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bioRxiv · 10.1101/103028

Efficacy of the β-lactam\β-lactamase inhibitor combination is linked to WhiB4 mediated changes in redox physiology of Mycobacterium tuberculosis

Singh, A.·Mishra, S.·Shukla, P.·Bhaskar, A.·Anand, K.·Baloni, P.·Jha, R. K.·Mohan, A.·Rajmani, R. S.·Nagaraja, V.·Chandra, N.
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Abstract

AimsInhibition of {beta}-lactamase by clavulanate (Clav) sensitizes multi-and extensively drug-resistant Mycobacterium tuberculosis (Mtb) strains towards {beta}-lactams such as amoxicillin (Amox). However, the underlying mechanism of how Mtb responds to Amox-Clav combination (Augmentin; AG) is not characterized.\n\nResultsWe integrated global expression profiling with the protein-protein interaction landscape and generated a genome-scale network of Mtb in response to AG. In addition to specific targets (e.g., peptidoglycan biosynthesis and {beta}-lactamase), the response to AG was also centered on redox-balance, central carbon metabolism (CCM), and respiration in Mtb. We discovered that AG modulates superoxide levels, NADH/NAD+ balance and mycothiol redox potential (EMSH) of Mtb. Higher intra-mycobacterial EMSH potentiates mycobactericidal efficacy of AG, whereas lower EMSH induces tolerance. Further, Mtb responds to AG via a redox-sensitive transcription factor, WhiB4. Mtb{Delta}whiB4 displayed higher expression of genes involved in {beta}-lactam resistance along with those mediating respiration, CCM and redox balance. Moreimportantly, WhiB4 binds to the promoter regions and represses transcription of genes involved in {beta}-lactamase expression in a redox-dependent manner. Lastly, while Mtb{Delta}whiB4 maintained internal EMSH, exhibited greater {beta}-lactamase activity and displayed AG-tolerance, overexpression of WhiB4 induced oxidative shift in EMSH and repressed {beta}-lactamase activity to aggravate AG-mediated killing of drug-sensitive and -resistant strains of Mtb.\n\nInnovation and ConclusionsThis work demonstrate that efficacy of {beta}-lactam\\{beta}-lactamase inhibitor combination can be attenuated by elevating mycobacterial antioxidant capabilities and potentiated by impairing redox buffering capacity of Mtb. The functional linkage between {beta}-lactams, redox balance, and WhiB4 can be exploited to potentiate AG action against drug-resistant Mtb.

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Singh, A., Mishra, S., Shukla, P., Bhaskar, A., Anand, K., Baloni, P., Jha, R. K., Mohan, A., Rajmani, R. S., Nagaraja, V., Chandra, N.. 2017-01-27. Efficacy of the β-lactam\β-lactamase inhibitor combination is linked to WhiB4 mediated changes in redox physiology of Mycobacterium tuberculosis. https://doi.org/10.1101/103028

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