Abstract
Antithrombin III (ATIII) is a key antiproteinase involved in blood coagulation. Previous investigations have shown that ATIII is degraded by Staphylococcus aureus V8 protease, leading to release of heparin binding fragments derived from its D helix. As heparin binding and antimicrobial activity of peptides frequently overlap, we here set out to explore possible antibacterial effects of intact and degraded ATIII. In contrast to intact ATIII, the results showed that extensive degradation of the molecule yielded fragments with antimicrobial activity. Correspondingly, the heparin-binding, helix D-derived, peptide FFFAKLNCRLYRKANKSSKLV (FFF21) of human ATIII, was found to be antimicrobial against particularly the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. Fluorescence microscopy and electron microscopy studies demonstrated that FFF21 binds to and permeabilizes bacterial membranes. Analogously, FFF21 was found to induce membrane leakage of model anionic liposomes. In vivo, FFF21 significantly reduced P. aeruginosa infection in mice. Additionally, FFF21 displayed anti-endotoxic effects in vitro. Taken together, our results suggest novel roles for ATIII-derived peptide fragments in host defense.
Highlights
Antithrombin III (ATIII), an antiproteinase-inhibiting coagulation, was investigated for roles in host defense
We evaluated whether more extensive proteolysis of ATIII, previously demonstrated to generate low molecular weight fragments encompassing an epitope of helix D [5] could uncover cryptic antimicrobial activity
RDA analyses of fractions showed that these digested ATIII fractions were antimicrobial, it was noted that the V8-digested material displayed activity against E. coli, whereas S. aureus was not inhibited (Fig. 1B, upper panels)
Summary
Antithrombin III (ATIII), an antiproteinase-inhibiting coagulation, was investigated for roles in host defense. Previous investigations have shown that ATIII is degraded by Staphylococcus aureus V8 protease, leading to release of heparin binding fragments derived from its D helix. Plasma-derived ATIII has been found to inhibit bacterial outgrowth and limited the inflammatory response, neutrophil influx, and histopathological changes in Streptococcus pneumoniae pneumonia [15], it was unclear whether these beneficial effects were due to prostacyclin formation, interference with bacterial toxins such as pneumolysin, or reduced coagulation and related modulation of extracellular proteins and peptides. The relatedness to HCII, the observation that ATIII contains a heparin-binding region represented by helix D, the multifunctionality of ATIII, as well as the above-mentioned suppressive effects on pneumococcal infections, prompted us to investigate possible antimicrobial effects exerted by ATIII or peptides derived from its helix D
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
