Identification of a Treponema denticola OppA Homologue That Binds Host Proteins Present in the Subgingival Environment

Abstract

Proteins secreted or exported by Treponema denticola have been implicated as mediators of specific interactions between the spirochete and subgingival tissues in periodontal diseases. However, limited information is available on the ability of this peptidolytic organism to bind or transport soluble peptides present in the subgingival environment. A prominent 70-kDa protein was isolated from surface extracts of T. denticola ATCC 35405. A clone expressing a portion of the protein was identified in an Escherichia coli expression library of T. denticola DNA. DNA sequence analysis showed that the cloned gene encoded a peptide homologous to OppA, the solute binding protein of an ATP-binding cassette-type peptide transporter involved in peptide uptake and environmental signaling in a wide range of bacteria. Genes encoding OppB, -C, -D, and -F were identified directly downstream of oppA in T. denticola. OppA was present in representative strains of T. denticola and in Treponema vincentii but was not detected in Treponema pectinovorum or Treponema socranskii. Immunogold electron microscopy suggested that OppA was accessible to proteins at the surface of the spirochete. Native OppA bound soluble plasminogen and fibronectin but did not bind to immobilized substrates or epithelial cells. A T. denticola oppA mutant bound reduced amounts of soluble plasminogen, and plasminogen binding to the parent strain was inhibited by the lysine analog -aminocaproic acid. Binding of soluble host proteins by OppA may be important both for spirochete-host interactions in the subgingival environment and for uptake of peptide nutrients.Treponema denticola is recognized as one of several potential pathogens in acute and chronic forms of human periodontal disease (50,55,62), and closely related spirochetes have been identified in bovine digital dermatitis lesions (10). Likely virulence factors of oral spirochetes include the ability to attach to host tissue and other microorganisms, motility and chemotaxis, immunomodulation, production of toxic metabolic byproducts, and direct cytopathogenicity (reviewed in reference 22). In the case of periodontal diseases, bacterial factors that contribute to the overgrowth of subgingival microflora must also be considered as potential virulence factors. These could include, for instance, uptake systems for peptide nutrients present in a high concentration in the inflamed gingival sulcus. Characterization of these processes will aid in understanding the biology of this organism and may suggest targets for treatment or prophylaxis.T. denticola derives energy primarily from anaerobic degradation of peptides and amino acids (63). Nutrient requirements of this organism are complex (71), and the mechanisms of nutrient uptake are not well understood (12,27,28,61). Peptide uptake requires specific systems for the binding and transport of substrates across the bacterial cell envelope. Oligopeptide uptake systems, members of a superfamily of highly conserved ATP-binding cassette (ABC) transporters, have been described...

Virulence Factors of the Oral Spirochete Treponema denticola

“…OppA is a 70-kDa cell-surface, membrane-associated lipoprotein that has significant similarity to the solute binding protein of a highly conserved ATP-binding cassette-type transporter involved in peptide uptake and environmental signaling in a wide range of bacteria (Fenno et al, 2000). OppA can bind soluble host proteins such as plasminogen and fibrinogen, but not immobilized insoluble host proteins or epithelial cells.…”

Detection of soluble expression and in vivo interactions of the inner membrane protein OppC using green fluorescent protein

“…Besides transporting oligopeptides, the Opp systems in several pathogenic bacteria (Wang et al, 2004;Moutran et al, 2004;Flores-Valdez et al, 2009;Moraes et al, 2014) participate in distinct life processes, including the binding of soluble host proteins (Cundell et al, 1995;Henrich et al, 1999;Fenno et al, 2000), cellular signal transudation (Ruhfel et al, 1993), recycling of cell-wall peptides released from the growing peptidoglycan (Goodell and Higgins, 1987), and initiation of sporulation (Perego et al, 1991). The Opp system plays a leading role in imparting cell sensitivity to aminoglycoside antibiotics (Kashiwagi et al, 1992), and imparts virulence and pathogenicity to the organisms (Moraes et al, 2014).…”

Interactions of Francisella Tularensis With Components of the Host Fibrinolytic System

“…Several members of the genus Borrelia use complement regulator-acquiring surface proteins (CRASP) to bind both PLG and complement factor H to aid in the ability of the organism to both disseminate and to resist innate immunity (90)(91)(92)(93)(94)(95)). An additional example of a PLG-binding lipoprotein is OppA of Treponema denticola, which has been suggested to play a role in periodontal disease in humans (96). With this in mind, there lies the possibility that lipoproteins of Francisella species may have the capacity to bind multiple host-derived proteins in addition to PLG.…”