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Molecular Architecture of the Helicobacter pylori Cag Type IV Secretion System.
Hu B, Khara P, Song L, Lin AS, Frick-Cheng AE, Harvey ML, Cover TL, Christie PJ
(2019) MBio 10:
MeSH Terms: Antigens, Bacterial, Bacterial Proteins, Cryoelectron Microscopy, Genomic Islands, Helicobacter pylori, Humans, Type IV Secretion Systems
Show Abstract · Added July 14, 2019
colonizes about half of humans worldwide, and its presence in the gastric mucosa is associated with an increased risk of gastric adenocarcinoma, gastric lymphoma, and peptic ulcer disease. strains carrying the pathogenicity island (PAI) are associated with increased risk of disease progression. The PAI encodes the Cag type IV secretion system (Cag), which delivers the CagA oncoprotein and other effector molecules into human gastric epithelial cells. We visualized structures of native and mutant Cag machines on the cell envelope by cryoelectron tomography. Individual cells contain multiple Cag nanomachines, each composed of a wheel-shaped outer membrane complex (OMC) with 14-fold symmetry and an inner membrane complex (IMC) with 6-fold symmetry. CagX, CagY, and CagM are required for assembly of the OMC, whereas strains lacking Cag3 and CagT produce outer membrane complexes lacking peripheral components. The IMC, which has never been visualized in detail, is configured as six tiers in cross-section view and three concentric rings surrounding a central channel in end-on view. The IMC contains three T4SS ATPases: (i) VirB4-like CagE, arranged as a hexamer of dimers at the channel entrance; (ii) a hexamer of VirB11-like Cagα, docked at the base of the CagE hexamer; and (iii) VirD4-like Cagβ and other unspecified Cag subunits, associated with the stacked CagE/Cagα complex and forming the outermost rings. The Cag and recently solved Dot/Icm system comprise new structural prototypes for the T4SS superfamily. Bacterial type IV secretion systems (T4SSs) have been phylogenetically grouped into two subfamilies. The T4ASSs, represented by the VirB/VirD4, include "minimized" machines assembled from 12 VirB- and VirD4-like subunits and compositionally larger systems such as the Cag T4BSSs encompass systems closely related in subunit composition to the Dot/Icm Here, we present structures of native and mutant Cag machines determined by cryoelectron tomography. We identify distinct outer and inner membrane complexes and, for the first time, visualize structural contributions of all three "signature" ATPases of T4SSs at the cytoplasmic entrance of the translocation channel. Despite their evolutionary divergence, the Cag aligns structurally much more closely to the Dot/Icm than an available VirB/VirD4 subcomplex. Our findings highlight the diversity of T4SSs and suggest a structural classification scheme in which T4SSs are grouped as minimized VirB/VirD4-like or larger Cag-like and Dot/Icm-like systems.
Copyright © 2019 Hu et al.
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Toll-like receptor 3-mediated inflammation by p38 is enhanced by endothelial nitric oxide synthase knockdown.
Koch SR, Choi H, Mace EH, Stark RJ
(2019) Cell Commun Signal 17: 33
MeSH Terms: Capillary Permeability, Cells, Cultured, Chemokine CXCL10, Endothelium, Vascular, Gene Knockdown Techniques, Humans, Inflammation, Interleukin-6, Interleukin-8, Nitric Oxide Synthase Type III, Poly I-C, RNA, Small Interfering, Toll-Like Receptor 3, p38 Mitogen-Activated Protein Kinases
Show Abstract · Added April 17, 2019
BACKGROUND - Vascular dysfunction is commonly seen during severe viral infections. Endothelial nitric oxide synthase (eNOS), has been postulated to play an important role in regulating vascular homeostasis as well as propagation of the inflammatory reaction. We hypothesized that the loss of eNOS would negatively impact toll-like receptor 3 (TLR3) signaling and worsen vascular function to viral challenge.
METHODS - Human microvascular endothelial cells (HMVECs) were exposed to either control or eNOS siRNA and then treated with Poly I:C, a TLR3 agonist and mimicker of dsRNA viruses. Cells were assessed for protein-protein associations, cytokine and chemokine analysis as well as transendothelial electrical resistance (TEER) as a surrogate of permeability.
RESULTS - HMVECs that had reduced eNOS expression had a significantly elevated increase in IL-6, IL-8 and IP-10 production after Poly I:C. In addition, the knockdown of eNOS enhanced the change in TEER after Poly I:C stimulation. Western blot analysis showed enhanced phosphorylation of p38 in sieNOS treated cells with Poly I:C compared to siControl cells. Proximity ligation assays further demonstrated direct eNOS-p38 protein-protein interactions. The addition of the p38 inhibitor, SB203580, in eNOS knockdown cells reduced both cytokine production after Poly I:C, and as well as mitigated the reduction in TEER, suggesting a direct link between eNOS and p38 in TLR3 signaling.
CONCLUSIONS - These results suggest that reduction of eNOS increases TLR3-mediated inflammation in human endothelial cells in a p38-dependent manner. This finding has important implications for understanding the pathogenesis of severe viral infections and the associated vascular dysfunction.
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14 MeSH Terms
Using In Vitro Pull-Down and In-Cell Overexpression Assays to Study Protein Interactions with Arrestin.
Perry NA, Zhan X, Gurevich EV, Iverson TM, Gurevich VV
(2019) Methods Mol Biol 1957: 107-120
MeSH Terms: Animals, Arrestin, Biological Assay, COS Cells, Cercopithecus aethiops, HEK293 Cells, Humans, Immobilized Proteins, Mice, Protein Binding, Protein Interaction Mapping, Recombinant Fusion Proteins
Show Abstract · Added April 1, 2019
Nonvisual arrestins (arrestin-2/arrestin-3) interact with hundreds of G protein-coupled receptor (GPCR) subtypes and dozens of non-receptor signaling proteins. Here we describe the methods used to identify the interaction sites of arrestin-binding partners on arrestin-3 and the use of monofunctional individual arrestin-3 elements in cells. Our in vitro pull-down assay with purified proteins demonstrates that relatively few elements in arrestin engage each partner, whereas cell-based functional assays indicate that certain arrestin elements devoid of other functionalities can perform individual functions in living cells.
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12 MeSH Terms
Aberrant FGFR signaling mediates resistance to CDK4/6 inhibitors in ER+ breast cancer.
Formisano L, Lu Y, Servetto A, Hanker AB, Jansen VM, Bauer JA, Sudhan DR, Guerrero-Zotano AL, Croessmann S, Guo Y, Ericsson PG, Lee KM, Nixon MJ, Schwarz LJ, Sanders ME, Dugger TC, Cruz MR, Behdad A, Cristofanilli M, Bardia A, O'Shaughnessy J, Nagy RJ, Lanman RB, Solovieff N, He W, Miller M, Su F, Shyr Y, Mayer IA, Balko JM, Arteaga CL
(2019) Nat Commun 10: 1373
MeSH Terms: Aminopyridines, Animals, Antineoplastic Agents, Hormonal, Antineoplastic Combined Chemotherapy Protocols, Breast Neoplasms, Circulating Tumor DNA, Cyclin D1, Cyclin-Dependent Kinase 4, Cyclin-Dependent Kinase 6, Drug Resistance, Neoplasm, Female, Fulvestrant, High-Throughput Nucleotide Sequencing, Humans, MCF-7 Cells, Mice, Mutation, Naphthalenes, Piperazines, Progression-Free Survival, Proportional Hazards Models, Protein Kinase Inhibitors, Purines, Pyrazoles, Pyridines, Quinolines, Quinoxalines, Receptor, Fibroblast Growth Factor, Type 1, Receptor, Fibroblast Growth Factor, Type 2, Receptors, Estrogen, Signal Transduction, Xenograft Model Antitumor Assays
Show Abstract · Added April 2, 2019
Using an ORF kinome screen in MCF-7 cells treated with the CDK4/6 inhibitor ribociclib plus fulvestrant, we identified FGFR1 as a mechanism of drug resistance. FGFR1-amplified/ER+ breast cancer cells and MCF-7 cells transduced with FGFR1 were resistant to fulvestrant ± ribociclib or palbociclib. This resistance was abrogated by treatment with the FGFR tyrosine kinase inhibitor (TKI) lucitanib. Addition of the FGFR TKI erdafitinib to palbociclib/fulvestrant induced complete responses of FGFR1-amplified/ER+ patient-derived-xenografts. Next generation sequencing of circulating tumor DNA (ctDNA) in 34 patients after progression on CDK4/6 inhibitors identified FGFR1/2 amplification or activating mutations in 14/34 (41%) post-progression specimens. Finally, ctDNA from patients enrolled in MONALEESA-2, the registration trial of ribociclib, showed that patients with FGFR1 amplification exhibited a shorter progression-free survival compared to patients with wild type FGFR1. Thus, we propose breast cancers with FGFR pathway alterations should be considered for trials using combinations of ER, CDK4/6 and FGFR antagonists.
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32 MeSH Terms
VacA Targets Myeloid Cells in the Gastric Lamina Propria To Promote Peripherally Induced Regulatory T-Cell Differentiation and Persistent Infection.
Altobelli A, Bauer M, Velez K, Cover TL, Müller A
(2019) MBio 10:
MeSH Terms: Animals, Bacterial Proteins, Cell Differentiation, Dendritic Cells, Disease Models, Animal, Gastric Mucosa, Helicobacter Infections, Helicobacter pylori, Immune Evasion, Interleukin-10, Interleukin-23, Lung, Macrophages, Mice, Mucous Membrane, Myeloid Cells, T-Lymphocytes, Regulatory, Transforming Growth Factor beta
Show Abstract · Added April 11, 2019
The gastric bacterium causes a persistent infection that is directly responsible for gastric ulcers and gastric cancer in some patients and protective against allergic and other immunological disorders in others. The two outcomes of the -host interaction can be modeled in mice that are infected as immunocompetent adults and as neonates, respectively. Here, we have investigated the contribution of the immunomodulator VacA to -specific local and systemic immune responses in both models. We found that neonatally infected mice are colonized at higher levels than mice infected as adults and fail to generate effector T-cell responses to the bacteria; rather, T-cell responses in neonatally infected mice are skewed toward Foxp3-positive (Foxp3) regulatory T cells that are neuropilin negative and express RORγt. We found these peripherally induced regulatory T cells (pTregs) to be enriched, in a VacA-dependent manner, not only in the gastric mucosa but also in the lungs of infected mice. Pulmonary pTreg accumulation was observed in mice that have been infected neonatally with wild-type but not in mice that have been infected as adults or mice infected with a VacA null mutant. Finally, we traced VacA to gastric lamina propria myeloid cells and show that it suppressed interleukin-23 (IL-23) expression by dendritic cells and induced IL-10 and TGF-β expression in macrophages. Taken together, the results are consistent with the idea that creates a tolerogenic environment through its immunomodulator VacA, which skews T-cell responses toward Tregs, favors persistence, and affects immunity at distant sites. has coexisted with humans for at least 60.000 years and has evolved persistence strategies that allow it to evade host immunity and colonize its host for life. The VacA protein is expressed by all strains and is required for high-level persistent infection in experimental mouse models. Here, we show that VacA targets myeloid cells in the gastric mucosa to create a tolerogenic environment that facilitates regulatory T-cell differentiation, while suppressing effector T-cell priming and functionality. Tregs that are induced in the periphery during infection can be found not only in the stomach but also in the lungs of infected mice, where they are likely to affect immune responses to allergens.
Copyright © 2019 Altobelli et al.
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18 MeSH Terms
Gastroesophageal Reflux Induces Protein Adducts in the Esophagus.
Caspa Gokulan R, Adcock JM, Zagol-Ikapitte I, Mernaugh R, Williams P, Washington KM, Boutaud O, Oates JA, Dikalov SI, Zaika AI
(2019) Cell Mol Gastroenterol Hepatol 7: 480-482.e7
MeSH Terms: Acetylcysteine, Animals, Benzylamines, Bile Acids and Salts, Cell Line, Cyclic N-Oxides, Esophagus, Gastroesophageal Reflux, Humans, Lipids, Mice, Spin Labels, Tumor Suppressor Protein p53
Added March 26, 2019
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13 MeSH Terms
Cuts Both Ways: Proteases Modulate Virulence of Enterohemorrhagic .
Palmer LD, Skaar EP
(2019) MBio 10:
MeSH Terms: Enterohemorrhagic Escherichia coli, Escherichia coli Proteins, Humans, Microbiota, Peptide Hydrolases, Virulence
Show Abstract · Added April 2, 2019
Enterohemorrhagic (EHEC) is a major cause of foodborne gastrointestinal illness. EHEC uses a specialized type III secretion system (T3SS) to form attaching and effacing lesions in the colonic epithelium and outcompete commensal gut microbiota to cause disease. A recent report in (E. A. Cameron, M. M. Curtis, A. Kumar, G. M. Dunny, et al., mBio 9:e02204-18, 2018, https://doi.org/10.1128/mBio.02204-18) describes a new role for gut commensals in potentiating disease caused by EHEC. Proteases produced by EHEC and the prevalent human commensal cleave proteins in the EHEC T3SS translocon that modulate T3SS function. protease activity promotes translocation of bacterial effectors required for lesion formation. These results describe a new role for the microbiota in gastrointestinal disease that could uncover future treatments to prevent the spread of gastroenteritis.
Copyright © 2019 Palmer and Skaar.
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Manganese Detoxification by MntE Is Critical for Resistance to Oxidative Stress and Virulence of .
Grunenwald CM, Choby JE, Juttukonda LJ, Beavers WN, Weiss A, Torres VJ, Skaar EP
(2019) MBio 10:
MeSH Terms: Animals, Cation Transport Proteins, Disease Models, Animal, Gene Expression Regulation, Bacterial, Homeostasis, Iron, Manganese, Mice, Inbred BALB C, Microbial Viability, Oxidative Stress, Staphylococcal Infections, Staphylococcus aureus, Transcription Factors, Transcription, Genetic, Virulence
Show Abstract · Added April 2, 2019
Manganese (Mn) is an essential micronutrient critical for the pathogenesis of , a significant cause of human morbidity and mortality. Paradoxically, excess Mn is toxic; therefore, maintenance of intracellular Mn homeostasis is required for survival. Here we describe a Mn exporter in , MntE, which is a member of the cation diffusion facilitator (CDF) protein family and conserved among Gram-positive pathogens. Upregulation of transcription in response to excess Mn is dependent on the presence of MntR, a transcriptional repressor of the Mn uptake system. Inactivation of or leads to reduced growth in media supplemented with Mn, demonstrating MntE is required for detoxification of excess Mn. Inactivation of results in elevated levels of intracellular Mn, but reduced intracellular iron (Fe) levels, supporting the hypothesis that MntE functions as a Mn efflux pump and Mn efflux influences Fe homeostasis. Strains inactivated for are more sensitive to the oxidants NaOCl and paraquat, indicating Mn homeostasis is critical for resisting oxidative stress. Furthermore, and are required for full virulence of during infection, suggesting experiences Mn toxicity Combined, these data support a model in which MntR controls Mn homeostasis by balancing transcriptional repression of and induction of , both of which are critical for pathogenesis. Thus, Mn efflux contributes to bacterial survival and virulence during infection, establishing MntE as a potential antimicrobial target and expanding our understanding of Mn homeostasis. Manganese (Mn) is generally viewed as a critical nutrient that is beneficial to pathogenic bacteria due to its function as an enzymatic cofactor and its capability of acting as an antioxidant; yet paradoxically, high concentrations of this transition metal can be toxic. In this work, we demonstrate utilizes the cation diffusion facilitator (CDF) family protein MntE to alleviate Mn toxicity through efflux of excess Mn. Inactivation of leads to a significant reduction in resistance to oxidative stress and mediated mortality within a mouse model of systemic infection. These results highlight the importance of MntE-mediated Mn detoxification in intracellular Mn homeostasis, resistance to oxidative stress, and virulence. Therefore, this establishes MntE as a potential target for development of anti- therapeutics.
Copyright © 2019 Grunenwald et al.
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15 MeSH Terms
α-Difluoromethylornithine reduces gastric carcinogenesis by causing mutations in .
Sierra JC, Suarez G, Piazuelo MB, Luis PB, Baker DR, Romero-Gallo J, Barry DP, Schneider C, Morgan DR, Peek RM, Gobert AP, Wilson KT
(2019) Proc Natl Acad Sci U S A 116: 5077-5085
MeSH Terms: Animals, Bacterial Proteins, Carcinogenesis, DNA Damage, Eflornithine, Gene Deletion, Gene Rearrangement, Gerbillinae, Helicobacter pylori, Male, Mutation, Oxidative Stress, RNA, Messenger, Stomach Neoplasms, Virulence
Show Abstract · Added February 26, 2019
Infection by is the primary cause of gastric adenocarcinoma. The most potent virulence factor is cytotoxin-associated gene A (CagA), which is translocated by a type 4 secretion system (T4SS) into gastric epithelial cells and activates oncogenic signaling pathways. The gene encodes for a key component of the T4SS and can undergo gene rearrangements. We have shown that the cancer chemopreventive agent α-difluoromethylornithine (DFMO), known to inhibit the enzyme ornithine decarboxylase, reduces -mediated gastric cancer incidence in Mongolian gerbils. In the present study, we questioned whether DFMO might directly affect pathogenicity. We show that output strains isolated from gerbils treated with DFMO exhibit reduced ability to translocate CagA in gastric epithelial cells. Further, we frequently detected genomic modifications in the middle repeat region of the gene of output strains from DFMO-treated animals, which were associated with alterations in the CagY protein. Gerbils did not develop carcinoma when infected with a DFMO output strain containing rearranged or the parental strain in which the wild-type was replaced by with DFMO-induced rearrangements. Lastly, we demonstrate that in vitro treatment of by DFMO induces oxidative DNA damage, expression of the DNA repair enzyme MutS2, and mutations in , demonstrating that DFMO directly affects genomic stability. Deletion of abrogated the ability of DFMO to induce rearrangements directly. In conclusion, DFMO-induced oxidative stress in leads to genomic alterations and attenuates virulence.
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15 MeSH Terms
S100 Proteins in the Innate Immune Response to Pathogens.
Kozlyuk N, Monteith AJ, Garcia V, Damo SM, Skaar EP, Chazin WJ
(2019) Methods Mol Biol 1929: 275-290
MeSH Terms: Calcium, Host-Pathogen Interactions, Humans, Immunity, Innate, Inflammation, Manganese, Models, Molecular, Protein Conformation, S100 Proteins, Toll-Like Receptor 4
Show Abstract · Added March 26, 2019
S100 proteins are distinct dimeric EF-hand Ca-binding proteins that can bind Zn, Mn, and other transition metals with high affinity at two sites in the dimer interface. Certain S100 proteins, including S100A7, S100A12, S100A8, and S100A9, play key roles in the innate immune response to pathogens. These proteins function via a "nutritional immunity" mechanism by depleting essential transition metals in the infection that are required for the invading organism to grow and thrive. They also act as damage-associated molecular pattern ligands, which activate pattern recognition receptors (e.g., Toll-like receptor 4, RAGE) that mediate inflammation. Here we present protocols for these S100 proteins for high-level production of recombinant protein, measurement of binding affinities using isothermal titration calorimetry, and an assay of antimicrobial activity.
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10 MeSH Terms