ABSTRACT
Mitochondrial abnormalities have been noted in lupus, but the causes and consequences remain obscure. Autophagy-related genes ATG5, ATG7 and IRGM have been previously implicated in autoimmune disease. We reasoned that failure to clear defective mitochondria via mitophagy might be a foundational driver in autoimmunity by licensing mitochondrial DNA-dependent induction of type I interferon. Here, we show that mice lacking the GTPase IRGM1 (IRGM homolog) exhibited a type I interferonopathy with autoimmune features. Irgm1 deletion impaired the execution of mitophagy with cell-specific consequences. In fibroblasts, mitochondrial DNA soiling of the cytosol induced cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)-dependent type I interferon, whereas in macrophages, lysosomal Toll-like receptor 7 was activated. In vivo, Irgm1-/- tissues exhibited mosaic dependency upon nucleic acid receptors. Whereas salivary and lacrimal gland autoimmune pathology was abolished and lung pathology was attenuated by cGAS and STING deletion, pancreatic pathology remained unchanged. These findings reveal fundamental connections between mitochondrial quality control and tissue-selective autoimmune disease.
Subject(s)
Autoimmune Diseases/metabolism , Autoimmunity , Fibroblasts/metabolism , GTP-Binding Proteins/metabolism , Mitochondria/metabolism , Mitophagy , Animals , Autoimmune Diseases/genetics , Autoimmune Diseases/immunology , Autoimmune Diseases/pathology , Cells, Cultured , Fibroblasts/immunology , Fibroblasts/pathology , GTP-Binding Proteins/deficiency , GTP-Binding Proteins/genetics , Gene Expression Regulation , Macrophages/immunology , Macrophages/metabolism , Membrane Glycoproteins/genetics , Membrane Glycoproteins/metabolism , Membrane Proteins/genetics , Membrane Proteins/metabolism , Mice, Inbred C57BL , Mitochondria/genetics , Mitochondria/immunology , Mitochondria/pathology , Nucleotidyltransferases/genetics , Nucleotidyltransferases/metabolism , Signal Transduction , Toll-Like Receptor 7/genetics , Toll-Like Receptor 7/metabolismABSTRACT
Multiple modes of cell death have been identified, each with a unique function and each induced in a setting-dependent manner. As billions of cells die during mammalian embryogenesis and daily in adult organisms, clearing dead cells and associated cellular debris is important in physiology. In this Review, we present an overview of the phagocytosis of dead and dying cells, a process known as efferocytosis. Efferocytosis is performed by macrophages and to a lesser extent by other 'professional' phagocytes (such as monocytes and dendritic cells) and 'non-professional' phagocytes, such as epithelial cells. Recent discoveries have shed light on this process and how it functions to maintain tissue homeostasis, tissue repair and organismal health. Here, we outline the mechanisms of efferocytosis, from the recognition of dying cells through to phagocytic engulfment and homeostatic resolution, and highlight the pathophysiological consequences that can arise when this process is abrogated.
Subject(s)
Apoptosis , Host-Pathogen Interactions , Inflammation/physiopathology , Macrophages/physiology , Phagocytes/physiology , Phagocytosis/physiology , Animals , Homeostasis , Humans , Signal TransductionABSTRACT
Receptor-interacting protein kinase-3 (RIPK3) is an activator of necroptotic cell death, but recent work has implicated additional roles for RIPK3 in inflammatory signaling independent of cell death. However, while necroptosis has been shown to contribute to antiviral immunity, death-independent roles for RIPK3 in host defense have not been demonstrated. Using a mouse model of West Nile virus (WNV) encephalitis, we show that RIPK3 restricts WNV pathogenesis independently of cell death. Ripk3-/- mice exhibited enhanced mortality compared to wild-type (WT) controls, while mice lacking the necroptotic effector MLKL, or both MLKL and caspase-8, were unaffected. The enhanced susceptibility of Ripk3-/- mice arose from suppressed neuronal chemokine expression and decreased central nervous system (CNS) recruitment of T lymphocytes and inflammatory myeloid cells, while peripheral immunity remained intact. These data identify pleiotropic functions for RIPK3 in the restriction of viral pathogenesis and implicate RIPK3 as a key coordinator of immune responses within the CNS.
Subject(s)
Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , West Nile Fever/immunology , West Nile virus/physiology , Animals , Central Nervous System/metabolism , Chemokines/immunology , Leukocytes/immunology , Macrophages/immunology , Mice , Mice, Inbred C57BL , Necrosis , Neurons/metabolismABSTRACT
Constitutive cell-autonomous immunity in metazoans predates interferon-inducible immunity and comprises primordial innate defense. Phagocytes mobilize interferon-inducible responses upon engagement of well-characterized signaling pathways by pathogen-associated molecular patterns (PAMPs). The signals controlling deployment of constitutive cell-autonomous responses during infection have remained elusive. Vita-PAMPs denote microbial viability, signaling the danger of cellular exploitation by intracellular pathogens. We show that cyclic-di-adenosine monophosphate in live Gram-positive bacteria is a vita-PAMP, engaging the innate sensor stimulator of interferon genes (STING) to mediate endoplasmic reticulum (ER) stress. Subsequent inactivation of the mechanistic target of rapamycin mobilizes autophagy, which sequesters stressed ER membranes, resolves ER stress, and curtails phagocyte death. This vita-PAMP-induced ER-phagy additionally orchestrates an interferon response by localizing ER-resident STING to autophagosomes. Our findings identify stress-mediated ER-phagy as a cell-autonomous response mobilized by STING-dependent sensing of a specific vita-PAMP and elucidate how innate receptors engage multilayered homeostatic mechanisms to promote immunity and survival after infection.
Subject(s)
Gram-Positive Bacteria/physiology , Gram-Positive Bacterial Infections/immunology , Membrane Proteins/metabolism , Phagocytes/immunology , Animals , Autophagy , Endoplasmic Reticulum/metabolism , Endoplasmic Reticulum Stress , Female , Male , Mice , Pathogen-Associated Molecular Pattern Molecules/metabolism , TOR Serine-Threonine Kinases/metabolismABSTRACT
As long-lived post-mitotic cells, neurons employ unique strategies to resist pathogen infection while preserving cellular function. Here, using a murine model of Zika virus (ZIKV) infection, we identified an innate immune pathway that restricts ZIKV replication in neurons and is required for survival upon ZIKV infection of the central nervous system (CNS). We found that neuronal ZIKV infection activated the nucleotide sensor ZBP1 and the kinases RIPK1 and RIPK3, core components of virus-induced necroptotic cell death signaling. However, activation of this pathway in ZIKV-infected neurons did not induce cell death. Rather, RIPK signaling restricted viral replication by altering cellular metabolism via upregulation of the enzyme IRG1 and production of the metabolite itaconate. Itaconate inhibited the activity of succinate dehydrogenase, generating a metabolic state in neurons that suppresses replication of viral genomes. These findings demonstrate an immunometabolic mechanism of viral restriction during neuroinvasive infection.
Subject(s)
Glycoproteins/metabolism , Hydro-Lyases/metabolism , Neurons/physiology , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Receptors, Pattern Recognition/metabolism , Zika Virus Infection/immunology , Zika Virus/physiology , Animals , Cell Death , Cells, Cultured , Disease Models, Animal , Glycoproteins/genetics , Humans , Hydro-Lyases/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Neuroprotection , RNA, Viral/immunology , RNA-Binding Proteins , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Succinate Dehydrogenase/metabolism , Succinates/metabolism , Virus ReplicationABSTRACT
Phagocytosis and degradation of photoreceptor outer segments (POS) by retinal pigment epithelium (RPE) is fundamental to vision. Autophagy is also responsible for bulk degradation of cellular components, but its role in POS degradation is not well understood. We report that the morning burst of RPE phagocytosis coincided with the enzymatic conversion of autophagy protein LC3 to its lipidated form. LC3 associated with single-membrane phagosomes containing engulfed POS in an Atg5-dependent manner that required Beclin1, but not the autophagy preinitiation complex. The importance of this process was verified in mice with Atg5-deficient RPE cells that showed evidence of disrupted lysosomal processing. These mice also exhibited decreased photoreceptor responses to light stimuli and decreased chromophore levels that were restored with exogenous retinoid supplementation. These results establish that the interplay of phagocytosis and autophagy within the RPE is required for both POS degradation and the maintenance of retinoid levels to support vision.
Subject(s)
Autophagy , Photoreceptor Cells, Vertebrate/metabolism , Retinal Pigment Epithelium/cytology , Retinal Pigment Epithelium/metabolism , Vision, Ocular , Animals , Apoptosis Regulatory Proteins/metabolism , Autophagy-Related Protein 5 , Beclin-1 , Cattle , Lysosomes/metabolism , Mice , Microtubule-Associated Proteins/genetics , Microtubule-Associated Proteins/metabolism , Phagocytosis , Phagosomes/metabolism , Retinoids/metabolismABSTRACT
The importance of autophagy in the generation of memory CD8(+) T cells in vivo is not well defined. We report here that autophagy was dynamically regulated in virus-specific CD8(+) T cells during acute infection of mice with lymphocytic choriomeningitis virus. In contrast to the current paradigm, autophagy decreased in activated proliferating effector CD8(+) T cells and was then upregulated when the cells stopped dividing just before the contraction phase. Consistent with those findings, deletion of the gene encoding either of the autophagy-related molecules Atg5 or Atg7 had little to no effect on the proliferation and function of effector cells, but these autophagy-deficient effector cells had survival defects that resulted in compromised formation of memory T cells. Our studies define when autophagy is needed during effector and memory differentiation and warrant reexamination of the relationship between T cell activation and autophagy.
Subject(s)
Autophagy/immunology , CD8-Positive T-Lymphocytes/immunology , Cell Differentiation/immunology , Immunologic Memory/immunology , Animals , Cell Separation , Cell Survival/immunology , Chromatography, Liquid , Flow Cytometry , Immunoblotting , Lymphocyte Activation/immunology , Lymphocytic Choriomeningitis/immunology , Mass Spectrometry , Mice , Mice, Mutant Strains , Oligonucleotide Array Sequence Analysis , Real-Time Polymerase Chain Reaction , Transduction, GeneticABSTRACT
Autophagy is a core molecular pathway for the preservation of cellular and organismal homeostasis. Pharmacological and genetic interventions impairing autophagy responses promote or aggravate disease in a plethora of experimental models. Consistently, mutations in autophagy-related processes cause severe human pathologies. Here, we review and discuss preclinical data linking autophagy dysfunction to the pathogenesis of major human disorders including cancer as well as cardiovascular, neurodegenerative, metabolic, pulmonary, renal, infectious, musculoskeletal, and ocular disorders.
Subject(s)
Autophagy , Disease Susceptibility , Animals , Autophagy/drug effects , Autophagy/genetics , Autophagy/immunology , Biomarkers , Gene Expression Regulation , Genetic Predisposition to Disease , Homeostasis , Host-Pathogen Interactions , Humans , Organ Specificity , Signal TransductionABSTRACT
NOD2 receptor and the cytosolic protein kinase RIPK2 regulate NF-κB and MAP kinase signaling during bacterial infections, but the role of this immune axis during viral infections has not been addressed. We demonstrate that Nod2(-/-) and Ripk2(-/-) mice are hypersusceptible to infection with influenza A virus. Ripk2(-/-) cells exhibited defective autophagy of mitochondria (mitophagy), leading to enhanced mitochondrial production of superoxide and accumulation of damaged mitochondria, which resulted in greater activation of the NLRP3 inflammasome and production of IL-18. RIPK2 regulated mitophagy in a kinase-dependent manner by phosphorylating the mitophagy inducer ULK1. Accordingly, Ulk1(-/-) cells exhibited enhanced mitochondrial production of superoxide and activation of caspase-1. These results demonstrate a role for NOD2-RIPK2 signaling in protection against virally triggered immunopathology by negatively regulating activation of the NLRP3 inflammasome and production of IL-18 via ULK1-dependent mitophagy.
Subject(s)
Alphainfluenzavirus/immunology , Carrier Proteins/metabolism , Inflammasomes/metabolism , Mitochondria/physiology , Mitophagy , Orthomyxoviridae Infections/immunology , Receptor-Interacting Protein Serine-Threonine Kinase 2/metabolism , Animals , Autophagy-Related Protein-1 Homolog , Caspase 1/metabolism , Cells, Cultured , Immunity, Active/genetics , Interleukin-18/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , NLR Family, Pyrin Domain-Containing 3 Protein , Nod2 Signaling Adaptor Protein/genetics , Nod2 Signaling Adaptor Protein/metabolism , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinase 2/genetics , Signal Transduction/genetics , Superoxides/metabolism , Virulence Factors/geneticsABSTRACT
Phagocytes clear dying cells within an organism to prevent damaging inflammation and autoimmunity. In this issue of Immunity, Luo et al. (2016) describe how "find-me" signals from apoptotic cells induce erythropoietin signaling within macrophages to prime them for efferocytosis.
Subject(s)
Erythropoietin/metabolism , Lupus Erythematosus, Systemic/immunology , Lysophospholipids/metabolism , Macrophages/physiology , Receptors, Erythropoietin/metabolism , Sphingosine/analogs & derivatives , Animals , FemaleABSTRACT
Mucosal sites, such as the lung, serve as crucial, yet vulnerable barriers to environmental insults such as pathogens, allergens, and toxins. Often, these exposures induce massive infiltration and death of short-lived immune cells in the lung, and efficient clearance of these cells is important for preventing hyperinflammation and resolving immunopathology. Herein, we review recent advances in our understanding of efferocytosis, a process whereby phagocytes clear dead cells in a noninflammatory manner. We further discuss how efferocytosis impacts the onset and severity of asthma in humans and mammalian animal models of disease. Finally, we explore how recently identified genetic perturbations or biological pathway modulations affect pathogenesis and shed light on novel therapies aimed at treating or preventing asthma.
Subject(s)
Asthma , Inflammation , Animals , Apoptosis , Humans , Phagocytes , PhagocytosisABSTRACT
Although serum from patients with Parkinson's disease contains elevated levels of numerous pro-inflammatory cytokines including IL-6, TNF, IL-1ß, and IFNγ, whether inflammation contributes to or is a consequence of neuronal loss remains unknown1. Mutations in parkin, an E3 ubiquitin ligase, and PINK1, a ubiquitin kinase, cause early onset Parkinson's disease2,3. Both PINK1 and parkin function within the same biochemical pathway and remove damaged mitochondria from cells in culture and in animal models via mitophagy, a selective form of autophagy4. The in vivo role of mitophagy, however, is unclear, partly because mice that lack either PINK1 or parkin have no substantial Parkinson's-disease-relevant phenotypes5-7. Mitochondrial stress can lead to the release of damage-associated molecular patterns (DAMPs) that can activate innate immunity8-12, suggesting that mitophagy may mitigate inflammation. Here we report a strong inflammatory phenotype in both Prkn-/- and Pink1-/- mice following exhaustive exercise and in Prkn-/-;mutator mice, which accumulate mutations in mitochondrial DNA (mtDNA)13,14. Inflammation resulting from either exhaustive exercise or mtDNA mutation is completely rescued by concurrent loss of STING, a central regulator of the type I interferon response to cytosolic DNA15,16. The loss of dopaminergic neurons from the substantia nigra pars compacta and the motor defect observed in aged Prkn-/-;mutator mice are also rescued by loss of STING, suggesting that inflammation facilitates this phenotype. Humans with mono- and biallelic PRKN mutations also display elevated cytokines. These results support a role for PINK1- and parkin-mediated mitophagy in restraining innate immunity.
Subject(s)
Immunity, Innate , Inflammation/metabolism , Membrane Proteins/metabolism , Mitophagy , Protein Kinases/metabolism , Ubiquitin-Protein Ligases/metabolism , Alarmins/metabolism , Animals , DNA, Mitochondrial/blood , DNA, Mitochondrial/genetics , Humans , Inflammation/genetics , Inflammation/prevention & control , Membrane Proteins/deficiency , Membrane Proteins/genetics , Mice , Mice, Inbred C57BL , Parkinson Disease/metabolism , Physical Conditioning, Animal , Protein Kinases/deficiency , Protein Kinases/genetics , Receptor, Interferon alpha-beta/antagonists & inhibitors , Receptor, Interferon alpha-beta/immunology , Stress, Physiological , Ubiquitin-Protein Ligases/deficiency , Ubiquitin-Protein Ligases/geneticsABSTRACT
Lipid imaging mass spectrometry (LIMS) has been tested in several pathological contexts, demonstrating its ability to segregate and isolate lipid signatures in complex tissues, thanks to the technique's spatial resolution. However, it cannot yet compete with the superior identification power of high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS), and therefore, very often, the latter is used to refine the assignment of the species detected by LIMS. Also, it is not clear if the differences in sensitivity and spatial resolution between the two techniques lead to a similar panel of biomarkers for a given disease. Here, we explore the capabilities of LIMS and HPLC-MS to produce a panel of lipid biomarkers to screen nephrectomy samples from 40 clear cell renal cell carcinoma patients. The same set of samples was explored by both techniques, and despite the important differences between them in terms of the number of detected and identified species (148 by LIMS and 344 by HPLC-MS in negative-ion mode) and the presence/absence of image capabilities, similar conclusions were reached: using the lipid fingerprint, it is possible to set up classifiers that correctly identify the samples as either healthy or tumor samples. The spatial resolution of LIMS enables extraction of additional information, such as the existence of necrotic areas or the existence of different tumor cell populations, but such information does not seem determinant for the correct classification of the samples, or it may be somehow compensated by the higher analytical power of HPLC-MS. Similar conclusions were reached with two very different techniques, validating their use for the discovery of lipid biomarkers.
Subject(s)
Carcinoma, Renal Cell , Kidney Neoplasms , Humans , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods , Chromatography, High Pressure Liquid/methods , Lipidomics/methods , Carcinoma, Renal Cell/diagnosis , Kidney Neoplasms/diagnosis , Lipids/analysisABSTRACT
BACKGROUND: Development of precision medicine requires the identification of easily detectable and druggable biomarkers. Despite recent targeted drug approvals, prognosis of acute myeloid leukemia (AML) patients needs to be greatly improved, as relapse and refractory disease are still difficult to manage. Thus, new therapeutic approaches are needed. Based on in silico-generated preliminary data and the literature, the role of the prolactin (PRL)-mediated signaling was interrogated in AML. METHODS: Protein expression and cell viability were determined by flow cytometry. Repopulation capacity was studied in murine xenotransplantation assays. Gene expression was measured by qPCR and luciferase-reporters. SA-ß-Gal staining was used as a senescence marker. RESULTS: The prolactin receptor (PRLR) was upregulated in AML cells, as compared to their healthy counterpart. The genetic and molecular inhibition of this receptor reduced the colony-forming potential. Disruption of the PRLR signaling, either using a mutant PRL or a dominant-negative isoform of PRLR, reduced the leukemia burden in vivo, in xenotransplantation assays. The expression levels of PRLR directly correlated with resistance to cytarabine. Indeed, acquired cytarabine resistance was accompanied with the induction of PRLR surface expression. The signaling associated to PRLR in AML was mainly mediated by Stat5, in contrast to the residual function of Stat3. In concordance, Stat5 mRNA was significantly overexpressed at mRNA levels in relapse AML samples. A senescence-like phenotype, measured by SA-ß-gal staining, was induced upon enforced expression of PRLR in AML cells, partially dependent on ATR. Similar to the previously described chemoresistance-induced senescence in AML, no cell cycle arrest was observed. Additionally, the therapeutic potential of PRLR in AML was genetically validated. CONCLUSIONS: These results support the role of PRLR as a therapeutic target for AML and the further development of drug discovery programs searching for specific PRLR inhibitors.
ABSTRACT
The LDL receptor-related protein 1 (LRP1) partakes in metabolic and signaling events regulated in a tissue-specific manner. The function of LRP1 in airways has not been studied. We aimed to study the function of LRP1 in smoke-induced disease. We found that bronchial epithelium of patients with chronic obstructive pulmonary disease and airway epithelium of mice exposed to smoke had increased LRP1 expression. We then knocked out LRP1 in human bronchial epithelial cells in vitro and in airway epithelial club cells in mice. In vitro, LRP1 knockdown decreased cell migration and increased transforming growth factor ß activation. Tamoxifen-inducible airway-specific LRP1 knockout mice (club Lrp1-/-) induced after complete lung development had increased inflammation in the bronchoalveolar space and lung parenchyma at baseline. After 6 months of smoke exposure, club Lrp1-/- mice showed a combined restrictive and obstructive phenotype, with lower compliance, inspiratory capacity, and forced expiratory volume0.05/forced vital capacity than WT smoke-exposed mice. This was associated with increased values of Ashcroft fibrotic index. Proteomic analysis of room air exposed-club Lrp1-/- mice showed significantly decreased levels of proteins involved in cytoskeleton signaling and xenobiotic detoxification as well as decreased levels of glutathione. The proteome fingerprint created by smoke eclipsed many of the original differences, but club Lrp1-/- mice continued to have decreased lung glutathione levels and increased protein oxidative damage and airway cell proliferation. Therefore, LRP1 deficiency leads to greater lung inflammation and damage and exacerbates smoke-induced lung disease.
Subject(s)
Airway Remodeling , Low Density Lipoprotein Receptor-Related Protein-1 , Oxidative Stress , Smoke , Animals , Epithelium/metabolism , Glutathione/metabolism , Humans , Low Density Lipoprotein Receptor-Related Protein-1/genetics , Low Density Lipoprotein Receptor-Related Protein-1/metabolism , Lung/metabolism , Mice , Proteomics , Smoke/adverse effectsABSTRACT
Mutations in the leucine-rich repeat kinase 2 (LRRK2) are associated with Parkinson's disease, chronic inflammation and mycobacterial infections. Although there is evidence supporting the idea that LRRK2 has an immune function, the cellular function of this kinase is still largely unknown. By using genetic, pharmacological and proteomics approaches, we show that LRRK2 kinase activity negatively regulates phagosome maturation via the recruitment of the Class III phosphatidylinositol-3 kinase complex and Rubicon to the phagosome in macrophages. Moreover, inhibition of LRRK2 kinase activity in mouse and human macrophages enhanced Mycobacterium tuberculosis phagosome maturation and mycobacterial control independently of autophagy. In vivo, LRRK2 deficiency in mice resulted in a significant decrease in M. tuberculosis burdens early during the infection. Collectively, our findings provide a molecular mechanism explaining genetic evidence linking LRRK2 to mycobacterial diseases and establish an LRRK2-dependent cellular pathway that controls M. tuberculosis replication by regulating phagosome maturation.
Subject(s)
Leucine-Rich Repeat Serine-Threonine Protein Kinase-2/immunology , Macrophages/immunology , Mycobacterium tuberculosis/immunology , Phagosomes/immunology , Tuberculosis/immunology , Animals , Autophagy-Related Proteins , Humans , Intracellular Signaling Peptides and Proteins/genetics , Intracellular Signaling Peptides and Proteins/immunology , Leucine-Rich Repeat Serine-Threonine Protein Kinase-2/genetics , Macrophages/microbiology , Mice , Mice, Knockout , Phagosomes/genetics , Phagosomes/microbiology , Phosphatidylinositol 3-Kinases/genetics , Phosphatidylinositol 3-Kinases/immunology , Tuberculosis/geneticsABSTRACT
We report innovative scalable, vertical, ultra-sharp nanowire arrays that are individually addressable to enable long-term, native recordings of intracellular potentials. Stable amplitudes of intracellular potentials from 3D tissue-like networks of neurons and cardiomyocytes are obtained. Individual electrical addressability is necessary for high-fidelity intracellular electrophysiological recordings. This study paves the way toward predictive, high-throughput, and low-cost electrophysiological drug screening platforms.
ABSTRACT
The retrograde transport inhibitor Retro-2 has a protective effect on cells and in mice against Shiga-like toxins and ricin. Retro-2 causes toxin accumulation in early endosomes and relocalization of the Golgi SNARE protein syntaxin-5 to the endoplasmic reticulum. The molecular mechanisms by which this is achieved remain unknown. Here, we show that Retro-2 targets the endoplasmic reticulum exit site component Sec16A, affecting anterograde transport of syntaxin-5 from the endoplasmic reticulum to the Golgi. The formation of canonical SNARE complexes involving syntaxin-5 is not affected in Retro-2-treated cells. By contrast, the interaction of syntaxin-5 with a newly discovered binding partner, the retrograde trafficking chaperone GPP130, is abolished, and we show that GPP130 must indeed bind to syntaxin-5 to drive Shiga toxin transport from the endosomes to the Golgi. We therefore identify Sec16A as a druggable target and provide evidence for a non-SNARE function for syntaxin-5 in interaction with GPP130.
Subject(s)
Benzamides/metabolism , Qa-SNARE Proteins/metabolism , Thiophenes/metabolism , Vesicular Transport Proteins/metabolism , Benzamides/pharmacology , Biological Transport , Endoplasmic Reticulum/drug effects , Endoplasmic Reticulum/metabolism , Endosomes/metabolism , Golgi Apparatus/metabolism , HeLa Cells , Humans , Protein Transport , Ricin/metabolism , Shiga Toxin/metabolism , Shiga Toxins/metabolism , Thiophenes/pharmacology , Vesicular Transport Proteins/physiologyABSTRACT
Severe sepsis remains a poorly understood systemic inflammatory condition with high mortality rates and limited therapeutic options in addition to organ support measures. Here we show that the clinically approved group of anthracyclines acts therapeutically at a low dose regimen to confer robust protection against severe sepsis in mice. This salutary effect is strictly dependent on the activation of DNA damage response and autophagy pathways in the lung, as demonstrated by deletion of the ataxia telangiectasia mutated (Atm) or the autophagy-related protein 7 (Atg7) specifically in this organ. The protective effect of anthracyclines occurs irrespectively of pathogen burden, conferring disease tolerance to severe sepsis. These findings demonstrate that DNA damage responses, including the ATM and Fanconi Anemia pathways, are important modulators of immune responses and might be exploited to confer protection to inflammation-driven conditions, including severe sepsis.