Mycobacterium tuberculosis Ser/Thr protein kinase B mediates an oxygen-dependent replication switch

Area of Science:

• Microbiology
• Molecular Biology
• Cellular Signaling

Background:

• Tuberculosis (TB) is a major global health issue, with most Mycobacterium tuberculosis (Mtb) infections establishing a latent state characterized by drug tolerance and minimal replication.
• Low oxygen tension (hypoxia) is a critical host factor inducing Mtb bacteriostasis, but the molecular mechanisms governing oxygen-dependent replication remain poorly understood.

Purpose of the Study:

• To investigate the role of serine/threonine phosphorylation in the Mtb response to altered oxygen levels, specifically focusing on mechanisms of latency and reactivation.
• To identify key kinases involved in regulating Mtb replication transitions under varying oxygen conditions.

Main Methods:

• Utilized an in vitro model simulating Mtb latency (hypoxia) and reactivation (reaeration).
• Employed broad kinase inhibition, activity-based protein profiling, and genetic mutation analyses.
• Assessed Mtb viability, replication rates, and morphological changes under different oxygen tensions and PknB activity levels.

Main Results:

• Broad kinase inhibition impaired Mtb survival during reaeration.
• Identified PknB as a critical kinase for Mtb survival during hypoxia.
• Demonstrated that Mtb replication is highly sensitive to PknB levels, with overexpression in hypoxia causing significant viability loss and morphological defects.
• Showed that reducing PknB activity during hypoxia specifically hindered growth resumption upon reaeration.

Conclusions:

• Phosphosignaling pathways, particularly involving PknB, regulate replicative transitions crucial for Mtb latency and reactivation.
• PknB activity is dynamically controlled: reduced for bacteriostasis in hypoxia and elevated for replication resumption.
• PknB represents a potential therapeutic target for combating active TB, latent infections, and reactivation.