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

Area of Science:

• Microbiology
• Molecular Biology
• Tuberculosis Research

Background:

• The PhoP-PhoR two-component system (TCS) in Mycobacterium tuberculosis is vital for virulence and adaptation.
• Understanding the signals and regulatory mechanisms of PhoP-PhoR is critical for developing new anti-TB therapies.

Purpose of the Study:

• To identify the environmental signals sensed by the PhoP-PhoR TCS.
• To elucidate the mechanisms regulating PhoP activation and its downstream effects.
• To investigate the role of PhoP-PhoR in M. tuberculosis virulence and host adaptation.

Main Methods:

• Phosphorylation assays to study PhoP activation.
• Transcriptomic analysis to identify PhoP regulon genes.
• Genome-wide interaction screening to identify novel kinases.
• Site-directed mutagenesis to identify functional motifs in PhoR.

Main Results:

• PhoR acts as a sensor for acidic pH and high salt conditions, leading to PhoP phosphorylation.
• A non-canonical PhoP activation pathway involving the sensor kinase PrrB was identified.
• PhoR exhibits dual kinase and phosphatase activity, regulating P~PhoP levels.
• PhoR deletion significantly attenuates M. tuberculosis in macrophages and animal models.

Conclusions:

• PhoR is a key regulator of M. tuberculosis adaptation to low pH environments, particularly within macrophage phagosomes.
• The dual kinase/phosphatase activity of PhoR establishes a homeostatic mechanism for P~PhoP regulation.
• Targeting the PhoP-PhoR system offers a promising strategy for novel anti-TB drug development.