Enolase AmEno15, a Promising Candidate for Understanding the Infectious Process of Anaplasma marginale

Bovine anaplasmosis is a serious health problem in the livestock industry. Currently, there is a lack of information regarding the molecular mechanisms by which Anaplasma marginale adheres and invades bovine erythrocytes. Even more is unknown about how it binds to tick gut cells when the tick feeds on infected blood. In other pathogens, enolase has been shown to play a significant role in adhesion to host tissue, serving as the first step in invasion and colonization. Therefore, the elucidation of the role of the moonlighting protein enolase AmEno15 of A. marginale in the adhesion to erythrocytes, tick gut tissue, and plasminogen is addressed in this work. We explored the role of A. marginale recombinant AmEno15 in the adhesion to spectrin, stomatin, fibronectin, and plasminogen. Firstly, we modeled AmEno15 tridimensionally and performed a molecular dynamics approach to determine whether AmEno15 could bind to the proteins mentioned above. Then, we expressed recombinant AmEno15 and performed a microplate binding assay using fixed concentrations of the erythrocyte proteins, fibronectin, and plasminogen, as well as variable concentrations of AmEno15. We found that AmEno15 binds to all assessed proteins in a specific and concentration-dependent manner. Spectrin and fibronectin-AmEno15 binding occurs at high concentrations, while stomatin and plasminogen-AmEno15 binding occurs at lower concentrations. Our findings bring us closer to understanding the role of the moonlighting protein enolase and suggest its participation in the A. marginale adhesion and invasion processes, providing a basis for the control of tick-borne diseases.