Phthiocerol Dimycocerosates of M. tuberculosis Participate in Macrophage Invasion by Inducing Changes in the Organization of Plasma Membrane Lipids
Open Access
- 6 February 2009
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLoS Pathogens
- Vol. 5 (2), e1000289
- https://doi.org/10.1371/journal.ppat.1000289
Abstract
Phthiocerol dimycocerosates (DIM) are major virulence factors of Mycobacterium tuberculosis (Mtb), in particular during the early step of infection when bacilli encounter their host macrophages. However, their cellular and molecular mechanisms of action remain unknown. Using Mtb mutants deleted for genes involved in DIM biosynthesis, we demonstrated that DIM participate both in the receptor-dependent phagocytosis of Mtb and the prevention of phagosomal acidification. The effects of DIM required a state of the membrane fluidity as demonstrated by experiments conducted with cholesterol-depleting drugs that abolished the differences in phagocytosis efficiency and phagosome acidification observed between wild-type and mutant strains. The insertion of a new cholesterol-pyrene probe in living cells demonstrated that the polarity of the membrane hydrophobic core changed upon contact with Mtb whereas the lateral diffusion of cholesterol was unaffected. This effect was dependent on DIM and was consistent with the effect observed following DIM insertion in model membrane. Therefore, we propose that DIM control the invasion of macrophages by Mtb by targeting lipid organisation in the host membrane, thereby modifying its biophysical properties. The DIM-induced changes in lipid ordering favour the efficiency of receptor-mediated phagocytosis of Mtb and contribute to the control of phagosomal pH driving bacilli in a protective niche. Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis, is an extremely successful human pathogen. The pathogenesis of bacterium is associated with its ability to invade macrophages and to circumvent bactericidal functions of the host cell in order to survive within a protective niche. The cellular mechanisms are largely investigated but the bacterial factors are poorly known. The outermost layer of the mycobacterial cell envelope is particularly of interest because of its localization at the interface with macrophages. An interesting feature of this envelope is its high lipid content. One group of lipids, the phthiocerol dimycocerosates (DIM), has been studied intensively since being shown to promote Mtb virulence. We investigated the cellular and molecular mechanisms of DIM and demonstrated that DIM participate in the receptor-dependent phagocytosis of Mtb in human macrophages through a mechanism involving a reorganization of the plasma membrane following recognition of bacilli. This modification of the plasma membrane biophysical properties might help Mtb to create a protective niche by preventing acidification of its phagosome. Our results provide a first hint on the molecular mechanism of action of DIM, a key Mtb lipidic virulence factor.Keywords
This publication has 82 references indexed in Scilit:
- Acquisition of the Vacuolar ATPase Proton Pump and Phagosome Acidification Are Essential for Escape of Francisella tularensis into the Macrophage CytosolInfection and Immunity, 2008
- Changes of the Membrane Lipid Organization Characterized by Means of a New Cholesterol-Pyrene ProbeBiophysical Journal, 2007
- Mycobacterial Mutants with Defective Control of Phagosomal AcidificationPLoS Pathogens, 2005
- High‐Polarity Mycobacterium avium‐Derived Lipids Interact with Murine Macrophage Lipid RaftsScandinavian Journal of Immunology, 2004
- Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequenceNature, 1998
- Lateral Organization of Pyrene-labeled Lipids in Bilayers as Determined from the Deviation from Equilibrium between Pyrene Monomers and ExcimersPublished by Elsevier BV ,1996
- Lack of Acidification in Mycobacterium Phagosomes Produced by Exclusion of the Vesicular Proton-ATPaseScience, 1994
- Distribution of Phthiocerol Diester, Phenolic Mycosides and Related Compounds in MycobacteriaMicrobiology, 1988
- Incorporation of palmitic acid or oleic acid into macrophage membrane lipids exerts differential effects on the function of normal mouse peritoneal macrophagesBiochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1984
- Evidence for Penetration in Liposomes and in Mitochondrial Membranes of a Fluorescent Analogue of Cord FactorEuropean Journal of Biochemistry, 1980