An ancestral host defence peptide within human β-defensin 3 recapitulates the antibacterial and antiviral activity of the full-length molecule

Abstract

Host defence peptides (HDPs) are critical components of innate immunity. Despite their diversity, they share common features including a structural signature, designated "γ-core motif". We reasoned that for each HDPs evolved from an ancestral γ-core, the latter should be the evolutionary starting point of the molecule, i.e. it should represent a structural scaffold for the modular construction of the full-length molecule, and possess biological properties. We explored the γ-core of human β-defensin 3 (HBD3) and found that it: (a) is the folding nucleus of HBD3; (b) folds rapidly and is stable in human serum; (c) displays antibacterial activity; (d) binds to CD98, which mediates HBD3 internalization in eukaryotic cells; (e) exerts antiviral activity against human immunodeficiency virus and herpes simplex virus; and (f) is not toxic to human cells. These results demonstrate that the γ-core within HBD3 is the ancestral core of the full-length molecule and is a viable HDP per se, since it is endowed with the most important biological features of HBD3. Notably, the small, stable scaffold of the HBD3 γ-core can be exploited to design disease-specific antimicrobial agents.Host defence peptides (HDPs) are a critical component of innate immunity, and represent a first line of defence against infection by a broad spectrum of pathogens. HDP expression is found in the host tissues most exposed to microorganisms (skin and internal epithelia of e.g. the respiratory and gastrointestinal tracts) and in the cells of the immune system (macrophages, lymphocytes, platelets etc.)1 . Since a number of pathogens that are refractory to conventional antibiotics are sensitive to HDPs, there is considerable interest in the development of these peptides as therapeutics 2 . Moreover, it is becoming increasingly clear that these multifunctional peptides exert other functions besides antimicrobial action, for example, they are involved in the immune surveillance against cancer 3 . Accordingly, almost 1,000 different HDPs have been identified 4 . Despite this diversity, all HDPs share the following features: a small size (< 10 kDa), a positive charge at neutral pH, and an amphipathic structure. This secondary structure drives the interaction of HDP with lipid bilayers and, critically, it enables selectivity between

Different dynamics and pathway of disulfide bonds reduction of two human defensins, a molecular dynamics simulation study

“…Thus, the tail of hBD‐3 (RES22‐45) is more flexible than other regions of hBD‐3. That can agree with the experimental findings from Nigro et al, who found that the γ ‐core motif of hBD‐3 (which corresponds to RES22‐45 of full length hBD‐3) had very flexible structure in neutral pH solvent, while hBD‐3 in whole had relatively rigid structure.…”

“…Nigro et al worked on the disulfide bond forming pathway of reduced hBD‐3 (with 6 cysteine residues alkylated) in oxidizing condition. They found that Cys23‐Cys41 and Cys18‐Cys33 formed disulfide bonds almost simultaneously in oxidizing condition, while the Cys11‐Cys40 pair formed disulfide bond lastly.…”

IL-1β–Induced Protection of Keratinocytes against Staphylococcus aureus-Secreted Proteases Is Mediated by Human β-Defensin 2

“…β-Defensins are not characterized as exhibiting direct anti-protease activity; however, this has been reported for neutrophil α-defensins (Van Wetering et al., 1997) and other antimicrobial proteins including SLPI and elafin (Moreau et al., 2008, Williams et al., 2006). Furthermore, hBD2 and hBD3 contain an evolutionarily conserved “gamma-core” structural motif sufficient for antimicrobial activity and, interestingly, also for resistance to proteolytic degradation (Nigro et al., 2015). The significance of these structural features with respect to protection against V8 protease remains to be determined.…”

Host defense peptide‐derived privileged scaffolds for anti‐infective drug discovery

“…Overall, the potency of the γ‐core is comparable with the full‐length peptide across this whole spectrum of properties, and the peptide is not toxic to human cells. Remarkably, the peptide folds very rapidly in human serum, where it remains stable for a prolonged period of time .…”

“…Like full‐length HBD3, Peptide γ displayed potent antibacterial activity against gram‐negative ( Escherichia coli and Pseudomonas aeruginosa ) and gram‐positive ( Staphylococcus aureus ) bacteria, as well as antiviral activity against HIV and HSV . Notably, the disulfide bridge was important for the antiviral but not for the antibacterial activity, paralleling the SAR observed for HBD3.…”