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Interaction of surface molecules on Cryptococcus neoformans with plasminogen
1Department of Microbial Science and Host Defense, Meiji Pharmaceutical University, Noshio, Kiyose, Tokyo, Japan.
Abstract:
Microbial pathogens are known to express molecules that interact with host proteins, leading to invasion and colonization. For example, some pathogenic microorganisms express proteins that bind to and enhance the activity of plasminogen. In this way, pathogens utilize the host fibrinolytic system to promote invasion. We found that triosephosphate isomerase (TPI), a glycolytic enzyme produced by Staphylococcus aureus, bound to mannooligosaccharides from the pathogenic capsulated fungus Cryptococcus neoformans and human plasminogen, suggesting that TPI is a moonlighting protein. Several C. neoformans surface proteins are thought to be plasminogen-binding proteins. Here, we examined the ability of surface polymers (including polysaccharides) to bind plasminogen. Heat-killed C. neoformans cells transformed plasminogen into plasmin in a dose-dependent manner in the presence of tissue plasminogen activator. Soluble polysaccharides were found to bind plasminogen based on surface plasmon resonance (SPR) analysis. Neutral polysaccharides fractionated using DEAE column chromatography bound and activated plasminogen. However, the fraction containing glucuronoxylomannan (the primary component of the capsule) did not activate plasminogen. In addition, binding between glucuronoxylomannan and plasminogen was weak. Components of the neutral polysaccharides were identified as mannose, galactose, glucose and xylose. In conclusion, neutral polysaccharides that may affect fibrinolysis were detected on the surface of C. neoformans.
Insights
Cryptococcus neoformans surface polysaccharides bind and activate plasminogen, a key component of the host fibrinolytic system. This interaction may facilitate pathogen invasion by influencing blood clot breakdown.
Area of Science:
- Microbiology
- Biochemistry
- Immunology
Background:
- Pathogenic microorganisms often express molecules that interact with host proteins to facilitate invasion.
- The host fibrinolytic system, involving plasminogen, is a target for microbial exploitation.
- Staphylococcus aureus triosephosphate isomerase (TPI) is a known moonlighting protein that binds plasminogen.
Purpose of the Study:
- To investigate the interaction between Cryptococcus neoformans surface polymers and human plasminogen.
- To determine if C. neoformans surface components can activate plasminogen, potentially aiding in host tissue invasion.
Main Methods:
- Surface plasmon resonance (SPR) analysis to detect plasminogen binding to soluble polysaccharides.
- DEAE column chromatography to fractionate C. neoformans surface polysaccharides.
- Assay to measure plasminogen activation by C. neoformans components in the presence of tissue plasminogen activator.
Main Results:
- Heat-killed C. neoformans cells activated plasminogen in a dose-dependent manner.
- Neutral polysaccharides from C. neoformans bound to plasminogen and activated it.
- The major capsular component, glucuronoxylomannan, showed weak binding and did not activate plasminogen.
- Neutral polysaccharides contained mannose, galactose, glucose, and xylose.
Conclusions:
- C. neoformans possesses surface neutral polysaccharides capable of binding and activating plasminogen.
- These polysaccharides may influence the host fibrinolytic system, potentially contributing to fungal invasion.
- The primary capsule component, glucuronoxylomannan, does not appear to play a significant role in plasminogen activation.
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