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Inhibition of mammalian cathepsins by Plesiomonas shigelloides
A Pavlova1, K Krovácek, I Ciznár
1Department of Laboratory Medicine, Karolinska Institute, 141 86 Stockholm, Sweden. alona.pavlova@biovica.com
Abstract:
To study molecular mechanisms underlying self-defense of the bacterial pathogen Plesiomonas shigelloides against host inflammatory and immune responses, we evaluated its interactions with mammalian papain-like cathepsins that are essential for host immunity. When grown under anaerobic, but not aerobic, conditions, P. shigelloides was shown to bind and inhibit papain, a model representative of the papain family of cysteine proteinases. This points to mammalian cathepsins as likely physiological targets of a novel cysteine-proteinase inhibitor expressed on bacterial cell surface. Both papain and mammalian cathepsins L and B were inhibited by periplasmic extracts of aerobically and anaerobically grown bacteria, the inhibitory activity being higher in the latter. Inhibition by both intact cells and periplasmic samples was rapid and efficient. The results suggest a possible defensive role of bacterial inhibitors of cathepsins during invasion of a mammalian host. The bacteria thus may modulate host protective responses through inhibiting cathepsins involved in antigen processing and presentation.
Insights
Plesiomonas shigelloides bacteria inhibit host immune responses by targeting mammalian cathepsins. This bacterial defense mechanism, involving a novel cell-surface inhibitor, is more active under anaerobic conditions.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Plesiomonas shigelloides is a bacterial pathogen.
- Host immune responses are crucial for defense against pathogens.
- Papain-like cathepsins are essential mammalian immune components.
Purpose of the Study:
- To investigate the molecular mechanisms of P. shigelloides self-defense against host immunity.
- To evaluate interactions between P. shigelloides and mammalian papain-like cathepsins.
- To identify potential bacterial inhibitors targeting host immune proteins.
Main Methods:
- Culturing P. shigelloides under aerobic and anaerobic conditions.
- Assessing the binding and inhibition of papain and mammalian cathepsins (L and B) by bacteria and their periplasmic extracts.
- Measuring the efficiency and speed of inhibition.
Main Results:
- P. shigelloides binds and inhibits papain, a cysteine proteinase, under anaerobic conditions.
- A novel cysteine-proteinase inhibitor is expressed on the bacterial cell surface, targeting mammalian cathepsins.
- Periplasmic extracts from both aerobic and anaerobic cultures inhibited papain and cathepsins L and B, with higher activity in anaerobic cultures.
- Inhibition by intact cells and periplasmic samples was rapid and efficient.
Conclusions:
- P. shigelloides employs bacterial inhibitors to defend against host immune responses.
- Mammalian cathepsins are likely physiological targets of these bacterial inhibitors.
- Bacterial cathepsin inhibition may modulate host immunity, affecting antigen processing and presentation during infection.
