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Characterization of thiamine uptake and utilization in Candida spp. subjected to oxidative stress

100%
Wolak N., Tomasi M., Kozik A., Rapala-Kozik M.
Acta Biochimica Polonica
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2015
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vol. 62
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issue 3
445-455
EN
Candida species are associated with an increasing number of life-threatening infections (candidiases), mainly due to the high resistance of these yeast-like fungi to antifungal drugs and oxidative stress. Recently, thiamine (vitamin B1) was found to alleviate stress responses in Saccharomyces cerevisiae; however, thiamine influence on defense systems in pathogenic fungi has never been investigated. The current work was aimed to elucidate the role of thiamine in stress reactions of C. albicans, C. glabrata, C. tropicalis and C. dubliniensis, subjected to hydrogen peroxide treatment. As compared to S. cerevisiae, Candida strains exposed to oxidative stress showed: (i) a much higher dependence on exogenous thiamine; (ii) an increased demand for thiamine diphosphate (TDP) and TDP-dependent enzyme, transketolase; (iii) no changes in gene expression of selected stress markers - superoxide dismutase and catalase - depending on thiamine availability in medium; (iv) a similar decrease of reactive oxygen species (ROS) generation in the presence of thiamine. Moreover, the addition of therapeutic doses of thiamine to yeast culture medium revealed differences in its accumulation between various Candida species. The current findings implicate that the protective action of thiamine observed in S. cerevisiae differs significantly form that in pathogenic Candida strains, both in terms of the cofactor functions of TDP and the effects on fungal defense systems.
2
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The action of ten secreted aspartic proteases of pathogenic yeast Candida albicans on major human salivary antimicrobial peptide, histatin 5

76%
Bochenska O., Rapala-Kozik M., Wolak N., Aoki W., Ueda M., Kozik A.
Acta Biochimica Polonica
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2016
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vol. 63
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issue 3
403-410
EN
Candida albicans, belonging to the most common fungal pathogens of humans, exploits many virulence factors to infect the host, of which the most important is a family of ten secreted aspartic proteases (Saps) that cleave numerous peptides and proteins, often deregulating the host's biochemical homeostasis. It was recently shown that C. albicans cells can inactivate histatin5 (His5), a salivary histidine-rich anticandidal peptide, through the hydrolytic action of Saps. However, the current data on this subject are incomplete as only four out of ten Saps have been studied with respect to hydrolytic processing of His5 (Sap2, Sap5, Sap9-10). The aim of the study was to investigate the action of all Saps on His5 and to characterize this process in terms of peptide chemistry. It was shown that His5 was degraded by seven out of ten Saps (Sap1-4, Sap7-9) over a broad range of pH. The cleavage rate decreased in an order of Sap2>Sap9>Sap3>Sap7>Sap4>Sap1>Sap8. The degradation profiles for Sap2 and Sap9 were similar to those previously reported; however, in contrast to the previous study, Sap10 was shown to be unable to cleave His5. On a long-time scale, the peptide was completely degraded and lost its antimicrobial potential but after a short period of Sap treatment several shorter peptides (His1-13, His1-17, His1-21) that still decreased fungal survival were released. The results, presented hereby, provide extended characteristics of the action of C. albicans extracellular proteases on His5. Our study contribute to deepening the knowledge on the interactions between fungal pathogens and the human host.
3
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Kinetic and thermodynamic characterization of the interactions between the components of human plasma kinin-forming system and isolated and purified cell wall proteins of Candida albicans

76%
Seweryn K., Karkowska-Kuleta J., Wolak N., Bochenska O., Kedracka-Krok S., Kozik A., Rapala-Kozik M.
Acta Biochimica Polonica
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2015
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vol. 62
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issue 4
825-835
EN
Cell wall proteins of Candida albicans, besides their best known role in the adhesion of this fungal pathogen to host's tissues, also bind some soluble proteins, present in body fluids and involved in maintaining the biochemical homeostasis of the human organism. In particular, three plasma factors - high-molecular-mass kininogen (HK), factor XII (FXII) and prekallikrein (PPK) - have been shown to adhere to candidal cells. These proteins are involved in the surface-contact-catalyzed production of bradykinin-related peptides (kinins) that contribute to inflammatory states associated with microbial infections. We recently identified several proteins, associated with the candidal cell walls, and probably involved in the binding of HK. In our present study, a list of potential FXII- and PPK-binding proteins was proposed, using an affinity selection (on agarose-coupled FXII or PPK) from a whole mixture of β-1,3-glucanase-extrated cell wall-associated proteins and the mass-spectrometry protein identification. Five of these fungal proteins, including agglutinin-like sequence protein 3 (Als3), triosephosphate isomerase 1 (Tpi1), enolase 1 (Eno1), phosphoglycerate mutase 1 (Gpm1) and glucose-6-phosphate isomerase 1 (Gpi1), were purified and characterized in terms of affinities to the human contact factors, using the surface plasmon resonance measurements. Except Gpm1 that bound only PPK, and Als3 that exhibited an affinity to HK and FXII, the other isolated proteins interacted with all three contact factors. The determined dissociation constants for the identified protein complexes were of 10-7 M order, and the association rate constants were in a range of 104-105 M-1s-1. The identified fungal pathogen-host protein interactions are potential targets for novel anticandidal therapeutic approaches.
4
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Inactivation of α1-proteinase inhibitor by Candida albicans aspartic proteases favors the epithelial and endothelial cell colonization in the presence of neutrophil extracellular traps

64%
Gogol M., Ostrowska D., Klaga K., Bochenska O., Wolak N., Aoki W., Ueda M., Kozik A., Rapala-Kozik M.
Acta Biochimica Polonica
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2016
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vol. 63
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issue 1
167-175
EN
Candida albicans, a causative agent of opportunistic fungal infections in immunocompromised patients, uses ten secreted aspartic proteases (SAPs) to deregulate the homeostasis of the host organism on many levels. One of these deregulation mechanisms involves a SAP-dependent disturbance of the control over proteolytic enzymes of the host by a system of dedicated proteinase inhibitors, with one important example being the neutrophil elastase and alpha1-proteinase inhibitor (A1PI). In this study, we found that soluble SAPs 1-4 and the cell membrane-anchored SAP9 efficiently cleaved A1PI, with the major cleavage points located at the C-terminal part of A1PI in a close vicinity to the reactive-site loop that plays a critical role in the inhibition mechanism. Elastase is released by neutrophils to the environment during fungal infection through two major processes, a degranulation or formation of neutrophil extracellular traps (NET). Both, free and NET-embedded elastase forms, were found to be controlled by A1PI. A local acidosis, resulting from the neutrophil activity at the infection sites, favors A1PI degradation by SAPs. The deregulation of NET-connected elastase affected a NET-dependent damage of epithelial and endothelial cells, resulting in the increased susceptibility of these host cells to candidal colonization. Moreover, the SAP-catalyzed cleavage of A1PI was found to decrease its binding affinity to a proinflammatory cytokine, interleukin-8. The findings presented here suggest a novel strategy used by C. albicans for the colonization of host tissues and overcoming the host defense.
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