Itaconate can covalently modify cysteine residues on proteins to form S-itaconation. Increasing research suggests that this novel post-translational modification plays a crucial role in regulating the host's immune response. For pathogens, itaconate can either help certain bacteria, such as Pseudomonas aeruginosa and Klebsiella pneumoniae, better adapt to the host’s immune system, leading to chronic infections, or inhibit the growth of Salmonella. However, the specific molecular mechanisms remain unclear.
Recently, Professor Chu Wang's group from the College of Chemistry and Molecular Engineering at Peking University and the Peking-Tsinghua Center for Life Sciences, published a research paper in Cell Reports entitled "In situ chemoproteomic profiling reveals itaconate inhibits de novo purine biosynthesis in pathogens". In this work, the authors took advantage of chemoproteomic techniques to explore potential cysteine S-itaconation targets in the proteomes of three drug-resistant pathogens. They revealed the molecular mechanism by which itaconate exerts its antibacterial function by inhibiting the de novo purine biosynthesis pathway in Salmonella Typhimurium SL1344.
Fig. 1 Itaconate inhibits de novo purine biosynthesis in Salmonella
To investigate which proteins are modified by itaconate, this study utilized a previously developed itaconate probe, C3A (Zhang et al., Chemical Science, 2022). The authors tested the compatibility of C3A with in situ labeling and optimised the sample preparation proceduresfor mass spectrometry, leading to the identification of more S-itaconated cysteines. This strategy quantitatively profiled S-itaconation targets in three drug-resistant pathogens, such as S. aureus, P. aeruginosa, and Salmonella.
In the case of Salmonella, the authors aimed to answer the unresolved question of how itaconate inhibits its growth. The authors discovered that itaconate primarily targets the de novo purine biosynthesis pathway. They verified that itaconate covalently modifies the active site of purF and guaABC in purified protein, inhibiting their in vitro enzymatic activities. Targeted metabolomics further confirmed that itaconate reduces the levels of AMP and GMP, the products of this metabolic pathway. Bacterial growth experiments also demonstrated that supplementing AMP and GMP rescues bacterial growth, overcoming the inhibitory effects of itaconate on Salmonella. Finally, through gene knockout and rescue assays, the authors showed the importance of S-itaconated cysteine on purF and guaB proteins for bacterial growth both in vitro and in vivo.
In summary, this study explains how itaconate exerts its antibacterial function in more physiologically relevant conditions: by targeting purF at the beginning of the pathway to down-regulate the synthesis of IMP, and simultaneously inhibiting the guaABC cluster to inhibit the salvage pathway, thereby limiting bacterial growth. This work will provide insights for developing novel antibacterial strategies in the future.
The corresponding author of this work is Professor Chu Wang from the College of Chemistry and Molecular Engineering at Peking University and the Peking-Tsinghua Center for Life Sciences. Zihua Liu (Ph.D. candidate, 2018) is the first author, and Dongyang Liu made significant contributions to this research. This work was supported by funding from the Ministry of Science and Technology's National Key R&D Program (2022YFA1304700) and the National Natural Science Foundation of China’s major research program (21925701, 92153301 and 22321005).
Original link for the paper: https://www.cell.com/cell-reports/fulltext/S2211-1247(24)01088-X
