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

Abstract

Borrelia burgdorferi, a tick-borne bacterial pathogen, causes a disseminated infection involving multiple organs known as Lyme disease. Surface proteins can directly participate in microbial virulence by facilitating pathogen dissemination via interaction with host factors. We show here that a fraction of the B. burgdorferi chromosomal gene product BB0337, annotated as enolase or phosphopyruvate dehydratase, is associated with spirochete outer membrane and is surface exposed. B. burgdorferi enolase, either in a recombinant form or as a membrane-bound native antigen, displays enzymatic activities intrinsic to the glycolytic pathway. However, the protein also interacts with host plasminogen, potentially leading to its activation and resulting in B. burgdorferi-induced fibrinolysis. As expected, enolase displayed consistent expression in vivo, however, with a variable temporal and spatial expression during spirochete infection in mice and ticks. Despite an extracellular exposure of the antigen and a potential role in host-pathogen interaction, active immunization of mice with recombinant enolase failed to evoke protective immunity against subsequent B. burgdorferi infection. In contrast, enolase immunization of murine hosts significantly reduced the acquisition of spirochetes by feeding ticks, suggesting that the protein could have a stage-specific role in B. burgdorferi survival in the feeding vector. Strategies to interfere with the function of surface enolase could contribute to the development of novel preventive measures to interrupt the spirochete infection cycle and reduce the incidences of Lyme disease.

Characterization of pyruvate dehydrogenase subunit B and enolase as plasminogen-binding proteins in Mycoplasma pneumoniae

“…The identification of M. pneumoniae enolase as a binding partner of plasminogen confirmed the theoretical prediction based on homology modelling (Chumchua et al, 2008) and was in accordance with experimental results from the mycoplasma species Mycoplasma fermentans (Yavlovich et al, 2007), M. gallisepticum (Chen et al, 2011) and Mycoplasma suis (Schreiner et al, 2012). Besides GAPDH, enolase is one of most frequent members of the class of surface-localized glycolytic enzymes, as described in phylogenetically different species such as Aeromonas hydrophila (Sha et al, 2009), Bacillus anthracis (Agarwal et al, 2008), Borrelia burgdorferi (Nogueira et al, 2012), Bifidobacterium sp. , C. albicans (Jong et al, 2003), Lactobacillus plantarum (Castaldo et al, 2009), Paracoccidioides brasiliensis (Donofrio et al, 2009), Staphylococcus aureus (Carneiro et al, 2004), S. pneumoniae (Bergmann et al, 2001) and Trichomonas vaginalis (Mundodi et al, 2008).…”

Expression, purification, and biological characterization of <i>Anaplasma phagocytophilum</i> enolase

“…In recent years, enolase has also been identified on the surface of a variety of eukaryotic cells, and there acts as a plasminogen receptor promoting conversion to plasmin when in the presence of plasminogen activator (8). Furthermore, it has been confirmed that surface-expressed enolase on vector-borne pathogens plays an essential role during pathogen invasion of vector gut by binding mammalian plasminogen (9,10).…”

“…Many reports have demonstrated that enolase can also be expressed on the surface of organisms, and act as the plasminogen receptor (10,13,(21)(22)(23). In order to characterize rApEno plasminogen binding, ELISA experiments were performed.…”

“…The analysis was performed in 96-well plates as previously described (10). In brief, each well was coated overnight at 4°C with 100 μL PBS containing 0.04 μg/ μL human plasminogen.…”

“…To analyze the effects of pH and temperature on rApEno activation, the assay was performed using a reaction buffer system at different pH values (3,4,5,6,7,8,9,10, and 11) and temperature (4, 22, 30, 37, 50, 60, 70, and 80°C). Reactions were initiated by the addition of rApEno (1 μg/reaction) diluted in the corresponding buffer.…”