The human digestive system contains trillions of bacteria that normally help break down food and support health. Scientists call this community of microbes the gut microbiome.
While many of these bacteria are beneficial, some can produce toxins that damage tissues and contribute to disease.
A new international study led by Johns Hopkins University has uncovered how one of these toxins attacks the bowel. The research was published in Nature and solves a scientific mystery that had remained unanswered for more than 15 years. The discovery could eventually help researchers develop new ways to prevent colorectal cancer.
The focus of the study was a toxin called BFT, produced by certain strains of Bacteroides fragilis. Previous research showed that BFT weakens the protective barrier lining the colon and promotes long-term inflammation. Chronic inflammation is known to increase the risk of cancer developing over time.
Researchers knew the toxin damaged a protein called E-cadherin, but they could not explain how it first attached to the cell. To investigate, they carried out a genome-wide CRISPR screen that tested thousands of genes. This allowed them to identify the proteins needed for the toxin to work.
The experiments revealed that claudin-4 is the missing receptor. Without claudin-4, the toxin could not bind to colon cells or begin its harmful activity. This was an unexpected finding because scientists had predicted a completely different type of receptor.
Further laboratory studies confirmed that the toxin and claudin-4 fit together very tightly. Animal experiments then showed that blocking this interaction protected the bowel from injury. These results strongly support the idea that claudin-4 is essential for the toxin’s harmful effects.
The team took the work one step further by creating a molecular decoy. Instead of attaching to real colon cells, the toxin attached to the decoy proteins. Mice receiving this approach were protected from toxin-related bowel damage, suggesting a possible path toward future treatments.
Although the results are exciting, several important questions remain unanswered. Researchers still need to determine the exact structure of the toxin while it is attached to claudin-4. Current artificial intelligence tools have not yet been able to fully solve this puzzle.
Future studies will also need to test whether similar treatments are safe and effective in people. If successful, drugs based on this approach might help prevent diseases linked to this toxin, including bowel inflammation and colorectal cancer.
This research represents a major advance in understanding how harmful gut bacteria affect human health. The study carefully combined advanced genetics, structural biology and animal research, making the evidence convincing.
Even so, the work is still experimental, and people should not expect new treatments immediately. The discovery instead provides an important foundation for future therapies that could reduce the effects of dangerous bacterial toxins.
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Source: Johns Hopkins University.
