Modulation of the In Vitro Candidacidal Activity of Human Neutrophil Defensins by Target Cell Metabolism and Divalent Cations

Department of Medicine, UCLA School of Medicine, Los Angeles 90024.
Journal of Clinical Investigation (Impact Factor: 13.22). 07/1988; 81(6):1829-35. DOI: 10.1172/JCI113527
Source: PubMed


We tested the in vitro susceptibility of Candida albicans to three defensins from human neutrophilic granulocytes (HNP-1, 2, and 3), a homologous defensin from rabbit leukocytes (NP-1), and four unrelated cationic peptides. Although the primary amino acid sequences of HNP-1, 2, and 3 are identical except for a single amino-terminal amino acid alteration, HNP-1 and HNP-2 killed C. albicans but HNP-3 did not. C. albicans blastoconidia were protected from HNP-1 when incubations were performed in the absence of oxygen or in the presence of inhibitors that blocked both of its mitochondrial respiratory pathways. Neither anaerobiosis nor mitochondrial inhibitors substantially protected C. albicans exposed to NP-1, poly-L-arginine, poly-L-lysine, or mellitin. Human neutrophilic granulocyte defensin-mediated candidacidal activity was inhibited by both Mg2+ and Ca2+, and was unaffected by Fe2+. In contrast, Fe2+ inhibited the candidacidal activity of NP-1 and all of the model cationic peptides, whereas Mg2+ inhibited none of them. These data demonstrate that susceptibility of C. albicans to human defensins depends both on the ionic environment and on the metabolic state of the target cell. The latter finding suggests that leukocyte-mediated microbicidal mechanisms may manifest oxygen dependence for reasons unrelated to the production of reactive oxygen intermediates by the leukocyte.

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    • "peptides, which are present in various multicellular organisms, including fungi, plants and animals. Defensins and defensin-like peptides are recognized as involved in the host's defense against bacteria [88], fungi [57] [87] and viruses [19] [56] [112] and also acting in the plant's tolerance response to abiotic stresses [46] [66] [92]. "
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    ABSTRACT: Antimicrobial peptides (AMPs) seem to be promising alternatives to common antibiotics, which are facing increasing bacterial resistance. Among them are the cysteine-stabilized αβ defensins. These peptides are small, with a length ranging from 34 to 54 amino acid residues, cysteine-rich and extremely stable, normally composed of an α-helix and three β-strands stabilized by three or four disulfide bonds and commonly found in several organisms. Moreover, animal and plant CSαβ defensins present different specificities, the first being mainly active against bacteria and the second against fungi. The role of the CSαβ-motif remains unknown, but a common antibacterial mechanism of action, based on the inhibition of the cell-wall formation, has already been observed in some fungal and invertebrate defensins. In this context, the present work aims to group the data about CSαβ defensins, highlighting their evolution, conservation, structural characteristics, antibacterial activity and biotechnological perspectives. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · Apr 2015 · Peptides
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    • "It could be concluded that WD showed highest resistance against F. oxysporum followed by E. lycopersici, B. cinerea, and A. solani (Fig. 8). Being cationic peptide, antifungal activity of most antifungal plant defensins, as well as other types of defensins, as commonly observed, is reduced when the cationic strength of the medium is increased (Lehrer et al. 1988; Terras et al. 1992, 1993; Cociancich et al. 1993; Osborn et al. 1995). This antagonistic effect of cations is strongly dependent on the test fungus, indicating that electrostatic interactions probably change the conformation of the target site on the fungal membrane rather than the conformation of the defensin itself (Broekaert et al. 1995). "
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    ABSTRACT: The selection marker genes, imparting antibiotic or herbicide resistance, in the final transgenics have been criticized by the public and considered a hindrance in their commercialization. Multi-auto-transformation (MAT) vector system has been one of the strategies to produce marker-free transgenic plants without using selective chemicals and plant growth regulators (PGRs). In the study reported here, isopentenyltransferase (ipt) gene was used as a selection marker and wasabi defensin (WD) gene, isolated from Wasabia japonica as a target gene. WD was cloned from the binary vector, pEKH-WD to an ipt-type MAT vector, pMAT21 by gateway cloning and transferred to Agrobacterium tumefaciens strain EHA105. Infected cotyledons of tomato cv. Reiyo were cultured on PGR- and antibiotic-free MS medium. Adventitious shoots were developed by the explants infected with the pMAT21/wasabi defensin. The same PGR- and antibiotic-free MS medium was used in subcultures of the adventitious shoot lines (ASLs) to produce ipt and normal shoots. Approximately, 6 months after infection morphologically normal shoots were produced. Molecular analyses of the developed shoots confirmed the integration of gene of interest (WD) and excision of the selection marker (ipt). Expression of WD was confirmed by Northern blot and Western blot analyses. The marker-free transgenic plants exhibited enhanced resistance against Botrytis cinerea (gray mold), Alternaria solani (early blight), Fusarium oxysporum (Fusarium wilt) and Erysiphe lycopersici (powdery mildew).
    Full-text · Article · Jun 2011 · Plant Cell Reports
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    • "Hsa6 (HNP1) and Hsa8 (HNP2) are different from Hsa10 (HNP3) in the activities to kill Candida albicans (Lehrer et al. 1988). The selective replacements of Arg residues in Hsa13 (HD5) at positions 81 (numbering is according to the alignment of α-defensins presented in fig. "
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    ABSTRACT: Defensin genes encode small cationic antimicrobial peptides that form an important part of the innate immune system. They are divided into three families, alpha (α), beta (β), and theta (), according to arrangement of the disulfide bonding pattern between cysteine residues. Considering the functional importance of defensins, investigators have studied the evolution and the genomic organization of defensin genes. However, these studies have been restricted mainly to β-defensins. To understand the evolutionary dynamics of α-defensin genes among primates, we identified the α-defensin repertoires in human, chimpanzee, orangutan, macaque, and marmoset. The α-defensin genes in primates can be classified into three phylogenetic classes (class I, II, and III). The presence of all three classes in the marmoset indicates that their divergence occurred before the separation of New World and Old World monkeys. Comparative analysis of the α-defensin genomic clusters suggests that the makeup of the α-defensin gene repertoires between primates is quite different, as their genes have undergone dramatic birth-and-death evolution. Analysis of the encoded peptides of the α-defensin genes indicates that despite the overall high level of sequence divergence, certain amino acid residues or motifs are conserved within and between the three phylogenetic classes. The evolution of α-defensins in primates, therefore, appears to be governed by two opposing evolutionary forces. One force stabilizes specific amino acid residues and motifs to preserve the functional and structural integrity of the molecules and the other diversifies the sequences generating molecules with a wide range of activities against a large number of pathogens.
    Full-text · Article · May 2010 · Molecular Biology and Evolution
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