Anil Kumar, V. | Search bioRxiv

bioRxiv2023

Dual functioning by the PhoR sensor is a key determinant to Mycobacterium tuberculosis virulence

PhoP-PhoR empowers M. tuberculosis to adapt to diverse environmental conditions, and remains essential for virulence. Although PhoP and PhoR have been structurally characterized, the signal(s) that this TCS responds to remains unknown. In this study, we show that PhoR is a sensor of acidic pH/high salt conditions, which activate PhoP via phosphorylation. Transcriptomic studies uncover that acidic pH-inducible expression of PhoP regulon is significantly inhibited in a PhoR-deleted M. tuberculosis. Using genome-wide screening we further identify a non-canonical mechanism of PhoP phosphorylation by the sensor kinase PrrB. To investigate how phosphorylation of PhoP is regulated, we discovered that PhoR functions as a phosphatase. Our results identify the motif/residues responsible for contrasting kinase/phosphatase dual functioning of PhoP, and collectively determine the homeostatic regulation of intra-mycobacterial P~PhoP which controls the final output of PhoP regulon. Together, these data uncover that PhoR plays a central role in mycobacterial adaptation to low pH conditions within the host macrophage phagosome. Consistent with these results a PhoR-deleted M. tuberculosis remains significantly attenuated in macrophages and animal models.

microbiology↗

bioRxiv2019

Metabolic switching of Mycobacterium tuberculosis during hypoxia is controlled by the virulence regulator PhoP

Mycobacterium tuberculosis (Mtb) retains the unique ability to establish an asymptomatic latent infection. A fundamental question in mycobacterial physiology is to understand the mechanisms involved in hypoxic stress, a critical player in persistence. Here, we show that the virulence regulator PhoP responds to hypoxia, the dormancy signal and effectively integrates hypoxia with nitrogen metabolism. We also provide evidence to demonstrate that both under nitrogen limiting conditions and during hypoxia, phoP locus controls key genes involved in nitrogen metabolism. Consistently, under hypoxia{Delta} phoP shows growth attenuation even with surplus nitrogen, the alternate electron acceptor, and complementation of the mutant restores bacterial growth. Together, our observations provide new biological insights into the role of PhoP in integrating nitrogen metabolism with hypoxia by the assistance of the hypoxia regulator DosR. The results have significant implications on the mechanism of intracellular survival and growth of the tubercle bacilli under a hypoxic environment within the phagosome. ImportanceMtb retains the unique ability to establish an asymptomatic latent infection. To understand the mechanisms involved in hypoxic stress which plays a critical role in persistence, we show that the virulence regulator PhoP responds to hypoxia, the dormancy signal. In keeping with this, phoP was shown to play a major role in Mtb growth under hypoxia even in presence of surplus nitrogen, the alternate electron acceptor. Our results showing regulation of hypoxia-responsive genes provide new biological insights into role of the virulence regulator in metabolic switching by sensing hypoxia and integrating nitrogen metabolism with hypoxia by the assistance of the hypoxia regulator DosR.

microbiology↗