CgCYN1, a Plasma Membrane Cystine-specific Transporter of Candida glabrata with Orthologues Prevalent among Pathogenic Yeast and Fungi

Abstract

We describe a novel plasma membrane cystine transporter, CgCYN1, from Candida glabrata, the first such transporter to be described from yeast and fungi. C. glabrata met15⌬ strains, organic sulfur auxotrophs, were observed to utilize cystine as a sulfur source, and this phenotype was exploited in the discovery of CgCYN1. Heterologous expression of CgCYN1 in Saccharomyces cerevisiae met15⌬ strains conferred the ability of S. cerevisiae strains to grow on cystine. Deletion of the CgCYN1 ORF (CAGL0M00154g) in C. glabrata met15⌬ strains caused abrogation of growth on cystine with growth being restored when CgCYN1 was reintroduced. The CgCYN1 protein belongs to the amino acid permease family of transporters, with no similarity to known plasma membrane cystine transporters of bacteria and humans, or lysosomal cystine transporters of humans/ yeast. Kinetic studies revealed a K m of 18 ؎ 5 M for cystine. Cystine uptake was inhibited by cystine, but not by other amino acids, including cysteine. The structurally similar cystathionine, lanthionine, and selenocystine alone inhibited transport, confirming that the transporter was specific for cystine. CgCYN1 localized to the plasma membrane and transport was energy-dependent. Functional orthologues could be demonstrated from other pathogenic yeast like Candida albicans and Histoplasma capsulatum, but were absent in Schizosaccharomyces pombe and S. cerevisiae.

Regulation of Sulphur Assimilation Is Essential for Virulence and Affects Iron Homeostasis of the Human-Pathogenic Mould Aspergillus fumigatus

“…Nevertheless, expression of the putative cysteine transporter-encoding gene cynA , an orthologue to a C. glabrata -specific cysteine transporter [54], was not upregulated in the metRΔ strain under sulphur starving conditions (Fig. 5C), which would partially explain the observed phenotype.…”

Comparative Transcriptomics of Infectious Spores from the Fungal Pathogen Histoplasma capsulatum Reveals a Core Set of Transcripts That Specify Infectious and Pathogenic States

“…Cystine is composed of two covalently attached cysteine molecules, and H. capsulatum yeasts require cysteine supplementation for in vitro growth. Although LYP1 was originally identified as a putative yeast-phase-specific lysine permease gene (12), we reannotated it CYN1 here, since its C. glabrata ortholog was recently shown to function in cystine transport (71).…”

Thiol trapping and metabolic redistribution of sulfur metabolites enable cells to overcome cysteine overload

“…Cysteine transporters have been described across phyla 78910. Contrastingly, cystine transporters, though not as ubiquitous, are also prevalent in different organisms 1112131415.…”

“…We have therefore engineered and utilized a simple system where the specific cysteine transporter, YCT1 , is constitutively expressed under a strong promoter in order to generate high cysteine levels in the cell, while adding relatively lower levels of the amino acid in the medium. Furthermore, we also employed a similarly expressed high affinity cystine transporter ( CgCYN1 ) 12. To understand cellular responses in yeast cells to high levels of intracellular cysteine we adopted a two-pronged approach.…”