Aqueous medium-induced micropore formation in plasma polymerized polystyrene: an effective route to inhibit bacteria adhesion

International audienc

Mutation of Tyr137 of the universal Escherichia coli fimbrial adhesin FimH relaxes the tyrosine gate prior to mannose binding

The most prevalent diseases manifested by Escherichia coli are acute and recurrent bladder infections and chronic inflammatory bowel diseases such as Crohn's disease. E. coli clinical isolates express the FimH adhesin, which consists of a mannose-specific lectin domain connected via a pilin domain to the tip of type 1 pili. Although the isolated FimH lectin domain has affinities in the nanomolar range for all high-mannosidic glycans, differentiation between these glycans is based on their capacity to form predominantly hydrophobic interactions within the tyrosine gate at the entrance to the binding pocket. In this study, novel crystal structures of tyrosine-gate mutants of FimH, ligand-free or in complex with heptyl α - D - O -mannopyranoside or 4-biphenyl α - D - O- mannopyranoside, are combined with quantum-mechanical calculations and molecular-dynamics simulations. In the Y48A FimH crystal structure, a large increase in the dynamics of the alkyl chain of heptyl α - D - O -mannopyranoside attempts to compensate for the absence of the aromatic ring; however, the highly energetic and stringent mannose-binding pocket of wild-type FimH is largely maintained. The Y137A mutation, on the other hand, is the most detrimental to FimH affinity and specificity: (i) in the absence of ligand the FimH C-terminal residue Thr158 intrudes into the mannose-binding pocket and (ii) ethylenediaminetetraacetic acid interacts strongly with Glu50, Thr53 and Asn136, in spite of multiple dialysis and purification steps. Upon mutation, pre-ligand-binding relaxation of the backbone dihedral angles at position 137 in the tyrosine gate and their coupling to Tyr48 via the interiorly located Ile52 form the basis of the loss of affinity of the FimH adhesin in the Y137A mutant

Intervening with Urinary Tract Infections Using Anti-Adhesives Based on the Crystal Structure of the FimH–Oligomannose-3 Complex

Escherichia coli strains adhere to the normally sterile human uroepithelium using type 1 pili, that are long, hairy surface organelles exposing a mannose-binding FimH adhesin at the tip. A small percentage of adhered bacteria can successfully invade bladder cells, presumably via pathways mediated by the high-mannosylated uroplakin-Ia and alpha3beta1 integrins found throughout the uroepithelium. Invaded bacteria replicate and mature into dense, biofilm-like inclusions in preparation of fluxing and of infection of neighbouring cells, being the major cause of the troublesome recurrent urinary tract infections.We demonstrate that alpha-D-mannose based inhibitors of FimH not only block bacterial adhesion on uroepithelial cells but also antagonize invasion and biofilm formation. Heptyl alpha-D-mannose prevents binding of type 1-piliated E. coli to the human bladder cell line 5637 and reduces both adhesion and invasion of the UTI89 cystitis isolate instilled in mouse bladder via catheterization. Heptyl alpha-D-mannose also specifically inhibited biofilm formation at micromolar concentrations. The structural basis of the great inhibitory potential of alkyl and aryl alpha-D-mannosides was elucidated in the crystal structure of the FimH receptor-binding domain in complex with oligomannose-3. FimH interacts with Man alpha1,3Man beta1,4GlcNAc beta1,4GlcNAc in an extended binding site. The interactions along the alpha1,3 glycosidic bond and the first beta1,4 linkage to the chitobiose unit are conserved with those of FimH with butyl alpha-D-mannose. The strong stacking of the central mannose with the aromatic ring of Tyr48 is congruent with the high affinity found for synthetic inhibitors in which this mannose is substituted for by an aromatic group.The potential of ligand-based design of antagonists of urinary tract infections is ruled by the structural mimicry of natural epitopes and extends into blocking of bacterial invasion, intracellular growth and capacity to fluxing and of recurrence of the infection

Recurrent Signature Patterns in HIV-1 B Clade Envelope Glycoproteins Associated with either Early or Chronic Infections

Here we have identified HIV-1 B clade Envelope (Env) amino acid signatures from early in infection that may be favored at transmission, as well as patterns of recurrent mutation in chronic infection that may reflect common pathways of immune evasion. To accomplish this, we compared thousands of sequences derived by single genome amplification from several hundred individuals that were sampled either early in infection or were chronically infected. Samples were divided at the outset into hypothesis-forming and validation sets, and we used phylogenetically corrected statistical strategies to identify signatures, systematically scanning all of Env. Signatures included single amino acids, glycosylation motifs, and multi-site patterns based on functional or structural groupings of amino acids. We identified signatures near the CCR5 co-receptor-binding region, near the CD4 binding site, and in the signal peptide and cytoplasmic domain, which may influence Env expression and processing. Two signatures patterns associated with transmission were particularly interesting. The first was the most statistically robust signature, located in position 12 in the signal peptide. The second was the loss of an N-linked glycosylation site at positions 413–415; the presence of this site has been recently found to be associated with escape from potent and broad neutralizing antibodies, consistent with enabling a common pathway for immune escape during chronic infection. Its recurrent loss in early infection suggests it may impact fitness at the time of transmission or during early viral expansion. The signature patterns we identified implicate Env expression levels in selection at viral transmission or in early expansion, and suggest that immune evasion patterns that recur in many individuals during chronic infection when antibodies are present can be selected against when the infection is being established prior to the adaptive immune response

Binding of the F18 fimbrial adhesin FedF to piglet intestinal epithelium involves specific receptor recognition and non-specific electrostatic attraction with the phospholipid membrane

Post-weaning diarrhoea and oedema disease are serious infectious diseases of piglets caused by pathogenic E. coli strains, including enterotoxigenic E. coli (ETEC) and Shiga toxin-producing E. coli (STEC). These strains account for substantial economical losses in the pig industry (Bertschinger et al., 1994; E. coli in Domestic Animals and Humans (Gyles, C. L. ed) pp. 193, CAB, Wallingford, Oxon, UK). The first and crucial step during most of these pathogenic infections is the recognition and adhesion of these pathogens to a specific host tissue. Adhesins mediating such an interaction are often presented to the host cell receptors by pili or fimbriae. We examined FedF, the adhesive tipsubunit of F18 fimbriae expressed by STEC which infect recently weaned piglets. Recently, the carbohydrates interacting with the FedF adhesin were identified by Coddens et al. (2009, J. Biol. Chem. 284, 9713). The authors showed that FedF is interacting with ABH blood group type 1 determinants

Structures of C-mannosylated anti-adhesives bound to the type 1 fimbrial FimH adhesin

Selective inhibitors of the type 1 fimbrial adhesin FimH are recognized as attractive alternatives for antibiotic therapies and prophylaxes against Escherichia coli infections such as urinary-tract infections. To construct these inhibitors, the α-d-mannopyranoside of high-mannose N-glycans, recognized with exclusive specificity on glycoprotein receptors by FimH, forms the basal structure. A hydrophobic aglycon is then linked to the mannose by the O1 oxygen inherently present in the α-anomeric configuration. Substitution of this O atom by a carbon introduces a C-glycosidic bond, which may enhance the therapeutic potential of such compounds owing to the inability of enzymes to degrade C-glycosidic bonds. Here, the first crystal structures of the E. coli FimH adhesin in complex with C-glycosidically linked mannopyranosides are presented. These findings explain the role of the spacer in positioning biphenyl ligands for interactions by means of aromatic stacking in the tyrosine gate of FimH and how the normally hydrated C-glycosidic link is tolerated. As these new compounds can bind FimH, it can be assumed that they have the potential to serve as potent new antagonists of FimH, paving the way for the design of a new family of anti-adhesive compounds against urinary-tract infections

Rational design and development of HDAC inhibitors for breast cancer treatment

Background: Breast cancer is the most prevalent cancer amongst females across the globe, and with over 2 million new cases reported in 2018, it poses a huge economic burden to the already dwindling public health. A dearth of therapies in the pipeline to treat triple-negative breast cancers and acquisition of resistance against the existing line of treatments urge the need to strategize novel therapeutics in order to add new drugs to the pipeline. HDAC inhibitors (HDACi) is one such class of small molecule inhibitors that target histone deacetylases to bring about chromosomal remodelling and normalize dysregulated gene expression that marks breast cancer progression. Objective: While four HDACi have been approved by the FDA for the treatment of different cancer types, no HDACi is specifically earmarked for clinical management of breast cancer. Owing to the differential HDAC expression pertaining to different types of breast cancers, isoform-selective HDAC inhibitors need to be discovered. Conclusion: This review attempts to set the stage for the rational structure-based discovery of isoform-selective HDACi by providing structural insights into different HDACs and their catalytic folds based on their classes and individual landscape. The development of inhibitors in accordance with the differential expression of HDAC isoforms exhibited in breast cancer cells is a promising strategy to rationally design selective and effective inhibitors, adopting a 'personalized-medicine' approach

Natural antibodies : protecting role of IgM in glioblastoma and brain tumours

Background: Glioblastoma is a grade IV astrocytoma with an average survival span for patients of 18 months after initial diagnosis and no standard treatment protocol is available. Therefore, there is a need to search for novel approaches to target glioblastoma. Objectives: This review intends to capture the role of immunoglobulin-M in cancer, more specifically in glioblastoma multiforme (GBM), and to compile the latest developments and immunological pathways relevant to glioblastoma. Methods: Information on glioblastoma, cancer microenvironment, cancer therapeutics, and how to improve the scenario were obtained from scientific literature databases such as Pubmed, Medline, Google Scholar, Science Direct, Springer, Wiley online library, and some data was harvested from regulatory and compliance databases such as clinicaltrials.gov, FDA database, and WHO Globocan. Results and Conclusion: Currently, only a limited number of therapies are approved for GBM, and no standard care is in place in case of disease relapse, necessitating a possible broader perspective in looking at the disease and its underlying mechanisms

Glycosylation changes as important factors for the susceptibility to urinary tract infection

FimH is the type 1 fimbrial tip adhesin and invasin of Escherichia coli. Its ligands are the glycans on specific proteins enriched in membrane microdomains. FimH binding shows high-affinity recognition of paucimannosidic glycans, which are shortened high-mannose glycans such as oligomannose-3 and -5. FimH can recognize equally the (single) high-mannose glycan on uroplakin la, on the urinary defence protein uromodulin or Tamm-Horsfall glycoprotein and on the intestinal GP2 glycoprotein present in Peyer's patches. E. coil bacteria may attach to epithelial cells via hundreds of fimbriae in a multivalent fashion. This binding is considered to provoke conformational changes in the glycoprotein receptor that translate into signalling in the cytoplasm of the infected epithelial cell. Bladder cell invasion by the uropathogenic bacterium is the prelude to recurrent and persistent urinary tract infections in humans. Patients suffering from diabetes mellitus are more prone to contract urinary tract infections. in a study of women, despite longer treatments with a more potent antibiotic, these patients also have more often recurrences of urinary tract infections compared with women without diabetes. Type 1 fimbriae are the most important virulence factors used not only for adhesion of E. coli in the urinary tract, but also for the colonization by E. coli in patients with Crohn's disease or ulcerative colitis. It appears that the increased prevalence of urinary tract infections in diabetic women is not the result of a difference in the bacteria, but is due to changes in the uroepithelial cells leading to an increased adherence of E. coil expressing type 1 fimbriae. Hypothetically, these changes are in the glycosylation of the infected cells. The present article focuses on possible underlying mechanisms for glycosylation changes in the uroepithelial cell receptors for FimH. Like diabetes, bacterial adhesion induces apoptosis that may bring the endoplasmic reticulum membrane with immature mannosylated glycoproteins to the surface. Indicatively, clathrin-mediated vesicle trafficking of glucose transporters is disturbed in diabetics, which would interfere further with the biosynthesis and localization of complex N-linked glycans

Structure of chymopapain at 1.7 Å resolution

The X-ray structure of chymopapain, a cysteine proteinase isolated from the latex of the fruits of Carica papaya L. has been determined by molecular replacement methods and refined to a conventional R factor of 0.19 for all observed reflections in the range from 9.5 to 1.7 Å resolution. The crystals used in this study contained a unique molecular species of chymopapain with two moles of thiomethyl attached to the two free cysteines per mole of enzyme. A comparison is made with the other known papaya proteinase X-ray structures: papain, caricain, and glycyl endopeptidase. Their backbone conformations are extremely similar except for two loop regions. Both regions are located at the surface of the protein and far away of the active site cleft. In each X-ray structure the same water network was found at the interface between the two domains of the enzyme. A close examination of the active site groove showed that the specificity restrictions dictated by the S2 subsite did not differ significantly among the four proteinases.SCOPUS: ar.jinfo:eu-repo/semantics/publishe