Characterisation of Pga1, a putative Candida albicans cell wall protein necessary for proper adhesion and biofilm formation

Abstract

The fungal pathogen Candida albicans is a leading causative agent of death in immunocompromised individuals. Many factors have been implicated in virulence including filamentation-inducing transcription factors, adhesins, lipases and proteases. Many of these factors are glycosylphosphatidylinositol-anchored cell surface antigenic determinant proteins. Pga1 is one such protein shown to be upregulated during cell wall regeneration. The purpose of this study was to characterise the role Pga1 plays by creating a homozygous pga1 null strain and comparing the phenotype with the parental strain. It was observed that the mutant strain showed less oxidative stress tolerance and an increased susceptibility to calcofluor white, a cell surface disrupting agent that inhibits chitin fibre assembly which translated as a 40% decrease in cell wall chitin content. Furthermore, the mutant exhibited a 50% reduction in adhesion and a 33% reduction in biofilm formation compared with the parental strain, which was reflected as a slight reduction in virulence. Our data suggest that Pga1 plays an important role in cell wall rigidity and stability. It was also observed that the pga1 null was over filamentous on both liquid and solid media and exhibited increased resistance to SDS suggesting upregulation of filamentation-inducing genes and cell surface components to partially compensate for the deletion.

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

“…The GPI7-null mutant showed reduced hyphal growth on solid media, increased sensitivity to Calcofluor white (CFW), reduced virulence in mice, and lytic action of macrophages (50). 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 expression of the Candida albicans gene SAP4 during hyphal formation in human serum and in adhesion to monolayer cell culture of colorectal carcinoma Caco-2 (ATCC)

“…Literature data [12] point out that there are transcriptional factors (other than Cph1 and Efg1) involved in regulation of both [7], the EED1 gene seems to encode a key regulator of hyphal growth and other virulence factors like SAP5 which is hyphaeassociated and up-regulated during RHE infections and patient samples. Previous studies identified another key transcriptional factor, Ume6 which is necessary for the extension of germ tubes into hyphae as well as other genes' expression [35,36,39]. Taken together, it should be noted that SAP4 may be regulated by neither Efg1 nor Cph1 and other transcriptional factors may regulate this gene expression under human serum influence [3,11,12].…”

“…Taken together, it should be noted that SAP4 may be regulated by neither Efg1 nor Cph1 and other transcriptional factors may regulate this gene expression under human serum influence [3,11,12]. Moreover, the proteinase encoded by this gene, if translated, may be associated with C. albicans infection and is quite different from laboratory culture conditions [35,41].…”

“…Adherence of C. albicans to the Caco-2 cell line (ATCC HTB-37 TM ) was performed as described previously Hashash et al [35]. Briefly, the Caco-2 cell line was cultivated in EMEM at 37°C at 5% (v/v) CO 2 .…”

TheCandida albicansDse1 Protein Is Essential and Plays a Role in Cell Wall Rigidity, Biofilm Formation, and Virulence

“…The RM 1000 parental strain was transformed with plasmid p ABSK2 to restore uridine prototrophy as described previously [16, 17]. Successful transformants were selected on selective YNB medium supplemented with the appropriate amino acids.…”