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Characterization of Treponema denticola mutants defective in the major antigenic proteins, Msp and TmpC.

ABSTRACT: Treponema denticola, a gram-negative and anaerobic spirochete, is associated with advancing severity of chronic periodontitis. In this study, we confirmed that two major antigenic proteins were Msp and TmpC, and examined their physiological and pathological roles using gene-deletion mutants. Msp formed a large complex that localized to the outer membrane, while TmpC existed as a monomer and largely localized to the inner membrane. However, TmpC was also detected in the outer membrane fraction, but its cell-surface exposure was not detected. Msp defects increased cell-surface hydrophobicity and secretion of TNF-? from macrophage-like cells, whereas TmpC defects decreased autoagglutination and chymotrypsin-like protease activities. Both mutants adhered to gingival epithelial cells similarly to the wild-type and showed slightly decreased motility. In addition, in Msp-defective mutants, the TDE1072 protein, which is a major membrane protein, was abolished; therefore, phenotypic changes in the mutant can be, at least in part, attributed to the loss of the TDE1072 protein. Thus, the major antigenic proteins, Msp and TmpC, have significant and diverse impacts on the characteristics of T. denticola, especially cell surface properties.

SUBMITTER: Abiko Y

PROVIDER: S-EPMC4234677 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Characterization of Treponema denticola mutants defective in the major antigenic proteins, Msp and TmpC.

Abiko Yuki Y Nagano Keiji K Yoshida Yasuo Y Yoshimura Fuminobu F

PloS one 20141117 11

Treponema denticola, a gram-negative and anaerobic spirochete, is associated with advancing severity of chronic periodontitis. In this study, we confirmed that two major antigenic proteins were Msp and TmpC, and examined their physiological and pathological roles using gene-deletion mutants. Msp formed a large complex that localized to the outer membrane, while TmpC existed as a monomer and largely localized to the inner membrane. However, TmpC was also detected in the outer membrane fraction, b ...[more]

PMID: 25401769

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Project description:Treponema denticola, one of several recognized periodontal pathogens, is a model organism for studying Treponema physiology and host-microbe interactions. Its major surface protein Msp (or MOSP) comprises an oligomeric outer membrane-associated complex that binds fibronectin, has cytotoxic pore-forming activity, and disrupts several intracellular responses. There are two hypotheses regarding native Msp structure and membrane topology. One hypothesis predicts that the entire Msp protein forms a β-barrel structure similar to that of well-studied outer membrane porins of Gram-negative bacteria. The second hypothesis predicts a bipartite Msp with distinct and separate periplasmic N-terminal and porin-like β-barrel C-terminal domains. The bipartite model, based on bioinformatic analysis of the orthologous Treponema pallidum Tpr proteins, is supported largely by studies of recombinant TprC and Msp polypeptides. The present study reports immunological studies in both T. denticola and Escherichia coli backgrounds to identify a prominent Msp surface epitope (residues 229 to 251 in ATCC 35405) in a domain that differs between strains with otherwise highly conserved Msps. These results were then used to evaluate a series of in silico structural models of representative T. denticola Msps. The data presented here are consistent with a model of Msp as a large-diameter β-barrel porin. This work adds to the knowledge regarding the diverse Msp-like proteins in oral treponemes and may contribute to an understanding of the evolutionary and potential functional relationships between Msps of oral Treponema and the orthologous group of Tpr proteins of T. pallidum. IMPORTANCE Treponema denticola is among a small subset of the oral microbiota contributing to severe periodontal disease. Due to its relative genetic tractability, T. denticola is a model organism for studying Treponema physiology and host-microbe interactions. T. denticola Msp is a highly expressed outer membrane-associated oligomeric protein that binds fibronectin, has cytotoxic pore-forming activity, and disrupts intracellular regulatory pathways. It shares homology with the orthologous group of T. pallidum Tpr proteins, one of which is implicated in T. pallidum in vivo antigenic variation. The outer membrane topologies of both Msp and the Tpr family proteins are unresolved, with conflicting reports on protein domain localization and function. In this study, we combined empirical immunological data derived both from diverse T. denticola strains and from recombinant Msp expression in E. coli with in silico predictive structural modeling of T. denticola Msp membrane topology, to move toward resolution of this important issue in Treponema biology.

Project description:Periodontal disease is a significant health burden, causing tooth loss and poor oral and overall systemic health. Dysbiosis of the oral biofilm and a dysfunctional immune response drive chronic inflammation, causing destruction of soft tissue and alveolar bone supporting the teeth. Treponema denticola, a spirochete abundant in the plaque biofilm of patients with severe periodontal disease, perturbs neutrophil function by modulating appropriate phosphoinositide (PIP) signaling. Through a series of immunoblotting and quantitative PCR (qPCR) experiments, we show that Msp does not alter the gene transcription or protein content of key enzymes responsible for PIP3 signaling: 3' phosphatase and tensin homolog (PTEN), phosphatidylinositol 3-kinase (PI3K), or 5' Src homology 2 domain-containing inositol phosphatase 1 (SHIP1). Instead, using immunoblotting and enzyme-linked immunosorbent assays (ELISAs), we found that Msp activates PTEN through dephosphorylation specifically at the S380 site. Msp in intact organisms or outer membrane vesicles also restricts PIP signaling. SHIP1 phosphatase release was assessed using chemical inhibition and immunoprecipitation to show that Msp moderately decreases SHIP1 activity. Msp also prevents secondary activation of the PTEN/PI3K response. We speculate that this result is due to the redirection of the PIP3 substrate away from SHIP1 to PTEN. Immunofluorescence microscopy revealed a redistribution of PTEN from the cytoplasm to the plasma membrane following exposure to Msp, which may contribute to PTEN activation. Mechanisms of how T. denticola modulates and evades the host immune response are still poorly described, and here we provide further mechanistic evidence of how spirochetes modify PIP signaling to dampen neutrophil function. Understanding how oral bacteria evade the immune response to perpetuate the cycle of inflammation and infection is critical for combating periodontal disease to improve overall health outcomes.

Project description:The gene encoding the major outer sheath protein (Msp) of the oral spirochete Treponema denticola ATCC 35405 was cloned, sequenced, and expressed in Escherichia coli. Preliminary sequence analysis showed that the 5' end of the msp gene was not present on the 5.5-kb cloned fragment described in a recent study (M. Haapasalo, K. H. Müller, V. J. Uitto, W. K. Leung, and B. C. McBride, Infect. Immun. 60:2058-2065,1992). The 5' end of msp was obtained by PCR amplification from a T. denticola genomic library, and an open reading frame of 1,629 bp was identified as the coding region for Msp by combining overlapping sequences. The deduced peptide consisted of 543 amino acids and had a molecular mass of 58,233 Da. The peptide had a typical prokaryotic signal sequence with a potential cleavage site for signal peptidase 1. Northern (RNA) blot analysis showing the msp transcript to be approximately 1.7 kb was consistent with the identification of a promoter consensus sequence located optimally upstream of msp and a transcription termination signal found downstream of the stop codon. The entire msp sequence was amplified from T. denticola genomic DNA and cloned in E. coli by using a tightly regulated T7 RNA polymerase vector system. Expression of Msp was toxic to E. coli when the entire msp gene was present. High levels of Msp were produced as inclusion bodies when the putative signal peptide sequence was deleted and replaced by a vector-encoded T7 peptide sequence. Recombinant Msp purified to homogeneity from a clone containing the full-length msp gene adhered to immobilized laminin and fibronectin but not to bovine serum albumin. Attachment of recombinant Msp was decreased in the presence of soluble substrate. Attachment of T. denticola to immobilized laminin and fibronectin was increased by pretreatment of the substrate with recombinant Msp. These studies lend further support to the hypothesis that Msp mediates the extracellular matrix binding activity of T. denticola.

Dataset Information

Characterization of Treponema denticola mutants defective in the major antigenic proteins, Msp and TmpC.

Publications

Characterization of Treponema denticola mutants defective in the major antigenic proteins, Msp and TmpC.

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