Actin-Based Motility of Intracellular Microbial Pathogens

SUMMARY A diverse group of intracellular microorganisms, including Listeria monocytogenes, Shigella spp., Rickettsia spp., and vaccinia virus, utilize actin-based motility to move within and spread between mammalian host cells. These organisms have in common a pathogenic life cycle that involves a stage within the cytoplasm of mammalian host cells. Within the cytoplasm of host cells, these organisms activate components of the cellular actin assembly machinery to induce the formation of actin tails on the microbial surface. The assembly of these actin tails provides force that propels the organisms through the cell cytoplasm to the cell periphery or into adjacent cells. Each of these organisms utilizes preexisting mammalian pathways of actin rearrangement to induce its own actin-based motility. Particularly remarkable is that while all of these microbes use the same or overlapping pathways, each intercepts the pathway at a different step. In addition, the microbial molecules involved are each distinctly different from the others. Taken together, these observations suggest that each of these microbes separately and convergently evolved a mechanism to utilize the cellular actin assembly machinery. The current understanding of the molecular mechanisms of microbial actin-based motility is the subject of this review.

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The novel Dbl homology/BAR domain protein, MsgA, of Talaromyces marneffei regulates yeast morphogenesis during growth inside host cells

Scientific Reports ◽

10.1038/s41598-020-79593-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Harshini Weerasinghe ◽

Hayley E. Bugeja ◽

Alex Andrianopoulos

Keyword(s):

Pathogenic Fungi ◽

Host Cells ◽

Microbial Pathogens ◽

Mammalian Host ◽

Host Immune System ◽

Nucleotide Exchange ◽

Phagocytic Cells ◽

Macrophage Infection ◽

Bar Domain ◽

Talaromyces Marneffei

AbstractMicrobial pathogens have evolved many strategies to evade recognition by the host immune system, including the use of phagocytic cells as a niche within which to proliferate. Dimorphic pathogenic fungi employ an induced morphogenetic transition, switching from multicellular hyphae to unicellular yeast that are more compatible with intracellular growth. A switch to mammalian host body temperature (37 °C) is a key trigger for the dimorphic switch. This study describes a novel gene, msgA, from the dimorphic fungal pathogen Talaromyces marneffei that controls cell morphology in response to host cues rather than temperature. The msgA gene is upregulated during murine macrophage infection, and deletion results in aberrant yeast morphology solely during growth inside macrophages. MsgA contains a Dbl homology domain, and a Bin, Amphiphysin, Rvs (BAR) domain instead of a Plekstrin homology domain typically associated with guanine nucleotide exchange factors (GEFs). The BAR domain is crucial in maintaining yeast morphology and cellular localisation during infection. The data suggests that MsgA does not act as a canonical GEF during macrophage infection and identifies a temperature independent pathway in T. marneffei that controls intracellular yeast morphogenesis.

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Identification of Metabolically Quiescent Leishmania mexicana Parasites in Peripheral and Cured Dermal Granulomas Using Stable Isotope Tracing Imaging Mass Spectrometry

mBio ◽

10.1128/mbio.00129-21 ◽

2021 ◽

Vol 12 (2) ◽

Author(s):

Joachim Kloehn ◽

Berin A. Boughton ◽

Eleanor C. Saunders ◽

Sean O’Callaghan ◽

Katrina J. Binger ◽

...

Keyword(s):

Mass Spectrometry ◽

Heavy Water ◽

Large Population ◽

Imaging Mass Spectrometry ◽

Host Cells ◽

Microbial Pathogens ◽

Mammalian Host ◽

Leishmania Mexicana ◽

First Line

ABSTRACT Leishmania are sandfly-transmitted protists that induce granulomatous lesions in their mammalian host. Although infected host cells in these tissues can exist in different activation states, the extent to which intracellular parasites stages also exist in different growth or physiological states remains poorly defined. Here, we have mapped the spatial distribution of metabolically quiescent and active subpopulations of Leishmania mexicana in dermal granulomas in susceptible BALB/c mice, using in vivo heavy water labeling and ultra high-resolution imaging mass spectrometry. Quantitation of the rate of turnover of parasite and host-specific lipids at high spatial resolution, suggested that the granuloma core comprised mixed populations of metabolically active and quiescent parasites. Unexpectedly, a significant population of metabolically quiescent parasites was also identified in the surrounding collagen-rich, dermal mesothelium. Mesothelium-like tissues harboring quiescent parasites progressively replaced macrophage-rich granuloma tissues following treatment with the first-line drug, miltefosine. In contrast to the granulomatous tissue, neither the mesothelium nor newly deposited tissue sequestered miltefosine. These studies suggest that the presence of quiescent parasites in acute granulomatous tissues, together with the lack of miltefosine accumulation in cured lesion tissue, may contribute to drug failure and nonsterile cure. IMPORTANCE Many microbial pathogens switch between different growth and physiological states in vivo in order to adapt to local nutrient levels and host microbicidal responses. Heterogeneity in microbial growth and metabolism may also contribute to nongenetic mechanisms of drug resistance and drug failure. In this study, we have developed a new approach for measuring spatial heterogeneity in microbial metabolism in vivo using a combination of heavy water (2H2O) labeling and imaging mass spectrometry. Using this approach, we show that lesions contain a patchwork of metabolically distinct parasite populations, while the underlying dermal tissues contain a large population of metabolically quiescent parasites. Quiescent parasites also dominate drug-depleted tissues in healed animals, providing an explanation for failure of some first line drugs to completely eradicate parasites. This approach is broadly applicable to study the metabolic and growth dynamics in other host-pathogen interactions.

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Proteoglycans in host–pathogen interactions: molecular mechanisms and therapeutic implications

Expert Reviews in Molecular Medicine ◽

10.1017/s1462399409001367 ◽

2010 ◽

Vol 12 ◽

Cited By ~ 62

Author(s):

Allison H. Bartlett ◽

Pyong Woo Park

Keyword(s):

Cell Surface ◽

Virulence Factors ◽

Molecular Mechanisms ◽

Biological Significance ◽

Host Cells ◽

Microbial Pathogens ◽

Therapeutic Implications ◽

Core Proteins

Many microbial pathogens subvert proteoglycans for their adhesion to host tissues, invasion of host cells, infection of neighbouring cells, dissemination into the systemic circulation, and evasion of host defence mechanisms. Where studied, specific virulence factors mediate these proteoglycan–pathogen interactions, which are thus thought to affect the onset, progression and outcome of infection. Proteoglycans are composites of glycosaminoglycan (GAG) chains attached covalently to specific core proteins. Proteoglycans are expressed ubiquitously on the cell surface, in intracellular compartments, and in the extracellular matrix. GAGs mediate the majority of ligand-binding activities of proteoglycans, and many microbial pathogens elaborate cell-surface and secreted factors that interact with GAGs. Some pathogens also modulate the expression and function of proteoglycans through known virulence factors. Several GAG-binding pathogens can no longer attach to and invade host cells whose GAG expression has been reduced by mutagenesis or enzymatic treatment. Furthermore, GAG antagonists have been shown to inhibit microbial attachment and host cell entry in vitro and reduce virulence in vivo. Together, these observations underscore the biological significance of proteoglycan–pathogen interactions in infectious diseases.

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Characterization of Sec-Translocon-Dependent Extracytoplasmic Proteins of Rickettsia typhi

Journal of Bacteriology ◽

10.1128/jb.00794-08 ◽

2008 ◽

Vol 190 (18) ◽

pp. 6234-6242 ◽

Cited By ~ 19

Author(s):

Nicole C. Ammerman ◽

M. Sayeedur Rahman ◽

Abdu F. Azad

Keyword(s):

Host Cell ◽

Mammalian Cells ◽

Molecular Mechanisms ◽

Host Cells ◽

Transcriptional Analysis ◽

Mammalian Host ◽

Signal Peptides ◽

Cell Infection ◽

Rickettsia Typhi ◽

Sec Translocon

ABSTRACT As obligate intracellular, vector-borne bacteria, rickettsiae must adapt to both mammalian and arthropod host cell environments. Deciphering the molecular mechanisms of the interactions between rickettsiae and their host cells has largely been hindered by the genetic intractability of these organisms; however, research in other gram-negative pathogens has demonstrated that many bacterial determinants of attachment, entry, and pathogenesis are extracytoplasmic proteins. The annotations of several rickettsial genomes indicate the presence of homologs of the Sec translocon, the major route for bacterial protein secretion from the cytoplasm. For Rickettsia typhi, the etiologic agent of murine typhus, homologs of the Sec-translocon-associated proteins LepB, SecA, and LspA have been functionally characterized; therefore, the R. typhi Sec apparatus represents a mechanism for the secretion of rickettsial proteins, including virulence factors, into the extracytoplasmic environment. Our objective was to characterize such Sec-dependent R. typhi proteins in the context of a mammalian host cell infection. By using the web-based programs LipoP, SignalP, and Phobius, a total of 191 R. typhi proteins were predicted to contain signal peptides targeting them to the Sec translocon. Of these putative signal peptides, 102 were tested in an Escherichia coli-based alkaline phosphatase (PhoA) gene fusion system. Eighty-four of these candidates exhibited signal peptide activity in E. coli, and transcriptional analysis indicated that at least 54 of the R. typhi extracytoplasmic proteins undergo active gene expression during infections of HeLa cells. This work highlights a number of interesting proteins possibly involved in rickettsial growth and virulence in mammalian cells.

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The Glycan-Rich Outer Layer of the Cell Wall of Mycobacterium tuberculosis Acts as an Antiphagocytic Capsule Limiting the Association of the Bacterium with Macrophages

Infection and Immunity ◽

10.1128/iai.72.10.5676-5686.2004 ◽

2004 ◽

Vol 72 (10) ◽

pp. 5676-5686 ◽

Cited By ~ 86

Author(s):

Richard W. Stokes ◽

Raymond Norris-Jones ◽

Donald E. Brooks ◽

Terry J. Beveridge ◽

Dan Doxsee ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Surface Hydrophobicity ◽

Host Cells ◽

Microbial Pathogens ◽

Mammalian Host ◽

Human Macrophage ◽

Bacterial Surface ◽

Important Virulence Factor ◽

Complement Receptor 3 ◽

Macrophage Populations

ABSTRACT Mycobacterium tuberculosis, the causative agent of tuberculosis, is a facultative intracellular pathogen that infects macrophages and other host cells. We show that sonication of M. tuberculosis results in the removal of material from the surface capsule-like layer of the bacteria, resulting in an enhanced propensity of the bacteria to bind to macrophages. This effect is observed with disparate murine and human macrophage populations though, interestingly, not with freshly explanted alveolar macrophages. Enhanced binding to macrophages following sonication is significantly greater within members of the M. tuberculosis family (pathogens) than within the Mycobacterium avium complex (opportunistic pathogens) or for Mycobacterium smegmatis (saprophyte). Sonication does not affect the viability or the surface hydrophobicity of M. tuberculosis but does result in changes in surface charge and in the binding of mannose-specific lectins to the bacterial surface. The increased binding of sonicated M. tuberculosis was not mediated through complement receptor 3. These results provide evidence that the surface capsule on members of the M. tuberculosis family may be an important virulence factor involved in the survival of M. tuberculosis in the mammalian host. They also question the view that M. tuberculosis is readily ingested by any macrophage it encounters and support the contention that M. tuberculosis, like many other microbial pathogens, has an antiphagocytic capsule that limits and controls the interaction of the bacterium with macrophages.

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Plasmodium sporozoites require the protein B9 to invade hepatocytes

10.1101/2021.10.25.465731 ◽

2021 ◽

Author(s):

Priyanka Fernandes ◽

Manon Loubens ◽

Carine Marinach ◽

Romain Coppee ◽

Morgane Grand ◽

...

Keyword(s):

Protein Function ◽

Molecular Mechanisms ◽

Protein Complexes ◽

Protein A ◽

Blood Feeding ◽

Host Cells ◽

Infected Mosquito ◽

Mammalian Host ◽

Genetic Tagging ◽

Structural Levels

Plasmodium sporozoites are transmitted to a mammalian host during blood feeding by an infected mosquito and invade hepatocytes for initial replication of the parasite in the liver. This leads to the release of thousands of merozoites into the blood circulation and initiation of the pathogenic blood stages of malaria. Merozoite invasion of erythrocytes has been well characterized at the molecular and structural levels. In sharp contrast, the molecular mechanisms of sporozoite invasion of hepatocytes are poorly characterized. Here we report a new role during sporozoite entry for the B9 protein, a member of the 6-cysteine domain protein family. Using genetic tagging and gene deletion approaches in rodent malaria parasites, we show that B9 is secreted from sporozoite micronemes and is required for productive invasion of hepatocytes. Structural modelling indicates that the N-terminus of B9 forms a beta-propeller domain structurally related to CyRPA, a cysteine-rich protein forming an invasion complex with Rh5 and RIPR in P. falciparum merozoites. We provide evidence that the beta-propeller domain of B9 is essential for protein function during sporozoite entry and interacts with P36 and P52, both also essential for productive invasion of hepatocytes. Our results suggest that, despite using distinct sets of parasite and host entry factors, Plasmodium sporozoites and merozoites may share common structural modules to assemble protein complexes for invasion of host cells.

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Molecular mechanisms of cytoadherence in malaria

AJP Cell Physiology ◽

10.1152/ajpcell.1999.276.6.c1231 ◽

1999 ◽

Vol 276 (6) ◽

pp. C1231-C1242 ◽

Cited By ~ 113

Author(s):

May Ho ◽

Nicholas J. White

Keyword(s):

Adhesion Molecule ◽

Intracellular Signaling ◽

Molecular Mechanisms ◽

Multiorgan Failure ◽

Host Cells ◽

Microbial Pathogens ◽

Intercellular Adhesion Molecule ◽

Intercellular Adhesion Molecule 1 ◽

Metabolic Disturbances ◽

Adhesive Interactions

Microbial pathogens subvert host adhesion molecules to disseminate or to enter host cells to promote their own survival. One such subversion is the cytoadherence of Plasmodium falciparum-infected erythrocytes (IRBC) to vascular endothelium, which protects the parasite from being removed by the spleen. The process results in microcirculatory obstruction and subsequent hypoxia, metabolic disturbances, and multiorgan failure, which are detrimental to the host. Understanding the molecular events involved in these adhesive interactions is therefore critical both in terms of pathogenesis and implications for therapeutic intervention. Under physiological flow conditions, cytoadherence occurs in a stepwise fashion through parasite ligands expressed on the surface of IRBC and the endothelial receptors CD36, intercellular adhesion molecule-1 (ICAM-1), P-selectin, and vascular adhesion molecule-1. Moreover, rolling on ICAM-1 and P-selectin increases subsequent adhesion to CD36, indicating that receptors can act synergistically. Cytoadherence may activate intracellular signaling pathways in both endothelial cells and IRBC, leading to gene expression of mediators such as cytokines, which could modify the outcome of the infection.

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The Multiple Roles of Trogocytosis in Immunity, the Nervous System, and Development

BioMed Research International ◽

10.1155/2021/1601565 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Eileen Uribe-Querol ◽

Carlos Rosales

Keyword(s):

Nervous System ◽

Trichomonas Vaginalis ◽

Molecular Mechanisms ◽

Cell Communication ◽

Research Area ◽

Host Cells ◽

Microbial Pathogens ◽

Normal Functions ◽

The Central Nervous System ◽

Small Parts

Trogocytosis is a general biological process that involves one cell physically taking small parts of the membrane and other components from another cell. In trogocytosis, one cell seems to take little “bites” from another cell resulting in multiple outcomes from these cell-cell interactions. Trogocytosis was first described in protozoan parasites, which by taking pieces of host cells, kill them and cause tissue damage. Now, it is known that this process is also performed by cells of the immune system with important consequences such as cell communication and activation, elimination of microbial pathogens, and even control of cancer cells. More recently, trogocytosis has also been reported to occur in cells of the central nervous system and in various cells during development. Some of the molecules involved in phagocytosis also participate in trogocytosis. However, the molecular mechanisms that regulate trogocytosis are still a mystery. Elucidating these mechanisms is becoming a research area of much interest. For example, why neutrophils can engage trogocytosis to kill Trichomonas vaginalis parasites, but neutrophils use phagocytosis to eliminate already death parasites? Thus, trogocytosis is a significant process in normal physiology that multiple cells from different organisms use in various scenarios of health and disease. In this review, we present the basic principles known on the process of trogocytosis and discuss the importance in this process to host-pathogen interactions and to normal functions in the immune and nervous systems.

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SopB- and SifA-dependent shaping of the Salmonella-containing vacuole proteome in the social amoeba Dictyostelium discoideum

10.1101/2019.12.23.887745 ◽

2019 ◽

Author(s):

Camila Valenzuela ◽

Magdalena Gil ◽

Ítalo M. Urrutia ◽

Andrea Sabag ◽

Jost Enninga ◽

...

Keyword(s):

Dictyostelium Discoideum ◽

Molecular Mechanisms ◽

Intracellular Survival ◽

Effector Proteins ◽

Host Cells ◽

Mammalian Host ◽

Secretion Systems ◽

The Social ◽

Membrane Bound ◽

Type Three Secretion

AbstractThe ability of Salmonella to survive and replicate within mammalian host cells involves the generation of a membranous compartment known as the Salmonella-containing vacuole (SCV). Salmonella employs a number of effector proteins that are injected into host cells for SCV formation using its type-three secretion systems encoded in SPI-1 and SPI-2 (T3SSSPI-1 and T3SSSPI-2, respectively). Recently, we reported that S. Typhimurium requires T3SSSPI-1 and T3SSSPI-2 to survive in the model amoeba Dictyostelium discoideum. Despite these findings, the involved effector proteins have not been identified yet. Therefore, we evaluated the role of two major S. Typhimurium effectors SopB and SifA during D. discoideum intracellular niche formation. First, we established that S. Typhimurium resides in a vacuolar compartment within D. discoideum. Next, we isolated SCVs from amoebae infected with wild type or the ΔsopB and ΔsifA mutant strains of S. Typhimurium, and we characterized the composition of this compartment by quantitative proteomics. This comparative analysis suggests that S. Typhimurium requires SopB and SifA to modify the SCV proteome in order to generate a suitable intracellular niche in D. discoideum. Accordingly, we observed that SopB and SifA are needed for intracellular survival of S. Typhimurium in this organism. Thus, our results provide insight into the mechanisms employed by Salmonella to survive intracellularly in phagocytic amoebae.ImportanceThe molecular mechanisms involved in Salmonella survival to predation by phagocytic amoebae, such as D. discoideum, remains poorly understood. Although we established that S. Typhimurium requires two specialized type-three secretion systems to survive in D. discoideum, no effector protein has been implicated in this process so far. Here, we confirmed the presence of a membrane-bound compartment containing S. Typhimurium in D. discoideum, and purified the D. discoideum SCV to characterize the associated proteome. In doing so, we established a key role for effector proteins SopB and SifA in remodeling the protein content of the SCV that ultimately allow the intracellular survival of S. Typhimurium in D. discoideum. We also discuss similarities and differences with the proteomes of the human SCV. These findings contribute to unravel the mechanisms used by Salmonella to survive in the environment exploiting phagocytic amoebae as a reservoir.

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The novel Dbl homology/BAR domain protein, MsgA, of Talaromyces marneffei regulates yeast morphogenesis during growth inside host cells

10.1101/481408 ◽

2018 ◽

Author(s):

Harshini Weerasinghe ◽

Hayley E. Bugeja ◽

Alex Andrianopoulos

Keyword(s):

Pathogenic Fungi ◽

Host Cells ◽

Microbial Pathogens ◽

Mammalian Host ◽

Host Immune System ◽

Nucleotide Exchange ◽

Phagocytic Cells ◽

Macrophage Infection ◽

Bar Domain ◽

Talaromyces Marneffei

AbstractMicrobial pathogens have evolved many strategies to evade recognition by the host immune system, including the use of phagocytic cells as a niche within which to proliferate. Dimorphic pathogenic fungi employ an induced morphogenetic transition, switching from multicellular hyphae to unicellular yeast that are more compatible with intracellular growth. A switch to mammalian host body temperature (37°C) is a key trigger for the dimorphic switch. This study describes a novel gene, msgA, from the dimorphic fungal pathogen Talaromyces marneffei that controls cell morphology in response to host cues rather than temperature. The msgA gene is upregulated during murine macrophage infection, and deletion results in aberrant yeast morphology solely during growth inside macrophages. MsgA contains a Dbl homology domain, and a Bin, Amphiphysin, Rvs (BAR) domain instead of a Plekstrin homology domain typically associated with guanine nucleotide exchange factors (GEFs). The BAR domain is crucial in maintaining yeast morphology and cellular localisation during infection. The data suggests that MsgA does not act as a canonical GEF during macrophage infection and identifies a temperature independent pathway in T. marneffei that controls intracellular yeast morphogenesis.

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