The inlAB locus mediates the entry of Listeria monocytogenes into hepatocytes in vivo.

The intracellular parasite Listeria monocytogenes is able to induce its internalization by cultured mammalian cells that are not normally phagocytic. This process requires the expression of the chromosomal locus inlAB. We studied the virulence of an inlAB mutant and of its parent in murine listeriosis. Irrespective of the route of inoculation, the inlAB mutant was severely attenuated for growth in the liver. The livers of mice inoculated with the inlAB mutant displayed much smaller infectious foci than the parent as early as 24 h after infection. Electron microscopy showed that these foci consisted of a few inflammatory cells, with few bacteria; bacteria were rarely found within hepatocytes. In contrast, foci in livers of mice inoculated with the parent consisted of islets of heavily infected hepatocytes that were infiltrated by numerous neutrophils; bacteria seemed intact within hepatocytes and damaged within neutrophils. A direct role of inlAB for the entry of L. monocytogenes into hepatocytes was confirmed in a cell infection system using the murine embryonic hepatocyte cell line TIB73. The inlAB mutant was approximately 20-fold less invasive in trans. The "invasion locus" inlAB contributes to protect L. monocytogenes from the host's innate defense mechanisms by promoting its entry into hepatocytes.

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Molecular Characterization of Serine-, Alanine-, and Proline-Rich Proteins of Trypanosoma cruzi and Their Possible Role in Host Cell Infection

Infection and Immunity ◽

10.1128/iai.74.3.1537-1546.2006 ◽

2006 ◽

Vol 74 (3) ◽

pp. 1537-1546 ◽

Cited By ~ 26

Author(s):

Renata C. P. Baida ◽

Márcia R. M. Santos ◽

Mirian S. Carmo ◽

Nobuko Yoshida ◽

Danielle Ferreira ◽

...

Keyword(s):

Trypanosoma Cruzi ◽

Host Cell ◽

Mammalian Cells ◽

Receptor Interaction ◽

Cell Infection ◽

Extracellular Medium ◽

Metacyclic Trypomastigotes ◽

A Cell

ABSTRACT We previously reported the isolation of a novel protein gene family, termed SAP (serine-, alanine-, and proline-rich protein), from Trypanosoma cruzi. Aided by the availability of the completed genome sequence of T. cruzi, we have now identified 39 full-length sequences of SAP, six pseudogenes and four partial genes. SAPs share a central domain of about 55 amino acids and can be divided into four groups based on their amino (N)- and carboxy (C)-terminal sequences. Some SAPs have conserved N- and C-terminal domains encoding a signal peptide and a glycosylphosphatidylinositol anchor addition site, respectively. Analysis of the expression of SAPs in metacyclic trypomastigotes by two-dimensional electrophoresis and immunoblotting revealed that they are likely to be posttranslationally modified in vivo. We have also demonstrated that some SAPs are shed into the extracellular medium. The recombinant SAP exhibited an adhesive capacity toward mammalian cells, where binding was dose dependent and saturable, indicating a possible ligand-receptor interaction. SAP triggered the host cell Ca2+ response required for parasite internalization. A cell invasion assay performed in the presence of SAP showed inhibition of internalization of the metacyclic forms of the CL strain. Taken together, these results show that SAP is involved in the invasion of mammalian cells by metacyclic trypomastigotes, and they confirm the hypothesis that infective trypomastigotes exploit an arsenal of surface glycoproteins and shed proteins to induce signaling events required for their internalization.

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Autophagy-activating strategies to promote innate defense against mycobacteria

Experimental & Molecular Medicine ◽

10.1038/s12276-019-0290-7 ◽

2019 ◽

Vol 51 (12) ◽

pp. 1-10 ◽

Cited By ~ 12

Author(s):

Yi Sak Kim ◽

Prashanta Silwal ◽

Soo Yeon Kim ◽

Tamotsu Yoshimori ◽

Eun-Kyeong Jo

Keyword(s):

Host Defense ◽

Defense Mechanism ◽

Multidrug Resistant ◽

Peroxisome Proliferator ◽

Peroxisome Proliferator Activated Receptor ◽

Innate Defense ◽

Host Defense Mechanism ◽

A Cell

AbstractMycobacterium tuberculosis (Mtb) is a major causal pathogen of human tuberculosis (TB), which is a serious health burden worldwide. The demand for the development of an innovative therapeutic strategy to treat TB is high due to drug-resistant forms of TB. Autophagy is a cell-autonomous host defense mechanism by which intracytoplasmic cargos can be delivered and then destroyed in lysosomes. Previous studies have reported that autophagy-activating agents and small molecules may be beneficial in restricting intracellular Mtb infection, even with multidrug-resistant Mtb strains. Recent studies have revealed the essential roles of host nuclear receptors (NRs) in the activation of the host defense through antibacterial autophagy against Mtb infection. In particular, we discuss the function of estrogen-related receptor (ERR) α and peroxisome proliferator-activated receptor (PPAR) α in autophagy regulation to improve host defenses against Mtb infection. Despite promising findings relating to the antitubercular effects of various agents, our understanding of the molecular mechanism by which autophagy-activating agents suppress intracellular Mtb in vitro and in vivo is lacking. An improved understanding of the antibacterial autophagic mechanisms in the innate host defense will eventually lead to the development of new therapeutic strategies for human TB.

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Recombinant Listeria monocytogenes Expressing a Cell Wall-Associated Listeriolysin O Is Weakly Virulent but Immunogenic

Infection and Immunity ◽

10.1128/iai.00419-09 ◽

2009 ◽

Vol 77 (10) ◽

pp. 4371-4382 ◽

Cited By ~ 5

Author(s):

Javier A. Carrero ◽

Boris Calderon ◽

Hector Vivanco-Cid ◽

Emil R. Unanue

Keyword(s):

Listeria Monocytogenes ◽

Listeriolysin O ◽

Wild Type ◽

Positive Bacterium ◽

Cell Responses ◽

A Cell ◽

Weakly Virulent

ABSTRACT Listeriolysin O (LLO) is an essential virulence factor for the gram-positive bacterium Listeria monocytogenes. Our goal was to determine if altering the topology of LLO would alter the virulence and toxicity of L. monocytogenes in vivo. A recombinant strain was generated that expressed a surface-associated LLO (sLLO) variant secreted at 40-fold-lower levels than the wild type. In culture, the sLLO strain grew in macrophages, translocated to the cytosol, and induced cell death. However, the sLLO strain showed decreased infectivity, reduced lymphocyte apoptosis, and decreased virulence despite a normal in vitro phenotype. Thus, the topology of LLO in L. monocytogenes was a factor in the pathogenesis of the infection and points to a role of LLO secretion during in vivo infection. The sLLO strain was cleared by severe combined immunodeficient (SCID) mice. Despite the attenuation of virulence, the sLLO strain was immunogenic and capable of eliciting protective T-cell responses.

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Mammalian Cell Entry domains are required for bile resistance and virulence inSalmonella

10.1101/263871 ◽

2018 ◽

Cited By ~ 2

Author(s):

Georgia L. Isom ◽

Jessica L. Rooke ◽

Camila A. Antunes ◽

Emma Sheehan ◽

Timothy J. Wells ◽

...

Keyword(s):

Mammalian Cell ◽

Mammalian Cells ◽

Bile Salts ◽

Pathogenic Bacteria ◽

Cell Entry ◽

Direct Role ◽

Bile Resistance ◽

Mammalian Infection ◽

Membrane Physiology

AbstractMCE domains were first reported inMycobacteriaas having a role inMammalianCellEntry, with subsequent studies showing their importance during infection. Here, we have examined the function of MCE proteins inSalmonellaTyphimurium during mammalian infection. We report that MCE proteins are required forSalmonellavirulence, but that this is not related to decreased adherence, entry or survival in mammalian cells. Instead, we reveal that MCE proteins are required forSalmonellabile resistance, in particular to withstand bile salts such as cholate and deoxycholate. Based on our previous work inEscherichia coli, and other studies that have reported roles for MCE proteins in membrane biogenesis, we propose thatSalmonellalacking MCE domains have a defective outer membrane that results in bile sensitivity and decreased virulencein vivo. These results suggest that MCE domains mediate fundamental aspects of bacterial membrane physiology as opposed to a proposed direct role in mammalian cell entry, explaining their conservation across both pathogenic and non-pathogenic bacteria.

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The role of Leishmania GP63 in the modulation of innate inflammatory response to Leishmania major infection

PLoS ONE ◽

10.1371/journal.pone.0262158 ◽

2021 ◽

Vol 16 (12) ◽

pp. e0262158

Author(s):

Aretha Chan ◽

Jose-Mauricio Ayala ◽

Fernando Alvarez ◽

Ciriaco Piccirillo ◽

George Dong ◽

...

Keyword(s):

Inflammatory Response ◽

Leishmania Major ◽

Critical Role ◽

Protozoan Parasite ◽

Inflammatory Cells ◽

Host Cells ◽

Cell Infection ◽

Zinc Metalloprotease

Leishmaniasis is a disease caused by the protozoan parasite Leishmania and is known to affect millions of individuals worldwide. In recent years, we have established the critical role played by Leishmania zinc-metalloprotease GP63 in the modulation of host macrophage signalling and functions, favouring its survival and progression within its host. Leishmania major lacking GP63 was reported to cause limited infection in mice, however, it is still unclear how GP63 may influence the innate inflammatory response and parasite survival in an in vivo context. Therefore, we were interested in analyzing the early innate inflammatory events upon Leishmania inoculation within mice and establish whether Leishmania GP63 influences this initial inflammatory response. Experimentally, L. major WT (L. majorWT), L. major GP63 knockout (L. majorKO), or L. major GP63 rescue (L. majorR) were intraperitoneally inoculated in mice and the inflammatory cells recruited were characterized microscopically and by flow cytometry (number and cell type), and their infection determined. Pro-inflammatory markers such as cytokines, chemokines, and extracellular vesicles (EVs, e.g. exosomes) were monitored and proteomic analysis was performed on exosome contents. Data obtained from this study suggest that Leishmania GP63 does not significantly influence the pathogen-induced inflammatory cell recruitment, but rather their activation status and effector function. Concordantly, internalization of promastigotes during early infection could be influenced by GP63 as fewer L. majorKO amastigotes were found within host cells and appear to maintain in host cells over time. Collectively this study provides a clear analysis of innate inflammatory events occurring during L. major infection and further establish the prominent role of the virulence factor GP63 to provide favourable conditions for host cell infection.

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PACAP is a pathogen-inducible resident antimicrobial neuropeptide affording rapid and contextual molecular host defense of the brain

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1917623117 ◽

2020 ◽

Vol 118 (1) ◽

pp. e1917623117

Author(s):

Ernest Y. Lee ◽

Liana C. Chan ◽

Huiyuan Wang ◽

Juelline Lieng ◽

Mandy Hung ◽

...

Keyword(s):

Stress Responses ◽

Defense Mechanisms ◽

Immune Cell ◽

Membrane Integrity ◽

Antimicrobial Properties ◽

Antimicrobial Activities ◽

Immune Effector ◽

Innate Defense ◽

The Brain

Defense of the central nervous system (CNS) against infection must be accomplished without generation of potentially injurious immune cell-mediated or off-target inflammation which could impair key functions. As the CNS is an immune-privileged compartment, inducible innate defense mechanisms endogenous to the CNS likely play an essential role in this regard. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide known to regulate neurodevelopment, emotion, and certain stress responses. While PACAP is known to interact with the immune system, its significance in direct defense of brain or other tissues is not established. Here, we show that our machine-learning classifier can screen for immune activity in neuropeptides, and correctly identified PACAP as an antimicrobial neuropeptide in agreement with previous experimental work. Furthermore, synchrotron X-ray scattering, antimicrobial assays, and mechanistic fingerprinting provided precise insights into how PACAP exerts antimicrobial activities vs. pathogens via multiple and synergistic mechanisms, including dysregulation of membrane integrity and energetics and activation of cell death pathways. Importantly, resident PACAP is selectively induced up to 50-fold in the brain in mouse models of Staphylococcus aureus or Candida albicans infection in vivo, without inducing immune cell infiltration. We show differential PACAP induction even in various tissues outside the CNS, and how these observed patterns of induction are consistent with the antimicrobial efficacy of PACAP measured in conditions simulating specific physiologic contexts of those tissues. Phylogenetic analysis of PACAP revealed close conservation of predicted antimicrobial properties spanning primitive invertebrates to modern mammals. Together, these findings substantiate our hypothesis that PACAP is an ancient neuro-endocrine-immune effector that defends the CNS against infection while minimizing potentially injurious neuroinflammation.

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Glycobiology of syndecan-1 in bacterial infections

Biochemical Society Transactions ◽

10.1042/bst20170395 ◽

2018 ◽

Vol 46 (2) ◽

pp. 371-377 ◽

Cited By ~ 6

Author(s):

Rafael S. Aquino ◽

Yvonne Hui-Fang Teng ◽

Pyong Woo Park

Keyword(s):

Cell Surface ◽

Defense Mechanisms ◽

Bacterial Infections ◽

Bacterial Pathogens ◽

Innate Immune ◽

Host Cells ◽

Innate Defense ◽

Immune Clearance ◽

Bacterial Adhesins ◽

A Cell

Syndecan-1 (Sdc1) is a major cell surface heparan sulfate (HS) proteoglycan of epithelial cells, a cell type targeted by many bacterial pathogens early in their pathogenesis. Loss of Sdc1 in mice is a gain-of-function mutation that significantly decreases the susceptibility to several bacterial infections, suggesting that subversion of Sdc1 is an important virulence strategy. HS glycosaminoglycan (GAG) chains of cell surface Sdc1 promote bacterial pathogenesis by facilitating the attachment of bacteria to host cells. Engagement of cell surface Sdc1 HS chains by bacterial adhesins transmits signal through the highly conserved Sdc1 cytoplasmic domain, which can lead to uptake of intracellular bacterial pathogens. On the other hand, several bacteria that do not require Sdc1 for their attachment and invasion stimulate Sdc1 shedding and exploit the capacity of Sdc1 ectodomain HS GAGs to disarm innate defense mechanisms to evade immune clearance. Recent data suggest that select HS sulfate motifs, and not the overall charge of HS, are important in the inhibition of innate immune mechanisms. Here, we discuss several examples of Sdc1 subversion in bacterial infections.

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A Superoxide-Hypersusceptible Salmonella enterica Serovar Typhimurium Mutant Is Attenuated but Regains Virulence in p47phox−/− Mice

Infection and Immunity ◽

10.1128/iai.70.5.2614-2621.2002 ◽

2002 ◽

Vol 70 (5) ◽

pp. 2614-2621 ◽

Cited By ~ 19

Author(s):

Angela van Diepen ◽

Tahar van der Straaten ◽

Steven M. Holland ◽

Riny Janssen ◽

Jaap T. van Dissel

Keyword(s):

Salmonella Enterica ◽

Defense Mechanisms ◽

Mononuclear Phagocytes ◽

Wild Type ◽

Phagocytic Cells ◽

Bacterial Counts ◽

Innate Defense ◽

Serovar Typhimurium

ABSTRACT Salmonella enterica serovar Typhimurium is a gram-negative, facultative intracellular pathogen that predominantly invades mononuclear phagocytes and is able to establish persistent infections. One of the innate defense mechanisms of phagocytic cells is the production of reactive oxygen species, including superoxide. S. enterica serovar Typhimurium has evolved mechanisms to resist such radicals, and these mechanisms could be decisive in its ability to survive and replicate within macrophages. Recently, we described a superoxide-hypersusceptible S. enterica serovar Typhimurium mutant strain, DLG294, that carries a transposon in sspJ, resulting in the lack of expression of SspJ, which is necessary for resistance against superoxide and replication within macrophages. Here we show that DLG294, which is a 14028s derivative, hardly induced any granulomatous lesions in the livers upon subcutaneous infection of C3H/HeN (Ityr) mice with 3 × 104 bacteria and that its bacterial counts were reduced by 3 log units compared to those of wild-type S. enterica serovar Typhimurium 14028s on day 5 after infection. In contrast, DLG294 replicated like wild-type S. enterica serovar Typhimurium 14028s and induced a phenotypically similar liver pathology in p47phox−/− mice, which are deficient in the p47phox subunit of the NADPH oxidase complex and which do not produce superoxide. Consistent with these results, DLG294 reached bacterial counts identical to those of wild-type S. enterica serovar Typhimurium 14028s in bone marrow-derived macrophages from p47phox−/− mice and in X-CGD PLB-985 cells at 24 h after challenge. These results indicate that SspJ plays a role in the bacterium's resistance to oxidative stress and in the survival and replication of S. enterica serovar Typhimurium both in vitro and in vivo.

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Negative feedback between secretory and cytosolic phospholipase A2 and their opposing roles in ovalbumin-induced bronchoconstriction in rats

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00199.2004 ◽

2005 ◽

Vol 288 (3) ◽

pp. L523-L529 ◽

Cited By ~ 11

Author(s):

Sarit Offer ◽

Saul Yedgar ◽

Ouri Schwob ◽

Miron Krimsky ◽

Haim Bibi ◽

...

Keyword(s):

Negative Feedback ◽

Inflammatory Cells ◽

Airway Epithelial Cells ◽

Airway Epithelial ◽

Membrane Phospholipids ◽

Cytosolic Phospholipase ◽

Inflammatory Processes ◽

A Cell ◽

First Time

Phospholipase A2 (PLA2) hydrolyzes cell membrane phospholipids (PL) to produce arachidonic acid and lyso-PL. The PLA2 enzymes include the secretory (sPLA2) and cytosolic (cPLA2) isoforms, which are assumed to act synergistically in production of eicosanoids that are involved in inflammatory processes. However, growing evidence raises the possibility that in airways and asthma-related inflammatory cells (eosinophils, basophils), the production of the bronchoconstrictor cysteinyl leukotrienes (CysLT) is linked exclusively to sPLA2, whereas the bronchodilator prostaglandin PGE2 is produced by cPLA2. It has been further reported that the capacity of airway epithelial cells to produce CysLT is inversely proportional to PGE2 production. This seems to suggest that sPLA2 and cPLA2 play opposing roles in asthma pathophysiology and the possibility of a negative feedback between the two isoenzymes. To test this hypothesis, we examined the effect of a cell-impermeable extracellular sPLA2 inhibitor on bronchoconstriction and PLA2 expression in rats with ovalbumin (OVA)-induced asthma. It was found that OVA-induced bronchoconstriction was associated with elevation of lung sPLA2 expression and CysLT production, concomitantly with suppression of cPLA2 expression and PGE2 production. These were reversed by treatment with the sPLA2 inhibitor, resulting in amelioration of bronchoconstriction and reduced CysLT production and sPLA2 expression, concomitantly with enhanced PGE2 production and cPLA2 expression. This study demonstrates, for the first time in vivo, a negative feedback between sPLA2 and cPLA2 and assigns opposing roles for these enzymes in asthma pathophysiology: sPLA2 activation induces production of the bronchoconstrictor CysLT and suppresses cPLA2 expression and the subsequent production of the bronchodilator PGE2.

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The molecular chaperone Ydj1 is required for the p34CDC28-dependent phosphorylation of the cyclin Cln3 that signals its degradation.

Molecular and Cellular Biology ◽

10.1128/mcb.16.7.3679 ◽

1996 ◽

Vol 16 (7) ◽

pp. 3679-3684 ◽

Cited By ~ 50

Author(s):

J A Yaglom ◽

A L Goldberg ◽

D Finley ◽

M Y Sherman

Keyword(s):

Molecular Chaperone ◽

Terminal Segment ◽

Direct Role ◽

Yeast Saccharomyces Cerevisiae ◽

Free System ◽

Close Proximity ◽

Ubiquitin Proteasome ◽

A Cell ◽

Histone Kinase

The G1 cyclin Cln3 of the yeast Saccharomyces cerevisiae is rapidly degraded by the ubiquitin-proteasome pathway. This process is triggered by p34CDC28-dependent phosphorylation of Cln3. Here we demonstrate that the molecular chaperone Ydj1, a DnaJ homolog, is required for this phosphorylation. In a ydj1 mutant at the nonpermissive temperature, both phosphorylation and degradation of Cln3 were deficient. No change was seen upon inactivation of Sis1, another DnaJ homolog. The phosphorylation defect in the ydj1 mutant was specific to Cln3, because no reduction in the phosphorylation of Cln2 or histone H1, which also requires p34CDC28, was observed. Ydj1 was required for Cln3 phosphorylation and degradation rather than for the proper folding of this cyclin, since Cln3 produced in the ydj1 mutant was fully active in the stimulation of p34CDC28 histone kinase activity. Moreover, Ydj1 directly associates with Cln3 in close proximity to the segment that is phosphorylated and signals degradation. Thus, binding of Ydj1 to this domain of Cln3 seems to be essential for the phosphorylation and breakdown of this cyclin. In a cell-free system, purified Ydj1 stimulated the p34CDC28-dependent phosphorylation of the C-terminal segment of Cln3 and did not affect phosphorylation of Cln2 (as was found in vivo). The reconstitution of this process with pure components provides evidence of a direct role for the chaperone in the phosphorylation of Cln3.

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