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

Abstract

Streptococcus suis is an important swine pathogen that causes meningitis, endocarditis, arthritis and septicaemia. As a zoonotic agent, S. suis also causes similar diseases in humans. Binding of pathogenic bacteria to extracellular matrix components enhances their adhesion to and invasion of host cells. In the present study we isolated and identified a novel fibronectin-binding protein from S. suis. The native protein (designated SsEno) possessed not only high homology with other bacterial enolases but also enolase activity. We cloned, expressed and purified SsEno and showed that it is ubiquitously expressed by all S. suis serotypes and we identified its surface localization using immunoelectron microscopy. ELISA demonstrated that SsEno binds specifically to fibronectin and plasminogen in a lysine-dependent manner. Additional surface plasmon resonance assays demonstrated that SsEno binds to fibronectin or plasminogen with low nanomolar affinity. Inhibition experiments with anti-SsEno antibodies also showed that bacterial SsEno is important for the adhesion to and invasion of brain microvascular endothelial cells by S. suis. Overall, the present work is the first study, to our knowledge, to demonstrate a fibronectinbinding activity of a bacterial enolase, and shows that, similar to other bacterial fibronectin-binding proteins, SsEno may contribute to the virulence of S. suis. INTRODUCTIONStreptococcus suis is a major swine pathogen that causes septicaemia, meningitis, endocarditis and arthritis (Higgins & Gottschalk, 2005). Of the 35 known serotypes, serotype 2 is the most frequently isolated and associated with disease (Higgins & Gottschalk, 2005). It has been proposed that two serotypes (serotypes 32 and 34) be excluded from S. suis and redesignated Streptococcus orisratti (Hill et al., 2005). S. suis, especially serotype 2, has also been described as an important zoonotic agent that affects people in close contact with infected pigs or pork-derived products (Lun et al., 2007). Indeed, an important number of cases of human disease with a high rate of mortality in China were linked directly to a concurrent outbreak of S. suis infection in pigs (Ye et al., 2006).Little is known about S. suis virulence factors. The capsule polysaccharide (CPS) is a critical virulence factor, given that unencapsulated isogenic mutants are completely avirulent and rapidly cleared from the circulation in pig and mouse infection models (Charland et al., 2000;Smith et al., 1999). However, non-virulent strains are also encapsulated, indicating that the virulence of this pathogen is a multifactorial process . Other potential virulence factors have also been described in S. suis, including a haemolysin (suilysin), a 136 kDa muramidase-released protein (MRP), a 110 kDa extracellular factor (EF) protein, a hyaluronidase, a superoxide dismutase, various proteases, a serum opacity factor and different adhesins (Baums et al., 2006;.The pathogenesis of S. suis infection is not fully understood and likely involves many steps . Binding between b...

A Processed Multidomain Mycoplasma hyopneumoniae Adhesin Binds Fibronectin, Plasminogen, and Swine Respiratory Cilia

“…NhhA is a surface-located multi-functional protein expressed by Neisseria meningitides: NhhA is able to bind human epithelial cells, laminin, and heparin sulfate (47). The M protein virulence determinant of Streptococcus pyogenes is known to mediate binding to a range of extracellular matrix proteins and serum proteins including plasminogen (48), while ␣-enolase, a virulence factor of Streptococcus suis mediates binding to fibronectin, plasminogen and endothelial cells (49). Collectively, our findings suggest that P116 is a multifunctional virulence determinant involved in the M. hyopneumoniae disease process.…”

Bacterial Virulence in the Moonlight: Multitasking Bacterial Moonlighting Proteins Are Virulence Determinants in Infectious Disease

“…The recombinant protein binds to plasminogen and with high affinity (dissociation constant [K d ] of 21 nM). Furthermore, antibodies to this protein inhibit the adhesion and invasion of S. suis into microvascular endothelial cells (54). The pentose phosphate pathway enzyme, 6-phosphogluconate dehydrogenase, also acts as an adhesin in various pneumococcal strains (47).…”

A Surface Enolase Participates in Borrelia burgdorferi-Plasminogen Interaction and Contributes to Pathogen Survival within Feeding Ticks

“…To accomplish this, we used enolase antibodies and specific inhibitors, as extensively used in previous studies (18,22,23). Unlike antibodies against a control B. burgdorferi membrane protein, BBA52 (29), antibodies raised against recombinant enolase were able to decrease Pg binding to B. burgdorferi cells (Fig.…”

“…Since enolase is one of the well-known Pg-binding proteins detected in many pathogenic organisms (18,27,33,34,37,38), we next assessed whether enolase is involved in B. burgdorferi-Pg interaction. To accomplish this, we used enolase antibodies and specific inhibitors, as extensively used in previous studies (18,22,23).…”