Browsing by Subject "Cell wall"

Now showing 1 - 4 of 4
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    Deletion of GLX3 in Candida albicans affects temperature tolerance, biofilm formation, and virulence
    (Oxford University Press, 2018-11-21) Cabello, Laura; Gómez Herreros, Estefanía; Fernández Pereira, Jordan; Maicas, Sergi; Groot, Piet W. J. de; Valentín, Eulogio; Martínez-Esparza Alvargonzález, María Concepción; Bioquímica y Biología Molecular B e Inmunología
    Candida albicans is a predominant cause of fungal infections in mucosal tissues as well as life-threatening bloodstream infections in immunocompromised patients. Within the human body, C. albicans is mostly embedded in biofilms, which provides increased resistance to antifungal drugs. The glyoxalase Glx3 is an abundant proteomic component of the biofilm extracellular matrix. Here, we document phenotypic studies of a glx3 null mutant concerning its role in biofilm formation, filamentation, antifungal drug resistance, cell wall integrity and virulence. First, consistent with its function as glyoxalase, the glx3 null mutant showed impaired growth on media containing glycerol as the carbon source and in the presence of low concentrations of hydrogen peroxide. Importantly, the glx3 mutant showed decreased fitness at 37◦C and formed less biofilm as compared to wild type and a reintegrant strain. At the permissive temperature of 28◦C, the glx3 mutant showed impaired filamentation as well as increased sensitivity to Calcofluor white, Congo red, sodium dodecyl sulfate and zymolyase, indicating subtle alterations in wall architecture even though gross quantitative compositional changes were not detected. Interestingly, and consistent with its impaired filamentation, biofilm formation and growth at 37◦C, the glx3 mutant is avirulent. Our results underline the role of Glx3 in fungal pathogenesis and the involvement of the fungal wall in this process.
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    Glycoconjugate expression on the cell wall of tps1/tps1 trehalose-deficient Candida albicans strain and implications for its interaction with macrophages
    (Oxford University Press, 2011-01-20) Vitse-Standaert, Annie; García-Peñarrubia, Pilar; Argüelles, Juan Carlos; Poulain, Daniel; Jouault, Thierry; Martínez-Esparza Alvargonzález, María Concepción; Tapia Abellán, Ana; Bioquímica y Biología Molecular B e Inmunología
    The yeast Candida albicans has developed a variety of strategies to resist macrophage killing. In yeasts, accumulation of trehalose is one of the principal defense mechanisms under stress conditions. The gene-encoding trehalose-6-phosphate synthase (TPS1), which is responsible for trehalose synthesis, is induced in response to oxidative stress, as in phagolysosomes. Mutants unable to synthesize trehalose are sensitive to oxidative stress in vitro. In mice, the TPS1-deficient strain, tps1/tps1, displays a lower infection rate than its parental strain (CAI4). We have previously demonstrated the reduced binding capacity of tps1/tps1 and its lower resistance to macrophages. At the same time, its outer cell wall layer was seen to be altered. In this study, we show that depending on the culture conditions, the tps1/tps1 strain regulates the carbohydrate metabolism in a different way to CAI4, as reflected by the enhanced β-mannosylation of cell wall components, especially at the level of the 120 kDa glycoprotein species, accessible at the cell surface of tps1/tps1 when cultured in liquid medium, but not on solid medium. This leads to changes in its surface properties, as revealed by decreased hydrophobicity, and the lower levels of ERK1/2 phosphorylation and tumor necrosis factor-α (TNF-α) production in macrophages, thus increasing the resistance to these cells. In contrast, in solid medium, in which over-glycosylation was less evident, tps1/tps1 showed similar macrophage interaction properties to CAI4, but was less resistant to killing, confirming the protective role of trehalose. Thus, the lack of trehalose is compensated by an over-glycosylation of the cell wall components in the tps1/tps1 mutant, which reduces susceptibility to killing.
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    Pga26 mediates filamentation and biofilm formation and is required for virulence in Candida albicans.
    (Blackwell Publishing Ltd., 2011-08) Laforet, Leslie; Moreno, Inmaculada; Sánchez Fresneda, Ruth; Martínez, José P.; Argüelles, Juan Carlos; Groot, Piet W.J. de; Valentín Gómez, Eulogio; Martínez-Esparza Alvargonzález, María Concepción; Bioquímica y Biología Molecular B e Inmunología
    The Candida albicans gene PGA26 encodes a small cell wall protein and is upregulated during de novo wall synthesis in protoplasts. Disruption of PGA26 caused hypersensitivity to cell wall-perturbing compounds (Calcofluor white and Congo red) and to zymolyase, which degrades the cell wall β-1,3-glucan network. However, susceptibility to caspofungin, an inhibitor of β-1,3-glucan synthesis, was decreased. In addition, pga26Δ mutants show increased susceptibility to antifungals (fluconazol, posaconazol or amphotericin B) that target the plasma membrane and have altered sensitivities to environmental (heat, osmotic and oxidative) stresses. Except for a threefold increase in β-1,6-glucan and a slightly widened outer mannoprotein layer, the cell wall composition and structure was largely unaltered. Therefore, Pga26 is important for proper cell wall integrity, but does not seem to be directly involved in the synthesis of cell wall components. Deletion of PGA26 further leads to hyperfilamentation, increased biofilm formation and reduced virulence in a mouse model of disseminated candidiasis. We propose that deletion of PGA26 may cause an imbalance in the morphological switching ability of Candida, leading to attenuated dissemination and infection.
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    Solubilización y caracterización de la actividad trehalasa ligada a la pared celular de ascosporas de schizzosaccharomyces pombe
    (Murcia: Universidad de Murcia, Servicio de Publicaciones, 1990) Gacto Fernández, Mariano José; Vicente Soler, Jerónima; Facultad de Biología
    Se ha investigado la localización de la trehalasa en ascosporas aisladas de Schiiosacchar~omycfs pombe mediante un método citoquímico basado en la formación de complejos insolubles de eugenol, producidos extracelularmente en una reacción acoplada a la actividad trehalasa. La mayor parte de la actividad enzimática detectable en extractos celulares está unida a la pared celular de las ascosporas. Por tratamiento controlado de paredes celulares con el sistema Iítico iiovoenzima es posible lograr una solubilización parcial de la trehalasa particulada. El perfil de elución obtenido por filtración molecular del enzima solubilizado de paredes indica una amplia heterogeneidad molecular, lo que sugiere una posible naturaleza glicoproteica del enzima. Los ensayos de activación y el análisis de propiedades cinéticas revelan que esta actividad se debe a una trehalasa de las pertenecientes al tipo no regulador