The vast majority of systemic bacterial infections are caused by facultative, often antibiotic-resistant, pathogens colonizing human body surfaces. Nasal carriage of Staphylococcus aureus predisposes ...to invasive infection, but the mechanisms that permit or interfere with pathogen colonization are largely unknown. Whereas soil microbes are known to compete by production of antibiotics, such processes have rarely been reported for human microbiota. We show that nasal Staphylococcus lugdunensis strains produce lugdunin, a novel thiazolidine-containing cyclic peptide antibiotic that prohibits colonization by S. aureus, and a rare example of a non-ribosomally synthesized bioactive compound from human-associated bacteria. Lugdunin is bactericidal against major pathogens, effective in animal models, and not prone to causing development of resistance in S. aureus. Notably, human nasal colonization by S. lugdunensis was associated with a significantly reduced S. aureus carriage rate, suggesting that lugdunin or lugdunin-producing commensal bacteria could be valuable for preventing staphylococcal infections. Moreover, human microbiota should be considered as a source for new antibiotics.
Recently our groups discovered lugdunin, a new cyclic peptide antibiotic that inhibits Staphylococcus aureus epithelial colonization in humans and rodents. In this work, we analyzed its ...immuno-modulatory and antimicrobial potential as a single agent or in combination with other microbiota- or host-derived factors. We show that pretreatment of primary human keratinocytes or mouse skin with lugdunin in combination with microbiota-derived factors results in a significant reduction of S. aureus colonization. Moreover, lugdunin increases expression and release of LL-37 and CXCL8/MIP-2 in human keratinocytes and mouse skin, and results in the recruitment of monocytes and neutrophils in vivo, both by a TLR/MyD88-dependent mechanism. Interestingly, S. aureus elimination by lugdunin is additionally achieved by synergistic antimicrobial activity with LL-37 and dermcidin-derived peptides. In summary, our results indicate that lugdunin provides multi-level protection against S. aureus and may thus become a promising treatment option for S. aureus skin infections in the future.
A new solid-phase peptide synthesis and bioprofiling of the antimicrobial activity of lugdunin, a fibupeptide, enable a comprehensive structure–activity relationship (SAR) study (MRSA Staphylococcus ...aureus). Distinct lugdunin analogues with variation of the three important amino acids Val2, Trp3, and Leu4 are readily available based on the established high-output synthesis. This efficient synthesis concept takes advantage of the presynthesized thiazolidine building block. To gain further knowledge of SAR, d-Val2, and d-Leu4 were replaced with aliphatic amino acids. For l-Trp3 derivatization, a set of non-natural aromatic amino acids with manifold substitution and annulation patterns precisely shows structural imperatives, starting from the exchange of d-Val6 → d-Trp6 with a 2-fold improved biological activity. d-Trp6-lugdunin analogues with additional variation of d-Val2 and d-Leu4 residues were designed and synthesized followed by antimicrobial profiling. For the first time, these SAR studies deliver valuable information on the tolerance of other amino acids to d-Val2, l-Trp3, and d-Leu4 in the sequence of lugdunin.
Lugdunin, a novel thiazolidine cyclopeptide, exhibits micromolar activity against methicillin‐resistant Staphylococcus aureus (MRSA). For structure–activity relationship (SAR) studies, synthetic ...analogues obtained from alanine and stereo scanning as well as peptides with modified thiazolidine rings were tested for antimicrobial activity. The thiazolidine ring and the alternating d‐ and l‐amino acid backbone are essential. Notably, the non‐natural enantiomer displays equal activity, thus indicating the absence of a chiral target. The antibacterial activity strongly correlates with dissipation of the membrane potential in S. aureus. Lugdunin equalizes pH gradients in artificial membrane vesicles, thereby maintaining membrane integrity, which demonstrates that proton translocation is the mode of action (MoA). The incorporation of extra tryptophan or propargyl moieties further expands the diversity of this class of thiazolidine cyclopeptides.
Ornament clasp confers function: Synthetic analogues of lugdunin, the first antibiotic from the human nose, reveal essential motifs for conferring antimicrobial activity against methicillin‐resistant Staphylococcus aureus. In addition to an alternating d‐ and l‐configuration, the thiazolidine heterocycle—featured for the first time in a cyclopeptide—is invaluable for the proton translocation mode of action.
Antagonistic bacterial interactions often rely on antimicrobial bacteriocins, which attack only a narrow range of target bacteria. However, antimicrobials with broader activity may be advantageous. ...Here we identify an antimicrobial called epifadin, which is produced by nasal Staphylococcus epidermidis IVK83. It has an unprecedented architecture consisting of a non-ribosomally synthesized peptide, a polyketide component and a terminal modified amino acid moiety. Epifadin combines a wide antimicrobial target spectrum with a short life span of only a few hours. It is highly unstable under in vivo-like conditions, potentially as a means to limit collateral damage of bacterial mutualists. However, Staphylococcus aureus is eliminated by epifadin-producing S. epidermidis during co-cultivation in vitro and in vivo, indicating that epifadin-producing commensals could help prevent nasal S. aureus carriage. These insights into a microbiome-derived, previously unknown antimicrobial compound class suggest that limiting the half-life of an antimicrobial may help to balance its beneficial and detrimental activities.
Lugdunin, ein neues Thiazolidin‐Cyclopeptid, weist gegenüber Methicillin‐resistentem Staphylococcus aureus (MRSA) antimikrobielle Wirkung im mikromolaren Bereich auf. Für die Untersuchung von ...Struktur‐Aktivitätsbeziehungen (SAR) wurden synthetische Alanin‐ und Stereo‐Derivate sowie Peptide mit modifiziertem Thiazolidinring auf ihre antimikrobielle Aktivität getestet. Sowohl das Thiazolidin als auch die d‐, l‐alternierende Konfiguration stellen essentielle Strukturmotive dar. Bemerkenswert ist die identische Aktivität des Enantiomers, was eine stereospezifische Wechselwirkung mit einem Zielmolekül ausschließt. Die antibakterielle Wirkung korreliert stark mit dem Einbrechen des Membranpotentials von S. aureus. Lugdunin gleicht pH‐Gradienten in künstlichen Membranvesikeln unter Erhalt der Membranintegrität aus. Der Wirkmechanismus (MoA) beruht somit auf Protonentransport. Der Einbau eines zusätzlichen Tryptophans oder einer Propargylfunktion erweitert die Diversität dieser neuen Substanzklasse der Thiazolidin‐Cyclopeptide.
„Gewandspange” verleiht Wirkung: Synthetische Derivate von Lugdunin, dem ersten Antibiotikum aus der menschlichen Nase, enthüllen die essentiellen Strukturmotive für dessen Aktivität gegen Methicillin‐resistenten Staphylococcus aureus. Zusätzlich zur alternierenden d‐, l‐Konfiguration ist der Thiazolidinring – erstmals für ein Cyclopeptid beschrieben – unabdingbar für die protonentransportierende Wirkung.
Chitin is the second most abundant polysaccharide in nature and linked to fungal infection and asthma. However, bona fide immune receptors directly binding chitin and signaling immune activation and ...inflammation have not been clearly identified because polymeric crude chitin with unknown purity and molecular composition has been used. By using defined chitin (N‐acetyl‐glucosamine) oligomers, we here identify six‐subunit‐long chitin chains as the smallest immunologically active motif and the innate immune receptor Toll‐like receptor (TLR2) as a primary fungal chitin sensor on human and murine immune cells. Chitin oligomers directly bind TLR2 with nanomolar affinity, and this fungal TLR2 ligand shows overlapping and distinct signaling outcomes compared to known mycobacterial TLR2 ligands. Unexpectedly, chitin oligomers composed of five or less subunits are inactive, hinting to a size‐dependent system of immuno‐modulation that appears conserved in plants and humans. Since blocking of the chitin‐TLR2 interaction effectively prevents chitin‐mediated inflammation in vitro and in vivo, our study highlights the chitin‐TLR2 interaction as a potential target for developing novel therapies in chitin‐related pathologies and fungal disease.
Synopsis
Chitin, a polysaccharide linked to fungal infection and allergic asthma, directly binds to the innate immune receptor TLR2 and triggers inflammation dependent on oligomer size. Blocking the chitin‐TLR2 interaction effectively prevents chitin‐mediated inflammation.
Oligomeric chains of fungal chitin directly bind to TLR2 and trigger inflammation.
Blocking of the chitin‐TLR2 interaction prevents chitin‐mediated inflammation in vitro and in vivo.
Size‐dependent chitin recognition based on oligomers is found in both plants and humans.
Chitin, a polysaccharide linked to fungal infection and allergic asthma, directly binds to the innate immune receptor TLR2 and triggers inflammation dependent on oligomer size. Blocking the chitin‐TLR2 interaction effectively prevents chitin‐mediated inflammation.
Activity of the NLRP3 inflammasome, a critical mediator of inflammation, is controlled by accessory proteins, posttranslational modifications, cellular localization, and oligomerization. How these ...factors relate is unclear. We show that a well-established drug target, Bruton's tyrosine kinase (BTK), affects several levels of NLRP3 regulation. BTK directly interacts with NLRP3 in immune cells and phosphorylates four conserved tyrosine residues upon inflammasome activation, in vitro and in vivo. Furthermore, BTK promotes NLRP3 relocalization, oligomerization, ASC polymerization, and full inflammasome assembly, probably by charge neutralization, upon modification of a polybasic linker known to direct NLRP3 Golgi association and inflammasome nucleation. As NLRP3 tyrosine modification by BTK also positively regulates IL-1β release, we propose BTK as a multifunctional positive regulator of NLRP3 regulation and BTK phosphorylation of NLRP3 as a novel and therapeutically tractable step in the control of inflammation.
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