Mycobacterium tuberculosis resides in lysosome-poor monocyte-derived lung cells during chronic infection
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ABSTRACT: Mycobacterium tuberculosis (Mtb) infects multiple lung myeloid cell subsets and persists despite innate and adaptive immune responses. However, the mechanisms allowing Mtb to evade elimination by these subsets are not fully understood. Here, we determined that four weeks post infection, after development of adaptive immune responses, CD11clo monocyte-derived lung cells termed MNC1 (mononuclear cell subset 1), harbor more live Mtb compared to alveolar macrophages (AM), neutrophils, and less permissive CD11chi MNC2. Bulk RNA-seq analysis for these subsets identified that lysosome biogenesis pathway is underexpressed in MNC1. Functional assays confirmed that Mtb-permissive MNC1 are deficient in lysosome content, lysosomal acidification, and lysosomal activity compared to AM, and have less nuclear TFEB, a master regulator of lysosome biogenesis. Mtb infection does not alter lysosome deficiency in MNC1. Instead, Mtb recruits MNC1 and MNC2 to the lungs for its spread from AM to these subsets, which depend on Mtb ESX-1 secretion system. Furthermore, nilotinib-mediated TFEB activation enhances lysosome function of primary macrophages in vitro, and MNC1 and MNC2 in vivo, improving control of Mtb infection. Our results suggest that Mtb exploits lysosome-poor monocyte-derived lung cells for persistence; targeting lysosome biogenesis may be an effective approach to host-directed therapy for tuberculosis, enabling permissive lung cells to restrict and kill Mtb through autophagy and other mechanisms.
Project description:Lysosomal cathepsins regulate an exquisite range of biological functions, and their deregulation is associated with inflammatory, metabolic and degenerative disease in humans. Here, we identified a key cell-intrinsic role for cathepsin B as a negative feedback regulator of lysosomal biogenesis and autophagy. Mice and macrophages lacking cathepsin B activity had increased resistance to the cytosolic bacterial pathogen Francisella novicida. Genetic deletion or pharmacological inhibition of cathepsin B downregulated mTOR activity and prevented cleavage of the lysosomal calcium channel TRPML1. These events drove transcription of lysosomal and autophagy genes via the transcription factor TFEB, which increased lysosomal biogenesis and activation of autophagy-initiation kinase ULK1 for clearance of the bacteria. Our results identified a fundamental biological function of cathepsin B in providing a checkpoint for homeostatic maintenance of lysosome population and basic recycling functions in the cell. We used microarrays to explore the gene expression profiles differentially expressed in bone marrow-derived macrophages (BMDM) isolated from cathepsin B-/- and wild-type mice.
Project description:Infectious diseases, such as Mycobacterium tuberculosis (Mtb)-caused tuberculosis (TB), remain a global health threat exacerbated by increasing drug resistance. Host-directed therapy (HDT) is a complementing strategy for infection treatment through targeting host immune mechanisms. However, the limited understanding of the host factors and their regulatory mechanisms involved in host immune defense against infections has impeded HDT development. Here, we identify the E3 ubiquitin ligase tripartite motif-containing 27 (TRIM27) elicits host protective immunity against Mtb. Mechanistically, TRIM27 enters host cell nucleus upon Mtb infection to function as a transcription activator of transcription factor EB (TFEB). TRIM27 binds to TFEB promoter and the TFEB transcription factor cAMP responsive element binding protein 1 (CREB1), thus enhancing CREB1-TFEB promoter binding affinity and promoting CREB1 transcription activity towards TFEB, eventually leading to autophagy activation and pathogen clearance. Thus, TRIM27 contributes to host anti-Mtb immunity and targeting TRIM27/CREB1/TFEB axis serves as a promising HDT-based TB treatment.
Project description:Cells respond to mitochondrial energetic stress with rapid activation of the AMP-activated protein kinase (AMPK), which acutely inhibits anabolism and stimulates catabolism. AMPK also induces sustained transcriptional reprogramming of metabolism. The TFEB transcription factor is a major effector of AMPK signals, inducing lysosome genes following energetic stress. Yet the molecular mechanism underlying how AMPK activates TFEB remains unresolved. We demonstrate here that AMPK directly phosphorylates five conserved serine residues in FNIP1, which suppresses the function of the FLCN/FNIP1 RagC GAP complex, in turn controlling TFEB lysosomal localization. We demonstrate that FNIP1 phosphorylation is required for AMPK to induce nuclear translocation of TFEB, which is fully separable from AMPK control of canonical mTORC1 signaling. Using a non-phosphorylatable allele of FNIP1, we show that in parallel to lysosomal biogenesis, AMPK induces mitochondrial biogenesis via TFEB-dependent induction of PGC1a mRNA. This signaling from mitochondrial stress is also independent of amino-acid control of the Rags and TFEB, which still proceed normally in cells bearing the AMPK-non phosphorylatable allele of FNIP1. Taken together, mitochondrial energetic stress triggers AMPK/FNIP1-dependent TFEB nuclear translocation, inducing transcriptional waves of lysosomal and mitochondrial biogenesis.
Project description:Lysosomes are at the epicenter of cellular processes critical for inflammasome activation in macrophages, including autophagy and lipid metabolism. Inflammasome activation and IL1-beta secretion are implicated in atherogenesis, ischemic cardiac injury and resultant heart failure; however, little is known about the role of macrophage lysosome function in regulating these processes. We hypothesized that macrophages exhibit lysosome dysfunction in heart failure due to ischemic injury, and that augmentation of macrophage lysosomal biogenesis via macrophage-specific overexpression of transcription factor EB (mf-TFEB) would attenuate ischemic remodeling by modulating macrophage inflammatory responses. In both mice subject to ischemia-reperfusion injury, and human heart tissue from patients with ischemic cardiomyopathy, we find evidence of lysosome insufficiency and autophagic impairment, respectively. Mf-TFEB overexpression significantly attenuated post-IR adverse left ventricular remodeling at 4 weeks without affecting scar size. Mf-TFEB overexpression reduced the relative amounts of pro-inflammatory macrophage populations in the myocardium. RNA sequencing of flow-sorted cardiac macrophages post-IR confirmed that TFEB stimulated a lysosomal transcriptional program in macrophages, and upregulated key targets involved in lysosomal lipid metabolism, which we show are critical for inflammasome suppression. Both TFEB-dependent inflammasome suppression and effects on post-IR remodeling were independent of autophagy. Our findings suggest that TFEB reprograms macrophage lysosomal lipid metabolism to attenuate inflammasome activity and protect against post-ischemic cardiac remodeling and simultaneously shift our understanding of how autophagy and lipid metabolism impact acute inflammation.
Project description:The mechanisms that govern organelle remodeling remain poorly defined. Lysosomes degrade cargo from various routes including endocytosis, phagocytosis and autophagy. For phagocytes, lysosomes are a kingpin organelle since they are essential to kill pathogens and process and present antigens. During phagocyte activation, lysosomes undergo a striking reorganization, changing from dozens of globular structures to a tubular network, in a process that requires the phosphatidylinositol-3-kinase-AKT-mTOR signalling pathway. Here, we show that lysosomes undergo a remarkable expansion in volume and holding capacity during phagocyte activation within 2 h of LPS stimulation. Lysosome expansion was paralleled by an increase in lysosomal protein levels, but this was unexpectedly independent of TFEB and TFE3 transcription factors, known to scale up lysosome biogenesis. Instead, we demonstrate a hitherto unappreciated mechanism of acute organelle expansion via mTORC1-dependent increase in translation of mRNAs encoding key lysosomal proteins. Importantly, mTORC1-dependent increase in translation activity was necessary for efficient and rapid antigen presentation by dendritic cells. Collectively, we identified a previously unknown and functionally relevant mechanism for lysosome expansion that relies on mTORC1-dependent enhanced translation of mRNAs to boost protein synthesis and lysosome biogenesis in response to an infection signal.
Project description:Host resistance to Mycobacterium tuberculosis (Mtb) infection requires the activities of multiple leukocyte subsets, yet the roles of the different innate effector cells during tuberculosis (TB) are incompletely understood. Here we show a role for eosinophils in host resistance to Mtb infection. In humans, eosinophils are found in resected human TB lung lesions and autopsy granulomas. Eosinophils are also found in granulomas in zebrafish, mice, and non-human primates, where they are functionally activated and degranulate. Transcriptional profiling of lung tissue after Mtb infection of mice, that selectively lack eosinophils, revealed changes in neuronal associated pathways. Importantly, employing several independent models of eosinophil deficiency in mice, we demonstrate that eosinophils are required for optimal pulmonary bacterial control and host survival after Mtb infection. Collectively, our findings establish an unexpected role for eosinophils, granulocytes typically associated with type II inflammation, in host resistance against Mtb, a major human bacterial pathogen.
Project description:TFEB has been recently reported to be a key molecule for lysosomal regulation. Renal cell carcinoma (RCC) with t(6;11) (p21;q12) is known to be the only tumor in which TFEB is upregulated. Transcriptome analysis using a whole-genome expression array and pathway analysis using upregulated genes in tumor tissue revealed that the lysosome-associated pathways were significantly deregulated. Total RNA was extracted from non-tumor and tumor in patient of renal cell carcinoma with t(6;11) (p21;q12) and subjected to gene expression microarray analysis.
Project description:This is a four dimensionsal ordinary differential equation mathematical model that explores the contribution of PI3P during Mycobacterium tuberculosis (Mtb) phagocytosis. The model was built in an effort to understand the mechanisms by which Mtb eliminates phagosome-lysosome fusion during the hosts enactment of anti-microbial pathways.
Project description:Mycobacterium tuberculosis (Mtb) secretes several virulence determinants that alter phagosome biogenesis, enabling its survival within the cell. Nevertheless, the mechanism underlying this process remains considerably obscure. Here, we have identified a novel regulatory mechanism whereby SIRT7 mediates Rac1 activation in cytoskeletal remodelling during Mtb infection. We found that SIRT7 are significantly decreased during Mtb infection in both mRNA and protein levels. SIRT7 deficiency impairs macrophage phagocytosis and bacteriacidal activity by disrupts actin cytoskeleton dynamics. In the murine TB model, the deficiency of Sirt7 had an adverse effect on the host's response to Mtb since it led to an increase in bacterial burden and inflammation in the lung. Conversely, the overexpression of Sirt7 impeded bacterial growth. Mechanistically, we have shown that SIRT7 limits Mtb infection by directly interacting with and activating RAC1. Therefore, we conclude that SIRT7 is responsible for driving cytoskeletal remodeling through RAC1, thus providing crucial insight into host response during Mtb infection and offering a potential target for tuberculosis treatment.
Project description:Crosstalk between cell death programs confers appropriate host anti-infection immune responses, but how pathogens remodel this network to facilitate their infections remain largely unclear. Here, we identify mammalian cell entry 3C (Mce3C) as a key regulator of host cell death from Mycobacterium tuberculosis (Mtb), which causes tuberculosis featured with lung inflammation and necrosis. Mce3C binds host lysosomal protease cathepsin B (CTSB), which acts as a decision-maker of cell death modalities, to inhibit the protease activity of CTSB towards BH3-interacting domain death agonist (BID) and receptor-interacting protein kinase 1 (RIPK1), thus preventing the production of pro-apoptotic truncated BID (tBID) while maintaining the abundance of pro-necroptotic RIPK1. Disrupting the Mce3C-CTSB interaction promotes host apoptosis and suppresses necroptosis with attenuated Mtb survival and mitigated lung inflammation in mice. These findings reveal a unique strategy by which the pathogen manipulates host lysosomal protease activity-dependent plasticity between cell death pathways to promote infection and pathogenicity.