Klassert, T. | bioRxiv Science

bioRxiv2025

Expression of human CEACAMs promotes inflammation and organ damage during systemic Candida albicans infection in mice

Invasive candidiasis is a fungal infection characterized by a high mortality rate. CEACAM family receptors play a crucial role in regulating innate responses of both leukocytes and epithelia. Human CEACAM3, CEACAM5 and CEACAM6 receptors recognize C. albicans and are expressed in transgenic CEABAC10 mice. In a murine C. albicans infection model, CEABAC10 mice exhibited a shortened survival period attributed to an early cytokine storm, an exacerbated acute phase response, and heightened systemic inflammation compared to their wild-type littermates. The livers and kidneys of CEABAC10 mice displayed intensified purulent necrotizing inflammation, accompanied by increased infiltration of neutrophils and macrophages. Our in vivo and in vitro data indicated that the expression of CEACAM6 on monocytes of CEABAC10 mice caused the elevated cytokine levels and the subsequent exacerbation of the acute phase response upon C. albicans infection, resulting in decreased survival.

immunology↗

bioRxiv2024

MftG is crucial for alcohol metabolism of mycobacteria by linking mycofactocin oxidation to respiration

Mycofactocin is a redox cofactor essential for the alcohol metabolism of mycobacteria.. While the biosynthesis of mycofactocin is well established, the gene mftG, which encodes an oxidoreductase of the glucose-methanol-choline superfamily, remained functionally uncharacterized. Here, we show that MftG enzymes are almost exclusively found in genomes containing mycofactocin biosynthetic genes and are present in 75% of organisms harboring these genes. Gene deletion experiments in Mycolicibacterium smegmatis demonstrated a growth defect of the {Delta}mftG mutant on ethanol as a carbon source, accompanied by an arrest of cell division reminiscent of mild starvation. Investigation of carbon and cofactor metabolism implied a defect in mycofactocin reoxidation. Cell-free enzyme assays and respirometry using isolated cell membranes indicated that MftG acts as a mycofactocin dehydrogenase shuttling electrons toward the respiratory chain. Transcriptomics studies also indicated remodeling of redox metabolism to compensate for a shortage of redox equivalents. In conclusion, this work closes an important knowledge gap concerning the mycofactocin system and adds a new pathway to the intricate web of redox reactions governing the metabolism of mycobacteria.

microbiology↗