α-Enolase, a Novel Strong Plasmin(ogen) Binding Protein on the Surface of Pathogenic Streptococci

Abstract

The plasmin(ogen) binding property of group A streptococci is incriminated in tissue invasion processes. We have characterized a novel 45-kDa protein displaying strong plasmin(ogen) binding activity from the streptococcal surface. Based on its biochemical properties, we confirmed the identity of this protein as ␣-enolase, a key glycolytic enzyme. Dose-dependent ␣-enolase activity, immune electron microscopy of whole streptococci using specific antibodies, and the opsonic nature of polyclonal and monoclonal antibodies concluded the presence of this protein on the streptococcal surface. We, henceforth, termed the 45-kDa protein, SEN (streptococcal surface enolase). SEN is found ubiquitously on the surface of most streptococcal groups and serotypes and showed significantly greater plasmin(ogen) binding affinity compared with previously reported streptococcal plasminogen binding proteins. Both the C-terminal lysine residue of SEN and a region N-terminal to it play a critical role in plasminogen binding. Results from competitive plasminogen binding inhibition assays and cross-linking studies with intact streptococci indicate that SEN contributes significantly to the overall streptococcal ability to bind plasmin(ogen). Our findings, showing both the protected protease activity of SENbound plasmin and SEN-specific immune responses, provide evidence for an important role of SEN in the disease process and post-streptococcal autoimmune diseases.Streptococcus pyogenes is responsible for a wide variety of human diseases that range from suppurative infections of the throat (pharyngitis), skin (impetigo), and underlying tissues (necrotizing fasciitis), to an often fatal toxic shock syndrome, and the post-streptococcal sequelae, rheumatic fever, and acute glomerulonephritis. Bacterial surface proteins play a major role in these disease processes by exhibiting a wide range of functions. As data have become available, it is clear that most surface proteins found on Gram-positive bacteria, particularly those on group A streptococci, have a great deal of structural similarities (1, 2). Proteins for which the function(s) has been defined have been found to be multifunctional, whereas in others a function has only been attributed to one of two or more domains (2, 3). Thus, the multifunctional characteristics of these surface proteins increase the complexity of the Grampositive surface beyond what has been previously imagined.We recently described one such multifunctional protein, streptococcal surface dehydrogenase (SDH), 1 as a major surface protein on group A streptococci and other streptococcal groups which is structurally and functionally related to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (4). SDH also has an ADP-ribosylating activity (5) and exhibits multiple binding activities to several mammalian proteins such as fibronectin and cytoskeletal proteins (4). A structurally and enzymatically similar streptococcal protein, Plr, was also identified on group A streptococci, based on its ability to bind plasmin (6). SDH, how...

Exploiting death: apoptotic immunity in microbial pathogenesis

“…[26][27][28][29][30][31][32][33] Independent studies also have implicated externalized α-enolase and GAPDH on mammalian and pathogen surfaces as sites for plasminogen binding and subsequent activation by host or pathogen activities, [26][27][28]30,31,[34][35][36] and we have demonstrated that externalized glycolytic enzymes on the apoptotic cell surface, including α-enolase, also are sites for plasminogen binding. 12 Although enhanced virulence has been attributed to the presumptive augmentation in mobility through matrix or fibrin clots associated with localized plasminogen activation following binding on the pathogen surface, 37,38 no compelling physiological rationale exists for plasminogen binding on non-invasive bacteria and apoptotic cells.…”

Release of metabolic enzymes by Giardia in response to interaction with intestinal epithelial cells

“…We were not able to detect any signal sequences in the proteins but now there are many examples of secreted proteins in eukaryotes without signal sequences [35]. Enolase has been implicated in the pathogenesis of other microbes colonizing mucosal surfaces [29,36]; prokaryotic Streptococcus agalactiae, S. sobrinus, S. pyogenes and eukaryotic Candida albicans ␣-enolases are secreted [36,37], while other enolases are surface-associated [29,38,39]. Some of these enolases are immunodominant [29,36], as is Giardia enolase [24,25].…”

Anti-Alpha-Enolase Antibody as a Serologic Marker and Its Correlation with Disease Severity in Intestinal Behçet’s Disease

“…This protein apparently serves as a plasminogen receptor on the surface of a variety of hematopoietic, epithelial, and endothelial cells and plays a crucial role in intravascular and pericellular fibrinolytic systems [19,20]. This protein is also found on the surface of streptococci, which can cause acute rheumatic fever 3 Cumulative rate of steroid use for the IgM anti-a-enolase antibody positive and negative groups were 38 and 31% at 1 year, 40 and 35% at 2 years, 46 and 43% at 3 years, 51 and 48% at 4 years, and 60 and 48% at 5 years, respectively (P = 0.022) [21], and has been identified as a type of heat-shock protein [22].…”