The Cell Wall Lipid PDIM Contributes to Phagosomal Escape and Host Cell Exit of Mycobacterium tuberculosis.

Jeff Quigley,Carlos A Velikovsky,Najib M El-Sayed,Roy A Mariuzza,V Keith Hughitt,Volker Briken,Stefan H E Kaufmann

doi:10.1128/mbio.00148-17

Jeff Quigley, Carlos A Velikovsky + Show 5 more

Open Access

https://doi.org/10.1128/mbio.00148-17

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Abstract

ABSTRACTThe cell wall of Mycobacterium tuberculosis is composed of unique lipids that are important for pathogenesis. Indeed, the first-ever genetic screen in M. tuberculosis identified genes involved in the biosynthesis and transport of the cell wall lipid PDIM (phthiocerol dimycocerosates) as crucial for the survival of M. tuberculosis in mice. Here we show evidence for a novel molecular mechanism of the PDIM-mediated virulence in M. tuberculosis. We characterized the DNA interaction and the regulon of Rv3167c, a transcriptional repressor that is involved in virulence regulation of M. tuberculosis, and discovered that it controls the PDIM operon. A loss-of-function genetic approach showed that PDIM levels directly correlate with the capacity of M. tuberculosis to escape the phagosome and induce host cell necrosis and macroautophagy. In conclusion, our study attributes a novel role of the cell wall lipid PDIM in intracellular host cell modulation, which is important for host cell exit and dissemination of M. tuberculosis.

Highlights

The cell wall of Mycobacterium tuberculosis is composed of unique lipids that are important for pathogenesis
In order to test whether Rv3167c can dimerize, we made use of the mycobacterial protein fragment complementation (M-PFC) assay [28], where bacterial growth is seen on agar containing trimethoprim when the proteins of interest interact
Using thinlayer chromatography (TLC), we showed that the transcriptional upregulation manifested in an increase in PDIM lipid in the M. tuberculosis ΔRv3167c mutant (Fig. 2d)

Summary

Introduction

The cell wall of Mycobacterium tuberculosis is composed of unique lipids that are important for pathogenesis. The complex and unique cell wall of M. tuberculosis contains the lipid PDIM (phthiocerol dimycocerosates), which is crucial for virulence of the bacterium, but its function is not well understood. The discovery of a link between the cell wall lipid PDIM and a major pathogenesis pathway of M. tuberculosis provides important insights into the molecular mechanisms of host cell manipulation by M. tuberculosis. Mycobacterium tuberculosis is one of the most deadly human pathogens due to its ability to manipulate and evade host innate and acquired immune responses [1,2,3,4,5,6]. There is still a great deal of uncertainty about the molecular mechanisms of PDIM-mediated virulence regulation of M. tuberculosis [2]

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