Proteolytic Cleavage of Covalently Linked Cell Wall Proteins by Candida albicans Sap9 and Sap10

Schild, Lydia; Heyken, Antje; Groot, Piet W. J. de; Hiller, Ekkehard; Mock, Marlen; Koster, Chris G. de; Horn, Uwe; Rupp, Steffen; Hube, Bernhard

doi:10.1128/ec.00210-10

Cited by 89 publications

(124 citation statements)

References 73 publications

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“…However, only germinated cells exhibited this aggregation, suggesting that cell surface molecules that permit Sap6-mediated cell-cell aggregation are exposed upon germination. It is unclear from our experiments whether Sap proteinases have an enzymatic role in cell wall remodeling to expose these adhesins, either directly or through MAPK signaling (32,35), since experiments to epithelial cell monolayers were infected with the CAI4 and SAP deletion strains for 90 min. After extensive washing, the adherent cells were harvested using 0.1% Triton X-100 and plated on YPD agar plates, and the plates were incubated at 30°C for 24 h to determine the numbers of CFU of adherent fungal cells.…”

Section: Discussionmentioning

confidence: 98%

“…block Sap enzymatic activity with pepstatin A also inhibited germination. It is known that Sap9, a GPI-anchored cell wall proteinase, activates several cell surface proteins, including adhesins Ywp1, Hwp1, and Rbt1, by enzymatic cleavage (35). Thus, it is likely that Saps have dual roles, one enzymatic and involved in germination and a second, nonenzymatic, function for cell-cell aggregation that is mainly carried out by Sap6.…”

Section: Discussionmentioning

confidence: 99%

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Novel Aggregation Properties of Candida albicans Secreted Aspartyl Proteinase Sap6 Mediate Virulence in Oral Candidiasis

et al. 2015

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Candida albicans, a commensal fungus of the oral microbiome, causes oral candidiasis in humans with localized or systemic immune deficiencies. Secreted aspartic proteinases (Saps) are a family of 10 related proteases and are virulence factors due to their proteolytic activity, as well as their roles in adherence and colonization of host tissues. We found that mice infected sublingually with C. albicans cells overexpressing Sap6 (SAP6 OE and a ⌬sap8 strain) had thicker fungal plaques and more severe oral infection, while infection with the ⌬sap6 strain was attenuated. These hypervirulent strains had highly aggregative colony structure in vitro and higher secreted proteinase activity; however, the levels of proteinase activity of C. albicans Saps did not uniformly match their abilities to damage cultured oral epithelial cells (SCC-15 cells). Hyphal induction in cells overexpressing Sap6 (SAP6 OE and ⌬sap8 cells) resulted in formation of large cell-cell aggregates. These aggregates could be produced in germinated wild-type cells by addition of native or heat-inactivated Sap6. Sap6 bound only to germinated cells and increased C. albicans adhesion to oral epithelial cells. The adhesion properties of Sap6 were lost upon deletion of its integrin-binding motif (RGD) and could be inhibited by addition of RGD peptide or anti-integrin antibodies. Thus, Sap6 (but not Sap5) has an alternative novel function in cell-cell aggregation, independent of its proteinase activity, to promote infection and virulence in oral candidiasis. Candida albicans is a commensal fungus that is often part of the oral microflora of healthy people. Loss of host immunity, HIV infection, corticosteroid use, or alteration of the oral microflora following antibiotic therapies permits a pathogenic transition of C. albicans to cause oropharyngeal candidiasis (OPC) (1, 2). Acute pseudomembranous candidiasis is one of the most common forms of OPC, in which C. albicans forms white patches on the surface of the buccal mucosa, tongue, or soft palate. These superficial fungal plaques can be lifted from underlying tissues for purposes of clinical diagnosis and analysis (3).C. albicans expresses specific sets of virulence factors that promote hypha formation and adhesion and invasion of host tissues (4). Secreted aspartyl proteinases (Saps) are recognized virulence factors because they degrade host proteins to provide nitrogen for fungal cell metabolism, contribute to adherence, facilitate fungal epithelial and endothelial penetration, and are immunogenic during infection (5-7). Microbial proteinases are classified as serine, cysteine, metallo-, or aspartyl proteinases according to the site of catalytic hydrolysis of substrate peptide bonds; however, C. albicans produces only aspartyl proteinases (5, 6).C. albicans expresses a family of 10 SAP genes that are clustered into groups SAP1 to SAP3, SAP4 to SAP6, SAP7, SAP8, and SAP9 and SAP10 based upon their sequence homologies and pH activities (8, 9). Sap1 through Sap8 are processed and transported via the secreto...

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Novel Aggregation Properties of Candida albicans Secreted Aspartyl Proteinase Sap6 Mediate Virulence in Oral Candidiasis

et al. 2015

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“…These proteinases are known to perform many cell wallrelated functions, ranging from maintenance of cell wall integrity to interaction with epithelial cells and the cleavage of cell surface-associated proteins. 29,30 They cleave the substrate at basic or dibasic residues, in contrast to the pepsin-like secreted proteinase Sap2, which prefers the presence of hydrophobic amino acids around the cleavage site. Secreted proteinases retained in the cell wall can thus increase the proteolytic activity associated with the surface of yeast cells.…”

Section: Discussionmentioning

confidence: 99%

Evidence for the presence of proteolytically active secreted aspartic proteinase 1 of Candida parapsilosis in the cell wall

et al. 2011

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Pathogenic yeasts of the genus Candida produce secreted aspartic proteinases, which are known to enhance virulence. We focused on Sapp1p proteinase secreted by Candida parapsilosis and studied the final stage of its passage through the cell wall and release into the extracellular environment. We found that Sapp1p displays enzyme activity prior to secretion, and therefore, it is probably fully folded within the upper layer of the cell wall. The positioning of cell surface-associated Sapp1p was detected by cell wall protein labeling using biotinylation agents, extraction of cell wall proteins by b-mercaptoethanol, immunochemical detection, and mass spectrometry analysis. All lysine residues present in the structure of soluble, purified Sapp1p were labeled with biotin. In contrast, the accessibility of individual lysines in cell wall-associated Sapp1p varied with the exception of four lysine residues that were biotinylated in all experiments performed, suggesting that Sapp1p has a preferred orientation in the cell wall. As the molecular weight of this partially labeled Sapp1p did not differ among the experiments, we can assume that the retaining of Sapp1p in the cell wall is not a totally random process and that pathogenic yeasts might use this cell-associated proteinase activity to enhance degradation of appropriate substrates.

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“…Sap9 seems to be predominantly located in the cell membrane, and Sap10 is located in the cell wall and membrane [109] . Recently, Schild et al [110] demonstrated that Sap9 and Sap10 cleave covalently linked cell wall proteins, including chitinase Cht2 and the glucan-cross-linking protein Pir1. Deletion of the SAP9 and SAP10 genes resulted in a reduction of cell-associated chitinase activity similar to that upon deletion of CHT2, suggesting a direct influence of Sap9 and Sap10 on Cht2 function.…”

Section: F Pedrosoimentioning

confidence: 99%

Protease expression by microorganisms and its relevance to crucial physiological/pathological events

Santos¹

2011

WJBC

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The treatment of infections caused by fungi and trypanosomatids is difficult due to the eukaryotic nature of these microbial cells, which are similar in several biochemical and genetic aspects to host cells. Aggravating this scenario, very few antifungal and anti-trypanosomatidal agents are in clinical use and, therefore, therapy is limited by drug safety considerations and their narrow spectrum of activity, efficacy and resistance. The search for new bioactive agents against fungi and trypanosomatids has been expanded because progress in biochemistry and molecular biology has led to a better understanding of important and essential pathways in these microorganisms including nutrition, growth, proliferation, signaling, differentiation and death. In this context, proteolytic enzymes produced by these eukaryotic microorganisms are appointed and, in some cases, proven to be excellent targets for searching novel natural and/or synthetic pharmacological compounds, in order to cure or prevent invasive fungal/trypanosomatid diseases. With this task in mind, our research group and others have focused on aspartic-type proteases, since the activity of this class of hydrolytic enzymes is directly implicated in several facets of basic biological processes of both fungal and trypanosomatid cells as well as due to the participation in numerous events of interaction between these microorganisms and host structures. In the present paper, a concise revision of the beneficial effects of aspartic protease inhibitors, with emphasis on the aspartic protease inhibitors used in the anti-human immunodeficiency virus therapy, will be presented and discussed using our experience with the following microbial models: the yeast Candida albicans , the filamentous fungus Fonsecaea pedrosoi and the protozoan trypanosomatid Leishmania amazonensis .

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Proteolytic Cleavage of Covalently Linked Cell Wall Proteins by Candida albicans Sap9 and Sap10

Cited by 89 publications

References 73 publications

Novel Aggregation Properties of Candida albicans Secreted Aspartyl Proteinase Sap6 Mediate Virulence in Oral Candidiasis

Novel Aggregation Properties of Candida albicans Secreted Aspartyl Proteinase Sap6 Mediate Virulence in Oral Candidiasis

Evidence for the presence of proteolytically active secreted aspartic proteinase 1 of Candida parapsilosis in the cell wall

Protease expression by microorganisms and its relevance to crucial physiological/pathological events

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