Mammalian defensins: structures and mechanism of antibiotic activity

Sahl, Hans‐Georg; Pag, Ulrike; Bonness, Sonja; Wagner, Sandra; Antcheva, Nikolinka; Tossi, Alessandro

doi:10.1189/jlb.0804452

Cited by 195 publications

(156 citation statements)

References 56 publications

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“…The charged residues are not the only ones to play a role in the antimicrobial properties of defensins (43,47,54,55). In our anti-E. coli assays, mutants Y03A, N04A, V06A, S08A, and L13A are either inactive or very poorly active.…”

Section: Discussionmentioning

confidence: 95%

Studies of the Biological Properties of Human β-Defensin 1

Pazgier

Prahl²,

Hoover³

et al. 2007

Journal of Biological Chemistry

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Defensins are small (30 -45 amino acid residues) cationic proteins with broad antimicrobial activity against many bacteria and fungi, some enveloped viruses, and other activities such as chemoattraction of a range of different cell types to the sites of inflammation. These proteins represent attractive targets for developing novel antimicrobial agents and modulators of immune responses with therapeutic applicability. In this report, we present the results of functional and structural studies of 26 single-site mutants of human ␤-defensin 1 (hBD1). All mutants were assayed for antimicrobial activity against Escherichia coli (ATCC strain 25922) and for chemotactic activity with CCR6-transfected HEK293 cells. To analyze the structural implications of mutagenesis and to verify the correctness of the disulfide connectivity, we used x-ray crystallography to conduct complete structural studies for 10 mutants in which the topology of disulfides was the same as in the native hBD1. Mutations did not induce significant changes of the tertiary structure, suggesting that the observed alterations of biological properties of the mutants were solely associated with changes in the respective side chains. We found that cationic residues located near the C terminus (Arg Defensins are recognized as an important element of the human innate immune system (1-4). The defensin family is composed of small (3-5 kDa), cationic, and cysteine-rich proteins. In human defensins, the connectivity of three disulfide bridges forms the basis for assigning them into one of two classes, the ␣-and ␤-defensins (5-7). In ␤-defensins, the topology of the three disulfide bridges is 1-5, 2-4, and 3-6, meaning that the first cysteine in the sequence is covalently linked to the fifth, and so on. Three human ␤-defensins, hBD1-3, 4 have been isolated from natural sources and characterized in detail (8 -11). Additionally, the recombinant or synthetic preparations of hBD4, hBD27, and hBD28 have also been described and characterized functionally (12, 13). Analysis of the human genome indicates the existence of over 40 potential coding regions for these peptides (14,15).In addition to broad antimicrobial activity, hBDs have also been recognized as modulators of cell-mediated adaptive immunity, due to their chemotactic and immunoenhancing activity (16 -19). Recent studies revealed that ␤-defensins also play a role in cell differentiation, tissue remodeling, and sperm maturation (20 -22).The first human ␤-defensin to be discovered, hBD1, is constitutively expressed in the epithelial cells of the urinary and respiratory tracts and in keratinocytes of skin (9,23,24). A naturally occurring 36-amino acid hBD1 peptide shows anti-bacterial activity at micromolar concentrations against some Gramnegative bacteria (i.e. Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae), as well as yeast Candida albicans. When tested in vitro, hBD1 is relatively less potent against the Gram-positive Streptococcus aureus (9, 10, 23).HBD1 and hBD2 selectively chemoattract hum...

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Section: Discussionmentioning

confidence: 95%

Studies of the Biological Properties of Human β-Defensin 1

Pazgier

Prahl²,

Hoover³

et al. 2007

Journal of Biological Chemistry

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“…A dual mode of action was suggested previously for other synthetic peptides that were found to target the cell membrane when applied at high concentrations, and to have intracellular targets when used at low concentration (Patrzykat et al, 2002;Sahl et al, 2005;Gottschalk et al, 2013). Therefore, we investigated the possibility of FL9 having intracellular targets by assessing the synthesis of DNA molecules in S. aureus.…”

Section: Fl9 Interferes With Dna Synthesis and Binds Dna In Vitromentioning

confidence: 99%

Amphibian antimicrobial peptide fallaxin analogue FL9 affects virulence gene expression and DNA replication in Staphylococcus aureus

Gottschalk

Gottlieb

Vestergaard

et al. 2015

Journal of Medical Microbiology

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The rapid rise in antibiotic-resistant pathogens is causing increased health concerns, and consequently there is an urgent need for novel antimicrobial agents. Antimicrobial peptides (AMPs), which have been isolated from a wide range of organisms, represent a very promising class of novel antimicrobials. In the present study, the analogue FL9, based on the amphibian AMP fallaxin, was studied to elucidate its mode of action and antibacterial activity against the human pathogen Staphylococcus aureus. Our data showed that FL9 may have a dual mode of action against S. aureus. At concentrations around the MIC, FL9 bound DNA, inhibited DNA synthesis and induced the SOS DNA damage response, whereas at concentrations above the MIC the interaction between S. aureus and FL9 led to membrane disruption. The antibacterial activity of the peptide was maintained over a wide range of NaCl and MgCl 2 concentrations and at alkaline pH, while it was compromised by acidic pH and exposure to serum. Furthermore, at subinhibitory concentrations of FL9, S. aureus responded by increasing the expression of two major virulence factor genes, namely the regulatory rnaIII and hla, encoding a-haemolysin. In addition, the S. aureus-encoded natural tolerance mechanisms included peptide cleavage and the addition of positive charge to the cell surface, both of which minimized the antimicrobial activity of FL9. Our results add new information about FL9 and its effect on S. aureus, which may aid in the future development of analogues with improved therapeutic potential.

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“…Humans express six different ␣-defensins. Four were first discovered in neutrophils, and are called human neutrophil peptides (HNP) 3 1-4 (16,26,27). The other two human ␣-defensins (HD), HD5 and HD6, are expressed primarily by small intestinal Paneth cells (28) and in regions of the female urogenital tract (26,29).…”

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confidence: 99%

Multivalent Binding of Carbohydrates by the Human α-Defensin, HD5

Lehrer

Jung

Ruchala

et al. 2009

The Journal of Immunology

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Four of the six human α-defensins (human neutrophil peptides 1–3 and human α-defensin 5; HD5) have a lectin-like ability to bind glycosylated proteins. Using HD5 as a model, we applied surface plasmon resonance techniques to gain insights into this property. HD5 bound natural glycoproteins > neoglycoproteins based on BSA > nonglycosylated BSA ≫ free sugars. The affinity of HD5 for simple sugars covalently bound to BSA was orders of magnitude greater than its affinity for the same sugars in solution. The affinity of HD5 for protein-bound carbohydrates resulted from multivalent interactions which may also involve noncarbohydrate residues of the proteins. HD5 showed concentration-dependent self-association that began at submicromolar concentrations and proceeded to dimer and tetramer formation at concentrations below 5 μM. The (R9A, R28A) and (R13A, R32A) analogs of HD5 showed greatly reduced self-association as well as minimal binding to BSA and to BSA-affixed sugars. From this and other evidence, we conclude that the extensive binding of HD5 to (neo)glycoproteins results from multivalent nonspecific interactions of individual HD5 molecules with carbohydrate and noncarbohydrate moieties of the target molecule and that the primary binding events are magnified and enhanced by subsequent in situ assembly and oligomerization of HD5. Self-association and multivalent binding may play integral roles in the ability of HD5 to protect against infections caused by viruses and other infectious agents.

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Mammalian defensins: structures and mechanism of antibiotic activity

Cited by 195 publications

References 56 publications

Studies of the Biological Properties of Human β-Defensin 1

Studies of the Biological Properties of Human β-Defensin 1

Amphibian antimicrobial peptide fallaxin analogue FL9 affects virulence gene expression and DNA replication in Staphylococcus aureus

Multivalent Binding of Carbohydrates by the Human α-Defensin, HD5

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