Mycobacterium tuberculosis sensor kinase DosS modulates the autophagosome in a DosR-independent manner

Uma S Gautam,Xavier Alvarez,Smriti Mehra,Priyanka Kumari,Deepak Kaushal,Jaya S Tyagi,Tianhua Niu

doi:10.1038/s42003-019-0594-0

Abstract

Dormancy is a key characteristic of the intracellular life-cycle of Mtb. The importance of sensor kinase DosS in mycobacteria are attributed in part to our current findings that DosS is required for both persistence and full virulence of Mtb. Here we show that DosS is also required for optimal replication in macrophages and involved in the suppression of TNF-α and autophagy pathways. Silencing of these pathways during the infection process restored full virulence in MtbΔdosS mutant. Notably, a mutant of the response regulator DosR did not exhibit the attenuation in macrophages, suggesting that DosS can function independently of DosR. We identified four DosS targets in Mtb genome; Rv0440, Rv2859c, Rv0994, and Rv0260c. These genes encode functions related to hypoxia adaptation, which are not directly controlled by DosR, e.g., protein recycling and chaperoning, biosynthesis of molybdenum cofactor and nitrogen metabolism. Our results strongly suggest a DosR-independent role for DosS in Mtb.

Highlights

Dormancy is a key characteristic of the intracellular life-cycle of Mycobacterium tuberculosis (Mtb)
Concomitant with the induction of the DosR regulon, the physiology of Mtb undergoes reprogramming within granulomas, which impacts the acquisition of downstream adaptive responses[10]
We assessed the effect of autophagy in macrophages infected with the mutant MtbΔdosS, including those infected with Mtb

Summary

Introduction

Dormancy is a key characteristic of the intracellular life-cycle of Mtb. The importance of sensor kinase DosS in mycobacteria are attributed in part to our current findings that DosS is required for both persistence and full virulence of Mtb. We show that DosS is required for optimal replication in macrophages and involved in the suppression of TNF-α and autophagy pathways Silencing of these pathways during the infection process restored full virulence in MtbΔdosS mutant. Mtb persists within granuloma and encounters microenvironmental stressors such as hypoxia, nitric oxide, and carbon monoxide[4,5,6,7] The combination of these stressors with the direct actions of activated immune cells and nutritional restrictions within granuloma arrests Mtb replication[1,2]. As an extension of this hypothesis, we wanted to test whether DosR regulon mutants (dos mutants) exhibit altered interactions with macrophages, which could lead to differential antigen processing and presentation and, a more efficient adaptive immune response. We further demonstrate that DosS interacts with numerous other Mtb proteins via phosphorylation, which may impact and amplify the pathogen’s response to intraphagosomal and intragranulomatous stress

Methods

Results

Conclusion