Identification of Lysine Residues in the Borrelia burgdorferi DbpA Adhesin Required for Murine Infection

ABSTRACTDecorin-binding protein A (DbpA) ofBorrelia burgdorferimediates bacterial adhesion to heparin and dermatan sulfate associated with decorin. Lysines K82, K163, and K170 of DbpA are known to be important forin vitrointeraction with decorin, and the DbpA structure, initially solved by nuclear magnetic resonance (NMR) spectroscopy, suggests these lysine residues colocalize in a pocket near the C terminus of the protein. In the current study, we solved the structure of DbpA fromB. burgdorferistrain 297 using X-ray crystallography and confirmed the existing NMR structural data.In vitrobinding experiments confirmed that recombinant DbpA proteins with mutations in K82, K163, or K170 did not bind decorin, which was due to an inability to interact with dermatan sulfate. Most importantly, we determined that thein vitrobinding defect observed upon mutation of K82, K163, or K170 in DbpA also led to a defect during infection. The infectivity ofB. burgdorferiexpressing individualdbpAlysine point mutants was assessed in mice challenged via needle inoculation. Murine infection studies showed that strains expressingdbpAwith mutations in K82, K163, and K170 were significantly attenuated and could not be cultured from any tissue. Proper expression and cellular localization of the mutated DbpA proteins were examined, and NMR spectroscopy determined that the mutant DbpA proteins were structurally similar to wild-type DbpA. Taken together, these data showed that lysines K82, K163, and K170 potentiate the binding of DbpA to dermatan sulfate and that an interaction(s) mediated by these lysines is essential forB. burgdorferimurine infection.

Download Full-text

Use of an Endogenous Plasmid Locus for Stable intransComplementation in Borrelia burgdorferi

Applied and Environmental Microbiology ◽

10.1128/aem.03657-14 ◽

2014 ◽

Vol 81 (3) ◽

pp. 1038-1046 ◽

Cited By ~ 5

Author(s):

Irene N. Kasumba ◽

Aaron Bestor ◽

Kit Tilly ◽

Patricia A. Rosa

Keyword(s):

Borrelia Burgdorferi ◽

Shuttle Vector ◽

Targeted Mutagenesis ◽

Multiple Cloning Site ◽

Stable Gene ◽

Content Type ◽

Shuttle Vectors ◽

Stable Maintenance

ABSTRACTTargeted mutagenesis and complementation are important tools for studying genes of unknown function in the Lyme disease spirocheteBorrelia burgdorferi. A standard method of complementation is reintroduction of a wild-type copy of the targeted gene on a shuttle vector. However, shuttle vectors are present at higher copy numbers thanB. burgdorferiplasmids and are potentially unstable in the absence of selection, thereby complicating analyses in the mouse-tick infectious cycle.B. burgdorferihas over 20 plasmids, with some, such as linear plasmid 25 (lp25), carrying genes required by the spirochetein vivobut relatively unstable duringin vitrocultivation. We propose that complementation on an endogenous plasmid such as lp25 would overcome the copy number andin vivostability issues of shuttle vectors. In addition, insertion of a selectable marker on lp25 could ensure its stable maintenance by spirochetes in culture. Here, we describe the construction of a multipurpose allelic-exchange vector containing a multiple-cloning site and either of two selectable markers. This suicide vector directs insertion of the complementing gene into thebbe02locus, a site on lp25 that was previously shown to be nonessential during bothin vitroandin vivogrowth. We demonstrate the functional utility of this strategy by restoring infectivity to anospCmutant through complementation at this site on lp25 and stable maintenance of theospCgene throughout mouse infection. We conclude that this represents a convenient and widely applicable method for stable gene complementation inB. burgdorferi.

Download Full-text

Increasing the Interaction of Borrelia burgdorferi with Decorin Significantly Reduces the 50 Percent Infectious Dose and Severely Impairs Dissemination

Infection and Immunity ◽

10.1128/iai.00560-07 ◽

2007 ◽

Vol 75 (9) ◽

pp. 4272-4281 ◽

Cited By ~ 19

Author(s):

Qilong Xu ◽

Sunita V. Seemanaplli ◽

Kristy McShan ◽

Fang Ting Liang

Keyword(s):

Borrelia Burgdorferi ◽

Severe Combined Immunodeficiency ◽

Protein A ◽

Antigen Expression ◽

In Vitro Assays ◽

Infectious Dose ◽

Surface Antigen Expression ◽

Immunocompetent Mice ◽

Surface Adhesins

ABSTRACT Tight regulation of surface antigenic expression is crucial for the pathogenic strategy of the Lyme disease spirochete, Borrelia burgdorferi. Here, we report the influence of increasing expression of decorin-binding protein A (DbpA), one of the most investigated spirochetal surface adhesins, on the 50% infectious dose (ID50), dissemination, tissue colonization, pathogenicity, and persistence of B. burgdorferi in the murine host. Our in vitro assays showed that increasing DbpA expression dramatically increased the interaction of B. burgdorferi with decorin and sensitivity to growth inhibition/killing by anti-DbpA antibodies; however, this increased interaction did not affect spirochetal growth and replication in the presence of decorin. Increasing DbpA expression significantly reduced ID50 values and severely impaired dissemination in severe combined immunodeficiency (SCID) and immunocompetent mice. During infection of SCID mice, B. burgdorferi with increased DbpA expression was able to effectively colonize heart and skin tissues, but not joint tissues, completely abrogating arthritis virulence. Although increasing DbpA expression did not affect spirochetal persistence in the skin, it diminished the ability of B. burgdorferi to persist in the heart and joint tissues during chronic infection of immunocompetent mice. Taken together, the study highlights the importance of controlling surface antigen expression in the infectivity, dissemination, tissue colonization, pathogenicity, and persistence of B. burgdorferi during mammalian infection.

Download Full-text

Cell Division Protein FtsZ Is Unfolded for N-Terminal Degradation by Antibiotic-Activated ClpP

mBio ◽

10.1128/mbio.01006-20 ◽

2020 ◽

Vol 11 (3) ◽

Author(s):

Nadine Silber ◽

Stefan Pan ◽

Sina Schäkermann ◽

Christian Mayer ◽

Heike Brötz-Oesterhelt ◽

...

Keyword(s):

Cell Division ◽

Protein Unfolding ◽

Multidrug Resistant ◽

Unexpected Finding ◽

Bacterial Cells ◽

Clp Protease ◽

Content Type ◽

C Terminus ◽

Cell Division Protein

ABSTRACT Antibiotic acyldepsipeptides (ADEPs) deregulate ClpP, the proteolytic core of the bacterial Clp protease, thereby inhibiting its native functions and concomitantly activating it for uncontrolled proteolysis of nonnative substrates. Importantly, although ADEP-activated ClpP is assumed to target multiple polypeptide and protein substrates in the bacterial cell, not all proteins seem equally susceptible. In Bacillus subtilis, the cell division protein FtsZ emerged to be particularly sensitive to degradation by ADEP-activated ClpP at low inhibitory ADEP concentrations. In fact, FtsZ is the only bacterial protein that has been confirmed to be degraded in vitro as well as within bacterial cells so far. However, the molecular reason for this preferred degradation remained elusive. Here, we report the unexpected finding that ADEP-activated ClpP alone, in the absence of any Clp-ATPase, leads to an unfolding and subsequent degradation of the N-terminal domain of FtsZ, which can be prevented by the stabilization of the FtsZ fold via nucleotide binding. At elevated antibiotic concentrations, importantly, the C terminus of FtsZ is notably targeted for degradation in addition to the N terminus. Our results show that different target structures are more or less accessible to ClpP, depending on the ADEP level present. Moreover, our data assign a Clp-ATPase-independent protein unfolding capability to the ClpP core of the bacterial Clp protease and suggest that the protein fold of FtsZ may be more flexible than previously anticipated. IMPORTANCE Acyldepsipeptide (ADEP) antibiotics effectively kill multidrug-resistant Gram-positive pathogens, including vancomycin-resistant enterococcus, penicillin-resistant Streptococcus pneumoniae (PRSP), and methicillin-resistant Staphylococcus aureus (MRSA). The antibacterial activity of ADEP depends on a new mechanism of action, i.e., the deregulation of bacterial protease ClpP that leads to bacterial self-digestion. Our data allow new insights into the mode of ADEP action by providing a molecular explanation for the distinct bacterial phenotypes observed at low versus high ADEP concentrations. In addition, we show that ClpP alone, in the absence of any unfoldase or energy-consuming system, and only activated by the small molecule antibiotic ADEP, leads to the unfolding of the cell division protein FtsZ.

Download Full-text

Comparative Analysis of EspF Variants in Inhibition of Escherichia coli Phagocytosis by Macrophages and Inhibition of E. coli Translocation through Human- and Bovine-Derived M Cells

Infection and Immunity ◽

10.1128/iai.00023-11 ◽

2011 ◽

Vol 79 (11) ◽

pp. 4716-4729 ◽

Cited By ~ 19

Author(s):

Amin Tahoun ◽

Gabriella Siszler ◽

Kevin Spears ◽

Sean McAteer ◽

Jai Tree ◽

...

Keyword(s):

Escherichia Coli ◽

Epithelial Cells ◽

Cellular Localization ◽

M Cells ◽

Binding Assays ◽

M Cell ◽

Content Type ◽

E Coli ◽

Coculture System

ABSTRACTThe EspF protein is secreted by the type III secretion system of enteropathogenic and enterohemorrhagicEscherichia coli(EPEC and EHEC, respectively). EspF sequences differ between EHEC O157:H7, EHEC O26:H11, and EPEC O127:H6 in terms of the number of SH3-binding polyproline-rich repeats and specific residues in these regions, as well as residues in the amino domain involved in cellular localization. EspFO127is important for the inhibition of phagocytosis by EPEC and also limits EPEC translocation through antigen-sampling cells (M cells). EspFO127has been shown to have effects on cellular organelle function and interacts with several host proteins, including N-WASP and sorting nexin 9 (SNX9). In this study, we compared the capacities of differentespFalleles to inhibit (i) bacterial phagocytosis by macrophages, (ii) translocation through an M-cell coculture system, and (iii) uptake by and translocation through cultured bovine epithelial cells. TheespFgene fromE. coliserotype O157 (espFO157) allele was significantly less effective at inhibiting phagocytosis and also had reduced capacity to inhibitE. colitranslocation through a human-derivedin vitroM-cell coculture system in comparison toespFO127andespFO26. In contrast,espFO157was the most effective allele at restricting bacterial uptake into and translocation through primary epithelial cells cultured from the bovine terminal rectum, the predominant colonization site of EHEC O157 in cattle and a site containing M-like cells. Although LUMIER binding assays demonstrated differences in the interactions of the EspF variants with SNX9 and N-WASP, we propose that other, as-yet-uncharacterized interactions contribute to the host-based variation in EspF activity demonstrated here.

Download Full-text

Structural and Biomolecular Analyses of Borrelia burgdorferi BmpD Reveal a Substrate-Binding Protein of an ABC-Type Nucleoside Transporter Family

Infection and Immunity ◽

10.1128/iai.00962-19 ◽

2020 ◽

Vol 88 (4) ◽

Author(s):

Julia Cuellar ◽

Mia Åstrand ◽

Heli Elovaara ◽

Annukka Pietikäinen ◽

Saija Sirén ◽

...

Keyword(s):

Borrelia Burgdorferi ◽

Cellular Localization ◽

De Novo ◽

Binding Protein ◽

Substrate Binding ◽

Nucleoside Transporter ◽

Bacterial Survival ◽

Content Type ◽

Transporter Family ◽

Substrate Binding Protein

ABSTRACT Borrelia burgdorferi sensu lato, the causative agent of tick-borne Lyme borreliosis (LB), has a limited metabolic capacity and needs to acquire nutrients, such as amino acids, fatty acids, and nucleic acids, from the host environment. Using X-ray crystallography, liquid chromatography-mass spectrometry, microscale thermophoresis, and cellular localization studies, we show that basic membrane protein D (BmpD) is a periplasmic substrate-binding protein of an ABC transporter system binding to purine nucleosides. Nucleosides are essential for bacterial survival in the host organism, and these studies suggest a key role for BmpD in the purine salvage pathway of B. burgdorferi sensu lato. Because B. burgdorferi sensu lato lacks the enzymes required for de novo purine synthesis, BmpD may play a vital role in ensuring access to the purines needed to sustain an infection in the host. Furthermore, we show that, although human LB patients develop anti-BmpD antibodies, immunization of mice with BmpD does not confer protection against B. burgdorferi sensu lato infection.

Download Full-text

Mutational Analysis of Residues in PriA and PriC Affecting Their Ability To Interact with SSB in Escherichia coli K-12

Journal of Bacteriology ◽

10.1128/jb.00404-20 ◽

2020 ◽

Vol 202 (23) ◽

Author(s):

Anastasiia N. Klimova ◽

Steven J. Sandler

Keyword(s):

Escherichia Coli ◽

Mutational Analysis ◽

Wild Type ◽

Content Type ◽

Growth Defects ◽

C Terminus ◽

K 12 ◽

And Function

ABSTRACT Escherichia coli PriA and PriC recognize abandoned replication forks and direct reloading of the DnaB replicative helicase onto the lagging-strand template coated with single-stranded DNA-binding protein (SSB). Both PriA and PriC have been shown by biochemical and structural studies to physically interact with the C terminus of SSB. In vitro, these interactions trigger remodeling of the SSB on ssDNA. priA341(R697A) and priC351(R155A) negated the SSB remodeling reaction in vitro. Plasmid-carried priC351(R155A) did not complement priC303::kan, and priA341(R697A) has not yet been tested for complementation. Here, we further studied the SSB-binding pockets of PriA and PriC by placing priA341(R697A), priA344(R697E), priA345(Q701E), and priC351(R155A) on the chromosome and characterizing the mutant strains. All three priA mutants behaved like the wild type. In a ΔpriB strain, the mutations caused modest increases in SOS expression, cell size, and defects in nucleoid partitioning (Par−). Overproduction of SSB partially suppressed these phenotypes for priA341(R697A) and priA344(R697E). The priC351(R155A) mutant behaved as expected: there was no phenotype in a single mutant, and there were severe growth defects when this mutation was combined with ΔpriB. Analysis of the priBC mutant revealed two populations of cells: those with wild-type phenotypes and those that were extremely filamentous and Par− and had high SOS expression. We conclude that in vivo, priC351(R155A) identified an essential residue and function for PriC, that PriA R697 and Q701 are important only in the absence of PriB, and that this region of the protein may have a complicated relationship with SSB. IMPORTANCE Escherichia coli PriA and PriC recruit the replication machinery to a collapsed replication fork after it is repaired and needs to be restarted. In vitro studies suggest that the C terminus of SSB interacts with certain residues in PriA and PriC to recruit those proteins to the repaired fork, where they help remodel it for restart. Here, we placed those mutations on the chromosome and tested the effect of mutating these residues in vivo. The priC mutation completely abolished function. The priA mutations had no effect by themselves. They did, however, display modest phenotypes in a priB-null strain. These phenotypes were partially suppressed by SSB overproduction. These studies give us further insight into the reactions needed for replication restart.

Download Full-text

Reduced Immune Response to Borrelia burgdorferi in the Absence of γδ T Cells

Infection and Immunity ◽

10.1128/iai.00148-11 ◽

2011 ◽

Vol 79 (10) ◽

pp. 3940-3946 ◽

Cited By ~ 16

Author(s):

Cuixia Shi ◽

Bikash Sahay ◽

Jennifer Q. Russell ◽

Karen A. Fortner ◽

Nicholas Hardin ◽

...

Keyword(s):

Immune Response ◽

T Cells ◽

Borrelia Burgdorferi ◽

Adaptive Immune Response ◽

Γδ T Cells ◽

Content Type ◽

Adaptive Immune ◽

Cytokines And Chemokines

ABSTRACTLittle is known regarding the function of γδ T cells, although they accumulate at sites of inflammation in infections and autoimmune disorders. We previously observed that γδ T cellsin vitroare activated byBorrelia burgdorferiin a TLR2-dependent manner. We now observe that the activated γδ T cells can in turn stimulate dendritic cellsin vitroto produce cytokines and chemokines that are important for the adaptive immune response. This suggested thatin vivoγδ T cells may assist in activating the adaptive immune response. We examined this possibilityin vivoand observed that γδ T cells are activated and expand in number duringBorreliainfection, and this was reduced in the absence of TLR2. Furthermore, in the absence of γδ T cells, there was a significantly blunted response of adaptive immunity, as reflected in reduced expansion of T and B cells and reduced serum levels of anti-Borreliaantibodies, cytokines, and chemokines. This paralleled a greaterBorreliaburden in γδ-deficient mice as well as more cardiac inflammation. These findings are consistent with a model of γδ T cells functioning to promote the adaptive immune response during infection.

Download Full-text

Membrane Protein Complex ExbB4-ExbD1-TonB1from Escherichia coli Demonstrates Conformational Plasticity

Journal of Bacteriology ◽

10.1128/jb.00069-15 ◽

2015 ◽

Vol 197 (11) ◽

pp. 1873-1885 ◽

Cited By ~ 17

Author(s):

Aleksandr Sverzhinsky ◽

Jacqueline W. Chung ◽

Justin C. Deme ◽

Lucien Fabre ◽

Kristian T. Levey ◽

...

Keyword(s):

Escherichia Coli ◽

Iron Acquisition ◽

Proton Translocation ◽

Three Dimensional ◽

Structural Data ◽

Structural Features ◽

Gram Negative Bacteria ◽

Gram Negative ◽

Content Type

ABSTRACTIron acquisition at the outer membrane (OM) of Gram-negative bacteria is powered by the proton motive force (PMF) of the cytoplasmic membrane (CM), harnessed by the CM-embedded complex of ExbB, ExbD, and TonB. Its stoichiometry, ensemble structural features, and mechanism of action are unknown. By panning combinatorial phage libraries, periplasmic regions of dimerization between ExbD and TonB were predicted. Using overexpression of full-length His6-taggedexbB-exbDand S-taggedtonB, we purified detergent-solubilized complexes of ExbB-ExbD-TonB fromEscherichia coli. Protein-detergent complexes of ∼230 kDa with a hydrodynamic radius of ∼6.0 nm were similar to previously purified ExbB4-ExbD2complexes. Significantly, they differed in electronegativity by native agarose gel electrophoresis. The stoichiometry was determined to be ExbB4-ExbD1-TonB1. Single-particle electron microscopy agrees with this stoichiometry. Two-dimensional averaging supported the phage display predictions, showing two forms of ExbD-TonB periplasmic heterodimerization: extensive and distal. Three-dimensional (3D) particle classification showed three representative conformations of ExbB4-ExbD1-TonB1. Based on our structural data, we propose a model in which ExbD shuttles a proton across the CM via an ExbB interprotein rearrangement. Proton translocation would be coupled to ExbD-mediated collapse of extended TonB in complex with ligand-loaded receptors in the OM, followed by repositioning of TonB through extensive dimerization with ExbD. Here we present the first report for purification of the ExbB-ExbD-TonB complex, molar ratios within the complex (4:1:1), and structural biology that provides insights into 3D organization.IMPORTANCEReceptors in the OM of Gram-negative bacteria allow entry of iron-bound siderophores that are necessary for pathogenicity. Numerous iron-acquisition strategies rely upon a ubiquitous and unique protein for energization: TonB. Complexed with ExbB and ExbD, the Ton system links the PMF to OM transport. Blocking iron uptake by targeting a vital nanomachine holds promise in therapeutics. Despite much research, the stoichiometry, structural arrangement, and molecular mechanism of the CM-embedded ExbB-ExbD-TonB complex remain unreported. Here we demonstratein vitroevidence of ExbB4-ExbD1-TonB1complexes. Using 3D EM, we reconstructed the complex in three conformational states that show variable ExbD-TonB heterodimerization. Our structural observations form the basis of a model for TonB-mediated iron acquisition.

Download Full-text

Evaluation of RevA, a Fibronectin-Binding Protein of Borrelia burgdorferi, as a Potential Vaccine Candidate for Lyme Disease

Clinical and Vaccine Immunology ◽

10.1128/cvi.00758-12 ◽

2013 ◽

Vol 20 (6) ◽

pp. 892-899 ◽

Cited By ~ 12

Author(s):

Angela M. Floden ◽

Tammy Gonzalez ◽

Robert A. Gaultney ◽

Catherine A. Brissette

Keyword(s):

Lyme Disease ◽

Borrelia Burgdorferi ◽

Passive Immunization ◽

Surface Protein ◽

Surface Expression ◽

Content Type ◽

Good Target ◽

Potential Vaccine ◽

Mammalian Infection

ABSTRACTPrevious studies indicated that the Lyme disease spirocheteBorrelia burgdorferiexpresses the RevA outer surface protein during mammalian infection. As an adhesin that promotes bacterial interaction with fibronectin, RevA appears to be a good target for preventive therapies. RevA proteins are highly conserved across all Lyme borreliae, and antibodies against RevA protein are cross-reactive among RevA proteins from diverse strains. Mice infected withB. burgdorferimounted a rapid IgM response to RevA, followed by a strong IgG response that generally remained elevated for more than 12 months, suggesting continued exposure of RevA protein to the immune system. RevA antibodies were bactericidalin vitro. To evaluate the RevA antigen as a potential vaccine, mice were vaccinated with recombinant RevA and challenged withB. burgdorferiby inoculation with a needle or by a tick bite. Cultured tissues from all treatment groups were positive forB. burgdorferi. Vaccinated animals also appeared to have similar levels ofB. burgdorferiDNA compared to nonvaccinated controls. Despite its antigenicity, surface expression, and the production of bactericidal antibodies against it, RevA does not protect againstBorrelia burgdorferiinfection in a mouse model. However, passive immunization with anti-RevA antibodies did prevent infection, suggesting the possible utility of RevA-based immunotherapeutics or vaccine.

Download Full-text

Borrelia burgdorferi Needs Chemotaxis To Establish Infection in Mammals and To Accomplish Its Enzootic Cycle

Infection and Immunity ◽

10.1128/iai.00145-12 ◽

2012 ◽

Vol 80 (7) ◽

pp. 2485-2492 ◽

Cited By ~ 45

Author(s):

Ching Wooen Sze ◽

Kai Zhang ◽

Toru Kariu ◽

Utpal Pal ◽

Chunhao Li

Keyword(s):

Borrelia Burgdorferi ◽

Capillary Tube ◽

Virulent Strain ◽

Gene Encoding ◽

Content Type ◽

Immunodeficient Mice ◽

Passage Number ◽

Low Passage ◽

Enzootic Cycle

ABSTRACTBorrelia burgdorferi, the causative agent of Lyme disease, can be recovered from different organs of infected animals and patients, indicating that the spirochete is very invasive. Motility and chemotaxis contribute to the invasiveness ofB. burgdorferiand play important roles in the process of the disease. Recent reports have shown that motility is required for establishing infection in mammals. However, the role of chemotaxis in virulence remains elusive. Our previous studies showed thatcheA2, a gene encoding a histidine kinase, is essential for the chemotaxis ofB. burgdorferi. In this report, thecheA2gene was inactivated in a low-passage-number virulent strain ofB. burgdorferi. In vitroanalyses (microscopic observations, computer-based bacterial tracking analysis, swarm plate assays, and capillary tube assays) showed that thecheA2mutant failed to reverse and constantly ran in one direction; the mutant was nonchemotactic to attractants. Mouse needle infection studies showed that thecheA2mutant failed to infect either immunocompetent or immunodeficient mice and was quickly eliminated from the initial inoculation sites. Tick-mouse infection studies revealed that although the mutant was able to survive in ticks, it failed to establish a new infection in mice via tick bites. The altered phenotypes were completely restored when the mutant was complemented. Collectively, these data demonstrate thatB. burgdorferineeds chemotaxis to establish mammalian infection and to accomplish its natural enzootic cycle.

Download Full-text