Project description:Eubacterium limosum ATCC 8486 makes acetate and butyrate from various substrates and is found in the human intestine. The proteome of L-carnitine-grown Eubacterium limosum was obtained in order to identify enzymes required for growth on L-carnitine, in particular to identify components that are unique to growth on L-carnitine in comparison to other substrates for acetogenesis, such as lactic acid. L-carnitine and derviatives are converted to trimethylamine (TMA) by certain members of the gut microbiome, metabolism of TMA is now tied to progression of cardiovascular disease. Demethylation of carnitine is observed during growth of Eubacterium limosum on this substrate, and does not produce TMA. Carnitine demethylation by organisms like Eubacterium limosum could lessen TMA production in the gut, thereby lessening the propensity towards atherorsclerosis caused by metabolism of TMA in the body. The carnitine proteome led to the description of a carnitine:tetrahydrofolate methyltransferase system. The key carnitine demethylating enzyme is a member of the widespread TMA methyltransferase protein superfamily.
Project description:Eubacterium limosum ATCC 8486 makes acetate and butyrate from various substrates and is found in the human intestine. The proteome of gamma-butyrobetaine -grown Eubacterium limosum was obtained in order to identify enzymes required for growth on gamma-butyrobetaine, in particular to identify components that are unique to growth on gamma-butyrobetaine in comparison to other substrates for acetogenesis, such as lactic acid, L-carnitine, or proline betaine. Gamma-butyrobetaine is converted to trimethylamine (TMA) by certain members of the gut microbiome. Subsequent liver metabolism of TMA is now tied to progression of cardiovascular disease. Demethylation of gamma-butyrobetaine is observed during growth of Eubacterium limosum on this substrate, and does not produce TMA. Gamma-butyrobetaine demethylation by organisms like Eubacterium limosum could lessen TMA production in the gut, thereby lessening the propensity towards atherosclerosis caused by metabolism of TMA in the body. This proteome led to discovery of gamma-butyrobetaine:tetrahydrofolate methyltransferase system. The key gamma-butyrobetaine demethylating enzyme is a member of the widespread TMA methyltransferase protein superfamily.
Project description:NK cells, as a type of key immune cell, play essential roles in tumor cell immune escape and immunotherapy. Accumulating evidence has demonstrated that the gut microbiota community affects the efficacy of anti-PD1 immunotherapy and that remodeling the gut microbiota structure is a promising strategy to enhance anti-PD1 immunotherapy responsiveness in advanced melanoma patients; however, the details of the mechanism remain elusive. In this study, we found that Eubacterium rectale (E. rectale) was significantly enriched in melanoma patients who responded to anti-PD1 immunotherapy and a high E. rectale abundance was related to longer survival in melanoma patients. Furthermore, administration of E. rectale remarkably improved the efficacy of anti-PD1 therapy and benefited the overall survival of tumor-bearing mice; moreover, application of E. rectale significantly recruited NK cells into the tumor microenvironment. Interestingly, conditioned medium isolated from an E. rectale culture system dramatically enhanced NK-cell function. Through GC-MS/ UHPLC-MS/MS-based metabolomic analysis, L-serine production was found to be significantly decreased in the E. rectale group; moreover, administration of an L-serine synthesis inhibitor dramatically increased NK-cell activation, which led to enhanced anti-PD1 immunotherapy effects. Mechanistically, supplementation with L-serine or application of the L-serine synthesis inhibitor affected NK-cell activation through Fos/Fosl. In summary, our findings reveal the role of bacteria-modulated serine metabolic signaling in NK-cell activation and provide a novel therapeutic strategy to improve the efficacy of anti-PD1 immunotherapy in melanoma.