Protein kinase F regulates the virulence of Mycobacterium tuberculosis

Area of Science:

• Microbiology
• Immunology
• Molecular Biology

Background:

• Mycobacterium tuberculosis (Mtb) serine/threonine protein kinase F (PknF) is implicated in modulating innate immune responses.
• The role of PknF in Mtb virulence during in vivo infection remains largely uncharacterized.

Purpose of the Study:

• To investigate the role of PknF in Mtb virulence in a murine infection model.
• To determine if PknF's effect on virulence is linked to NLRP3 inflammasome activation.

Main Methods:

• Generation of a pknF deletion mutant (ΔpknF) of Mtb.
• Infection of mice (including Nlrp3-deficient and susceptible strains) with wild-type Mtb, ΔpknF mutant, and complemented strains.
• Quantification of bacterial loads in lungs, BAL fluid, and spleen.
• Analysis of host inflammatory responses and survival rates.
• Lipidomic analysis of Mtb strains to assess PDIM levels.

Main Results:

• The ΔpknF mutant exhibited significantly increased growth in mouse lungs at early and late time points compared to wild-type and complemented strains.
• Increased pulmonary bacterial burden in ΔpknF-infected mice was observed even in Nlrp3-deficient mice.
• ΔpknF infection led to increased lung inflammation and reduced survival in susceptible mouse strains.
• The ΔpknF mutant showed significantly increased levels of the pro-virulence lipid pthiocerol dimycoserosate (PDIM).

Conclusions:

• PknF restricts Mtb virulence in the mouse lung through an NLRP3 inflammasome-independent mechanism.
• PknF likely suppresses Mtb virulence by downregulating the expression of the lipid PDIM.
• These findings highlight PknF as a potential target for anti-TB therapies.