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2 Acta Biochimica Polonica

2 2016

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The action of ten secreted aspartic proteases of pathogenic yeast Candida albicans on major human salivary antimicrobial peptide, histatin 5

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Bochenska O. , Rapala-Kozik M. , Wolak N. , Aoki W. , Ueda M. , Kozik A.

Acta Biochimica Polonica

2016

tom 63

nr 3

403-410

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.

Inactivation of α1-proteinase inhibitor by Candida albicans aspartic proteases favors the epithelial and endothelial cell colonization in the presence of neutrophil extracellular traps

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Gogol M. , Ostrowska D. , Klaga K. , Bochenska O. , Wolak N. , Aoki W. , Ueda M. , Kozik A. , Rapala-Kozik M.

Acta Biochimica Polonica

2016

tom 63

nr 1

167-175

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.