The role of metabolic energy in the lethal action of basic proteins on <i>Candida albicans</i>

Olson, V. L.; Hansing, Ronald L.; McClary, Dan O.

doi:10.1139/m77-024

Cited by 20 publications

(14 citation statements)

References 14 publications

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“…In the present study we investigated the molecular mechanism underlying the long known phenomenon that energy depletion in yeast induces resistance against cationic peptides and proteins (1). At variance with the generally accepted explanation that implies a role for ATP-driven transport systems, we found that energy depletion induces membrane rigidification, possibly mediated by the cytoskeleton, which desensitizes C. albicans to antimicrobial peptides.…”

Section: Discussionmentioning

confidence: 81%

“…This promotes their insertion into and transmigration over the cytoplasmic membrane of the target cell, with killing of the cell as a final consequence. Interestingly, cellular sensitivity to cationic proteins and peptides such as salivary histatins and defensins is diminished by conditions that affect the energy status of the target cell (1)(2)(3)(4)(5)(6). This effect is not restricted to cationic peptides, because azoles are also sensitive to the energy status of Candida glabrata (7).…”

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confidence: 99%

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Energy Depletion Protects Candida albicans against Antimicrobial Peptides by Rigidifying Its Cell Membrane

Veerman

Valentijn-Benz

Nazmi

et al. 2007

Journal of Biological Chemistry

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Inhibitors of the energy metabolism, such as sodium azide and valinomycin, render yeast cells completely resistant against the killing action of a number of cationic antimicrobial peptides, including the salivary antimicrobial peptide Histatin 5. In this study the Histatin 5-mediated killing of the opportunistic yeast Candida albicans was used as a model system to comprehensively investigate the molecular basis underlying this phenomenon. Using confocal and electron microscopy it was demonstrated that the energy poison azide reversibly blocked the entry of Histatin 5 at the level of the yeast cell wall. Azide treatment hardly induced depolarization of the yeast cell membrane potential, excluding it as a cause of the lowered sensitivity. In contrast, the diminished sensitivity to Histatin 5 of energy-depleted C. albicans was restored by increasing the fluidity of the membrane using the membrane fluidizer benzyl alcohol. Furthermore, rigidification of the membrane by incubation at low temperature or in the presence of the membrane rigidifier Me 2 SO increased the resistance against Histatin 5, while not affecting the energy charge of the cell. In line, azide induced alterations in the physical state of the interior of the lipid bilayer. These data demonstrate that changes in the physical state of the membrane underlie the increased resistance to antimicrobial peptides.In the last few decades an expanding number of antimicrobial peptides have been isolated from virtually all classes of organisms, where they play an important role in the innate defense against microbial and viral infections. Characterization of these peptides has revealed a wide diversity in amino acid sequences, yet they share characteristic features; they are usually polycationic and amphipathic, containing both a hydrophilic and a hydrophobic side. This promotes their insertion into and transmigration over the cytoplasmic membrane of the target cell, with killing of the cell as a final consequence. Interestingly, cellular sensitivity to cationic proteins and peptides such as salivary histatins and defensins is diminished by conditions that affect the energy status of the target cell (1-6). This effect is not restricted to cationic peptides, because azoles are also sensitive to the energy status of Candida glabrata (7). In Chlorella metabolic inhibition abolishes the membrane-disruptive effects of the polyene nystatin and even of the detergent Triton X-100 (8). As explanation for the desensitizing effects of energy depletion, it has been proposed that interaction of cationic peptides with the target cell would involve active transport systems, which for their activity are dependent on the energy charge of the cell (1, 9 -12). However, direct experimental proof corroborating this hypothesis is still lacking.The present study addresses the question of how on a molecular level the energy metabolism is linked with the sensitivity of the Candida cell to antimicrobial peptides. Thus far, many different types of mechanisms have been identified that contr...

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Section: Discussionmentioning

confidence: 81%

mentioning

confidence: 99%

Energy Depletion Protects Candida albicans against Antimicrobial Peptides by Rigidifying Its Cell Membrane

Veerman

Valentijn-Benz

Nazmi

et al. 2007

Journal of Biological Chemistry

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“…Miller noted that comparable cell homogenates from murine macrophages had no bactericidal activity (38). However, cationic proteins and perhaps other granule constituents as well might act as ancillary antifungal mechanisms, enhancing effects of oxidative mechanisms (39). While these studies have not yet identified all mechanisms active in killing of hyphae by normal monocytes, the data using monocytes from both myeloperoxidase-deficient and one of the four chronic granulomatous disease patients suggest the existence of potent myeloperoxidase-independent or nonoxidative antihyphal systems.…”

Section: Resultsmentioning

confidence: 99%

Monocyte-mediated Serum-independent Damage to Hyphal and Pseudohyphal Forms of Candida albicans In Vitro

Diamond¹,

Haudenschild²

1981

J. Clin. Invest.

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A B S T R A C T Human peripheral blood monocytes attached to Candida albicans hyphae in the absence of serum and damaged the hyphae without completely ingesting them. Attachment and damage was not augmented by the addition of serum. Damage to hyphae was quantitated by a previously developed metabolic assay that measured leukocyte-induced reduction in uptake of [14C]cytosine by the hyphae. Use of cells from patients with hereditary disorders of leukocyte function, chronic granulomatous disease, and myeloperoxidase deficiency indicated that myeloperoxidaseindependent and nonoxidative mechanisms could sometimes damage hyphae where oxidative mechanisms were impaired. Damage to hyphae by normal monocytes was inhibited by concentrations of sodium azide and sodium cyanide that primarily affect myeloperoxidase activity, as well as by halide-free conditions, catalase, and putative antagonists of hypochlorous acid or singlet oxygen. Iodination ofhyphae, a myeloperoxidase and hydrogen peroxide-dependent process of monocytes, was similarly inhibited by sodium azide, sodium cyanide, and catalase. Under anaerobic conditions, damage to hyphae was reduced by 64.0-68.4%. In contrast, inhibitors ofpotential nonoxidative antifungal mechanisms, iron salts to saturate iron chelators, and polyanionic amino acid polymers to neutralize cationic proteins did not block damage to hyphae by monocytes. Preparations rich in lysosomal granules from fractionated normal monocytes also did not damage hyphae. Overall, it appeared that oxidative mechanisms were most important for damage to hyphae by normal monocytes.Dr.

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“…Decreased susceptibility to Hsts is a common feature of anaerobically grown C. albicans (Table 1), respiratory (petite) mutants (17), or cells pretreated with azide or the proton ionophores CCCP and DNP (23). In yeast, proton ionophores uncouple respiratory chain phosphorylation and induce endogenous fermentation; azide functions dually as a respiratory inhibitor and uncoupler (25,27,29,39). It is notable that cells with reduced susceptibility to Hst 5 lack or have inhibited mitochondrial function.…”

Section: Discussionmentioning

confidence: 99%

Released ATP Is an Extracellular Cytotoxic Mediator in Salivary Histatin 5-Induced Killing of Candida albicans

Koshlukova

Araujo²,

Baev³

et al. 2000

Infect Immun

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Salivary histatins (Hsts) are antifungal peptides with promise as therapeutic agents against candidiasis. Hst 5 kills the fungal pathogen Candida albicans via a mechanism that involves release of cellular ATP in the absence of cytolysis. Here we demonstrate that released ATP has a further role in Hst 5 killing. Incubation of the cells with ATP analogues induced cell death, and addition of the ATP scavenger apyrase to remove extracellular ATP released during Hst 5 treatment resulted in a reduction in cell killing. Experiments using anaerobically grown C. albicans with decreased susceptibility to Hst 5 confirmed that depletion of cellular ATP as a result of ATP efflux was not sufficient to cause cell death. In contrast to Hst-susceptible aerobic cultures, anaerobically grown cells were not killed by exogenously applied ATP. These findings established that Hst binding, subsequent entry into the cells, and ATP release precede the signal for cytotoxicity, which is mediated by extracellular ATP. In a higher-eukaryote paradigm, released ATP acts as a cytotoxic mediator by binding to membrane nucleotide P2X receptors. Based on a pharmacological profile and detection of a C. albicans 60-kDa membrane protein immunoreactive with antibody to P2X 7 receptor, we propose that released ATP in response to Hst 5 activates candidal P2X 7 -like receptors to cause cell death.Candida albicans is the most prevalent human fungal pathogen causing severe mucosal and systemic infections in hosts with compromised immune systems (5, 28). The toxicity of the currently used polyene antimycotic drugs and emergence of resistant candidal species to the less toxic azole-based agents have initiated a search for innate antibiotics as alternative drug therapies. Innate host defense systems are evolutionarily ancient and are characterized by production of potent antimicrobial molecules that limit infections based on their capacity to selectively discriminate pathogens from self species (21). The first-line host defense of human saliva includes many proteins with potent antibacterial and antifungal activity against resident microflora in the oral cavity.Histatins (Hsts) are 3-to 4-kDa structurally related histidine-rich basic proteins of salivary acinar cell origin that are expressed only in humans and higher subhuman primates (30). Hsts possess in vitro antimicrobial activities, and their efficacy is highest for oral yeasts, particularly C. albicans. Hst 3 (32 amino acids) and Hst 5 (the N-terminal 24 amino acids of Hst 3 generated by proteolytic cleavage) are the most potent candidacidal members of the family in vitro, killing yeast and filamentous forms of Candida species at physiological concentrations (15 to 30 M) (32, 44). Salivary Hsts have potential as therapeutic agents in patients with oral candidiasis, since they are potent antifungal agents while being nontoxic to humans.The physiological activities of the naturally occurring antimicrobial peptides, such as magainins (26), cecropins (2), defensins (20, 22), and bactenecins (33), have been ...

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The role of metabolic energy in the lethal action of basic proteins on Candida albicans

Cited by 20 publications

References 14 publications

Energy Depletion Protects Candida albicans against Antimicrobial Peptides by Rigidifying Its Cell Membrane

Energy Depletion Protects Candida albicans against Antimicrobial Peptides by Rigidifying Its Cell Membrane

Monocyte-mediated Serum-independent Damage to Hyphal and Pseudohyphal Forms of Candida albicans In Vitro

Released ATP Is an Extracellular Cytotoxic Mediator in Salivary Histatin 5-Induced Killing of Candida albicans

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