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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
Structural, functional, and behavioral insights of dopamine dysfunction revealed by a deletion in .
Campbell NG, Shekar A, Aguilar JI, Peng D, Navratna V, Yang D, Morley AN, Duran AM, Galli G, O'Grady B, Ramachandran R, Sutcliffe JS, Sitte HH, Erreger K, Meiler J, Stockner T, Bellan LM, Matthies HJG, Gouaux E, Mchaourab HS, Galli A
(2019) Proc Natl Acad Sci U S A 116: 3853-3862
MeSH Terms: Animals, Animals, Genetically Modified, Autism Spectrum Disorder, Crystallography, X-Ray, Dopamine, Dopamine Plasma Membrane Transport Proteins, Drosophila melanogaster, Electron Spin Resonance Spectroscopy, Fear, Humans, Interpersonal Relations, Locomotion, Models, Molecular, Mutation, Sequence Deletion
Show Abstract · Added March 18, 2020
The human dopamine (DA) transporter (hDAT) mediates clearance of DA. Genetic variants in hDAT have been associated with DA dysfunction, a complication associated with several brain disorders, including autism spectrum disorder (ASD). Here, we investigated the structural and behavioral bases of an ASD-associated in-frame deletion in hDAT at N336 (∆N336). We uncovered that the deletion promoted a previously unobserved conformation of the intracellular gate of the transporter, likely representing the rate-limiting step of the transport process. It is defined by a "half-open and inward-facing" state (HOIF) of the intracellular gate that is stabilized by a network of interactions conserved phylogenetically, as we demonstrated in hDAT by Rosetta molecular modeling and fine-grained simulations, as well as in its bacterial homolog leucine transporter by electron paramagnetic resonance analysis and X-ray crystallography. The stabilization of the HOIF state is associated both with DA dysfunctions demonstrated in isolated brains of expressing hDAT ∆N336 and with abnormal behaviors observed at high-time resolution. These flies display increased fear, impaired social interactions, and locomotion traits we associate with DA dysfunction and the HOIF state. Together, our results describe how a genetic variation causes DA dysfunction and abnormal behaviors by stabilizing a HOIF state of the transporter.
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Metabolic plasticity meets gene regulation.
Paudel BB, Quaranta V
(2019) Proc Natl Acad Sci U S A 116: 3370-3372
MeSH Terms: Biochemical Phenomena, Gene Expression Regulation, Humans, Metabolic Networks and Pathways, Neoplasms, Neuronal Plasticity
Added March 23, 2019
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6 MeSH Terms
Structural basis of a potent human monoclonal antibody against Zika virus targeting a quaternary epitope.
Long F, Doyle M, Fernandez E, Miller AS, Klose T, Sevvana M, Bryan A, Davidson E, Doranz BJ, Kuhn RJ, Diamond MS, Crowe JE, Rossmann MG
(2019) Proc Natl Acad Sci U S A 116: 1591-1596
MeSH Terms: Animals, Antibodies, Monoclonal, Antibodies, Neutralizing, Antibodies, Viral, Cryoelectron Microscopy, Disease Models, Animal, Epitopes, Humans, Male, Mice, Mice, Inbred C57BL, Vaccination, Viral Envelope Proteins, Zika Virus, Zika Virus Infection
Show Abstract · Added March 31, 2019
Zika virus (ZIKV) is a major human pathogen and member of the genus in the Flaviviridae family. In contrast to most other insect-transmitted flaviviruses, ZIKV also can be transmitted sexually and from mother to fetus in humans. During recent outbreaks, ZIKV infections have been linked to microcephaly, congenital disease, and Guillain-Barré syndrome. Neutralizing antibodies have potential as therapeutic agents. We report here a 4-Å-resolution cryo-electron microscopy structure of the ZIKV virion in complex with Fab fragments of the potently neutralizing human monoclonal antibody ZIKV-195. The footprint of the ZIKV-195 Fab fragment expands across two adjacent envelope (E) protein protomers. ZIKV neutralization by this antibody is presumably accomplished by cross-linking the E proteins, which likely prevents formation of E protein trimers required for fusion of the viral and cellular membranes. A single dose of ZIKV-195 administered 5 days after virus inoculation showed marked protection against lethality in a stringent mouse model of infection.
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Multistate design of influenza antibodies improves affinity and breadth against seasonal viruses.
Sevy AM, Wu NC, Gilchuk IM, Parrish EH, Burger S, Yousif D, Nagel MBM, Schey KL, Wilson IA, Crowe JE, Meiler J
(2019) Proc Natl Acad Sci U S A 116: 1597-1602
MeSH Terms: Amino Acid Sequence, Antibodies, Neutralizing, Antibodies, Viral, Crystallography, X-Ray, Hemagglutinin Glycoproteins, Influenza Virus, Humans, Influenza A virus, Influenza, Human, Seasons
Show Abstract · Added March 31, 2019
Influenza is a yearly threat to global public health. Rapid changes in influenza surface proteins resulting from antigenic drift and shift events make it difficult to readily identify antibodies with broadly neutralizing activity against different influenza subtypes with high frequency, specifically antibodies targeting the receptor binding domain (RBD) on influenza HA protein. We developed an optimized computational design method that is able to optimize an antibody for recognition of large panels of antigens. To demonstrate the utility of this multistate design method, we used it to redesign an antiinfluenza antibody against a large panel of more than 500 seasonal HA antigens of the H1 subtype. As a proof of concept, we tested this method on a variety of known antiinfluenza antibodies and identified those that could be improved computationally. We generated redesigned variants of antibody C05 to the HA RBD and experimentally characterized variants that exhibited improved breadth and affinity against our panel. C05 mutants exhibited improved affinity for three of the subtypes used in design by stabilizing the CDRH3 loop and creating favorable electrostatic interactions with the antigen. These mutants possess increased breadth and affinity of binding while maintaining high-affinity binding to existing targets, surpassing a major limitation up to this point.
Copyright © 2019 the Author(s). Published by PNAS.
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Arrestin-3 scaffolding of the JNK3 cascade suggests a mechanism for signal amplification.
Perry NA, Kaoud TS, Ortega OO, Kaya AI, Marcus DJ, Pleinis JM, Berndt S, Chen Q, Zhan X, Dalby KN, Lopez CF, Iverson TM, Gurevich VV
(2019) Proc Natl Acad Sci U S A 116: 810-815
MeSH Terms: MAP Kinase Kinase 4, MAP Kinase Kinase 7, MAP Kinase Signaling System, Mitogen-Activated Protein Kinase 10, Models, Biological, Phosphorylation, Software, beta-Arrestin 2
Show Abstract · Added April 1, 2019
Scaffold proteins tether and orient components of a signaling cascade to facilitate signaling. Although much is known about how scaffolds colocalize signaling proteins, it is unclear whether scaffolds promote signal amplification. Here, we used arrestin-3, a scaffold of the ASK1-MKK4/7-JNK3 cascade, as a model to understand signal amplification by a scaffold protein. We found that arrestin-3 exhibited >15-fold higher affinity for inactive JNK3 than for active JNK3, and this change involved a shift in the binding site following JNK3 activation. We used systems biochemistry modeling and Bayesian inference to evaluate how the activation of upstream kinases contributed to JNK3 phosphorylation. Our combined experimental and computational approach suggested that the catalytic phosphorylation rate of JNK3 at Thr-221 by MKK7 is two orders of magnitude faster than the corresponding phosphorylation of Tyr-223 by MKK4 with or without arrestin-3. Finally, we showed that the release of activated JNK3 was critical for signal amplification. Collectively, our data suggest a "conveyor belt" mechanism for signal amplification by scaffold proteins. This mechanism informs on a long-standing mystery for how few upstream kinase molecules activate numerous downstream kinases to amplify signaling.
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Yeast require redox switching in DNA primase.
O'Brien E, Salay LE, Epum EA, Friedman KL, Chazin WJ, Barton JK
(2018) Proc Natl Acad Sci U S A 115: 13186-13191
MeSH Terms: Crystallography, X-Ray, DNA Primase, Electron Transport, Iron-Sulfur Proteins, Models, Molecular, Mutation, Oxidation-Reduction, Protein Conformation, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Show Abstract · Added March 26, 2019
Eukaryotic DNA primases contain a [4Fe4S] cluster in the C-terminal domain of the p58 subunit (p58C) that affects substrate affinity but is not required for catalysis. We show that, in yeast primase, the cluster serves as a DNA-mediated redox switch governing DNA binding, just as in human primase. Despite a different structural arrangement of tyrosines to facilitate electron transfer between the DNA substrate and [4Fe4S] cluster, in yeast, mutation of tyrosines Y395 and Y397 alters the same electron transfer chemistry and redox switch. Mutation of conserved tyrosine 395 diminishes the extent of p58C participation in normal redox-switching reactions, whereas mutation of conserved tyrosine 397 causes oxidative cluster degradation to the [3Fe4S] species during p58C redox signaling. Switching between oxidized and reduced states in the presence of the Y397 mutations thus puts primase [4Fe4S] cluster integrity and function at risk. Consistent with these observations, we find that yeast tolerate mutations to Y395 in p58C, but the single-residue mutation Y397L in p58C is lethal. Our data thus show that a constellation of tyrosines for protein-DNA electron transfer mediates the redox switch in eukaryotic primases and is required for primase function in vivo.
Copyright © 2018 the Author(s). Published by PNAS.
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Amycomicin is a potent and specific antibiotic discovered with a targeted interaction screen.
Pishchany G, Mevers E, Ndousse-Fetter S, Horvath DJ, Paludo CR, Silva-Junior EA, Koren S, Skaar EP, Clardy J, Kolter R
(2018) Proc Natl Acad Sci U S A 115: 10124-10129
MeSH Terms: Anthraquinones, Anti-Bacterial Agents, DNA, Bacterial, DNA, Ribosomal, Microbial Sensitivity Tests, RNA, Ribosomal, 16S, Streptomyces coelicolor
Show Abstract · Added April 7, 2019
The rapid emergence of antibiotic-resistant pathogenic bacteria has accelerated the search for new antibiotics. Many clinically used antibacterials were discovered through culturing a single microbial species under nutrient-rich conditions, but in the environment, bacteria constantly encounter poor nutrient conditions and interact with neighboring microbial species. In an effort to recapitulate this environment, we generated a nine-strain actinomycete community and used 16S rDNA sequencing to deconvolute the stochastic production of antimicrobial activity that was not observed from any of the axenic cultures. We subsequently simplified the community to just two strains and identified sp. AA4 as the producing strain and M145 as an inducing strain. Bioassay-guided isolation identified amycomicin (AMY), a highly modified fatty acid containing an epoxide isonitrile warhead as a potent and specific inhibitor of Amycomicin targets an essential enzyme (FabH) in fatty acid biosynthesis and reduces infection in a mouse skin-infection model. The discovery of AMY demonstrates the utility of screening complex communities against specific targets to discover small-molecule antibiotics.
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Methylglyoxal-derived posttranslational arginine modifications are abundant histone marks.
Galligan JJ, Wepy JA, Streeter MD, Kingsley PJ, Mitchener MM, Wauchope OR, Beavers WN, Rose KL, Wang T, Spiegel DA, Marnett LJ
(2018) Proc Natl Acad Sci U S A 115: 9228-9233
MeSH Terms: Arginine, HEK293 Cells, Histones, Humans, Lactoylglutathione Lyase, Protein Processing, Post-Translational, Pyruvaldehyde, Transcription, Genetic
Show Abstract · Added April 12, 2019
Histone posttranslational modifications (PTMs) regulate chromatin dynamics, DNA accessibility, and transcription to expand the genetic code. Many of these PTMs are produced through cellular metabolism to offer both feedback and feedforward regulation. Herein we describe the existence of Lys and Arg modifications on histones by a glycolytic by-product, methylglyoxal (MGO). Our data demonstrate that adduction of histones by MGO is an abundant modification, present at the same order of magnitude as Arg methylation. These modifications were detected on all four core histones at critical residues involved in both nucleosome stability and reader domain binding. In addition, MGO treatment of cells lacking the major detoxifying enzyme, glyoxalase 1, results in marked disruption of H2B acetylation and ubiquitylation without affecting H2A, H3, and H4 modifications. Using RNA sequencing, we show that MGO is capable of altering gene transcription, most notably in cells lacking GLO1. Finally, we show that the deglycase DJ-1 protects histones from adduction by MGO. Collectively, our findings demonstrate the existence of a previously undetected histone modification derived from glycolysis, which may have far-reaching implications for the control of gene expression and protein transcription linked to metabolism.
Copyright © 2018 the Author(s). Published by PNAS.
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Intestinal host defense outcome is dictated by PGE production during efferocytosis of infected cells.
Dejani NN, Orlando AB, Niño VE, Penteado LA, Verdan FF, Bazzano JMR, Codo AC, Salina ACG, Saraiva AC, Avelar MR, Spolidorio LC, Serezani CH, Medeiros AI
(2018) Proc Natl Acad Sci U S A 115: E8469-E8478
MeSH Terms: Animals, Citrobacter rodentium, Colitis, Dendritic Cells, Dinoprostone, Enterobacteriaceae Infections, Female, Intestines, Macrophages, Mice, Receptors, Prostaglandin E, EP4 Subtype
Show Abstract · Added March 18, 2020
Inflammatory responses are terminated by the clearance of dead cells, a process termed efferocytosis. A consequence of efferocytosis is the synthesis of the antiinflammatory mediators TGF-β, PGE, and IL-10; however, the efferocytosis of infected cells favors Th17 responses by eliciting the synthesis of TGF-β, IL-6, and IL-23. Recently, we showed that the efferocytosis of apoptotic -infected macrophages by dendritic cells triggers PGE production in addition to pro-Th17 cytokine expression. We therefore examined the role of PGE during Th17 differentiation and intestinal pathology. The efferocytosis of apoptotic -infected cells by dendritic cells promoted high levels of PGE, which impaired IL-1R expression via the EP4-PKA pathway in T cells and consequently inhibited Th17 differentiation. The outcome of murine intestinal infection was dependent on the EP4 receptor. Infected mice treated with EP4 antagonist showed enhanced intestinal defense against compared with infected mice treated with vehicle control. Those results suggest that EP4 signaling during infectious colitis could be targeted as a way to enhance Th17 immunity and host defense.
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