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Receptor-mediated uptake of Clostridioides difficile Toxins A and B

Subject Area Public Health, Healthcare Research, Social and Occupational Medicine
Term from 2019 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 437104764
 
Final Report Year 2023

Final Report Abstract

The aim of the funded project was to reveal a possible synergy or hierarchy of the two known receptor binding regions of TcdB. Similarly, several interaction partners for TcdA are described in the literature, representing either a glycoprotein (Gp96) or different carbohydrate structures (sulfated glycosaminoglycans; Gal-Gal-GlcNac). Analogous to TcdB, (in)dependence of the receptor binding regions should also be investigated for this. Our results clearly demonstrate the complete independence of both receptor interactions for TcdB. Both toxin mutants with selective receptor specificity and CRISPR-Cas9-generated receptor-deficient cell lines confirm the completely independent function of both receptor binding regions in toxin uptake into the cell. In the context of elucidating an independent function of different receptor binding regions in TcdA, we were able to put the importance of sulfated glycosaminoglycans (sGAG) into perspective. The use of three different sGAG- deficient cell lines (HeLa, HT29, CHO) revealed that the uptake of TcdA was not significantly affected by the presence or absence of sGAG. The absence of the CROP domain (Gal-Gal- GlcNac binding) of TcdA or studies on cell lines showing decreased binding of the CROP domain reveal that TcdA from the reference strain VPI10463 and the hypervirulent strain R20291 have different affinity for the CROP-independent receptor. Even without knowing other specific receptors for TcdA, we can postulate the two-receptor model for TcdA as well. Here, both receptor interactions are independent and, as for TcdB, there appear to be different receptor affinities or even specificities for different TcdA variants.

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