PrrA modulates Mycobacterium tuberculosis response to multiple environmental cues and is critically regulated by serine/threonine protein kinases

Abstract

The ability of Mycobacterium tuberculosis (Mtb) to adapt to its surrounding environment is critical for the bacterium to successfully colonize its host. Transcriptional changes are a vital mechanism by which Mtb responds to key environmental signals experienced, such as pH, chloride (Cl-), nitric oxide (NO), and hypoxia. However, much remains unknown regarding how Mtb coordinates its response to the disparate signals seen during infection. Utilizing a transcription factor (TF) overexpression plasmid library in combination with a pH/Cl—responsive luciferase reporter, we identified the essential TF, PrrA, part of the PrrAB two-component system, as a TF involved in modulation of Mtb response to pH and Cl-. Further studies revealed that PrrA also affected Mtb response to NO and hypoxia, with prrA overexpression dampening induction of NO and hypoxia-responsive genes. PrrA is phosphorylated not just by its cognate sensor histidine kinase PrrB, but also by serine/threonine protein kinases (STPKs) at a second distinct site. Strikingly, a STPK-phosphoablative PrrA variant was significantly dampened in its response to NO versus wild type Mtb, disrupted in its ability to adaptively enter a non-replicative state upon extended NO exposure, and attenuated for in vivo colonization. Together, our results reveal PrrA as an important regulator of Mtb response to multiple environmental signals, and uncover a critical role of STPK regulation of PrrA in its function.

Mycobacterium tuberculosis response to cholesterol is integrated with environmental pH and potassium levels via a lipid metabolism regulator

“…To investigate the regulatory mechanism(s) underlying the relationship between environmental [K + ] and the acidic pH response of Mtb, a screening approach was employed using an arrayed inducible transcription factor overexpression library generated in the background of a pH-responsive rv2390c’ ::luciferase reporter [ 11 ]. 7H9, pH 7, 0.05 mM K + or 7H9, pH 5.85, 1.6 mM K + media served as negative and positive control conditions respectively, with an empty vector control included.…”

“…The Δ mce3R mutant and its complement were constructed as previously described [ 2 ], with the Δ mce3R mutation consisting of a deletion beginning at the mce3R start codon (as annotated in the Erdman Mtb strain) through 26 bp from the mce3R stop codon. The rv2390c’ ::luciferase transcription factor overexpression library has been previously described [ 11 ].…”

Shining a light on bacterial environmental cue integration and its relation to metabolism

“…For example, σ S (RpoS) has been extensively studied as a master regulator of the general stress response, particularly in enteric bacteria such as Escherichia coli and Salmonella (Battesti et al, 2011; Hengge‐Aronis, 2002). How about the role of post‐translational modifications mediated by other regulatory systems such as serine/threonine protein kinases (Dworkin, 2015; Giacalone et al, 2022)? Do these regulatory systems have differing importance depending on spatial location of the bacterium within a host tissue?…”

Dual functioning by the PhoR sensor is a key determinant toMycobacterium tuberculosisvirulence

“…We included nitrogen limiting conditions, because mycobacterial PrrAB was reported to be induced under nitrogen limiting conditions (Haydel et al, 2012). Also, a recent study uncovered that PrrA as a transcription factor modulates mycobacterial stress response during low pH conditions (Giacalone et al, 2022). Expectedly, PrrB was mostly in the unphosphorylated form under normal conditions (lane 1) of growth.…”