Characterized enolase of A

Here I have characterized enolase of A. fumigatus as a moonlighting protein that binds human Plg. Enolase, in addition to cytosolic location, is expressed on the surface of swollen conidia and hyphae of opportunistic fungal pathogen A. fumigatus. Enolase on the surface of the fungus binds human Plg and the binding is mediated by lysine residues. Furthermore, enolase bound Plg in presence of activator tPa, is functionally active and degrades the chromogenic substrate S2251, the natural substrate fibrinogen and complement proteins C3 and C3b.

Moreover, Plg bound to the surface of A. fumigatus in presence of tPa damages lung epithelial cells. In addition, enolase binds complement regulators Factor H, FHL-1 and C4BP, which retain functional activity. Thus, enolase is a moonlighting protein in the surface of the opportunistic fungal pathogen A. fumigatus and enolase binds human Plg, Factor H, FHL-1 and C4BP. The fungus A. fumigatus, in the course of causing infection, first has to gain entry into the human host and thereafter overcome the host immune defense, among others – the complement system.

In this interplay between human and the fungal pathogen, A. fumigatus expresses and uses an arsenal of virulence factors, among others moonlighting proteins are known to be implicated in virulence of pathogenic microbes (53, 56, 61, 73). Enolase is a moonlighting protein that mediates the glycolytic reaction of converting 2-phosphoglycerate to phosphoenol pyruvate in cytosol (97). In addition to cytosol, enolase is a surface expressed protein where it performs additional new functions, like binds various host components as human Plg, laminin, fibronectin (111).

The multiple alignment analysis show similarity between A. fumigatus enolase and other pathogenic microorganisms, 73% similarity with Candida albicans enolase, 61% Cryptococcus neoformans, 44% Streptoccocus pyogenes and Borrelia burgdorferi, 46% with Mycobacterium tuberculosis enolase. Moreover, the enolase from all above mentioned pathogens binds human Plg (9, 72, 106, 120). In addition, surface expressed enolase of various fungal pathogens with medical importance bind human Plg, among others also enolase expressed in the surface of the hyphae of A.

fumigatus (44). However, up to date the interaction of A. fumigatus enolase with human Plg has not been characterized, therefor we aimed to characterize this interaction. On this background and aiming to characterize the interaction of A. fumigatus enolase and human Plg, I first studied and characterized protein – protein interaction of recombinant enolase of A. fumigatus with human Plg . The enolase – Plg interaction was confirmed by ELISA results. Also, immobilized enolase acquired Plg from normal human serum.

In addition, A. fumigatus enolase interacts with human Plg with high affinity. The bio layer interferometry showed that the binding affinity of enolase and Plg is 5. 3 nM. Enolase of A. fumigatus interacts with human Plg with a comparable affinity with other microorganisms like S. pneumonia and S. pyogenes (8, 106). However, enolase of other pathogenic microorganisms interacts with human Plg with higher affinity, as is the case for B. burgdorferi and M. tuberculosis (42, 105) (Table 1).