Plasminogen binding by oral streptococci from dental plaque and inflammatory lesions

Abstract

Plasminogen binding by bacteria is a virulence factor important for the entry and dissemination of bacteria in the body. A wide variety of bacteria bind plasminogen, including both organisms causing disease and components of the normal oral flora. The purpose of this study was to examine the characteristics of plasminogen binding by six clinical isolates of oral streptococci from both dental plaque and inflammatory lesions. All the strains bound plasminogen with approximately the same affinity, and binding was specific and lysine-dependent as evidenced by its inhibition by e-aminocaproic acid. All of the test strains were capable of activating bound plasminogen to plasmin without the addition of a plasminogen activator, and subsequent analysis revealed the presence of streptokinase in all strains. However, the streptococci exhibited fibrinolytic activity only in the presence of plasminogen and this could be inhibited by the addition of e-aminocaproic acid. SDS-PAGE and 2D gel electrophoresis coupled with plasminogen ligand blotting showed that only a subset of the total proteins (2-15) were involved in the binding of plasminogen. Partial identification of the binding proteins revealed that four glycolytic enzymes, enolase, phosphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate mutase, were predominant in binding plasminogen. The binding of plasminogen by bacteria from pus did not differ from that of the strains from supragingival plaque. The findings illustrate how apparently innocuous commensal bacteria are capable of utilizing a mechanism that is generally regarded as being of importance to pathogenicity and suggest an additional role of plasminogen binding.

Isolation and characterization of α-enolase, a novel fibronectin-binding protein from Streptococcus suis

“…Both ELISA and SPR also demonstrated, as described for other pathogens, that the interaction between rSsEno and plasminogen is specific, suggesting that this interaction is also a biologically significant event. This provides further evidence to support the earlier finding that bacterial enolases interact with plasminogen with high affinity (Antikainen et al, 2007;Kinnby et al, 2008). In fact, the low nanomolar affinity constant between SsEno and plasminogen obtained in this study agrees with values obtained for the adhesion to plasminogen of enolases from S. pyogenes (Pancholi & Fischetti, 1998) and S. pneumoniae (Bergmann et al, 2003).…”

“…As a consequence of plasminogen activation on bacterial surfaces, bacteria become armed with the broad-substrate-spectrum proteolytic potential of plasmin that is not susceptible to regulation by host-derived inhibitors (Lottenberg et al, 1994). The capture of plasminogen by adhesins such as SsEno and GAPDH and its conversion to plasmin has been described for other pathogens (Antikainen et al, 2007;Kinnby et al, 2008) and can be used to facilitate bacterial penetration through biological membranes such as the blood-brain barrier, and therefore could represent an important determinant of virulence. The role of SsEno in studies using endothelial-cell monolayers in a trans-well system is currently under investigation in our laboratory.…”

StreptococcusAdherence and Colonization

“…A large proportion of the anchorless adhesin family comprises proteins with enzymatic functions. Five of the streptococcal anchorless adhesins identified to date are glycolytic enzymes typically found in the cytosol, namely, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ␣-enolase, phosphoglycerate kinase, phosphoglycerate mutase, and triosephosphate isomerase (298,447). Of these, GAPDH and ␣-enolase are the best characterized.…”

Porphyromonas gingivalis-derived RgpA-Kgp Complex Activates the Macrophage Urokinase Plasminogen Activator System

“…Despite its expression of chymotrypsin-like proteinase, we found that inoculation of mice with T. denticola alone failed to induce alveolar bone loss in a murine PD model (62). Relatedly, the discovery that apparently innocuous oral commensals were capable of inducing plasmin activity (via streptokinase) (63) suggests that plasmin activity per se may not contribute to virulence but might act as a general bacterial sur-FIGURE 7. Model of P. gingivalis activation of the destructive uPA/plasminogen proteolytic cascade.…”