Modulation of azole sensitivity and filamentation by GPI15, encoding a subunit of the first GPI biosynthetic enzyme, in Candida albicans

Abstract

Glycosylphosphatidylinositol (GPI)-anchored proteins are important for virulence of many pathogenic organisms including the human fungal pathogen, Candida albicans . GPI biosynthesis is initiated by a multi-subunit enzyme, GPI- N- acetylglucosaminyltransferase (GPI-GnT). We showed previously that two GPI-GnT subunits, encoded by CaGPI2 and CaGPI19 , are mutually repressive. CaGPI19 also co-regulates CaERG11 , the target of azoles while CaGPI2 controls Ras signaling and hyphal morphogenesis. Here, we investigated the role of a third subunit. We show that CaGpi15 is functionally homologous to Saccharomyces cerevisiae Gpi15. CaGPI15 is a master activator of CaGPI2 and CaGPI19 . Hence, CaGPI15 mutants are azole-sensitive and hypofilamentous. Altering CaGPI19 or CaGPI2 expression in CaGPI15 mutant can elicit alterations in azole sensitivity via CaERG11 expression or hyphal morphogenesis, respectively. Thus, CaGPI2 and CaGPI19 function downstream of CaGPI15 . One mode of regulation is via H3 acetylation of the respective GPI-GnT gene promoters by Rtt109. Azole sensitivity of GPI-GnT mutants is also due to decreased H3 acetylation at the CaERG11 promoter by Rtt109. Using double heterozygous mutants, we also show that CaGPI2 and CaGPI19 can independently activate CaGPI15 . CaGPI15 mutant is more susceptible to killing by macrophages and epithelial cells and has reduced ability to damage either of these cell lines relative to the wild type strain, suggesting that it is attenuated in virulence.

Role of Protein Glycosylation in Interactions of Medically Relevant Fungi with the Host

“…A third subunit has been described, GPI15, a master activator of GPI2 and GPI19, important for growth, cell wall integrity, and GPI synthesis in C. albicans. GPI15 mutants were hypofilamentous, ergosterol defective, and azole sensitive and exhibited the phenotypes of both GPI2 and GPI19 mutants [96]. Additionally, GPI15 mutants were less virulent in vitro, since this gene regulates hyphal filamentation and invasive growth, which are important for the establishment of the infection by C. albicans (Table 1) [96].…”

“…GPI15 mutants were hypofilamentous, ergosterol defective, and azole sensitive and exhibited the phenotypes of both GPI2 and GPI19 mutants [96]. Additionally, GPI15 mutants were less virulent in vitro, since this gene regulates hyphal filamentation and invasive growth, which are important for the establishment of the infection by C. albicans (Table 1) [96]. Thus, by controlling Gpi12 and Gpi19 activities, Gpi15 may be a good antifungal target.…”

yEvo: Experimental evolution in high school classrooms selects for novel mutations and epistatic interactions that impact clotrimazole resistance inS. cerevisiae

“…In a genome-wide screen CSF1 was implicated in maturation of glycosylphosphatidylinositol (GPI), a posttranslational modification that allows proteins to be targeted to the cell membrane (Čopič et al 2009). Genes involved in this maturation process have been shown to regulate ERG11 in Candida albicans and can thus modulate azole resistance (Jain et al 2019). Genome-wide genetic interaction mapping experiments have shown that the interaction profile of CSF1 is similar to that of many genes involved in cell surface GPI anchor maturation (Table S14) (Usaj et al 2017).…”

RTT109 and Fun30 proteins mediate epigenetic regulation of the DNA damage response pathway in C. albicans

“…Recently, we have shown that Rtt109 mediated acetylation of H3 regulates the expression of genes involved in GPI anchor biosynthesis and in ergosterol biosynthesis (18). However, the crosstalk between Rtt109 and Fun30 has not yet been investigated.…”

“…Rtt109 in C. albicans has been linked to pathogenesis; the cells lacking Rtt109 were found to be sensitive to genotoxic agents like camptothecin (CPT) and methyl methane sulfonate (MMS) indicating the role of the histone acetyltransferase in DNA damage response/repair (14). Recently, we have shown that Rtt109 mediated acetylation of H3 regulates the expression of genes involved in GPI anchor biosynthesis and in ergosterol biosynthesis (18). However, the crosstalk between Rtt109 and Fun30 has not yet been investigated.…”