can mediate receptor binding. This model was challenged by the glycosylated Clostridium perfringens large cell toxin (TpeL toxin), which lacks a CROP domain but still can poison cells. At present, Professor Klaus Aktories and Dr. Panagiotis Papatheodorou of the Institute of Experimental and Clinical Pharmacology and Toxicology at the University of Freiburg in Germany have discovered the receptor responsible for the transport of Capsular toxin into cells. TpeL is a toxin produced by C. perfringens, a pathogen that causes gas gangrene and food poisoning. It is very similar to the toxins produced by many other hospital bacteria in the genus Clostridium. The toxin can bind to surface molecules and spread into human cells, where they can cause cell death. Professor Aktories pointed out: "In order to prevent toxins from entering the cell, it is necessary to find a receptor as a 'gatekeeper'. But for a long time, the search for this key molecule has not been successful." Now, the University of Freiburg The researchers collaborated with colleagues in Düsseldorf and the Netherlands to discover for the first time a receptor for this clostridial toxin. Related research results were published in the "PNAS" magazine on April 15, 2014. Clostridia can cause intestinal and wound diseases in humans and animals, and these diseases are often fatal. Aktories explained: "At present, Clostridium difficile infection is a special problem in hospitals. Diseases often appear with antibiotic treatment, usually cause diarrhea, and can also cause fatal internal organ inflammation." The host cell, by attaching a sugar molecule to these cell switches, turns off the signaling molecule. Once this signaling pathway has been shut down, the cell will die-the infected tissue will die one after another. To find the receptor, the researchers applied a genetic selection procedure, a so-called screening, in which individual genes from cells of human cancer cell lines were randomly turned off. Using this procedure, the researchers found that when the gene encoding the LRP1 protein is turned off on the cell surface, the cell becomes immune to TpeL toxins. LRP1 (representing low-density lipoprotein receptor-associated protein 1) usually absorbs those proteins that are used as a means of transporting lipidsfats in the blood. The researchers pointed out that LRP1 is a key molecule that has long been popular: it can also regulate the intake of the toxin TpeL. The research team also proposed a new model, Aktories explained: "Our results show that there are two receptor proteins involved in the influence of other sugar-carrying Clostridial toxins." Researchers can use these results to develop anti-shuttle New drug for Bacillus bacilli. Aktories hopes that these findings will also provide researchers with new impetus to further discover toxin receptors.
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Scientists discover the door to clostridial toxins