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Published on: October 31, 2019
Relationships Between Plasminogen-Binding M-Protein and Surface Enolase for Human Plasminogen Acquisition and
Yetunde A Ayinuola1, Sheiny Tjia-Fleck1,2, Bradley M Readnour1,2
1W.M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN, United States.
Abstract:
The proteolytic activity of human plasmin (hPm) is utilized by various cells to provide a surface protease that increases the potential of cells to migrate and disseminate. Skin-trophic Pattern D strains of Streptococcus pyogenes (GAS), e.g., GAS isolate AP53, contain a surface M-protein (PAM) that directly and strongly interacts (K ~ 1 nM) with human host plasminogen (hPg), after which it is activated to hPm by a specific coinherited bacterial activator, streptokinase (SK2b), or by host activators. Another ubiquitous class of hPg binding proteins on GAS cells includes "moonlighting" proteins, such as the glycolytic enzyme, enolase (Sen). However, the importance of Sen in hPg acquisition, especially when PAM is present, has not been fully developed. Sen forms a complex with hPg on different surfaces, but not in solution. Isogenic AP53 cells with a targeted deletion of PAM do not bind hPg, but the surface expression of Sen is also greatly diminished upon deletion of the PAM gene, thus confounding this approach for defining the role of Sen. However, cells with point deletions in PAM that negate hPg binding, but fully express PAM and Sen, show that hPg binds weakly to Sen on GAS cells. Despite this, Sen does not stimulate hPg activation by SK2b, but does stimulate tissue-type plasminogen activator-catalyzed activation of hPg. These data demonstrate that PAM plays the dominant role as a functional hPg receptor in GAS cells that also contain surface enolase.
Insights
Streptococcus pyogenes uses surface M-protein (PAM) to bind human plasminogen (hPg), enhancing bacterial spread. Enolase (Sen) plays a minor role in hPg acquisition and activation by PAM-expressing GAS cells.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Proteolytic activity of human plasmin (hPm) aids cell migration and dissemination.
- Streptococcus pyogenes (GAS) utilizes surface proteins to bind human plasminogen (hPg), facilitating its activation to hPm.
- GAS possesses both plasminogen-binding M-protein (PAM) and moonlighting proteins like enolase (Sen), but Sen's role in hPg acquisition is unclear.
Purpose of the Study:
- To investigate the role of enolase (Sen) in human plasminogen (hPg) acquisition and activation by Streptococcus pyogenes (GAS), particularly in the presence of plasminogen-associated M-protein (PAM).
Main Methods:
- Utilized isogenic AP53 GAS cells with targeted deletions in PAM to assess hPg binding and activation.
- Investigated hPg interaction with Sen on GAS cells with modified PAM expression.
- Examined Sen's effect on hPg activation by streptokinase (SK2b) and tissue-type plasminogen activator (tPA).
Main Results:
- GAS cells lacking PAM showed diminished Sen surface expression, complicating direct analysis of Sen's function.
- GAS cells with intact PAM and Sen, but with impaired hPg binding to PAM, exhibited weak hPg binding to Sen.
- Sen did not enhance hPg activation by SK2b but did stimulate tPA-catalyzed hPg activation.
Conclusions:
- PAM is the primary functional human plasminogen (hPg) receptor on GAS cells, even when enolase (Sen) is present.
- Sen's contribution to hPg acquisition and activation by GAS is secondary to PAM.
- Understanding these interactions is crucial for developing strategies against GAS infections.
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