Functional analysis of Candida albicans GPI-anchored proteins: Roles in cell wall integrity and caspofungin sensitivity

Plaine, Armêl; Walker, Louise E.; Costa, Grégory Da; Mora-Montes, Héctor M.; McKinnon, Alastair D.; Gow, Neil A. R.; Gaillardin, Claude; Munro, Carol A.; Richard, Mathias L.

doi:10.1016/j.fgb.2008.08.003

Cited by 222 publications

(218 citation statements)

References 56 publications

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“…This is quite unlike the deletion of CaSMP3 and GPI7, which, though further downstream in the GPI biosynthetic pathway, show a marked sensitivity to CFW (Grimme et al, 2004;Richard et al, 2002). The reason for this difference is not clear, though it may be noted that deletions of different GPI-anchored proteins did not have the same effect on cell wall chitin (Plaine et al, 2008). In the A. nidulans pigP conditional null, there was also no sensitivity to any of the cell wall perturbing agents used (Piłsyk & Paszewski, 2009).…”

Section: Discussionmentioning

confidence: 98%

The Candida albicans homologue of PIG-P, CaGpi19p: gene dosage and role in growth and filamentation

2010

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Glycosylphosphatidyl inositol (GPI)-anchored proteins in Candida albicans are responsible for a vast range of functions, and deletions in certain GPI-anchored proteins severely reduce adhesion and virulence of this organism. In addition, completely modified GPIs are necessary for virulence. GPI anchor biosynthesis is essential for viability and starts with the transfer of N-acetylglucosamine to phosphatidylinositol. This step is catalysed by a multi-subunit complex, GPI–N-acetylglucosaminyltransferase (GPI–GnT). In this, the first report to our knowledge on a subunit of the Candida GPI–GnT complex, we show that CaGpi19p is the functional equivalent of the Saccharomyces cerevisiae Gpi19p. An N-terminal truncation mutant of CaGpi19p functionally complements a conditionally lethal S. cerevisiae gpi19 mutant. Further, we constructed a conditional null mutant of CaGPI19 by disrupting one allele and placing the remaining copy under the control of the MET3 promoter. Repression leads to growth defects, cell wall biogenesis aberrations, azole sensitivity and hyperfilamention. In addition, there is a noticeable gene dosage effect, with the heterozygote also displaying intermediate degrees of most phenotypes. The mutants also displayed a reduced susceptibility to the antifungal agent amphotericin B. Collectively, the results suggest that CaGPI19 is required for normal morphology and cell wall architecture.

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Section: Discussionmentioning

confidence: 98%

The Candida albicans homologue of PIG-P, CaGpi19p: gene dosage and role in growth and filamentation

2010

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“…Homology searches reveal homologs of ␣2␦-subunits in the genomes of animals but not fungi. Nevertheless, many of their structural features are evident in Mid1-related proteins, which can be found only in the genomes of fungi (51). 3 Therefore, Mid1 may be structurally and functionally analogous to ␣2␦-subunits if not demonstrably homologous.…”

Section: Discussionmentioning

confidence: 99%

New Regulators of a High Affinity Ca2+ Influx System Revealed through a Genome-wide Screen in Yeast

Martin¹,

Kim²,

Mackin

et al. 2011

Journal of Biological Chemistry

100

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The bakers' yeast Saccharomyces cerevisiae utilizes a high affinity Ca 2؉ influx system (HACS) to survive assaults by mating pheromones, tunicamycin, and azole-class antifungal agents. HACS consists of two known subunits, Cch1 and Mid1, that are homologous and analogous to the catalytic ␣-subunits and regulatory ␣2␦-subunits of mammalian voltage-gated calcium channels, respectively. To search for additional subunits and regulators of HACS, a collection of gene knock-out mutants was screened for abnormal uptake of Ca 2؉ after exposure to mating pheromone or to tunicamycin. The screen revealed that Ecm7 is required for HACS function in most conditions. Cycloheximide chase experiments showed that Ecm7 was stabilized by Mid1, and Mid1 was stabilized by Cch1 in non-signaling conditions, suggesting they all interact. Ecm7 is a member of the PMP-22/ EMP/MP20/Claudin superfamily of transmembrane proteins that includes ␥-subunits of voltage-gated calcium channels. Eleven additional members of this superfamily were identified in yeast, but none was required for HACS activity in response to the stimuli. Remarkably, many dozens of genes involved in vesicle-mediated trafficking and protein secretion were required to prevent spontaneous activation of HACS. Taken together, the findings suggest that HACS and calcineurin monitor performance of the membrane trafficking system in yeasts and coordinate compensatory processes. Conservation of this quality control system in Candida glabrata suggests that many pathogenic species of fungi may utilize HACS and calcineurin to resist azoles and other compounds that target membrane biosynthesis.

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“…Transcript profiling data suggested that Pga59 and Pga62 might play a role in cell wall stability, as both PGA59 and PGA62 are upregulated during protoplast regeneration (Castillo et al, 2006). Characterization of a pga62D/pga62D mutant in the framework of a global survey of the function of GPImodified proteins in C. albicans has suggested that Pga62 indeed plays a role in cell wall stability, as inactivation of PGA62 was associated with Calcofluor white sensitivity, resistance to caspofungin, and an increase in cell wall chitin content and thickness (Plaine et al, 2008). Data presented in this study confirm the involvement of Pga62 in C. albicans cell wall stability and extend this involvement to Pga59.…”

Section: Discussionmentioning

confidence: 99%

The GPI-modified proteins Pga59 and Pga62 of Candida albicans are required for cell wall integrity

et al. 2009

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The fungal cell wall is essential in maintaining cellular integrity and plays key roles in the interplay between fungal pathogens and their hosts. The PGA59 and PGA62 genes encode two short and related glycosylphosphatidylinositol-anchored cell wall proteins and their expression has been previously shown to be strongly upregulated when the human pathogen Candida albicans grows as biofilms. Using GFP fusion proteins, we have shown that Pga59 and Pga62 are cell-walllocated, N-and O-glycosylated proteins. The characterization of C. albicans pga59D/pga59D, pga62D/pga62D and pga59D/pga59D pga62D/pga62D mutants suggested a minor role of these two proteins in hyphal morphogenesis and that they are not critical to biofilm formation. Importantly, the sensitivity to different cell-wall-perturbing agents was altered in these mutants. In particular, simultaneous inactivation of PGA59 and PGA62 resulted in high sensitivity to Calcofluor white, Congo red and nikkomicin Z and in resistance to caspofungin. Furthermore, cell wall composition and observation by transmission electron microscopy indicated an altered cell wall structure in the mutant strains. Collectively, these data suggest that the cell wall proteins Pga59 and Pga62 contribute to cell wall stability and structure. INTRODUCTIONThe cell wall is an essential component of fungal cells, preserving cellular integrity and playing a central role in the interaction of fungi with their environment. This is particularly the case for pathogenic fungi such as the opportunistic yeast pathogen Candida albicans, where the cell wall has been shown to play central roles in adhesion, virulence, biofilm formation, infection and immunomodulation (Albrecht et al., 2006;Douglas, 2003;Netea et al., 2006;Richard et al., 2002b;Sundstrom, 2002). Because of the essential role of the cell wall in cellular integrity and fungal specificity of some enzymes involved in its biogenesis, it is a recognized target for the development of novel antifungals (e.g. echinocandins that target the b-1,3-glucan synthase) (Latge, 2007).The organization of the fungal cell wall has been mainly characterized in the yeasts Saccharomyces cerevisiae and C. albicans and in the filamentous fungus Aspergillus fumigatus (Klis et al., 2006;Latge, 2007;Lesage & Bussey, 2006;Ruiz-Herrera et al., 2006). The yeast cell wall has a bilayered structure. The inner part is composed of a network of b-1,3-glucan molecules linked by hydrogen bonds. These chains can be bound covalently to b-1,6-glucan molecules and to chitin chains. The outer part of the cell wall is composed mainly of mannoproteins (Klis et al., 2006Lesage & Bussey, 2006). Most proteins in the cell wall of ascomycetous yeasts are glycosylphosphatidylinositolanchored proteins (GPI-modified proteins) that become covalently linked to b-1,6-glucan through a remnant of their GPI anchor. As the b-1,6-glucan moiety can be linked to b-1,3-glucan or chitin, the cell wall GPI-modified proteins are strongly linked to the cell wall Klis et al., 2001;Richard & Plaine, 2007).GPI-...

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Functional analysis of Candida albicans GPI-anchored proteins: Roles in cell wall integrity and caspofungin sensitivity

Cited by 222 publications

References 56 publications

The Candida albicans homologue of PIG-P, CaGpi19p: gene dosage and role in growth and filamentation

The Candida albicans homologue of PIG-P, CaGpi19p: gene dosage and role in growth and filamentation

New Regulators of a High Affinity Ca2+ Influx System Revealed through a Genome-wide Screen in Yeast

The GPI-modified proteins Pga59 and Pga62 of Candida albicans are required for cell wall integrity

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