scholarly journals Plasma fibronectin stabilizes Borrelia burgdorferi–endothelial interactions under vascular shear stress by a catch-bond mechanism

2017 ◽  
Vol 114 (17) ◽  
pp. E3490-E3498 ◽  
Author(s):  
Alexandra F. Niddam ◽  
Rhodaba Ebady ◽  
Anil Bansal ◽  
Anne Koehler ◽  
Boris Hinz ◽  
...  
Keyword(s):  
Shear Stress ◽  
Borrelia Burgdorferi ◽  
Live Cell Imaging ◽  
Host Cells ◽  
Catch Bond ◽  
Bacterial Dissemination ◽  
Bacterial Interaction ◽  
Blood Constituent ◽  
Formed Part ◽  
Bond Mechanism

Bacterial dissemination via the cardiovascular system is the most common cause of infection mortality. A key step in dissemination is bacterial interaction with endothelia lining blood vessels, which is physically challenging because of the shear stress generated by blood flow. Association of host cells such as leukocytes and platelets with endothelia under vascular shear stress requires mechanically specialized interaction mechanisms, including force-strengthened catch bonds. However, the biomechanical mechanisms supporting vascular interactions of most bacterial pathogens are undefined. Fibronectin (Fn), a ubiquitous host molecule targeted by many pathogens, promotes vascular interactions of the Lyme disease spirochete Borrelia burgdorferi. Here, we investigated how B. burgdorferi exploits Fn to interact with endothelia under physiological shear stress, using recently developed live cell imaging and particle-tracking methods for studying bacterial–endothelial interaction biomechanics. We found that B. burgdorferi does not primarily target insoluble matrix Fn deposited on endothelial surfaces but, instead, recruits and induces polymerization of soluble plasma Fn (pFn), an abundant protein in blood plasma that is normally soluble and nonadhesive. Under physiological shear stress, caps of polymerized pFn at bacterial poles formed part of mechanically loaded adhesion complexes, and pFn strengthened and stabilized interactions by a catch-bond mechanism. These results show that B. burgdorferi can transform a ubiquitous but normally nonadhesive blood constituent to increase the efficiency, strength, and stability of bacterial interactions with vascular surfaces. Similar mechanisms may promote dissemination of other Fn-binding pathogens.

How Bacteria Bind More Strongly Under Mechanical Force: The Catch-Bond FimH

2003 ◽  
Author(s):  
Wendy E. Thomas ◽  
Evgeni V. Sokurenko ◽  
Viola Vogel
Keyword(s):  
Shear Stress ◽  
Structural Model ◽  
Intestinal Bacteria ◽  
Mechanical Force ◽  
The Body ◽  
Site Directed Mutagenesis ◽  
Host Cells ◽  
Structural Variations ◽  
Catch Bond ◽  
Static Conditions

We study a protein that responds to mechanical force in most striking manner. We demonstrate that Escherichia coli bacteria need shear stress to bind to certain tissues and model surfaces; they bind strongest precisely when the body tries to wash them off. We have determined that the protein responsible for this behavior is FimH, a ubiquitous adhesion protein in intestinal bacteria that mediates adhesion to host cells via the carbohydrate mannose. Although mechanical force noramlly decreases bond lifetimes, we have shown that the bond betweeen FimH and simple mono-mannose receptors is s “catch-bond” that lasts longer under shear stress. In contrast, structural variations in either FimH or the receptor cause a stronger mode of adhesion in static conditions with little or no activation under force. We derive a structural for how mechanical force switches FimH to a strong binding mode by using steered molecular dynamics simulations, and validate the predictions with subsequent site-directed mutagenesis. The physiological consequences as well as the engineering principles suggested by the structural model will be discussed.

scholarly journals Listeriolysin O: from bazooka to Swiss army knife

2017 ◽  
Vol 372 (1726) ◽  
pp. 20160222 ◽  
Author(s):  
Suzanne E. Osborne ◽  
John H. Brumell
Keyword(s):  
Systemic Disease ◽  
Membrane Damage ◽  
Host Cells ◽  
Listeriolysin O ◽  
Tissue Destruction ◽  
Membrane Repair ◽  
Membrane Pores ◽  
Bacterial Dissemination ◽  
Versatile Tool ◽  
Cell Spread

Listeria monocytogenes ( Lm ) is a Gram-positive facultative intracellular pathogen. Infections in humans can lead to listeriosis, a systemic disease with a high mortality rate. One important mechanism of Lm dissemination involves cell-to-cell spread after bacteria have entered the cytosol of host cells. Listeriolysin O (LLO; encoded by the hly gene) is a virulence factor present in Lm that plays a central role in the cell-to-cell spread process. LLO is a member of the cholesterol-dependent cytolysin (CDC) family of toxins that were initially thought to promote disease largely by inducing cell death and tissue destruction—essentially acting like a ‘bazooka’. This view was supported by structural studies showing CDCs can form large pores in membranes. However, it is now appreciated that LLO has many subtle activities during Lm infection of host cells, and many of these likely do not involve large pores, but rather small membrane perforations. It is also appreciated that membrane repair pathways of host cells play a major role in limiting membrane damage by LLO and other toxins. LLO is now thought to represent a ‘Swiss army knife’, a versatile tool that allows Lm to induce many membrane alterations and cellular responses that promote bacterial dissemination during infection. This article is part of the themed issue ‘Membrane pores: from structure and assembly, to medicine and technology’.

scholarly journals Effect of loading conditions on the dissociation behaviour of catch bond clusters

2011 ◽  
Vol 9 (70) ◽  
pp. 928-937 ◽  
Author(s):  
L. Sun ◽  
Q. H. Cheng ◽  
H. J. Gao ◽  
Y. W. Zhang
Keyword(s):  
Multiple Bond ◽  
Tensile Load ◽  
Load Sharing ◽  
Loading Conditions ◽  
Bond Behaviour ◽  
Catch Bond ◽  
Linear Load ◽  
Bond System ◽  
Bond Mechanism ◽  
Catch Bonds

Under increasing tensile load, the lifetime of a single catch bond counterintuitively increases up to a maximum and then decreases exponentially like a slip bond. So far, the characteristics of single catch bond dissociation have been extensively studied. However, it remains unclear how a cluster of catch bonds behaves under tensile load. We perform computational analysis on the following models to examine the characteristics of clustered catch bonds: (i) clusters of catch bonds with equal load sharing, (ii) clusters of catch bonds with linear load sharing, and (iii) clusters of catch bonds in micropipette-manipulated cell detachment. We focus on the differences between the slip and catch bond clusters, identifying the critical factors for exhibiting the characteristics of catch bond mechanism for the multiple-bond system. Our computation reveals that for a multiple-bond cluster, the catch bond behaviour could only manifest itself under relatively uniform loading conditions and at certain stages of decohesion, explaining the difficulties in observing the catch bond mechanism under real biological conditions.

scholarly journals Live-Cell Imaging of Phosphoinositide Dynamics and Membrane Architecture during Legionella Infection

mBio ◽  
2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Stephen Weber ◽  
Maria Wagner ◽  
Hubert Hilbi
Keyword(s):  
Host Cell ◽  
Legionella Pneumophila ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Effector Proteins ◽  
Host Cells ◽  
Wild Type ◽  
Host Cell Membrane ◽  
Content Type ◽  
Temporal And Spatial

ABSTRACTThe causative agent of Legionnaires’ disease,Legionella pneumophila, replicates in amoebae and macrophages in a distinct membrane-bound compartment, theLegionella-containing vacuole (LCV). LCV formation is governed by the bacterial Icm/Dot type IV secretion system that translocates ~300 different “effector” proteins into host cells. Some of the translocated effectors anchor to the LCV membrane via phosphoinositide (PI) lipids. Here, we use the soil amoebaDictyostelium discoideum, producing fluorescent PI probes, to analyze the LCV PI dynamics by live-cell imaging. Upon uptake of wild-type or Icm/Dot-deficientL. pneumophila, PtdIns(3,4,5)P3transiently accumulated for an average of 40 s on early phagosomes, which acquired PtdIns(3)Pwithin 1 min after uptake. Whereas phagosomes containing ΔicmTmutant bacteria remained decorated with PtdIns(3)P, more than 80% of wild-type LCVs gradually lost this PI within 2 h. The process was accompanied by a major rearrangement of PtdIns(3)P-positive membranes condensing to the cell center. PtdIns(4)Ptransiently localized to early phagosomes harboring wild-type or ΔicmT L. pneumophilaand was cleared within minutes after uptake. During the following 2 h, PtdIns(4)Psteadily accumulated only on wild-type LCVs, which maintained a discrete PtdIns(4)Pidentity spatially separated from calnexin-positive endoplasmic reticulum (ER) for at least 8 h. The separation of PtdIns(4)P-positive and ER membranes was even more pronounced for LCVs harboring ΔsidC-sdcAmutant bacteria defective for ER recruitment, without affecting initial bacterial replication in the pathogen vacuole. These findings elucidate the temporal and spatial dynamics of PI lipids implicated in LCV formation and provide insight into host cell membrane and effector protein interactions.IMPORTANCEThe environmental bacteriumLegionella pneumophilais the causative agent of Legionnaires’ pneumonia. The bacteria form in free-living amoebae and mammalian immune cells a replication-permissive compartment, theLegionella-containing vacuole (LCV). To subvert host cell processes, the bacteria secrete the amazing number of ~300 different proteins into host cells. Some of these proteins bind phosphoinositide (PI) lipids to decorate the LCV. PI lipids are crucial factors involved in host cell membrane dynamics and LCV formation. UsingDictyosteliumamoebae producing one or two distinct fluorescent probes, we elucidated the dynamic LCV PI pattern in high temporal and spatial resolution. Notably, the endocytic PI lipid PtdIns(3)Pwas slowly cleared from LCVs, thus incapacitating the host cell’s digestive machinery, while PtdIns(4)Pgradually accumulated on the LCV, enabling critical interactions with host organelles. The LCV PI pattern underlies the spatiotemporal configuration of bacterial effector proteins and therefore represents a crucial aspect of LCV formation.

scholarly journals 3-Dimensional Organization and Dynamics of the Microsporidian Polar Tube Invasion Machinery

2020 ◽  
Author(s):  
Pattana Jaroenlak ◽  
Michael Cammer ◽  
Alina Davydov ◽  
Joseph Sall ◽  
Mahrukh Usmani ◽  
...  
Keyword(s):  
Live Cell Imaging ◽  
High Speed ◽  
Cell Imaging ◽  
Host Cells ◽  
Polar Tube ◽  
3 Dimensional ◽  
Germination Process ◽  
Block Face ◽  
Very High

Microsporidia, a divergent group of single-celled eukaryotic parasites, harness a specialized harpoon-like invasion apparatus called the polar tube (PT) to gain entry into host cells. The PT is tightly coiled within the transmissible extracellular spore, and is about 20 times the length of the spore. Once triggered, the PT is rapidly ejected and is thought to penetrate the host cell, acting as a conduit for the transfer of infectious cargo into the host. The organization of this specialized infection apparatus in the spore, how it is deployed, and how the nucleus and other large cargo are transported through the narrow PT are not well understood. Here we use serial block-face scanning electron microscopy to reveal the 3-dimensional architecture of the PT and its relative spatial orientation to other organelles within the spore. Using high-speed optical microscopy, we also capture and quantify the entire PT germination process in vitro. Our results show that the emerging PT experiences very high accelerating forces to reach velocities exceeding 300 μm.s-1, and that firing kinetics differ markedly between species. Live-cell imaging reveals that the nucleus, which is approximately 7 times larger than the diameter of the PT, undergoes extreme deformation to fit through the narrow tube, and moves at speeds comparable to PT extension. Our study sheds new light on the 3-dimensional organization, dynamics, and mechanism of PT extrusion, and shows how infectious cargo moves through the tube to initiate infection.

scholarly journals Spatial and temporal localization of immune transcripts defines hallmarks and diversity in the tuberculosis granuloma

2019 ◽  
Author(s):  
Berit Carow ◽  
Thomas Hauling ◽  
Xiaoyan Qian ◽  
Igor Kramnik ◽  
Mats Nilsson ◽  
...  
Keyword(s):  
T Cells ◽  
Mycobacterium Tuberculosis ◽  
B Cell ◽  
Host Cells ◽  
Activated Macrophages ◽  
Activated T Cells ◽  
Cellular Resolution ◽  
Bacterial Dissemination ◽  
Temporal Localization

AbstractGranulomas are the pathological hallmark of Tuberculosis (TB), and the niche in which bacilli can either grow and disseminate or the immunological microenvironment in which host cells interact to prevent bacterial dissemination. Here, after in situ sequencing, thirty-four immune transcripts in lung sections fromMycobacterium tuberculosis-infected mice were aligned to the tissue morphology at cellular resolution, allowing the analysis of local immune interactions in the granuloma.Co-localizing transcript networks at <10 μm in C57BL/6 mouse granulomas increased in complexity with time after infection. B-cell clusters developed late after infection. Transcripts from activated macrophages were enriched at subcellular distances fromM. tuberculosis. Encapsulated C3HeB/FeJ granulomas showed necrotic centers with transcripts associated with immunosuppression (foxp3, il10), while those in the granuloma rims associated with activated T cells and macrophages. Highly diverse networks with common interactors were observed in similar lesions.Thus, different immune landscapes ofM. tuberculosisgranulomas depending on the time after infection, the histopathological features of the lesion and the proximity to bacteria were here defined.

scholarly journals High force catch bond mechanism of bacterial adhesion in the human gut

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhaowei Liu ◽  
Haipei Liu ◽  
Andrés M. Vera ◽  
Rafael C. Bernardi ◽  
Philip Tinnefeld ◽  
...  
Keyword(s):  
Bacterial Adhesion ◽  
Human Gut ◽  
Catch Bond ◽  
Bond Mechanism

scholarly journals Catch-Bond Mechanism of Force-Enhanced Adhesion: Counterintuitive, Elusive, but … Widespread?

2008 ◽  
Vol 4 (4) ◽  
pp. 314-323 ◽  
Author(s):  
Evgeni V. Sokurenko ◽  
Viola Vogel ◽  
Wendy E. Thomas
Keyword(s):  
Catch Bond ◽  
Bond Mechanism

scholarly journals Effect of calcium on the interaction of Acinetobacter baumannii with human respiratory epithelial cells

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Yi Chen ◽  
Tingjun Shao ◽  
Sanhua Fang ◽  
Ping Pan ◽  
Jiahui Jiang ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Acinetobacter Baumannii ◽  
Host Cells ◽  
Effective Control ◽  
Respiratory Epithelial Cells ◽  
Cellular Analysis ◽  
Bacterial Interaction ◽  
Dependent Cell ◽  
Human Respiratory Epithelial Cells ◽  
Respiratory Epithelial

Abstract Background Investigating the factors that influence Acinetobacter baumannii(Ab) adhesion/invasion of host cells is important to understand its pathogenicity. Metal cations have been shown to play an important role in regulating the biofilm formation and increasing the virulence of Ab; however, the effect of calcium on host-bacterial interaction has yet to be clarified. Here, the dynamic process of the interaction between Ab and human respiratory epithelial cells and the effect of calcium on host-bacterial interaction were explored using microscopic imaging, quantitative PCR and real time cellular analysis (RTCA). Results The concentration of calcium, multiplicity of infection and co-culture time were all demonstrated to have effects on host-bacterial interaction. A unique “double peak” phenomenon changed to a sharp “single peak” phenomenon during the process of Ab infection under the effect of calcium was observed in the time-dependent cell response profiles. Moreover, calcium can increase Ab adhesion/invasion of epithelial cells by regulating the expression of Ab-related genes (ompA, bfmRS, abaI). Conclusions Effective control of calcium concentrations can provide new approaches for the prevention and treatment of multi-drug resistant Ab.

scholarly journals Borrelia burgdorferi RevA Significantly Affects Pathogenicity and Host Response in the Mouse Model of Lyme Disease

2015 ◽  
Vol 83 (9) ◽  
pp. 3675-3683 ◽  
Author(s):  
Rebecca Byram ◽  
Robert A. Gaultney ◽  
Angela M. Floden ◽  
Christopher Hellekson ◽  
Brandee L. Stone ◽  
...  
Keyword(s):  
Lyme Disease ◽  
Borrelia Burgdorferi ◽  
Host Response ◽  
Collagen Deposition ◽  
Wild Type ◽  
Content Type ◽  
Cardiac Tissues ◽  
Monocyte Chemoattractant ◽  
Bacterial Interaction ◽  
Mammalian Infection

The Lyme disease spirochete,Borrelia burgdorferi, expresses RevA and numerous outer surface lipoproteins during mammalian infection. As an adhesin that promotes bacterial interaction with fibronectin, RevA is poised to interact with the extracellular matrix of the host. To further define the role(s) of RevA during mammalian infection, we created a mutant that is unable to produce RevA. The mutant was still infectious to mice, although it was significantly less well able to infect cardiac tissues. Complementation of the mutant with a wild-typerevAgene restored heart infectivity to wild-type levels. Additionally,revAmutants led to increased evidence of arthritis, with increased fibrotic collagen deposition in tibiotarsal joints. The mutants also induced increased levels of the chemokine CCL2, a monocyte chemoattractant, in serum, and this increase was abolished in the complemented strain. Therefore, whilerevAis not absolutely essential for infection, deletion ofrevAhad distinct effects on dissemination, arthritis severity, and host response.

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