bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fine Mapping of
Leishmania major
Susceptibility Locus
lmr2
and Evidence of a Role for
Fli1
in Disease and Wound Healing
Authors: Sakthianandeswaren Anuratha , Curtis Joan M. , Elso Colleen , Kumar Beena , Baldwin Tracey M. , Lopaticki Sash , Kedzierski Lukasz , Smyth Gordon K. , Foote Simon J. , Handman Emanuela 
Published: April 2010

ABSTRACT

Genetic linkage studies of the host response to
Leishmania major
, the causative agent of cutaneous leishmaniasis, have identified significant genetic complexity in humans and mice. In the mouse model, multiple loci have been implicated in susceptibility to infection, but to date, the genes underlying these loci have not been identified. We now describe the contribution of a novel candidate gene,
Fli1
, to both
L. major
resistance and enhanced wound healing. We have previously mapped the
L. major
response locus,
lmr2
, to proximal chromosome 9 in a genetic cross between the resistant C57BL/6 strain and the susceptible BALB/c strain. We now show that the presence of the resistant C57BL/6
lmr2
allele in susceptible BALB/c mice confers an enhanced
L. major
resistance and wound healing phenotype. Fine mapping of the
lmr2
locus permitted the localization of the
lmr2
quantitative trait locus to a 5-Mb interval comprising 21 genes, of which microarray analysis was able to identify differential expression in 1 gene—
Fli1
. Analysis of
Fli1
expression in wounded and
L. major
-infected skin and naïve and infected lymph nodes validated the importance of
Fli1
in lesion resolution and wound healing and identified 3 polymorphisms in the
Fli1
promoter, among which a GA repeat element may be the important contributor.
The C-Terminal Tail of
Yersinia pseudotuberculosis
YopM Is Critical for Interacting with RSK1 and for Virulence
Authors: McCoy Melissa W. , Marré Meghan L. , Lesser Cammie F. , Mecsas Joan 
Published: April 2010

ABSTRACT

Yersinia
spp. undermine the immune responses of infected animals by translocating Yops directly into host cells with a type III secretion system. YopM, a leucine-rich repeat protein, is a critical virulence factor in infection. YopM localizes to both the nucleus and the cytoplasm in cultured cells, interacts with mammalian p90 ribosomal S6 kinase 1 (RSK1), and causes a decrease in NK cell populations in spleens. Little is known about the molecular interaction between YopM and RSK1 and its significance in pathogenesis. We performed a systematic deletion analysis of YopM in
Yersinia pseudotuberculosis
to determine which regions are required for RSK1 interactions, nuclear localization, virulence, and changes in immune cell populations during infection of mice. Full-length YopM associated with RSK1 in at least two protein complexes in infected cells, and deletion of its C-terminal tail abrogated all RSK1 interactions. The C-terminal tail was required for tissue colonization, as
yopM
mutants that failed to interact with RSK1 were as defective for tissue colonization as was a Δ
yopM
mutant; however, nuclear localization of YopM was not dependent on its RSK1 interaction. Mutants expressing YopM proteins which do not interact with RSK1 caused more pathology than did the Δ
yopM
mutant, suggesting that there are other RSK1-independent functions of YopM. Histopathological and flow cytometric analyses of spleens showed that infection with wild-type
Y. pseudotuberculosis
caused an influx of neutrophils, while mice infected with
yopM
mutants had increased numbers of macrophages. Decreases in NK cells after
Y. pseudotuberculosis
infection did not correlate with YopM expression. In conclusion, the C terminus of YopM is essential for RSK1 interactions and for virulence.
Coupled Amino Acid Deamidase-Transport Systems Essential for
Helicobacter pylori
Colonization
Authors: Leduc Damien , Gallaud Julien , Stingl Kerstin , de Reuse Hilde 
Published: April 2010

ABSTRACT

In addition to their classical roles as carbon or nitrogen sources, amino acids can be used for bacterial virulence, colonization, or stress resistance. We found that original deamidase-transport systems impact colonization by
Helicobacter pylori
, a human pathogen associated with gastric pathologies, including adenocarcinoma. We demonstrated that
l
-asparaginase (Hp-AnsB) and γ-glutamyltranspeptidase (Hp-γGT) are highly active periplasmic deamidases in
H. pylori
, producing ammonia and aspartate or glutamate from asparagine and glutamine, respectively. Hp-GltS was identified as a sole and specialized transporter for glutamate, while aspartate was exclusively imported by Hp-DcuA. Uptake of Gln and Asn strictly relies on indirect pathways following prior periplasmic deamidation into Glu and Asp. Hence, in
H. pylori
, the coupled action of periplasmic deamidases with their respective transporters enables the acquisition of Glu and Asp from Gln and Asn, respectively. These systems were active at neutral rather than acidic pH, suggesting their function near the host epithelial cells. We showed that Hp-DcuA, the fourth component of these novel deamidase-transport systems, was as crucial as Hp-γGT, Hp-AnsB, and Hp-GltS for animal model colonization. In conclusion, the pH-regulated coupled amino acid deamidase-uptake system represents an original optimized system that is essential for
in vivo
colonization of the stomach environment by
H. pylori
. We propose a model in which these two nonredundant systems participate in
H. pylori
virulence by depleting gastric or immune cells from protective amino acids such as Gln and producing toxic ammonia close to the host cells.
Comparative Study of the Ability ofLeishmania mexicanaPromastigotes and Amastigotes To Alter Macrophage Signaling and Functions
Authors: Abu-Dayyeh Issa , Hassani Kasra , Westra Edze R. , Mottram Jeremy C. , Olivier Martin 
Published: April 2010

ABSTRACTLeishmaniaalternates between two morphologically different stages, promastigotes and amastigotes. While the majority of reports focused on how the promastigote form can alter macrophage (Mφ) signaling and function, fewer reports investigated signaling alterations mediated by amastigotes, and there is a lack of comparative studies. In this study, we performed a comparison between the ability of both forms of the parasite to alter Mφ signaling and functions. Here, we show that both promastigotes and amastigotes were able to rapidly activate host protein tyrosine phosphatases (PTPs), importantly the Src homology 2 domain-containing PTP (SHP-1). However, we found that PTP-1B is specifically activated by promastigote but not amastigote infection and thatlmcpb−/−promastigotes were no longer able to activate PTP-1B. We also show a similarity in the way promastigotes and amastigotes inactivate the transcription factors (TFs) STAT-1α and AP-1, but we show differences in the modulation of NF-κB, with promastigotes cleaving the p65 subunit, generating a smaller p35 subunit, and amastigotes fully degrading the p65 subunit with no p35 production. Importantly, we show that the cysteine proteinase LmCPb plays a key role in the alteration of NF-κB, STAT-1α, and AP-1 by promastigote and amastigote infections, ultimately leading to the inability of these TFs to translocate to the nucleus in response to gamma interferon (IFN-γ) stimulation and thus contributing to the ability of both parasite forms to effectively block IFN-γ-mediated nitric oxide (NO) production in Mφs.
Toll-Like Receptor 2- and MyD88-Dependent Phosphatidylinositol 3-Kinase and Rac1 Activation Facilitates the Phagocytosis ofListeria monocytogenesby Murine Macrophages
Authors: Shen Yanna , Kawamura Ikuo , Nomura Takamasa , Tsuchiya Kohsuke , Hara Hideki , Dewamitta Sita R. , Sakai Shunsuke , Qu Huixin , Daim Sylvia , Yamamoto Takeshi , Mitsuyama Masao 
Published: April 2010

ABSTRACTToll-like receptors (TLRs) play a key role in the innate immune response by sensing bacterial ligands. The mechanisms involved in the TLR-mediated cytokine response are well established; however, the possible contribution of TLR-dependent recognition of bacteria to macrophage phagocytosis remains unclear.Listeria monocytogenesis an intracellular, parasitic, Gram-positive bacterium recognized mainly by TLR2. In this study, we investigated whether TLR2-dependent signaling is involved in the phagocytosis ofL. monocytogenesby macrophages. We found no difference in the number ofL. monocytogenescells associating with wild-type (WT) and TLR2−/−macrophages 1 h after infection. However, the number ofL. monocytogenescells phagocytosed in TLR2−/−and MyD88−/−macrophages was significantly lower than that of WT macrophages. In addition, lipopolysaccharide (LPS) treatment restored impaired phagocytic activity of TLR2−/−macrophages but did not enhance the activity of MyD88−/−macrophages. The efficiency of phagocytosis was suppressed by inhibitors of phosphatidylinositol 3-kinase (PI3K) and the small Rho GTPases but not by cycloheximide. Moreover, functional activation of PI3K and Rac1 was impaired in TLR2−/−and MyD88−/−macrophages. In anin vivoinfection model, we found significantly lower numbers ofL. monocytogenescells phagocytosed in peritoneal macrophages of TLR2−/−and MyD88−/−mice after intraperitoneal infection. Moreover, a lower number of bacteria were detected in the spleens of TLR2−/−mice 1 day after intravenous infection than in WT mice. These results clearly indicated that TLR2-MyD88-dependent signaling enhances the basal level of phagocytosis ofL. monocytogenesby macrophages through activation of PI3K and Rac1, not by synthesis of proinflammatory cytokines or expression of phagocytic receptors.
Importance of CXC Chemokine Receptor 2 in Alveolar Neutrophil and Exudate Macrophage Recruitment in Response to Pneumococcal Lung Infection
Authors: Herbold Wiebke , Maus Regina , Hahn Ines , Ding Nadine , Srivastava Mrigank , Christman John W. , Mack Matthias , Reutershan Jörg , Briles David E. , Paton James C. , Winter Christine , Welte Tobias , Maus Ulrich A. 
Published: April 2010

ABSTRACTSustained neutrophilic infiltration is known to contribute to organ damage, such as acute lung injury. CXC chemokine receptor 2 (CXCR2) is the major receptor regulating inflammatory neutrophil recruitment in acute and chronic inflamed tissues. Whether or not the abundant neutrophil recruitment observed in severe pneumonia is essential for protective immunity againstStreptococcus pneumoniaeinfections is incompletely defined. Here we show that CXCR2 deficiency severely perturbs the recruitment of both neutrophils and exudate macrophages associated with a massive bacterial outgrowth in distal airspaces after infection withS. pneumoniae, resulting in 100% mortality in knockout (KO) mice within 3 days. Moreover, irradiated wild-type mice reconstituted with increasing amounts of CXCR2 KO bone marrow (10, 25, 50, and 75% KO) have correspondingly decreased numbers of both neutrophils and exudate macrophages, which is associated with a stepwise increase in bacterial burden and a reciprocal stepwise decrease in survival inS. pneumoniae-induced pulmonary infection. Finally, application of the CXCR2 antagonist SB-225002 resulted in decreased alveolar neutrophil and exudate macrophage recruitment in mice along with increased lung bacterial loads after infection withS. pneumoniae. Together, these data show that CXC chemokine receptor 2 serves a previously unrecognized nonredundant role in the regulation of both neutrophil and exudate macrophage recruitment to the lung in response toS. pneumoniaeinfection. In addition, we demonstrate that a threshold level of 10 to 25% of reduced neutrophil recruitment is sufficient to cause increased mortality in mice infected withS. pneumoniae.
Transcriptome of Swarming
Proteus mirabilis
Authors: Pearson Melanie M. , Rasko David A. , Smith Sara N. , Mobley Harry L. T. 
Published: April 2010

ABSTRACT

Swarming motility by the urinary tract pathogen
Proteus mirabilis
has been a long-studied but little understood phenomenon. On agar, a
P. mirabilis
colony grows outward in a bull's-eye pattern formed by consecutive waves of rapid swarming followed by consolidation into shorter cells. To examine differential gene expression in these growth phases, a microarray was constructed based on the completed genome sequence and annotation. RNA was extracted from broth-cultured, swarming, and consolidation-phase cells to assess transcription during each of these growth states. A total of 587 genes were differentially expressed in broth-cultured cells versus swarming cells, and 527 genes were differentially expressed in broth-cultured cells versus consolidation-phase cells (consolidate). Flagellar genes were highly upregulated in both swarming cells and consolidation-phase cells. Fimbriae were downregulated in swarming cells, while genes involved in cell division and anaerobic growth were upregulated in broth-cultured cells. Direct comparison of swarming cells to consolidation-phase cells found that 541 genes were upregulated in consolidate, but only nine genes were upregulated in swarm cells. Genes involved in flagellar biosynthesis, oligopeptide transport, amino acid import and metabolism, cell division, and phage were upregulated in consolidate. Mutation of
dppA
,
oppB
, and
cysJ
, upregulated during consolidation compared to during swarming, revealed that although these genes play a minor role in swarming,
dppA
and
cysJ
are required during ascending urinary tract infection. Swarming on agar to which chloramphenicol had been added suggested that protein synthesis is not required for swarming. These data suggest that the consolidation phase is a state in which
P. mirabilis
prepares for the next wave of swarming.
Discordant Influence of
Blastomyces dermatitidis
Yeast-Phase-Specific Gene
BYS1
on Morphogenesis and Virulence
Authors: Krajaejun Theerapong , Wüthrich Marcel , Gauthier Gregory M. , Warner Thomas F. , Sullivan Thomas D. , Klein Bruce S. 
Published: April 2010

ABSTRACT

Blastomyces dermatitidis
is a thermally induced dimorphic fungus capable of causing lung and systemic infections in immunocompetent animal hosts. With the publication of genomic sequences from three different strains of
B
.
dermatitidis
and the development of RNA interference as a gene-silencing tool, it has become possible to easily ascertain the virulence and morphological effects of knocking down the expression of candidate genes of interest.
BYS1
(
Blastomyces
yeast-phase-specific 1), first identified by Burg and Smith, is expressed at high levels in yeast cells and is undetectable in mold. The deduced protein sequence of
BYS1
has a putative signal sequence at its N terminus, opening the possibility that the
BYS1
-encoded protein is associated with the yeast cell wall. Herein, strains of
B
.
dermatitidis
with silenced expression of
BYS1
were engineered and tested for morphology and virulence. The silenced strains produced rough-surfaced cultures on agar medium and demonstrated a propensity to form pseudohyphal cells on prolonged culture
in vitro
and
in vivo
, as measured in the mouse lung. Tests using a mouse model of blastomycosis with either yeast or spore inocula showed that the
bys1
-silenced strains were as virulent as control strains. Thus, although silencing of
BYS1
alters morphology at 37°C, it does not appear to impair the pathogenicity of
B
.
dermatitidis
.
Temperature-Induced Changes in the Lipopolysaccharide ofYersinia pestisAffect Plasminogen Activation by the Pla Surface Protease
Authors: Suomalainen Marjo , Lobo Leandro Araujo , Brandenburg Klaus , Lindner Buko , Virkola Ritva , Knirel Yuriy A. , Anisimov Andrey P. , Holst Otto , Korhonen Timo K. 
Published: April 2010

ABSTRACTThe Pla surface protease ofYersinia pestisactivates human plasminogen and is a central virulence factor in bubonic and pneumonic plague. Pla is a transmembrane β-barrel protein and member of the omptin family of outer membrane proteases which require bound lipopolysaccharide (LPS) to be proteolytically active. Plasminogen activation and autoprocessing of Pla were dramatically higher inY. pestiscells grown at 37°C than in cells grown at 20°C; the difference in enzymatic activity by far exceeded the increase in the cellular content of the Pla protein.Y. pestismodifies its LPS structure in response to growth temperature. We purified His6-Pla under denaturing conditions and compared various LPS types for their capacity to enhance plasmin formation by His6-Pla solubilized in detergent. Reactivation of His6-Pla was higher withY. pestisLPSs isolated from bacteria grown at 37°C than with LPSs from cells grown at 25°C. Lack of O antigens and the presence of the outer core region as well as a lowered level of acylation in LPS were found to enhance the Pla-LPS interaction. Genetic substitution of arginine 138, which is part of a three-dimensional protein motif for binding to lipid A phosphates, decreased both the enzymatic activity of His6-Pla and the amount of Pla inY. pestiscells, suggesting the importance of the Pla-lipid A phosphate interaction. The temperature-induced changes in LPS are known to helpY. pestisto avoid innate immune responses, and our results strongly suggest that they also potentiate Pla-mediated proteolysis.
Salmonella entericaSerovar Typhimurium Invades Fibroblasts by Multiple Routes Differing from the Entry into Epithelial Cells
Authors: Aiastui Ana , Pucciarelli M. Graciela , García-del Portillo Francisco 
Published: April 2010

ABSTRACTFibroblasts are ubiquitous cells essential to tissue homeostasis. Despite their nonphagocytic nature, fibroblasts restrain replication of intracellular bacterial pathogens such asSalmonella entericaserovar Typhimurium. The extent to which the entry route of the pathogen determines this intracellular response is unknown. Here, we analyzedS.Typhimurium invasion in fibroblasts obtained from diverse origins, including primary cultures and stable nontransformed cell lines derived from normal tissues. Features distinct to the invasion of epithelial cells were found in all fibroblasts tested. In some fibroblasts, bacteria lacking the type III secretion system encoded in theSalmonellapathogenicity island 1 displayed significant invasion rates and induced the formation of lamellipodia and filopodia at the fibroblast-bacteria contact site. Other bacterial invasion traits observed in fibroblasts were the requirement of phosphatidylinositol 3-kinase, mitogen-activated protein kinase MEK1, and both actin filaments and microtubules. RNA interference studies showed that different Rho family GTPases are targeted byS.Typhimurium to enter into distinct fibroblasts. Rac1 and Cdc42 knockdown affected invasion of normal rat kidney fibroblasts, whereas none of the GTPases tested (Rac1, Cdc42, RhoA, or RhoG) was essential for invasion of immortalized human foreskin fibroblasts. Collectively, these data reveal a marked diversity in the modes used byS.Typhimurium to enter into fibroblasts.
A Deficiency in Arabinogalactan Biosynthesis AffectsCorynebacterium glutamicumMycolate Outer Membrane Stability
Authors: Bou Raad Roland , Méniche Xavier , de Sousa-d'Auria Celia , Chami Mohamed , Salmeron Christophe , Tropis Marielle , Labarre Cecile , Daffé Mamadou , Houssin Christine , Bayan Nicolas 
Published: April 2010

ABSTRACTCorynebacterineaeis a specific suborder of Gram-positive bacteria that includesMycobacterium tuberculosisandCorynebacterium glutamicum. The ultrastructure of the cell envelope is very atypical. It is composed of a heteropolymer of peptidoglycan and arabinogalactan (AG) covalently associated to an outer membrane. Five arabinosyltransferases are involved in the biosynthesis of AG inC. glutamicum. AftB catalyzes the transfer of Araf(arabinofuranosyl) onto the arabinan domain of the arabinogalactan to form terminal β(1 → 2)-linked Arafresidues. Here we show that ΔaftBcells lack half of the arabinogalactan mycoloylation sites but are still able to assemble an outer membrane. In addition, we show that a ΔaftBmutant grown on a rich medium has a perturbed cell envelope and sheds a significant amount of membrane fragments in the external culture medium. These fragments contain mono- and dimycolate of trehalose and PorA/H, the major porin ofC. glutamicum, but lack conventional phospholipids that typify the plasma membrane, suggesting that they are derived from the atypical mycolate outer membrane of the cell envelope. This is the first report of outer membrane destabilization in theCorynebacterineae, and it suggests that a strong interaction between the mycolate outer membrane and the underlying polymer is essential for cell envelope integrity. The presence of outer membrane-derived fragments (OMFs) in the external medium of the ΔaftBmutant is also a very promising tool for outer membrane characterization. Indeed, fingerprint analysis of major OMF-associated proteins has already led to the identification of 3 associated mycoloyltransferases and an unknown protein with a C-terminal hydrophobic anchoring domain reminiscent of that found for the S-layer protein PS2 ofC. glutamicum.
BacA Is Essential for Bacteroid Development in Nodules of Galegoid, but not Phaseoloid, Legumes
Authors: Karunakaran Ramakrishnan , Haag Andreas F. , East Alison K. , Ramachandran Vinoy K. , Prell Jurgen , James Euan K. , Scocchi Marco , Ferguson Gail P. , Poole Philip S. 
Published: April 2010

ABSTRACT

BacA is an integral membrane protein, the mutation of which leads to increased resistance to the antimicrobial peptides bleomycin and Bac7
1-35
and a greater sensitivity to SDS and vancomycin in
Rhizobium leguminosarum
bv.
viciae
,
R. leguminosarum
bv.
phaseoli
, and
Rhizobium etli
. The growth of
Rhizobium
strains on dicarboxylates as a sole carbon source was impaired in
bacA
mutants but was overcome by elevating the calcium level. While
bacA
mutants elicited indeterminate nodule formation on peas, which belong to the galegoid tribe of legumes, bacteria lysed after release from infection threads and mature bacteroids were not formed. Microarray analysis revealed almost no change in a
bacA
mutant of
R. leguminosarum
bv.
viciae
in free-living culture. In contrast, 45 genes were more-than 3-fold upregulated in a
bacA
mutant isolated from pea nodules. Almost half of these genes code for cell membrane components, suggesting that BacA is crucial to alterations that occur in the cell envelope during bacteroid development. In stark contrast,
bacA
mutants of
R. leguminosarum
bv.
phaseoli
and
R. etli
elicited the formation of normal determinate nodules on their bean host, which belongs to the phaseoloid tribe of legumes. Bacteroids from these nodules were indistinguishable from the wild type in morphology and nitrogen fixation. Thus, while
bacA
mutants of bacteria that infect galegoid or phaseoloid legumes have similar phenotypes in free-living culture, BacA is essential only for bacteroid development in indeterminate galegoid nodules.