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Proteinases of common pathogenic bacteria degrade and inactivate the antibacterial peptide LL-37
Artur Schmidtchen1, Inga-Maria Frick, Emma Andersson
1Section for Dermatology, Department of Medical Microbiology, Dermatology and Infection, Biomedical Center, B14, Tornavägen 10, S-22184 Lund, Sweden. artur.schmidtchen@derm.lu.se
Abstract:
Effectors of the innate immune system, the anti-bacterial peptides, have pivotal roles in preventing infection at epithelial surfaces. Here we show that proteinases of the significant human pathogens Pseudomonas aeruginosa, Enterococcus faecalis, Proteus mirabilis and Streptococcus pyogenes, degrade the antibacterial peptide LL-37. Analysis by mass spectrometry of fragments generated by P. aeruginosa elastase in vitro revealed that the initial cleavages occurred at Asn-Leu and Asp-Phe, followed by two breaks at Arg-Ile, thus inactivating the peptide. Proteinases of the other pathogens also degraded LL-37 as determined by SDS-PAGE. Ex vivo, P. aeruginosa elastase induced LL-37 degradation in human wound fluid, leading to enhanced bacterial survival. The degradation was blocked by the metalloproteinase inhibitors GM6001 and 1, 10-phenantroline (both of which inhibited P. aeruginosa elastase, P. mirabilis proteinase, and E. faecalis gelatinase), or the inhibitor E64 (which inhibited S. pyogenes cysteine proteinase). Additional experiments demonstrated that dermatan sulphate and disaccharides of the structure [DeltaUA(2S)-GalNAc(4,6S)], or sucroseoctasulphate, inhibited the degradation of LL-37. The results indicate that proteolytic degradation of LL-37 is a common virulence mechanism and that molecules which block this degradation could have therapeutic potential.
Insights
Pathogenic bacteria degrade the antibacterial peptide LL-37, a key immune effector. Inhibiting this degradation with specific molecules offers potential therapeutic strategies against bacterial infections.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Antimicrobial peptides, such as LL-37, are crucial for innate immunity at epithelial surfaces.
- Pathogenic bacteria employ various mechanisms to evade host defenses.
Purpose of the Study:
- To investigate the degradation of the antimicrobial peptide LL-37 by proteinases from common human pathogens.
- To identify potential therapeutic agents that inhibit LL-37 degradation.
Main Methods:
- Mass spectrometry and SDS-PAGE were used to analyze LL-37 degradation by bacterial proteinases.
- Ex vivo experiments utilized human wound fluid to assess LL-37 degradation in a relevant context.
- Inhibitors of metalloproteinases and cysteine proteinases were tested for their efficacy in blocking degradation.
Main Results:
- Proteinases from Pseudomonas aeruginosa, Enterococcus faecalis, Proteus mirabilis, and Streptococcus pyogenes were shown to degrade LL-37.
- P. aeruginosa elastase degraded LL-37 into inactive fragments.
- Inhibitors and specific molecules like dermatan sulphate blocked LL-37 degradation, enhancing bacterial survival.
- LL-37 degradation was observed ex vivo in human wound fluid.
Conclusions:
- Proteolytic degradation of LL-37 is a common virulence mechanism employed by human pathogens.
- Inhibitors of bacterial proteinases and specific blocking molecules demonstrate therapeutic potential for combating bacterial infections by preserving LL-37 activity.