RESUMEN
Myeloid cells are key drivers of physiological responses to pathogen invasion or tissue damage. Members of the C-type lectin receptor (CLR) family stand out among the specialized receptors utilized by myeloid cells to orchestrate these responses. CLR ligands include carbohydrate, protein, and lipid components of both pathogens and self, which variably trigger endocytic, phagocytic, proinflammatory, or anti-inflammatory reactions. These varied outcomes rely on a versatile system for CLR signaling that includes tyrosine-based motifs that recruit kinases, phosphatases, or endocytic adaptors as well as nontyrosine-based signals that modulate the activation of other pathways or couple to the uptake machinery. Here, we review the signaling properties of myeloid CLRs and how they impact the role of myeloid cells in innate and adaptive immunity.
Asunto(s)
Inmunidad , Lectinas Tipo C/metabolismo , Transducción de Señal , Animales , Homeostasis/inmunología , Humanos , Ligandos , Células Mieloides/metabolismo , Unión ProteicaRESUMEN
In vitro studies have associated oxidative phosphorylation (OXPHOS) with anti-inflammatory macrophages, whereas pro-inflammatory macrophages rely on glycolysis. However, the metabolic needs of macrophages in tissues (TMFs) to fulfill their homeostatic activities are incompletely understood. Here, we identified OXPHOS as the highest discriminating process among TMFs from different organs in homeostasis by analysis of RNA-seq data in both humans and mice. Impairing OXPHOS in TMFs via Tfam deletion differentially affected TMF populations. Tfam deletion resulted in reduction of alveolar macrophages (AMs) due to impaired lipid-handling capacity, leading to increased cholesterol content and cellular stress, causing cell-cycle arrest in vivo. In obesity, Tfam depletion selectively ablated pro-inflammatory lipid-handling white adipose tissue macrophages (WAT-MFs), thus preventing insulin resistance and hepatosteatosis. Hence, OXPHOS, rather than glycolysis, distinguishes TMF populations and is critical for the maintenance of TMFs with a high lipid-handling activity, including pro-inflammatory WAT-MFs. This could provide a selective therapeutic targeting tool.
Asunto(s)
Inflamación , Fosforilación Oxidativa , Humanos , Ratones , Animales , Inflamación/metabolismo , Macrófagos/metabolismo , Homeostasis , Lípidos , Tejido Adiposo/metabolismoRESUMEN
Whether screening the metabolic activity of immune cells facilitates discovery of molecular pathology remains unknown. Here we prospectively screened the extracellular acidification rate as a measure of glycolysis and the oxygen consumption rate as a measure of mitochondrial respiration in B cells from patients with primary antibody deficiency. The highest oxygen consumption rate values were detected in three study participants with persistent polyclonal B cell lymphocytosis (PPBL). Exome sequencing identified germline mutations in SDHA, which encodes succinate dehydrogenase subunit A, in all three patients with PPBL. SDHA gain-of-function led to an accumulation of fumarate in PPBL B cells, which engaged the KEAP1-Nrf2 system to drive the transcription of genes encoding inflammatory cytokines. In a single patient trial, blocking the activity of the cytokine interleukin-6 in vivo prevented systemic inflammation and ameliorated clinical disease. Overall, our study has identified pathological mitochondrial retrograde signaling as a disease modifier in primary antibody deficiency.
Asunto(s)
Linfocitos B/inmunología , Complejo II de Transporte de Electrones/genética , Inflamación/metabolismo , Linfocitosis/inmunología , Mitocondrias/metabolismo , Mutación/genética , Antiinflamatorios/farmacología , Respiración de la Célula , Células Cultivadas , Fumaratos/metabolismo , Glucólisis , Humanos , Inflamación/genética , Interleucina-6/antagonistas & inhibidores , Proteína 1 Asociada A ECH Tipo Kelch/metabolismo , Factor 2 Relacionado con NF-E2/metabolismo , Consumo de Oxígeno , Estudios Prospectivos , Transducción de Señal , Secuenciación del ExomaRESUMEN
Sensing tissue damage is an ancient function of immune cells that is central to the regulation of inflammation, tissue repair, and immunity. In this issue of Immunity, Lai et al. (2020) uncover a role for the C-type lectin receptor Clec2d as a sensor of cell death, which directly detects histones released during necrosis and thus contributes to inflammation and immunopathology.
Asunto(s)
Histonas , Lectinas Tipo C , Muerte Celular , Humanos , Inflamación , Necrosis , Receptores de Superficie CelularRESUMEN
Macrophages tightly scale their core metabolism after being activated, but the precise regulation of the mitochondrial electron-transport chain (ETC) and its functional implications are currently unknown. Here we found that recognition of live bacteria by macrophages transiently decreased assembly of the ETC complex I (CI) and CI-containing super-complexes and switched the relative contributions of CI and CII to mitochondrial respiration. This was mediated by phagosomal NADPH oxidase and the reactive oxygen species (ROS)-dependent tyrosine kinase Fgr. It required Toll-like receptor signaling and the NLRP3 inflammasome, which were both connected to bacterial viability-specific immune responses. Inhibition of CII during infection with Escherichia coli normalized serum concentrations of interleukin 1ß (IL-1ß) and IL-10 to those in mice treated with dead bacteria and impaired control of bacteria. We have thus identified ETC adaptations as an early immunological-metabolic checkpoint that adjusts innate immune responses to bacterial infection.
Asunto(s)
Proteínas del Complejo de Cadena de Transporte de Electrón/metabolismo , Infecciones por Escherichia coli/inmunología , Escherichia coli K12/inmunología , Macrófagos/inmunología , Mitocondrias/metabolismo , Animales , Células Cultivadas , Metabolismo Energético/genética , Interacciones Huésped-Parásitos , Inmunidad Innata/genética , Interleucina-10/metabolismo , Interleucina-1beta/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteína con Dominio Pirina 3 de la Familia NLR/genética , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Fagocitosis , Especies Reactivas de Oxígeno/metabolismoRESUMEN
Production of interleukin-17 (IL-17) and IL-22 by T helper 17 (Th17) cells and group 3 innate lymphoid cells (ILC3s) in response to the gut microbiota ensures maintenance of intestinal barrier function. Here, we examined the mechanisms whereby the immune system detects microbiota in the steady state. A Syk-kinase-coupled signaling pathway in dendritic cells (DCs) was critical for commensal-dependent production of IL-17 and IL-22 by CD4+ T cells. The Syk-coupled C-type lectin receptor Mincle detected mucosal-resident commensals in the Peyer's patches (PPs), triggered IL-6 and IL-23p19 expression, and thereby regulated function of intestinal Th17- and IL-17-secreting ILCs. Mice deficient in Mincle or with selective depletion of Syk in CD11c+ cells had impaired production of intestinal RegIIIγ and IgA and increased systemic translocation of gut microbiota. Consequently, Mincle deficiency led to liver inflammation and deregulated lipid metabolism. Thus, sensing of commensals by Mincle and Syk signaling in CD11c+ cells reinforces intestinal immune barrier and promotes host-microbiota mutualism, preventing systemic inflammation.
Asunto(s)
Células Dendríticas/inmunología , Microbioma Gastrointestinal/inmunología , Interleucina-17/inmunología , Interleucinas/inmunología , Lectinas Tipo C/inmunología , Proteínas de la Membrana/inmunología , Quinasa Syk/inmunología , Animales , Células Dendríticas/metabolismo , Microbioma Gastrointestinal/fisiología , Humanos , Interleucina-17/metabolismo , Interleucinas/metabolismo , Mucosa Intestinal/inmunología , Mucosa Intestinal/metabolismo , Mucosa Intestinal/microbiología , Lectinas Tipo C/genética , Lectinas Tipo C/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Ratones Endogámicos C57BL , Ratones Noqueados , Ganglios Linfáticos Agregados/inmunología , Ganglios Linfáticos Agregados/metabolismo , Ganglios Linfáticos Agregados/microbiología , Transducción de Señal/inmunología , Quinasa Syk/genética , Quinasa Syk/metabolismo , Células Th17/inmunología , Células Th17/metabolismo , Interleucina-22RESUMEN
Neutrophils eliminate pathogens efficiently but can inflict severe damage to the host if they over-activate within blood vessels. It is unclear how immunity solves the dilemma of mounting an efficient anti-microbial defense while preserving vascular health. Here, we identify a neutrophil-intrinsic program that enabled both. The gene Bmal1 regulated expression of the chemokine CXCL2 to induce chemokine receptor CXCR2-dependent diurnal changes in the transcriptional and migratory properties of circulating neutrophils. These diurnal alterations, referred to as neutrophil aging, were antagonized by CXCR4 (C-X-C chemokine receptor type 4) and regulated the outer topology of neutrophils to favor homeostatic egress from blood vessels at night, resulting in boosted anti-microbial activity in tissues. Mice engineered for constitutive neutrophil aging became resistant to infection, but the persistence of intravascular aged neutrophils predisposed them to thrombo-inflammation and death. Thus, diurnal compartmentalization of neutrophils, driven by an internal timer, coordinates immune defense and vascular protection.
Asunto(s)
Vasos Sanguíneos/inmunología , Ritmo Circadiano/inmunología , Neutrófilos/inmunología , Fagocitosis/inmunología , Animales , Vasos Sanguíneos/metabolismo , Candida albicans/inmunología , Candida albicans/fisiología , Células Cultivadas , Senescencia Celular/inmunología , Quimiocina CXCL2/inmunología , Quimiocina CXCL2/metabolismo , Interacciones Huésped-Patógeno/inmunología , Humanos , Inflamación/inmunología , Inflamación/metabolismo , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Infiltración Neutrófila/inmunología , Neutrófilos/metabolismo , Neutrófilos/microbiología , Receptores CXCR4/inmunología , Receptores CXCR4/metabolismo , Factores de TiempoRESUMEN
Neutrophils require directional cues to navigate through the complex structure of venular walls and into inflamed tissues. Here we applied confocal intravital microscopy to analyze neutrophil emigration in cytokine-stimulated mouse cremaster muscles. We identified differential and non-redundant roles for the chemokines CXCL1 and CXCL2, governed by their distinct cellular sources. CXCL1 was produced mainly by TNF-stimulated endothelial cells (ECs) and pericytes and supported luminal and sub-EC neutrophil crawling. Conversely, neutrophils were the main producers of CXCL2, and this chemokine was critical for correct breaching of endothelial junctions. This pro-migratory activity of CXCL2 depended on the atypical chemokine receptor 1 (ACKR1), which is enriched within endothelial junctions. Transmigrating neutrophils promoted a self-guided migration response through EC junctions, creating a junctional chemokine "depot" in the form of ACKR1-presented CXCL2 that enabled efficient unidirectional luminal-to-abluminal migration. Thus, CXCL1 and CXCL2 act in a sequential manner to guide neutrophils through venular walls as governed by their distinct cellular sources.
Asunto(s)
Quimiocina CXCL1 , Quimiocina CXCL2 , Sistema del Grupo Sanguíneo Duffy , Neutrófilos , Receptores de Superficie Celular , Migración Transendotelial y Transepitelial , Animales , Músculos Abdominales/efectos de los fármacos , Músculos Abdominales/inmunología , Músculos Abdominales/metabolismo , Quimiocina CXCL1/genética , Quimiocina CXCL1/inmunología , Quimiocina CXCL1/metabolismo , Quimiocina CXCL2/genética , Quimiocina CXCL2/inmunología , Quimiocina CXCL2/metabolismo , Sistema del Grupo Sanguíneo Duffy/genética , Sistema del Grupo Sanguíneo Duffy/inmunología , Sistema del Grupo Sanguíneo Duffy/metabolismo , Células Endoteliales/efectos de los fármacos , Células Endoteliales/inmunología , Células Endoteliales/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Uniones Intercelulares/efectos de los fármacos , Uniones Intercelulares/inmunología , Uniones Intercelulares/metabolismo , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Neutrófilos/citología , Neutrófilos/inmunología , Neutrófilos/metabolismo , Receptores de Superficie Celular/genética , Receptores de Superficie Celular/inmunología , Receptores de Superficie Celular/metabolismo , Migración Transendotelial y Transepitelial/efectos de los fármacos , Migración Transendotelial y Transepitelial/genética , Migración Transendotelial y Transepitelial/inmunología , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
Protein mechanical stability determines the function of a myriad of proteins, especially proteins from the extracellular matrix. Failure to maintain protein mechanical stability may result in diseases and disorders such as cancer, cardiomyopathies, or muscular dystrophy. Thus, developing mutation-free approaches to enhance and control the mechanical stability of proteins using pharmacology-based methods may have important implications in drug development and discovery. Here, we present the first approach that employs computational high-throughput virtual screening and molecular docking to search for small molecules in chemical libraries that function as mechano-regulators of the stability of human cluster of differentiation 4, receptor of HIV-1. Using single-molecule force spectroscopy, we prove that these small molecules can increase the mechanical stability of CD4D1D2 domains over 4-fold in addition to modifying the mechanical unfolding pathways. Our experiments demonstrate that chemical libraries are a source of mechanoactive molecules and that drug discovery approaches provide the foundation of a new type of molecular function, that is, mechano-regulation, paving the way toward mechanopharmacology.
Asunto(s)
Antígenos CD4 , Descubrimiento de Drogas , Bibliotecas de Moléculas Pequeñas , Humanos , Antígenos CD4/metabolismo , Antígenos CD4/química , Descubrimiento de Drogas/métodos , Ensayos Analíticos de Alto Rendimiento/métodos , VIH-1/metabolismo , VIH-1/química , Simulación del Acoplamiento Molecular , Estabilidad Proteica , Bibliotecas de Moléculas Pequeñas/química , Bibliotecas de Moléculas Pequeñas/farmacologíaRESUMEN
SUMMARY: Spatial transcriptomics has changed our way to study tissue structure and cellular organization. However, there are still limitations in its resolution, and most available platforms do not reach a single cell resolution. To address this issue, we introduce SpatialDDLS, a fast neural network-based algorithm for cell type deconvolution of spatial transcriptomics data. SpatialDDLS leverages single-cell RNA sequencing data to simulate mixed transcriptional profiles with predefined cellular composition, which are subsequently used to train a fully connected neural network to uncover cell type diversity within each spot. By comparing it with two state-of-the-art spatial deconvolution methods, we demonstrate that SpatialDDLS is an accurate and fast alternative to the available state-of-the art tools. AVAILABILITY AND IMPLEMENTATION: The R package SpatialDDLS is available via CRAN-The Comprehensive R Archive Network: https://CRAN.R-project.org/package=SpatialDDLS. A detailed manual of the main functionalities implemented in the package can be found at https://diegommcc.github.io/SpatialDDLS.
Asunto(s)
Algoritmos , Programas Informáticos , Perfilación de la Expresión Génica , Redes Neurales de la ComputaciónRESUMEN
Despite the crucial role of tissue-resident memory T (Trm) cells in protective immunity, their priming remains poorly understood. Here, we have shown differential priming requirements for Trm versus circulating memory CD8+ T cells. In vaccinia cutaneous-infected mice, DNGR-1-mediated crosspresentation was required for optimal Trm cell priming but not for their skin differentiation or for circulating memory T cell generation. DNGR-1+ dendritic cells (DCs) promoted T-bet transcription-factor induction and retention of CD8+ T cells in the lymph nodes (LNs). Inhibition of LN egress enhanced Trm cell generation, whereas genetic or antibody blockade of DNGR-1 or specific signals provided during priming by DNGR-1+ DCs, such as interleukin-12 (IL-12), IL-15, or CD24, impaired Trm cell priming. DNGR-1 also regulated Trm cell generation during influenza infection. Moreover, protective immunity depended on optimal Trm cell induction by DNGR-1+ DCs. Our results reveal specific priming requirements for CD8+ Trm cells during viral infection and vaccination.
Asunto(s)
Linfocitos T CD8-positivos/inmunología , Células Dendríticas/inmunología , Memoria Inmunológica/inmunología , Lectinas Tipo C/inmunología , Receptores Inmunológicos/inmunología , Virosis/inmunología , Animales , Antígeno CD24/inmunología , Reactividad Cruzada/inmunología , Interleucina-12/inmunología , Interleucina-15/inmunología , Ganglios Linfáticos/inmunología , Ganglios Linfáticos/virología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Piel/inmunología , Piel/virología , Vaccinia/inmunología , Vaccinia/virología , Virus Vaccinia/inmunología , Virosis/virologíaRESUMEN
C-type lectin receptors sense a diversity of endogenous and exogenous ligands that may trigger differential responses. Here, we have found that human and mouse Mincle bind to a ligand released by Leishmania, a eukaryote parasite that evades an effective immune response. Mincle-deficient mice had milder dermal pathology and a tenth of the parasite burden compared to wild-type mice after Leishmania major intradermal ear infection. Mincle deficiency enhanced adaptive immunity against the parasite, correlating with increased activation, migration, and priming by Mincle-deficient dendritic cells (DCs). Leishmania triggered a Mincle-dependent inhibitory axis characterized by SHP1 coupling to the FcRγ chain. Selective loss of SHP1 in CD11c+ cells phenocopies enhanced adaptive immunity to Leishmania. In conclusion, Leishmania shifts Mincle to an inhibitory ITAM (ITAMi) configuration that impairs DC activation. Thus, ITAMi can be exploited for immune evasion by a pathogen and may represent a paradigm for ITAM-coupled receptors sensing self and non-self.
Asunto(s)
Inmunidad Adaptativa/inmunología , Células Dendríticas/inmunología , Motivo de Activación del Inmunorreceptor Basado en Tirosina/inmunología , Lectinas Tipo C/inmunología , Leishmania major/inmunología , Proteínas de la Membrana/inmunología , Transducción de Señal/inmunología , Animales , Antígeno CD11c/inmunología , Diferenciación Celular/inmunología , Línea Celular Tumoral , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Proteína Tirosina Fosfatasa no Receptora Tipo 6/inmunología , Receptores Fc/inmunologíaRESUMEN
Alterations in RNA-splicing are a molecular hallmark of several neurological diseases, including muscular dystrophies, where mutations in genes involved in RNA metabolism or characterized by alterations in RNA splicing have been described. Here, we present five patients from two unrelated families with a limb-girdle muscular dystrophy (LGMD) phenotype carrying a biallelic variant in SNUPN gene. Snurportin-1, the protein encoded by SNUPN, plays an important role in the nuclear transport of small nuclear ribonucleoproteins (snRNPs), essential components of the spliceosome. We combine deep phenotyping, including clinical features, histopathology and muscle MRI, with functional studies in patient-derived cells and muscle biopsies to demonstrate that variants in SNUPN are the cause of a new type of LGMD according to current definition. Moreover, an in vivo model in Drosophila melanogaster further supports the relevance of Snurportin-1 in muscle. SNUPN patients show a similar phenotype characterized by proximal weakness starting in childhood, restrictive respiratory dysfunction and prominent contractures, although inter-individual variability in terms of severity even in individuals from the same family was found. Muscle biopsy showed myofibrillar-like features consisting of myotilin deposits and Z-disc disorganization. MRI showed predominant impairment of paravertebral, vasti, sartorius, gracilis, peroneal and medial gastrocnemius muscles. Conservation and structural analyses of Snurportin-1 p.Ile309Ser variant suggest an effect in nuclear-cytosol snRNP trafficking. In patient-derived fibroblasts and muscle, cytoplasmic accumulation of snRNP components is observed, while total expression of Snurportin-1 and snRNPs remains unchanged, which demonstrates a functional impact of SNUPN variant in snRNP metabolism. Furthermore, RNA-splicing analysis in patients' muscle showed widespread splicing deregulation, in particular in genes relevant for muscle development and splicing factors that participate in the early steps of spliceosome assembly. In conclusion, we report that SNUPN variants are a new cause of limb girdle muscular dystrophy with specific clinical, histopathological and imaging features, supporting SNUPN as a new gene to be included in genetic testing of myopathies. These results further support the relevance of splicing-related proteins in muscle disorders.
Asunto(s)
Distrofia Muscular de Cinturas , Humanos , Distrofia Muscular de Cinturas/genética , Distrofia Muscular de Cinturas/patología , Masculino , Femenino , Adulto , Animales , Músculo Esquelético/patología , Músculo Esquelético/metabolismo , Linaje , Drosophila melanogaster , Miofibrillas/patología , Miofibrillas/genética , Miofibrillas/metabolismo , Persona de Mediana Edad , Fenotipo , Adolescente , Adulto Joven , NiñoRESUMEN
The amyloid-forming Aß peptide is able to interact with metal cations to form very stable complexes that influence fibril formation and contribute to the onset of Alzheimer's disease. Multiple structures of peptides derived from Aß in complex with different metals have been resolved experimentally to provide an atomic-level description of the metal-protein interactions. However, Aß is intrinsically disordered, and hence more amenable to an ensemble description. Molecular dynamics simulations can now reach the timescales needed to generate ensembles for these type of complexes. However, this requires accurate force fields both for the protein and the protein-metal interactions. Here we use state-of-the-art methods to generate force field parameters for the Zn(II) cations in a set of complexes formed by different Aß variants and combine them with the Amber99SB*-ILDN optimized force field. Upon comparison of NMR experiments with the simulation results, further optimized with a Bayesian/Maximum entropy approach, we provide an accurate description of the molecular ensembles for most Aß-metal complexes. We find that the resulting conformational ensembles are more heterogeneous than the NMR models deposited in the Protein Data Bank.
Asunto(s)
Péptidos beta-Amiloides , Simulación de Dinámica Molecular , Péptidos beta-Amiloides/química , Teorema de Bayes , Conformación Proteica , Zinc , CationesRESUMEN
Interactions between proteins and α-helical peptides have been the focus of drug discovery campaigns. However, the large interfaces formed between multiple turns of an α-helix and a binding protein represent a significant challenge to inhibitor discovery. Modified peptides featuring helix-stabilizing macrocycles have shown promise as inhibitors of these interactions. Here, we tested the ability of N-terminal to side-chain thioether-cyclized peptides to inhibit the α-helix binding protein Mcl-1, by screening a trillion-scale library. The enriched peptides were lariats featuring a small, four-amino-acid N-terminal macrocycle followed by a short linear sequence that resembled the natural α-helical Mcl-1 ligands. These "Heliats" (helical lariats) bound Mcl-1 with tens of nM affinity, and inhibited the interaction between Mcl-1 and a natural peptide ligand. Macrocyclization was found to stabilize α-helical structures and significantly contribute to affinity and potency. Yet, the 2nd and 3rd positions within the macrocycle were permissible to sequence variation, so that a minimal macrocyclic motif, of an N-acetylated d-phenylalanine at the 1st position thioether connected to a cysteine at the 4th, could be grafted into a range of peptides and stabilize helical conformations. We found that d-stereochemistry is more helix-stabilizing than l- at the 1st position in the motif, as the d-amino acid can utilize polyproline II torsional angles that allow for more optimal intrachain hydrogen bonding. This mixed stereochemistry macrocyclic N-cap is synthetically accessible, requiring only minor modifications to standard solid-phase peptide synthesis, and its compatibility with peptide screening can provide ready access to helix-focused peptide libraries for de novo inhibitor discovery.
RESUMEN
DNGR-1 is a C-type lectin receptor that binds F-actin exposed by dying cells and facilitates cross-presentation of dead cell-associated antigens by dendritic cells. Here we present the structure of DNGR-1 bound to F-actin at 7.7 Å resolution. Unusually for F-actin binding proteins, the DNGR-1 ligand binding domain contacts three actin subunits helically arranged in the actin filament, bridging over two protofilaments, as well as two neighboring actin subunits along one protofilament. Mutation of residues predicted to mediate ligand binding led to loss of DNGR-1-dependent cross-presentation of dead cell-associated antigens, formally demonstrating that the latter depends on F-actin recognition. Notably, DNGR-1 has relatively modest affinity for F-actin but multivalent interactions allow a marked increase in binding strength. Our findings shed light on modes of actin binding by cellular proteins and reveal how extracellular detection of cytoskeletal components by dedicated receptors allows immune monitoring of loss of cellular integrity.
Asunto(s)
Actinas/química , Reactividad Cruzada , Células Dendríticas/inmunología , Lectinas Tipo C/química , Modelos Moleculares , Receptores Inmunológicos/química , Actinas/metabolismo , Animales , Células Cultivadas , Humanos , Ratones , Mutación , Unión ProteicaRESUMEN
BACKGROUND: Respiratory and urinary tract infections are frequent complications in patients with severe stroke. Stroke-associated infection is mainly due to opportunistic commensal bacteria of the microbiota that may translocate from the gut. We investigated the mechanisms underlying gut dysbiosis and poststroke infection. METHODS: Using a model of transient cerebral ischemia in mice, we explored the relationship between immunometabolic dysregulation, gut barrier dysfunction, gut microbial alterations, and bacterial colonization of organs, and we explored the effect of several drug treatments. RESULTS: Stroke-induced lymphocytopenia and widespread colonization of lung and other organs by opportunistic commensal bacteria. This effect correlated with reduced gut epithelial barrier resistance, and a proinflammatory sway in the gut illustrated by complement and nuclear factor-κB activation, reduced number of gut regulatory T cells, and a shift of gut lymphocytes to γδT cells and T helper 1/T helper 17 phenotypes. Stroke increased conjugated bile acids in the liver but decreased bile acids and short-chain fatty acids in the gut. Gut fermenting anaerobic bacteria decreased while opportunistic facultative anaerobes, notably Enterobacteriaceae, suffered an expansion. Anti-inflammatory treatment with a nuclear factor-κB inhibitor fully abrogated the Enterobacteriaceae overgrowth in the gut microbiota induced by stroke, whereas inhibitors of the neural or humoral arms of the stress response were ineffective at the doses used in this study. Conversely, the anti-inflammatory treatment did not prevent poststroke lung colonization by Enterobacteriaceae. CONCLUSIONS: Stroke perturbs homeostatic neuro-immuno-metabolic networks facilitating a bloom of opportunistic commensals in the gut microbiota. However, this bacterial expansion in the gut does not mediate poststroke infection.
Asunto(s)
Microbioma Gastrointestinal , Neumonía , Accidente Cerebrovascular , Ratones , Animales , FN-kappa B , Bacterias/genética , Accidente Cerebrovascular/complicaciones , PulmónRESUMEN
In order to understand the preferred modes of chelation in metal-binding peptides, quantum mechanical calculations can be used to compute energies, resulting in a hierarchy of binding affinities. These calculations often produce increasing stabilization energies the higher the coordination of the complex. However, as the coordination of a metal increases, the conformational freedom of the polypeptide chain is inevitably reduced, resulting in an entropic penalty. Estimating the magnitude of this penalty from the many different degrees of freedom of biomolecular systems is very challenging, and as a result this contribution to the free energy is often ignored. Here we explore this problem focusing on a family of phosphorylated neuropeptides that bind to aluminum. We find that there is a general negative correlation between both stabilization energy and entropy. Our results suggest that a subtle interplay between enthalpic and entropic forces will determine the population of the most favourable species. Additionally, we discuss the requirements for a possible "Metal Ion Hypothesis" based on our findings.
RESUMEN
Transition metals directly contribute to the neurotoxicity of the aggregates of the amyloid-forming Aß peptide. The understanding and rationalization of the coordination modes of metals to Aß amyloid is, therefore, of paramount importance to understand the capacity of a given metal to promote peptide aggregation. Experimentally, multiple Aß-metal structures have been resolved, which exhibit different modes of coordination in both the monomeric and oligomeric forms of Aß. Although Zn(II) metalloproteins are very abundant and often involve cysteine residues in the first coordination shell, in the case of Aß-Zn(II), though, Zn(II) is coordinated by glutamic/aspartic acid and/or histidine residues exclusively, making for an interesting case study. Here we present a systematic analysis of the underlying chemistry on Aß-Zn(II) coordination, where relative stabilities of different coordination arrangements indicate that a mixture of Glu/Asp and His residues is favored. A detailed comparison between different coordination shell geometries shows that tetrahedral coordination is generally favored in the aqueous phase. Our calculations show an interplay between dative covalent interactions and electrostatics which explains the observed trends. Multiple structures deposited in the Protein Data Bank support our findings, suggesting that the trends found in our work may be transferable to other Zn(II) metalloproteins with this type of coordination.