Salmonella Typhimurium enolase-like membrane protein is recognized by antibodies against human enolase and interacts with plasminogen

BACKGROUND: Enolase is generally known as the glycolytic pathway enzyme present in the cytoplasm of eukaryotic cells and in some microorganisms. In human cells, it is also a component of cell surface membranes, where it functions as a human plasminogen receptor. OBJECTIVES: The study aimed to purify Salmonella enterica serovar Typhimurium cytosolic enolase and obtain the antibodies against this protein; to identify enolase on the surface of bacteria; and to find cross-reactivity and plasminogen binding properties. MATERIAL AND METHODS: Cytosolic enolase from S. Typhimurium was purified using a five-step preparation method. Anti-cytosolic enolase antibodies combined with scanning electron microscopy (SEM) allowed us to detect enolase on the surface of intact S. Typhimurium cells. The binding of plasminogen to surface enolase and the cross-reactivity of this protein with antibodies against human enolases were tested with western blot. RESULTS: Antibodies against human α- and β-enolases cross-reacted with S. Typhimurium membrane protein, the identity of which was further confirmed using a mass spectrometry analysis of enolase tryptic peptides. The enolase form bacterial membrane also bound plasminogen. CONCLUSIONS: The cross-reactivity of membrane enolase with antibodies against human enolases suggests that this bacterium shares epitopes with human proteins. Surface exposition of enolase and the demonstrated affinity for human plasminogen indicates that Salmonella membrane enolase could play a role in the interaction of S. Typhimurium with host cells.