Publications by authors named "Felipe Viela"

19 Publications

  • Page 1 of 1

Staphylococcus aureus vWF-binding protein triggers a strong interaction between clumping factor A and host vWF.

Commun Biol 2021 Apr 12;4(1):453. Epub 2021 Apr 12.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium.

The Staphylococcus aureus cell wall-anchored adhesin ClfA binds to the very large blood circulating protein, von Willebrand factor (vWF) via vWF-binding protein (vWbp), a secreted protein that does not bind the cell wall covalently. Here we perform force spectroscopy studies on living bacteria to unravel the molecular mechanism of this interaction. We discover that the presence of all three binding partners leads to very high binding forces (2000 pN), largely outperforming other known ternary complexes involving adhesins. Strikingly, our experiments indicate that a direct interaction involving features of the dock, lock and latch mechanism must occur between ClfA and vWF to sustain the extreme tensile strength of the ternary complex. Our results support a previously undescribed mechanism whereby vWbp activates a direct, ultra-strong interaction between ClfA and vWF. This intriguing interaction represents a potential target for therapeutic interventions, including synthetic peptides inhibiting the ultra-strong interactions between ClfA and its ligands.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s42003-021-01986-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8041789PMC
April 2021

AFM Unravels the Unique Adhesion Properties of the Type IVc Pilus Nanomachine.

Nano Lett 2021 04 23;21(7):3075-3082. Epub 2021 Mar 23.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Croix du Sud, 4-5, bte, L7.07.07., B-1348 Louvain-la-Neuve, Belgium.

Bacterial pili are proteinaceous motorized nanomachines that play various functional roles including surface adherence, bacterial motion, and virulence. The surface-contact sensor type IVc (or Tad) pilus is widely distributed in both Gram-positive and Gram-negative bacteria. In , this nanofilament, though crucial for surface colonization, has never been thoroughly investigated at the molecular level. As assembles several surface appendages at specific stages of the cell cycle, we designed a fluorescence-based screen to selectively study single piliated cells and combined it with atomic force microscopy and genetic manipulation to quantify the nanoscale adhesion of the type IVc pilus to hydrophobic substrates. We demonstrate that this nanofilament exhibits high stickiness compared to the canonical type IVa/b pili, resulting mostly from multiple hydrophobic interactions along the fiber length, and that it features nanospring mechanical properties. Our findings may be helpful to better understand the structure-function relationship of bacterial pilus nanomachines.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.1c00215DOI Listing
April 2021

Adhesion of to During Co-Infection Promotes Bacterial Dissemination Through the Host Immune Response.

Front Cell Infect Microbiol 2020 2;10:624839. Epub 2021 Feb 2.

Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Department of Biology, KU Leuven, Leuven, Belgium.

Interspecies interactions greatly influence the virulence, drug tolerance and ultimately the outcome of polymicrobial biofilm infections. A synergistic interaction is observed between the fungus and the bacterium . These species are both normal commensals of most healthy humans and co-exist in several niches of the host. However, under certain circumstances, they can cause hospital-acquired infections with high morbidity and mortality rates. Using a mouse model of oral co-infection, we previously showed that an oral infection with predisposes to a secondary systemic infection with . Here, we unraveled this intriguing mechanism of bacterial dissemination. Using static and dynamic adhesion assays in combination with single-cell force spectroscopy, we identified Als1 and Als3 adhesins as the molecular players involved in the interaction with and in subsequent bacterial dissemination. Remarkably, we identified the host immune response as a key element required for bacterial dissemination. We found that the level of immunosuppression of the host plays a critical yet paradoxical role in this process. In addition, secretion of candidalysin, the peptide responsible for immune activation and cell damage, is required for colonization and subsequent bacterial dissemination. The physical interaction with enhances bacterial uptake by phagocytic immune cells, thereby enabling an opportunity to disseminate.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fcimb.2020.624839DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7884861PMC
June 2021

Single-cell fluidic force microscopy reveals stress-dependent molecular interactions in yeast mating.

Commun Biol 2021 01 4;4(1):33. Epub 2021 Jan 4.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Croix du Sud, 4-5, bte L7.07.07, 1348, Louvain-la-Neuve, Belgium.

Sexual agglutinins of the budding yeast Saccharomyces cerevisiae are proteins mediating cell aggregation during mating. Complementary agglutinins expressed by cells of opposite mating types "a" and "α" bind together to promote agglutination and facilitate fusion of haploid cells. By means of an innovative single-cell manipulation assay combining fluidic force microscopy with force spectroscopy, we unravel the strength of single specific bonds between a- and α-agglutinins (~100 pN) which require pheromone induction. Prolonged cell-cell contact strongly increases adhesion between mating cells, likely resulting from an increased expression of agglutinins. In addition, we highlight the critical role of disulfide bonds of the a-agglutinin and of histidine residue H of α-agglutinin. Most interestingly, we find that mechanical tension enhances the interaction strength, pointing to a model where physical stress induces conformational changes in the agglutinins, from a weak-binding folded state, to a strong-binding extended state. Our single-cell technology shows promises for understanding and controlling the complex mechanism of yeast sexuality.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s42003-020-01498-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7782832PMC
January 2021

Stress-Induced Catch-Bonds to Enhance Bacterial Adhesion.

Trends Microbiol 2021 Apr 19;29(4):286-288. Epub 2020 Dec 19.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium. Electronic address:

Physical forces have a profound influence on bacterial cell physiology and disease. A striking example is the formation of catch-bonds that reinforce under mechanical stress. While mannose-binding by the Escherichia coli FimH adhesin has long been the only thoroughly studied microbial catch-bond, it has recently become clear that proteins from other species, such as staphylococci, are also engaged in such stress-dependent interactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.tim.2020.11.009DOI Listing
April 2021

Single-Molecule Analysis Demonstrates Stress-Enhanced Binding between Surface Protein IsdB and Host Cell Integrins.

Nano Lett 2020 12 25;20(12):8919-8925. Epub 2020 Nov 25.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium.

Binding of surface proteins to endothelial cell integrins plays essential roles in host cell adhesion and invasion, eventually leading to life-threatening diseases. The staphylococcal protein IsdB binds to β3-containing integrins through a mechanism that has never been thoroughly investigated. Here, we identify and characterize at the nanoscale a previously undescribed stress-dependent adhesion between IsdB and integrin αβ. The strength of single IsdB-αβ interactions is moderate (∼100 pN) under low stress, but it increases dramatically under high stress (∼1000-2000 pN) to exceed the forces traditionally reported for the binding between integrins and Arg-Gly-Asp (RGD) sequences. We suggest a mechanism where high mechanical stress induces conformational changes in the integrin from a low-affinity, weak binding state to a high-affinity, strong binding state. This single-molecule study highlights that direct adhesin-integrin interactions represent potential targets to fight staphylococcal infections.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.0c04015DOI Listing
December 2020

Force-clamp spectroscopy identifies a catch bond mechanism in a Gram-positive pathogen.

Nat Commun 2020 10 27;11(1):5431. Epub 2020 Oct 27.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Croix du Sud, 4-5, bte L7.07.07, B-1348, Louvain-la-Neuve, Belgium.

Physical forces have profound effects on cellular behavior, physiology, and disease. Perhaps the most intruiguing and fascinating example is the formation of catch-bonds that strengthen cellular adhesion under shear stresses. Today mannose-binding by the Escherichia coli FimH adhesin remains one of the rare microbial catch-bond thoroughly characterized at the molecular level. Here we provide a quantitative demonstration of a catch-bond in living Gram-positive pathogens using force-clamp spectroscopy. We show that the dock, lock, and latch interaction between staphylococcal surface protein SpsD and fibrinogen is strong, and exhibits an unusual catch-slip transition. The bond lifetime first grows with force, but ultimately decreases to behave as a slip bond beyond a critical force (~1 nN) that is orders of magnitude higher than for previously investigated complexes. This catch-bond, never reported for a staphylococcal adhesin, provides the pathogen with a mechanism to tightly control its adhesive function during colonization and infection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-020-19216-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7591895PMC
October 2020

The Molecular Complex between Staphylococcal Adhesin SpsD and Fibronectin Sustains Mechanical Forces in the Nanonewton Range.

mBio 2020 07 7;11(4). Epub 2020 Jul 7.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium

The bacterial pathogen is involved in canine otitis externa and pyoderma as well as in surgical wound and urinary tract infections. Invasion of canine epithelial cells is promoted by fibronectin (Fn)-binding proteins SpsD and SpsL through molecular interactions that are currently unknown. By means of single-molecule experiments, we discover that both adhesins have distinct molecular mechanisms for binding to Fn. We show that the SpsD-Fn interaction has a strength equivalent to that of a covalent bond (∼1.5 to 1.8 nN), which is an order of magnitude stronger than the binding force of classical receptor-ligand complexes. We suggest that this extreme mechanostability originates from the β-sheet organization of a tandem β-zipper. Upon binding to FnI modules, the intrinsically disordered binding sequences of SpsD would shift into an ordered structure by forming additional β-strands along triple peptide β-sheets in the Fn molecule. Dynamic force measurements reveal an unexpected behavior, i.e., that strong bonds are activated by mechanical tension as observed with catch bonds. By contrast, the SpsL-Fn interaction involves multiple weak bonds (∼0.2 nN) that rupture sequentially under force. Together with the recently described dock, lock, and latch complex, the ultrastrong interaction unraveled here is among the strongest noncovalent biological interaction measured to date. Our findings may find applications for the identification of inhibitory compounds to treat infections triggered by pathogens engaged in tandem β-zipper interactions. Binding of surface proteins SpsD and SpsL to fibronectin (Fn) plays a critical role in the invasion of canine epithelial cells. Here, we discover that both adhesins have different mechanisms for binding to Fn. The force required to separate SpsD from Fn is extremely strong, consistent with the unusual β-sheet organization of a high-affinity tandem β-zipper. By contrast, unbinding of the SpsL-Fn complex involves the sequential rupture of single weak bonds. Our findings may be of biological relevance as SpsD and SpsL are likely to play complementary roles during invasion. While the SpsD β-zipper supports strong bacterial adhesion and triggers invasion, the weak SpsL interaction would favor fast detachment, enabling the pathogen to colonize new sites.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/mBio.00371-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7343985PMC
July 2020

Nanomechanics of the molecular complex between staphylococcal adhesin SpsD and elastin.

Nanoscale 2020 Jul 24;12(26):13996-14003. Epub 2020 Jun 24.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium.

Staphylococcus pseudintermedius surface protein SpsD binds to extracellular matrix proteins to invade canine epithelial cells. Using single-molecule experiments, we show that SpsD engages in two modes of interaction with elastin that are tightly controlled by physical stress. Binding is weak (∼100 pN) at low tensile force (i.e. loading rate), but is dramatically enhanced (up to ∼1500 pN) by mechanical tension. Consistent with a "dock, lock, and latch" (DLL) mechanism, this force represents among the highest mechanical strengths known for a non-covalent biological interaction. The transition from weak to strong binding correlates with an increase in molecular stiffness but, surprisingly, with a decrease in molecular extension. This unanticipated mechanical behavior indicates that the adhesin is engaged in two distinct interaction mechanisms. Our results emphasize the crucial role of protein nanomechanics in the adhesion of staphylococci, and illustrate their wide diversity of force-dependent ligand-binding activities. These single-molecule mechanical experiments may contribute to the development of antiadhesion approaches to treat infections caused by S. pseudintermedius and other bacterial pathogens engaged in DLL interactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0nr02745fDOI Listing
July 2020

Fast chemical force microscopy demonstrates that glycopeptidolipids define nanodomains of varying hydrophobicity on mycobacteria.

Nanoscale Horiz 2020 06 21;5(6):944-953. Epub 2020 Apr 21.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium.

Mycobacterium abscessus is an emerging multidrug-resistant bacterial pathogen causing severe lung infections in cystic fibrosis patients. A remarkable trait of this mycobacterial species is its ability to form morphologically smooth (S) and rough (R) colonies. The S-to-R transition is caused by the loss of glycopeptidolipids (GPLs) in the outer layer of the cell envelope and correlates with an increase in cording and virulence. Despite the physiological and medical importance of this morphological transition, whether it involves changes in cell surface properties remains unknown. Herein, we combine recently developed quantitative imaging (QI) atomic force microscopy (AFM) with hydrophobic tips to quantitatively map the surface structure and hydrophobicity of M. abscessus at high spatiotemporal resolution, and to assess how these properties are modulated by the S-to-R transition and by treatment with an inhibitor of the mycolic acid transporter MmpL3. We discover that loss of GPLs leads to major modifications in surface hydrophobicity, without any apparent change in cell surface ultrastructure. While R bacilli are homogeneously hydrophobic, S bacilli feature unusual variations of nanoscale hydrophobic properties. These previously undescribed cell surface nanodomains are likely to play critical roles in bacterial adhesion, aggregation, phenotypic heterogeneity and transmission, and in turn in virulence and pathogenicity. Our study also suggests that MmpL3 inhibitors show promise in nanomedicine as chemotherapeutic agents to interfere with the highly hydrophobic nature of the mycobacterial cell wall. The advantages of QI-AFM with hydrophobic tips are the ability to map chemical and structural properties simultaneously and at high resolution, applicable to a wide range of biosystems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9nh00736aDOI Listing
June 2020

How Microbes Use Force To Control Adhesion.

J Bacteriol 2020 05 27;202(12). Epub 2020 May 27.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium

Microbial adhesion and biofilm formation are usually studied using molecular and cellular biology assays, optical and electron microscopy, or laminar flow chamber experiments. Today, atomic force microscopy (AFM) represents a valuable addition to these approaches, enabling the measurement of forces involved in microbial adhesion at the single-molecule level. In this minireview, we discuss recent discoveries made applying state-of-the-art AFM techniques to microbial specimens in order to understand the strength and dynamics of adhesive interactions. These studies shed new light on the molecular mechanisms of adhesion and demonstrate an intimate relationship between force and function in microbial adhesins.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JB.00125-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7253613PMC
May 2020

What makes bacterial pathogens so sticky?

Mol Microbiol 2020 04 16;113(4):683-690. Epub 2020 Jan 16.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium.

Pathogenic bacteria use a variety of cell surface adhesins to promote binding to host tissues and protein-coated biomaterials, as well as cell-cell aggregation. These cellular interactions represent the first essential step that leads to host colonization and infection. Atomic force microscopy (AFM) has greatly contributed to increase our understanding of the specific interactions at play during microbial adhesion, down to the single-molecule level. A key asset of AFM is that adhesive interactions are studied under mechanical force, which is highly relevant as surface-attached pathogens are often exposed to physical stresses in the human body. These studies have identified sophisticated binding mechanisms in adhesins, which represent promising new targets for antiadhesion therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/mmi.14448DOI Listing
April 2020

Mechanostability of the Fibrinogen Bridge between Staphylococcal Surface Protein ClfA and Endothelial Cell Integrin αβ.

Nano Lett 2019 10 18;19(10):7400-7410. Epub 2019 Sep 18.

Louvain Institute of Biomolecular Science and Technology, UCLouvain , Croix du Sud, 4-5, bte L7.07.06, B-1348 Louvain-la-Neuve , Belgium.

Binding of the surface protein clumping factor A (ClfA) to endothelial cell integrin αβ plays a crucial role during sepsis, by causing endothelial cell apoptosis and loss of barrier integrity. ClfA uses the blood plasma protein fibrinogen (Fg) to bind to αβ but how this is achieved at the molecular level is not known. Here we investigate the mechanical strength of the three-component ClfA-Fg-αβ interaction on living bacteria, by means of single-molecule experiments. We find that the ClfA-Fg-αβ ternary complex is extremely stable, being able to sustain forces (∼800 pN) that are much stronger than those of classical bonds between integrins and the Arg-Gly-Asp (RGD) tripeptide sequence (∼100 pN). Adhesion forces between single bacteria and αβ are strongly inhibited by an anti-αβ antibody, the RGD peptide, and the cyclic RGD peptide cilengitide, showing that formation of the complex involves RGD-dependent binding sites and can be efficiently inhibited by αβ blockers. Collectively, our experiments favor a binding mechanism involving the extraordinary elasticity of Fg. In the absence of mechanical stress, RGD sequences in the Aα chains mediate weak binding to αβ, whereas under high mechanical stress exposure of cryptic Aα chain RGD sequences leads to extremely strong binding to the integrin. Our results identify an unexpected and previously undescribed force-dependent binding mechanism between ClfA and αβ on endothelial cells, which could represent a potential target to fight staphylococcal bloodstream infections.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.9b03080DOI Listing
October 2019

Bacterial pathogens under high-tension: adhesion to von Willebrand factor is activated by force.

Microb Cell 2019 Jun 11;6(7):321-323. Epub 2019 Jun 11.

Institute of Life Sciences, Université catholique de Louvain, Croix du Sud, 4-5, bte L7.07.06, B-1348 Louvain-la-Neuve, Belgium.

Attachment of to platelets and endothelial cells involves binding of bacterial cell surface protein A (SpA) to the large plasma glycoprotein von Willebrand factor (vWF). SpA-mediated bacterial adhesion to vWF is controlled by fluid shear stress, yet little is currently known about the underlying molecular mechanism. In a recent publication, we showed that the SpA-vWF interaction is tightly regulated by mechanical force. By means of single-molecule pulling experiments, we found that the SpA-vWF bond is extremely strong, being able to resist forces which largely outperform the strength of typical receptor-ligand bonds. In line with flow experiments, strong adhesion is activated by mechanical tension. These results suggest that force induces conformational changes in the vWF molecule, from a globular to an extended state, leading to the exposure of cryptic binding sites to which SpA strongly binds. This force-sensitive mechanism may largely contribute to help bacteria to resist shear stress of flowing blood during infection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.15698/mic2019.07.684DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6600117PMC
June 2019

Binding of Protein A to von Willebrand Factor Is Regulated by Mechanical Force.

mBio 2019 04 30;10(2). Epub 2019 Apr 30.

Institute of Life Sciences, Université Catholique de Louvain, Louvain-la-Neuve, Belgium

Binding of to the large plasma glycoprotein von Willebrand factor (vWF) is controlled by hydrodynamic flow conditions. Currently, we know little about the molecular details of this shear-stress-dependent interaction. Using single-molecule atomic force microscopy, we demonstrate that vWF binds to the surface protein A (SpA) via a previously undescribed force-sensitive mechanism. We identify an extremely strong SpA-vWF interaction, capable of withstanding forces of ∼2 nN, both in laboratory and in clinically relevant methicillin-resistant (MRSA) strains. Strong bonds are activated by mechanical stress, consistent with flow experiments revealing that bacteria adhere in larger amounts to vWF surfaces when the shear rate is increased. We suggest that force-enhanced adhesion may involve conformational changes in vWF. Under force, elongation of vWF may lead to the exposure of a high-affinity cryptic SpA-binding site to which bacteria firmly attach. In addition, force-induced structural changes in the SpA domains may also promote strong, high-affinity binding. This force-regulated interaction might be of medical importance as it may play a role in bacterial adherence to platelets and to damaged blood vessels. protein A (SpA) binds to von Willebrand factor (vWF) under flow. While vWF binding to SpA plays a role in adherence to platelets and endothelial cells under shear stress, the molecular basis of this stress-dependent interaction has not yet been elucidated. Here we show that the SpA-vWF interaction is regulated by a new force-dependent mechanism. The results suggest that mechanical extension of vWF may lead to the exposure of a high-affinity cryptic SpA-binding site, consistent with the shear force-controlled functions of vWF. Moreover, strong binding may be promoted by force-induced structural changes in the SpA domains. This study highlights the role of mechanoregulation in controlling the adhesion of and shows promise for the design of small inhibitors capable of blocking colonization under high shear stress.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/mBio.00555-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6495375PMC
April 2019

Single-imprint moth-eye anti-reflective and self-cleaning film with enhanced resistance.

Nanoscale 2018 Aug;10(33):15496-15504

Madrid Institute for Advanced Studies in Nanoscience (IMDEA Nanoscience), C/Faraday 9, Ciudad Universitaria de Cantoblanco. 28049 Madrid, Spain.

Antireflective transparent materials are essential for a myriad of applications to allow for clear vision and efficient light transmission. Despite the advances, efficient and low cost solutions to clean antireflective surfaces have remained elusive. Here, we present a practical approach that enables the production of antireflective polymer surfaces based on moth-eye inspired features incorporating photoinduced self-cleaning properties and enhanced mechanical resistance. The methodology involves the fabrication of sub-wavelength moth-eye nanofeatures onto transparent surface composite films in a combined processing step of nanoparticle coating and surface nanoimprinting. The resulting surfaces reduced the optical reflection losses from values of 9% of typical PMMA plastic films to an optimum value of 0.6% in the case of double-sided moth-eye nanoimprinted films. The composite moth-eye topography also showed an improved stiffness and scratch resistance. This technology represents a significant advancement not limited by scale, for the development of antireflective films for low cost application products.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c8nr02386gDOI Listing
August 2018

Mechanical Forces Guiding Staphylococcus aureus Cellular Invasion.

ACS Nano 2018 04 10;12(4):3609-3622. Epub 2018 Apr 10.

Institute of Life Sciences , Université catholique de Louvain , Croix du Sud, 4-5, bte L7.07.06 , B-1348 Louvain-la-Neuve , Belgium.

Staphylococcus aureus can invade various types of mammalian cells, thereby enabling it to evade host immune defenses and antibiotics. The current model for cellular invasion involves the interaction between the bacterial cell surface located fibronectin (Fn)-binding proteins (FnBPA and FnBPB) and the α5β1 integrin in the host cell membrane. While it is believed that the extracellular matrix protein Fn serves as a bridging molecule between FnBPs and integrins, the fundamental forces involved are not known. Using single-cell and single-molecule experiments, we unravel the molecular forces guiding S. aureus cellular invasion, focusing on the prototypical three-component FnBPA-Fn-integrin interaction. We show that FnBPA mediates bacterial adhesion to soluble Fn via strong forces (∼1500 pN), consistent with a high-affinity tandem β-zipper, and that the FnBPA-Fn complex further binds to immobilized α5β1 integrins with a strength much higher than that of the classical Fn-integrin bond (∼100 pN). The high mechanical stability of the Fn bridge favors an invasion model in which Fn binding by FnBPA leads to the exposure of cryptic integrin-binding sites via allosteric activation, which in turn engage in a strong interaction with integrins. This activation mechanism emphasizes the importance of protein mechanobiology in regulating bacterial-host adhesion. We also find that Fn-dependent adhesion between S. aureus and endothelial cells strengthens with time, suggesting that internalization occurs within a few minutes. Collectively, our results provide a molecular foundation for the ability of FnBPA to trigger host cell invasion by S. aureus and offer promising prospects for the development of therapeutic approaches against intracellular pathogens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.8b00716DOI Listing
April 2018

Moth-eye mimetic cytocompatible bactericidal nanotopography: a convergent design.

Bioinspir Biomim 2018 02 27;13(2):026011. Epub 2018 Feb 27.

Madrid Institute for Advanced Studies in Nanoscience (IMDEA Nanoscience), C/Faraday 9, Ciudad Universitaria de Cantoblanco, Madrid 28049, Spain.

The rapid emergence of antibiotic resistant bacteria has prompted the need for radically different approaches to combat bacterial infections. Among these, bioinspired surface topographies have emerged as an effective sustainable strategy to deter bacterial infection. This study demonstrates the bactericidal activity and cytocompatibility of the moth-eye mimetic topography produced by thermal polymer nanoimprinting. The moth-eye topography was found to have bactericidal capabilities against Gram negative and Gram positive bacteria. Electron microscopy imaging revealed the bactericidal effect caused by mechanical rupture of the bacteria wall inflicted by the topography on the adhered cells. The cytocompatibility of the surfaces was evidenced by assessing the proliferation and morphology of keratinocytes cultured on the nanotopography. The technology meets important needs in medical implant technology for materials that not only have good biocompatibility but also antibacterial properties for reducing the risk of infections and related health complications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1748-3190/aaa903DOI Listing
February 2018

Multifunctional Nano-engineered Polymer Surfaces with Enhanced Mechanical Resistance and Superhydrophobicity.

Sci Rep 2017 03 6;7:43450. Epub 2017 Mar 6.

Madrid Institute for Advanced Studies in Nanoscience (IMDEA Nanoscience), C/Faraday 9, Ciudad Universitaria de Cantoblanco. 28049 Madrid, Spain.

This paper presents a multifunctional polymer surface that provides superhydrophobicity and self-cleaning functions together with an enhancement in mechanical and electrical performance. These functionalities are produced by nanoimprinting high aspect ratio pillar arrays on polymeric matrix incorporating functional reinforcing elements. Two distinct matrix-filler systems are investigated specifically, Carbon Nanotube reinforced Polystyrene (CNT-PS) and Reduced Graphene Oxide reinforced Polyvinylidene Difluoride (RGO-PVDF). Mechanical characterization of the topographies by quantitative nanoindentation and nanoscratch tests are performed to evidence a considerable increase in stiffness, Young's modulus and critical failure load with respect to the pristine polymers. The improvement on the mechanical properties is rationalized in terms of effective dispersion and penetration of the fillers into the imprinted structures as determined by confocal Raman and SEM studies. In addition, an increase in the degree of crystallization for the PVDF-RGO imprinted nanocomposite possibly accounts for the larger enhancement observed. Improvement of the mechanical ruggedness of functional textured surfaces with appropriate fillers will enable the implementation of multifunctional nanotextured materials in real applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/srep43450DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5337973PMC
March 2017