Mycobacterium tuberculosis (Mtb) lipid mediated lysosomal rewiring in infected macrophages modulates intracellular Mtb trafficking and survival

Abstract

<jats:p>Intracellular pathogens commonly manipulate the host lysosomal system for their survival. However, whether this pathogen-induced alteration affects the organization and functioning of the lysosomal system itself is not known. Here, using <jats:italic>in vitro</jats:italic> and <jats:italic>in vivo</jats:italic> infections and quantitative image analysis, we show that the lysosomal content and activity are globally elevated in <jats:italic>Mycobacterium tuberculosis</jats:italic> (<jats:italic>Mtb</jats:italic>)-infected macrophages. We observed that this enhanced lysosomal state is sustained over time and defines an adaptive homeostasis in the infected macrophage. Lysosomal alterations are caused by mycobacterial surface components, notably the cell wall-associated lipid sulfolipid-1 (SL-1), which functions through the mTOR complex 1 (mTORC1)–transcription factor EB (TFEB) axis in the host cells. An <jats:italic>Mtb</jats:italic> mutant lacking SL-1, <jats:italic>Mtb</jats:italic>Δ<jats:italic>pks2,</jats:italic> shows attenuated lysosomal rewiring compared with the WT <jats:italic>Mtb</jats:italic> in both <jats:italic>in vitro</jats:italic> and <jats:italic>in vivo</jats:italic> infections. Exposing macrophages to purified SL-1 enhanced the trafficking of phagocytic cargo to lysosomes. Correspondingly, <jats:italic>Mtb</jats:italic>Δ<jats:italic>pks2</jats:italic> exhibited a further reduction in lysosomal delivery compared with the WT. Reduced trafficking of this mutant <jats:italic>Mtb</jats:italic> strain to lysosomes correlated with enhanced intracellular bacterial survival. Our results reveal that global alteration of the host lysosomal system is a defining feature of <jats:italic>Mtb</jats:italic>-infected macrophages and suggest that this altered lysosomal state protects host cell integrity and contributes to the containment of the pathogen.</jats:p>

Heterogeneity in the endocytic capacity of individual macrophage in a population determines its subsequent phagocytosis, infectivity and subcellular trafficking

“…The data on differential trafficking of Mtb to lysosomes in cells with high vs low endocytic capacities in the same population corroborates our previous result that lysosomal content could influence the trafficking of Mtb 22,32 . While these correlations need to be better understood in detailed mechanistic terms, our data showing differential trafficking of Mtb to lysosomes in distinct subsets of cells in a non‐perturbed macrophage population identifies endocytic capacity as a crucial determinant of phagocytic uptake as well as downstream trafficking.…”

“…At a population level, the proportion of Mtb delivered to lysosomes is thus an average of these two bins. Our previous results suggested that the lysosomal content of the cell influences Mtb trafficking 22,32 . Hence, we assessed if the total lysosomal content of cells co‐varies with endocytic capacity in the two bins.…”

“…Animal infections with M . tuberculosis were performed following previously established procedures 22 . Briefly, BALB/c or C57BL/6 mice were infected with M .…”

“…Mycobacterium tuberculosis , the causative agent of tuberculosis, is taken up in macrophages by phagocytosis. Upon uptake, the pathogen significantly interferes with host cell trafficking pathways, such as phagosome maturation, 17‐19 autophagy 20,21 and lysosomal system, 22 to establish and sustain a suitable subcellular niche for its survival. Phagosome maturation requires sequential fusion with distinct endosomes, 23,24 hence optimal endocytosis is necessary for phagosome maturation.…”

Variations in Antimicrobial Activities of Human Monocyte-Derived Macrophage and Their Associations With Tuberculosis Clinical Manifestations

“…Macrophages are thought to exhibit different levels of antimicrobial activities depending on the nature of stimuli, but the pattern of difference is not consistent between different in vitro macrophage models (Yates et al, 2005;Podinovskaia et al, 2013;Sachdeva et al, 2020). For example, in mouse bone marrow-derived macrophages (BMDM) phagocytosis of Mycobacterium tuberculosis (Mtb) results in a higher proteolytic activity than phagocytosis of non-immunogenic IgG, but the induced acidification activity is at a similar level (Podinovskaia et al, 2013).…”