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

Abstract

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.

E1210, a New Broad-Spectrum Antifungal, Suppresses Candida albicans Hyphal Growth through Inhibition of Glycosylphosphatidylinositol Biosynthesis

“…The PGA1 mutant showed reduced adherence and biofilm formation and increased sensitivity to CFW but increased filamentation (18). The conditional null mutation of GPI19 led to reduced surface GPI anchor levels, cell wall biogenesis aberrations (aggregation), and increased filamentation, but not increased CFW sensitivity (67). The conditional null mutant of SMP3 exhibited reduced surface GPI anchor levels, aberrant morphology (aggregation of irregularly shaped cells), and increased CFW sensitivity (17).…”

N-Acetyl-d-glucosaminylphosphatidylinositol De-N-acetylase from Entamoeba histolytica

“…Complementation of ScGPI12 by EhPIG-L-To ascertain whether the EhPIG-L gene is capable of functionally complementing the ScGPI12 gene, a haploid yeast (YPH500) (supplemental Table I) mutant was generated in which the native promoter of ScGPI12 was replaced by the regulatable GAL1 promoter (YPH-GAL1-ScGPI12 (supplemental Table I) (17). This strain grew normally in galactose (Gal) but was defective in growth in glucose (Glc) medium (a condition where the expression from GAL1 promoter is shut down) because ScGPI12 is essential for yeast growth (8).…”

Mutual co-regulation between GPI-N-acetylglucosaminyltransferase and ergosterol biosynthesis in Candida albicans

“…The heterozygote, Cagpi19/CaGPI19, and conditional-null, Cagpi19/MET3-GFP-CaGPI19, strains were made in BWP17 and grown in minimal medium containing methionine/cysteine to repress CaGPI19 expression [7]. The chs2 mutant in SGY243 background was a gift from Professor N. Gow [9].…”

“…We previously characterized CaGPI19, which encodes an accessory subunit of the GPI-GnT and reported a link between GPI biosynthesis and drug response in C. albicans [7]. Heterozygous and conditional-null mutants of CaGPI19 were resistant to Amp B (amphotericin B); the conditional null had higher azole sensitivity also.…”