Structural mannequin of CbpF binding to CEACAM1/CEACAM5 and the proposed “Velcro” adhesion mechanism. Credit score: Prof. George F. Gao’s group
Fusobacterium nucleatum (F. nucleatum) is an anaerobic bacterium notably enriched within the intestine microbiota of colorectal most cancers (CRC) sufferers and will play a job in CRC each by colonizing tumor cells and suppressing immune mechanisms. Understanding how this bacterium adheres to most cancers cells may present key targets for creating novel antitumor therapies.
Researchers led by Prof. George F. Gao from the Institute of Microbiology of the Chinese language Academy of Sciences (CAS) have recognized the important thing mechanism by which F. nucleatum binds to the human cell receptors CEACAM1 and CEACAM5, that are often overexpressed on many varieties of most cancers cells.
This work was revealed in Proceedings of the Nationwide Academy of Sciences on September 10.
The adhesion mechanism between pathogenic micro organism and host cells represents a basic side of pathogenic biology. Such micro organism make use of specialised floor molecules referred to as adhesins to determine a good attachment to host cells through exact molecular interactions. This adhesion course of is dynamically regulated throughout an infection, permitting micro organism to adapt to altering circumstances. Nonetheless, how micro organism management the power of adhesion on the bacterium-host interface was poorly understood till now.
F. nucleatum makes use of its adhesin protein CbpF to particularly bind to CEACAM1 and CEACAM5. Notably, when engaged, CEACAM1 additionally acts as an inhibitory receptor on immune cells, suppressing immune exercise. Due to this fact, elucidating how CbpF interacts with CEACAM1 and CEACAM5 is vital for designing focused therapeutic methods that disrupt bacteria-driven tumor development.
Utilizing cryo-electron microscopy, the researchers resolved high-resolution buildings of CbpF sure to CEACAM1 and CEACAM5. Within the complicated buildings, CbpF assembles as a trimer, with every monomer binding one CEACAM1 or CEACAM5 molecule, forming a symmetric 3:3 binding sample.
Moreover, the researchers noticed one other sort of complicated, that includes two CbpF trimers sure to a single receptor dimer.
Based mostly on these findings, the researchers proposed a “Velcro model” of bacterial adhesion: The extremely versatile CbpF protein acts because the “loop” aspect, interacting with the host receptor, which serves because the “hook” aspect, by means of a number of binding websites. This mechanism permits micro organism to dynamically regulate adhesion power underneath mechanical stress, enabling tight attachment and simple detachment when wanted for adaptation to complicated physiological environments. This mannequin exhibits how micro organism dynamically regulate adhesion on the molecular degree.
Extra info:
Fan Shen et al, Binding ofFusobacterium nucleatumautotransporter adhesin CbpF to human CEACAM1 and CEACAM5: A Velcro mannequin for bacterium adhesion, Proceedings of the Nationwide Academy of Sciences (2025). DOI: 10.1073/pnas.2516574122
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Intestine bacterial adhesion mechanism revealed as goal for novel colorectal most cancers therapies (2025, September 19)
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