Distinct Antifungal Mechanisms: β-Defensins Require<i>Candida albicans</i>Ssa1 Protein, while Trk1p Mediates Activity of Cysteine-Free Cationic Peptides

Vylkova, Slavena; Li, Xuewei S.; Berner, Jennifer C.; Edgerton, Mira

doi:10.1128/aac.50.1.324-331.2006

Cited by 85 publications

(84 citation statements)

References 27 publications

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“…This observation suggested that the two peptides shared a binding protein on the fungal surface. When neutrophil defensin 1 was incubated with wildtype, hsp70⌬/⌬, and ssa2⌬/⌬ strains, the mutant strains remained susceptible to killing (401). This observation is at odds with the first observation of competition for the binding site.…”

Section: Mp65pcontrasting

confidence: 46%

Candida albicansCell Wall Proteins

Chaffin

2008

Microbiol Mol Biol Rev

424

404

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SUMMARY The Candida albicans cell wall maintains the structural integrity of the organism in addtion to providing a physical contact interface with the environment. The major components of the cell wall are fibrillar polysaccharides and proteins. The proteins of the cell wall are the focus of this review. Three classes of proteins are present in the candidal cell wall. One group of proteins attach to the cell wall via a glycophosphatidylinositol remnant or by an alkali-labile linkage. A second group of proteins with N-terminal signal sequences but no covalent attachment sequences are secreted by the classical secretory pathway. These proteins may end up in the cell wall or in the extracellular space. The third group of proteins lack a secretory signal, and the pathway(s) by which they become associated with the surface is unknown. Potential constituents of the first two classes have been predicted from analysis of genome sequences. Experimental analyses have identified members of all three classes. Some members of each class selected for consideration of confirmed or proposed function, phenotypic analysis of a mutant, and regulation by growth conditions and transcription factors are discussed in more detail.

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Section: Mp65pcontrasting

confidence: 46%

Candida albicansCell Wall Proteins

Chaffin

2008

Microbiol Mol Biol Rev

424

404

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“…The antifungal protein from tobacco, osmotin, for example, requires the presence of particular mannoproteins in the cell wall of S. cerevisiae for its activity (21). The cell wall of C. albicans also contains proteins that are essential for the internalization and antifungal activity of the human protein histatin 5 (22,23). This suggests that the cell wall may play an essential role in the activity of antifungal proteins.…”

Section: Discussionmentioning

confidence: 99%

The Plant Defensin, NaD1, Enters the Cytoplasm of Fusarium Oxysporum Hyphae

Weerden

Lay

Anderson

2008

Journal of Biological Chemistry

180

169

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The plant defensin, NaD1, from the flowers of Nicotiana alata displays potent antifungal activity against a variety of agronomically important filamentous fungi including Fusarium oxysporum f. sp. vasinfectum (Fov). To understand the mechanism of this antifungal activity, the effect of NaD1 on Fov fungal membranes and the location of NaD1 in treated hyphae was examined using various fluorescence techniques. NaD1 permeabilized fungal plasma membranes via the formation of an aperture with an internal diameter of between 14 and 22 Å . NaD1 bound to the cell walls of all treated hyphae and entered several hyphae, resulting in granulation of the cytoplasm and cell death. These results suggest that the activity of antifungal plant defensins may not be restricted to the hyphal membrane and that they enter cells and affect intracellular targets.Plants produce a number of cationic peptides for protection against infection by potential microbial pathogens. These include defensins, which are one of the largest families of antimicrobial peptides found in plants. They are particularly abundant in seeds but have also been described in leaves, pods, tubers, fruit, and floral tissues (1, 2). Plant defensins are small (45-54 amino acids), basic proteins with 4 -5 disulfide bonds (3). They share structural and functional similarities with defensins from insects (4), mammals (5), and fungi (6). Most plant defensins exhibit antifungal activity; however, antibacterial activity and the inhibition of protein synthesis, ␣-amylases, and proteases have also been reported (2,7,8). Plant defensins, even those with similar activities, share little sequence identity and may act via differing mechanisms. So far, only a limited number of seed defensins have been studied in detail. Defensins from radish (RsAFP2) and dahlia (DmAMP1) interact with specific sphingolipids on fungal plasma membranes and require the presence of these lipids for their antifungal activity. They permeabilize the fungal membrane and induce Ca 2ϩ influx and K ϩ efflux, which disrupts the Ca 2ϩ gradient essential for fungal tip growth (9 -11). Another plant defensin, MsDef1 from alfalfa, blocks mammalian L-type Ca 2ϩ channels, although interaction with fungal Ca 2ϩ channels has not been demonstrated (12).Membrane permeabilization is a common activity for many antimicrobial peptides, although the mechanism of permeabilization can differ significantly, and in some cases, remains unclear. A number of models have been suggested, including the barrel-stave pore, toroidal pore, and carpet models (for review, see Ref. 13). Antimicrobial peptides were initially thought to act solely at the plasma membrane, although some exert their cytotoxic effects via interaction with intracellular targets (for review, see Ref. 14). The human proline-rich protein PR-39, for example, enters bacterial cells without disrupting the plasma membrane and inhibits DNA and protein synthesis (15).NaD1 is an antifungal plant defensin that is expressed at high concentrations in the flowers of the ornamental...

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“…Gene profiling of oral mucosal tissue showed strong induction of Th17 signature genes, including beta defensin-3 and CXC chemokines. hBD-3 has candidacidal activity in vitro (Vylkova et al, 2006), and saliva from wild-type mice, but not IL-17Ra -/-mice, has candidacidal activity, indicating that IL-17 also controls C. albicans proliferation by promoting secretion of antimicrobial peptides (Conti et al, 2009). However, more work is needed to understand whether Th17 responses also govern the response to oral candidiasis in humans, because it is unclear whether mouse and human diseases have the same etiology.…”

Section: Oral Mucosal T-cell Responses To C Albicansmentioning

confidence: 99%

Epithelial Cells and Innate Antifungal Defense

2010

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The human pathogenic fungus Candida albicans is the predominant cause of both superficial and invasive forms of candidiasis. Clinical observations indicate that mucocutaneous Candida infections are commonly associated with defective cell-mediated immune responses. The importance of the innate immune system as a first-line defense against pathogenic challenge has long been recognized. Over the last decade, many key molecules mediating innate host defense have been identified. Central to these developments is the discovery of pattern recognition receptors such as Toll-like receptors and C-type lectin-receptors that induce innate immune responses and also modulate cellular and humoral adaptive immunity during Candida infections. Although a large amount of information is now available in systemic infections, little is known about localized infections. We address the most relevant pattern recognition receptors and their signaling mechanisms in oral epithelial cells, to gain a better understanding of their contributions to antifungal innate immunity.

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Distinct Antifungal Mechanisms: β-Defensins RequireCandida albicansSsa1 Protein, while Trk1p Mediates Activity of Cysteine-Free Cationic Peptides

Cited by 85 publications

References 27 publications

Candida albicansCell Wall Proteins

Candida albicansCell Wall Proteins

The Plant Defensin, NaD1, Enters the Cytoplasm of Fusarium Oxysporum Hyphae

Epithelial Cells and Innate Antifungal Defense

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