scholarly journals Covalent host-targeting by thioester domains of Gram-positive pathogens

2014 ◽  
Vol 70 (a1) ◽  
pp. C848-C848
Author(s):  
Miriam Walden ◽  
John Edwards ◽  
Aleksandra Dziewulska ◽  
Uli Schwarz-Linek ◽  
Mark Banfield
Keyword(s):  
Cell Surface ◽  
Host Cell ◽  
Molecular Mechanisms ◽  
Cell Attachment ◽  
Surface Proteins ◽  
Host Cells ◽  
Covalent Attachment ◽  
Gram Positive ◽  
Covalent Bonds ◽  
Isopeptide Bonds

Gram-positive pathogens are a major concern to global health, with increasing resistance to antimicrobials and the lack of preventative therapeutics. Understanding how these bacteria interact with host cells is vital for the development of novel strategies to combat disease. One of the most crucial steps in infection is adhesion to the host cell. The discovery of complex cell-surface associated proteins, such as pili, has advanced our knowledge of this interaction, however the precise molecular mechanisms underlying this process remain unclear. Structural studies of pili revealed the presence of highly unusual intramolecular covalent bonds between amino acid side chains. These include isopeptide bonds between Lys and Asp/Asn residues, conferring mechanical strength, thermal stability and resistance to proteases [1,2]. In Streptococcus pyogenes pili, the adhesin Spy0125 (or Cpa) interacts with the host cell. It comprises three domains, two of which contain stabilising isopeptide bonds [2,3]. Intriguingly, the third domain contains an extremely rare thioester bond, between a Cys and a Gln residue. A Cys to Ala mutation results in a 75% reduction in adhesion, suggesting that this internal linkage may mediate direct attachment [3]. We have now discovered putative thioester domains (TEDs) in cell-surface proteins of several clinically important pathogens. The only other example of an internal thioester is found in complement proteins, where the reactive bond enables the formation of covalent attachment to pathogens. The presence of these bonds in bacterial proteins suggests the possibility of an as-yet uncharacterised, conserved mechanism of covalent host cell attachment. For a selection of pathogens, we have used mass spectrometry and crystallography to confirm the presence of the covalent link between the Cys and Gln residues within the TEDs. Furthermore, we have identified putative host cell targets of TEDs and confirmed covalent linkages between the TED and the target.

scholarly journals Surface Proteins of Gram-Positive Bacteria and Mechanisms of Their Targeting to the Cell Wall Envelope

1999 ◽  
Vol 63 (1) ◽  
pp. 174-229 ◽  
Author(s):  
William Wiley Navarre ◽  
Olaf Schneewind
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Protein A ◽  
Surface Proteins ◽  
Covalent Attachment ◽  
Lytic Enzymes ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Binding Domains ◽  
Internalin B

SUMMARY The cell wall envelope of gram-positive bacteria is a macromolecular, exoskeletal organelle that is assembled and turned over at designated sites. The cell wall also functions as a surface organelle that allows gram-positive pathogens to interact with their environment, in particular the tissues of the infected host. All of these functions require that surface proteins and enzymes be properly targeted to the cell wall envelope. Two basic mechanisms, cell wall sorting and targeting, have been identified. Cell well sorting is the covalent attachment of surface proteins to the peptidoglycan via a C-terminal sorting signal that contains a consensus LPXTG sequence. More than 100 proteins that possess cell wall-sorting signals, including the M proteins of Streptococcus pyogenes, protein A of Staphylococcus aureus, and several internalins of Listeria monocytogenes, have been identified. Cell wall targeting involves the noncovalent attachment of proteins to the cell surface via specialized binding domains. Several of these wall-binding domains appear to interact with secondary wall polymers that are associated with the peptidoglycan, for example teichoic acids and polysaccharides. Proteins that are targeted to the cell surface include muralytic enzymes such as autolysins, lysostaphin, and phage lytic enzymes. Other examples for targeted proteins are the surface S-layer proteins of bacilli and clostridia, as well as virulence factors required for the pathogenesis of L. monocytogenes (internalin B) and Streptococcus pneumoniae (PspA) infections. In this review we describe the mechanisms for both sorting and targeting of proteins to the envelope of gram-positive bacteria and review the functions of known surface proteins.

scholarly journals A Single-Pass Type I Membrane Protein from the Apicomplexan Parasite Cryptosporidium parvum with Nanomolar Binding Affinity to Host Cell Surface

2021 ◽  
Vol 9 (5) ◽  
pp. 1015
Author(s):  
Tianyu Zhang ◽  
Xin Gao ◽  
Dongqiang Wang ◽  
Jixue Zhao ◽  
Nan Zhang ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Cell Surface ◽  
Host Cell ◽  
Binding Affinity ◽  
Cryptosporidium Parvum ◽  
Host Cells ◽  
Watery Diarrhea ◽  
Type I ◽  
Single Pass ◽  
Host Cell Surface

Cryptosporidium parvum is a globally recognized zoonotic parasite of medical and veterinary importance. This parasite mainly infects intestinal epithelial cells and causes mild to severe watery diarrhea that could be deadly in patients with weakened or defect immunity. However, its molecular interactions with hosts and pathogenesis, an important part in adaptation of parasitic lifestyle, remain poorly understood. Here we report the identification and characterization of a C. parvum T-cell immunomodulatory protein homolog (CpTIPH). CpTIPH is a 901-aa single-pass type I membrane protein encoded by cgd5_830 gene that also contains a short Vibrio, Colwellia, Bradyrhizobium and Shewanella (VCBS) repeat and relatively long integrin alpha (ITGA) N-terminus domain. Immunofluorescence assay confirmed the location of CpTIPH on the cell surface of C. parvum sporozoites. In congruence with the presence of VCBS repeat and ITGA domain, CpTIPH displayed high, nanomolar binding affinity to host cell surface (i.e., Kd(App) at 16.2 to 44.7 nM on fixed HCT-8 and CHO-K1 cells, respectively). The involvement of CpTIPH in the parasite invasion is partly supported by experiments showing that an anti-CpTIPH antibody could partially block the invasion of C. parvum sporozoites into host cells. These observations provide a strong basis for further investigation of the roles of CpTIPH in parasite-host cell interactions.

scholarly journals Heterologously Expressed Staphylococcus aureusFibronectin-Binding Proteins Are Sufficient for Invasion of Host Cells

2000 ◽  
Vol 68 (12) ◽  
pp. 6871-6878 ◽  
Author(s):  
Bhanu Sinha ◽  
Patrice Francois ◽  
Yok-Ai Que ◽  
Muzaffar Hussain ◽  
Christine Heilmann ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Binding Proteins ◽  
Surface Protein ◽  
Latex Agglutination ◽  
Surface Proteins ◽  
Host Cells ◽  
Gram Positive ◽  
Fibronectin Receptor ◽  
293 Cells ◽  
Accessible Surface

ABSTRACT Staphylococcus aureus invasion of mammalian cells, including epithelial, endothelial, and fibroblastic cells, critically depends on fibronectin bridging between S. aureusfibronectin-binding proteins (FnBPs) and the host fibronectin receptor integrin α5β1 (B. Sinha et al., Cell. Microbiol. 1:101–117, 1999). However, it is unknown whether this mechanism is sufficient for S. aureus invasion. To address this question, various S. aureus adhesins (FnBPA, FnBPB, and clumping factor [ClfA]) were expressed in Staphylococcus carnosus and Lactococcus lactis subsp.cremoris. Both noninvasive gram-positive microorganisms are genetically distinct from S. aureus, lack any knownS. aureus surface protein, and do not bind fibronectin. Transformants of S. carnosus and L. lactisharboring plasmids coding for various S. aureus surface proteins (FnBPA, FnBPB, and ClfA) functionally expressed adhesins (as determined by bacterial clumping in plasma, specific latex agglutination, Western ligand blotting, and binding to immobilized and soluble fibronectin). FnBPA or FnBPB but not of ClfA conferred invasiveness to S. carnosus and L. lactis. Invasion of 293 cells by transformants was comparable to that of strongly invasive S. aureus strain Cowan 1. Binding of soluble and immobilized fibronectin paralleled invasiveness, demonstrating that the amount of accessible surface FnBPs is rate limiting. Thus, S. aureus FnBPs confer invasiveness to noninvasive, apathogenic gram-positive cocci. Furthermore, FnBP-coated polystyrene beads were internalized by 293 cells, demonstrating that FnBPs are sufficient for invasion of host cells without the need for (S. aureus-specific) coreceptors.

scholarly journals Heparan Sulfate Facilitates Spike Protein-Mediated SARS-CoV-2 Host Cell Invasion and Contributes to Increased Infection of SARS-CoV-2 G614 Mutant and in Lung Cancer

2021 ◽  
Vol 8 ◽  
Author(s):  
Jingwen Yue ◽  
Weihua Jin ◽  
Hua Yang ◽  
John Faulkner ◽  
Xuehong Song ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Cell Surface ◽  
Heparan Sulfate ◽  
Host Cell ◽  
Host Cells ◽  
Cell Surface Receptor ◽  
Spike Protein ◽  
Effective Prevention ◽  
Heparin Derivatives ◽  
Host Cell Surface

The severe acute respiratory syndrome (SARS)-like coronavirus disease (COVID-19) is caused by SARS-CoV-2 and has been a serious threat to global public health with limited treatment. Cellular heparan sulfate (HS) has been found to bind SARS-CoV-2 spike protein (SV2-S) and co-operate with cell surface receptor angiotensin-converting enzyme 2 (ACE2) to mediate SARS-CoV-2 infection of host cells. In this study, we determined that host cell surface SV2-S binding depends on and correlates with host cell surface HS expression. This binding is required for SARS-Cov-2 virus to infect host cells and can be blocked by heparin lyase, HS antagonist surfen, heparin, and heparin derivatives. The binding of heparin/HS to SV2-S is mainly determined by its overall sulfation with potential, minor contribution of specific SV2-S binding motifs. The higher binding affinity of SV2-S G614 mutant to heparin and upregulated HS expression may be one of the mechanisms underlying the higher infectivity of the SARS-CoV-2 G614 variant and the high vulnerability of lung cancer patients to SARS-CoV-2 infection, respectively. The higher host cell infection by SARS-CoV-2 G614 variant pseudovirus and the increased infection caused by upregulated HS expression both can be effectively blocked by heparin lyase and heparin, and possibly surfen and heparin derivatives too. Our findings support blocking HS-SV2-S interaction may provide one addition to achieve effective prevention and/treatment of COVID-19.

scholarly journals Significance of thiol-disulfide balance in SARS-CoV-2 infection

2021 ◽  
Vol 72 (3) ◽  
pp. 30-36
Author(s):  
Tatjana Simić
Keyword(s):  
Cell Surface ◽  
Host Cell ◽  
Protein Interactions ◽  
Viral Entry ◽  
Molecular Mechanisms ◽  
Alkylating Agents ◽  
Protein S ◽  
Protein Protein Interactions ◽  
Virus Surface ◽  
Host Cell Surface

Studies of the molecular mechanisms regarding interaction of different viruses with receptors on the host cell surface have shown that the viral entry depends on the specific relationship between free thiol (SH) groups and disulfides on the virus surface, as well as the thiol disulfide balance on the host cell surface. The presence of oxidizing compounds or alkylating agents, which disturb the thiol-disulfide balance on the surface of the virus, can also affect its infectious potential. Disturbed thiol-disulfide balance may also influence protein-protein interactions between SARS-CoV-2 protein S and ACE2 receptors of the host cell. This review presents the basic mechanisms of maintaining intracellular and extracellular thiol disulfide balance and previous experimental and clinical evidence in favor of impaired balance in SARS-CoV-2 infection. Besides, the results of the clinical application or experimental analysis of compounds that induce changes in the thiol disulfide balance towards reduction of disulfide bridges in proteins of interest in COVID-19 infection are presented.

scholarly journals Invasion mechanisms of Gram-positive pathogenic cocci

2007 ◽  
Vol 98 (09) ◽  
pp. 488-496 ◽  
Author(s):  
Patric Nitsche-Schmitz ◽  
Manfred Rohde ◽  
Gursharan Chhatwal
Keyword(s):  
Surface Proteins ◽  
Host Cells ◽  
Human Pathogens ◽  
Gram Positive ◽  
Bacterial Surface ◽  
Surface Receptors ◽  
Major Threat ◽  
Invasion Mechanisms ◽  
Invasive Infections ◽  
Gram Positive Cocci

SummaryGram-positive cocci are important human pathogens. Streptococci and staphylococci in particular are a major threat to human health,since they cause a variety of serious invasive infections. Their invasion into normally sterile sites of the host depends on elaborated bacterial mechanisms that involve adhesion to the host tissue, its degradation, internalisation by host cells, and passage through epithelia and endothelia. Interactions of bacterial surface proteins with proteins of the host’s extracellular matrix as well as with cell surface receptors are crucial factors in these processes, and some of the key mechanisms are similar in many pathogenic Gram-positive cocci.Therapies that interfere with these mechanisms may become efficient alternatives to today’s antibiotic treatments.

scholarly journals Complementation of the fadA Mutation in Fusobacterium nucleatum Demonstrates that the Surface-Exposed Adhesin Promotes Cellular Invasion and Placental Colonization

2009 ◽  
Vol 77 (7) ◽  
pp. 3075-3079 ◽  
Author(s):  
Akihiko Ikegami ◽  
Peter Chung ◽  
Yiping W. Han
Keyword(s):  
Host Cell ◽  
Cell Attachment ◽  
Adverse Pregnancy Outcome ◽  
Fusobacterium Nucleatum ◽  
Host Cells ◽  
Mouse Placenta ◽  
Host Cell Attachment ◽  
Adverse Pregnancy

ABSTRACT Fusobacterium nucleatum is a gram-negative oral anaerobe implicated in periodontal disease and adverse pregnancy outcome. The organism colonizes the mouse placenta, causing localized infection and inflammation. The mechanism of placental colonization has not been elucidated. Previous studies identified a novel adhesin from F. nucleatum, FadA, as being involved in the attachment and invasion of host cells. The fadA deletion mutant F. nucleatum 12230 US1 was defective in host cell attachment and invasion in vitro, but it also exhibited pleiotropic effects with altered cell morphology and growth rate. In this study, a fadA-complementing clone, F. nucleatum 12230 USF81, was constructed. The expression of FadA on USF81 was confirmed by Western blotting and immunofluorescent labeling. USF81 restored host cell attachment and invasion activities. The ability of F. nucleatum 12230, US1, and USF81 to colonize the mouse placenta was examined. US1 was severely defective in placental colonization compared to the wild type and USF81. Thus, FadA plays an important role in F. nucleatum colonization in vivo. These results also represent the first complementation studies for F. nucleatum. FadA may be a therapeutic target for preventing F. nucleatum colonization of the host.

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

2010 ◽  
Vol 12 ◽  
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.

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

2008 ◽  
Vol 190 (18) ◽  
pp. 6234-6242 ◽  
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.

scholarly journals Sulfated Glycans and Related Digestive Enzymes in the Zika Virus Infectivity: Potential Mechanisms of Virus-Host Interaction and Perspectives in Drug Discovery

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Vitor H. Pomin
Keyword(s):  
Neural Development ◽  
Zika Virus ◽  
Molecular Mechanisms ◽  
Surface Proteins ◽  
Host Cells ◽  
Future Research ◽  
Virus Infectivity ◽  
Virus Attachment ◽  
Chemical Structures ◽  
Host Interaction

As broadly reported, there is an ongoing Zika virus (ZIKV) outbreak in countries of Latin America. Recent findings have demonstrated that ZIKV causes severe defects on the neural development in fetuses in utero and newborns. Very little is known about the molecular mechanisms involved in the ZIKV infectivity. Potential therapeutic agents are also under investigation. In this report, the possible mechanisms of action played by glycosaminoglycans (GAGs) displayed at the surface proteoglycans of host cells, and likely in charge of interactions with surface proteins of the ZIKV, are highlighted. As is common for the most viruses, these sulfated glycans serve as receptors for virus attachment onto the host cells and consequential entry during infection. The applications of (1) exogenous sulfated glycans of different origins and chemical structures capable of competing with the virus attachment receptors (supposedly GAGs) and (2) GAG-degrading enzymes able to digest the virus attachment receptors on the cells may be therapeutically beneficial as anti-ZIKV. This communication attempts, therefore, to offer some guidance for the future research programs aimed to unveil the molecular mechanisms underlying the ZIKV infectivity and to develop therapeutics capable of decreasing the devastating consequences caused by ZIKV outbreak in the Americas.

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