Regulatory Responses to Copper Ions in Fungi

Labbé, Simon; Beaudoin, Jude; Bellemare, Daniel R.; Pelletier, Benoît

doi:10.1385/1-59259-288-0:571

Handbook of Copper Pharmacology and Toxicology

DOI: 10.1385/1-59259-288-0:571

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Regulatory Responses to Copper Ions in Fungi

Simon Labbé¹,

Jude Beaudoin²,

Daniel R. Bellemare³

et al.

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Cited by 4 publications

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“…A third copper chaperone, Ccs1, donates copper specifically to the cytosolic copper zinc-superoxide dismutase (17). For the fission yeast S. pombe, although candidate molecules for copper trafficking into cells have been inferred from sequence homology to the S. cerevisiae chaperones (31), only one has been characterized experimentally, namely, Pccs (34). This protein is orthologous to the S. cerevisiae Ccs1 cytosolic copper chaperone.…”

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Copper Distributed by Atx1 Is Available to Copper Amine Oxidase 1 in Schizosaccharomyces pombe

et al. 2008

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Copper amine oxidases (CAOs) have been proposed to be involved in the metabolism of xenobiotic and biogenic amines. The requirement for copper is absolute for their activity. In the fission yeast Schizosaccharomyces pombe, cao1؉ and cao2 ؉ genes are predicted to encode members of the CAO family. While both genes are expressed in wild-type cells, we determined that the expression of only cao1 ؉ but not cao2 ؉ results in the production of an active enzyme. Site-directed mutagenesis identified three histidine residues within the C-terminal region of Cao1 that are necessary for amine oxidase activity. By use of a cao1 ؉ -GFP allele that retained wild-type function, Cao1-GFP was localized in the cytosol (GFP is green fluorescent protein). Under copper-limiting conditions, disruption of ctr4 ؉ , ctr5 ؉ , and cuf1 ؉ produced a defect in amine oxidase activity, indicating that a functionally active Cao1 requires Ctr4/5-mediated copper transport and the transcription factor Cuf1. Likewise, atx1 null cells exhibited substantially decreased levels of amine oxidase activity. In contrast, deletion of ccc2, cox17, and pccs had no significant effect on Cao1 activity. Residual amine oxidase activity in cells lacking atx1 ؉ can be restored to normal levels by returning an atx1 ؉ allele, underscoring the critical importance of the presence of Atx1 in cells. Using two-hybrid analysis, we demonstrated that Cao1 physically interacts with Atx1 and that this association is comparable to that of Atx1 with the N-terminal region of Ccc2. Collectively, these results describe the first example of the ability of Atx1 to act as a copper carrier for a molecule other than Ccc2 and its critical role in delivering copper to Cao1.

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Copper Distributed by Atx1 Is Available to Copper Amine Oxidase 1 in Schizosaccharomyces pombe

et al. 2008

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“…For growth under copper limiting conditions, the molecular mechanisms in the early steps of copper assimilation in S. pombe differ from those in S. cerevisiae (53). Two integral membrane proteins, Ctr4 and Ctr5, form a two-component copper transporting complex at the cell surface (54,55).…”

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The Schizosaccharomyces pombe Pccs Protein Functions in Both Copper Trafficking and Metal Detoxification Pathways

Laliberté

Whitson

Beaudoin

et al. 2004

Journal of Biological Chemistry

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Because copper is both an essential cofactor and a toxic metal, different strategies have evolved to appropriately regulate its homeostasis as a function of changing environmental copper levels. In this report, we describe a metallochaperone-like protein from Schizosaccharomyces pombe that maintains the delicate balance between essentiality and toxicity. This protein, designated Pccs, has four distinct domains. SOD activity assays reveal that the first three domains of Pccs are necessary and sufficient to deliver copper to its target, copper-zinc superoxide dismutase (SOD1). Pccs domain IV, which is absent in Saccharomyces cerevisiae CCS1, contains seventeen cysteine residues, eight pairs of which are in a potential metal coordination arrangement, Cys-Cys. We show that S. cerevisiae ace1⌬ mutant cells expressing the full-length Pccs molecule are resistant to copper toxicity. Furthermore, we demonstrate that the Pccs domain IV enhances copper resistance of the ace1⌬ cells by an order of magnitude compared with that observed in the same strain expressing a pccs ؉

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“…An elegant study has demonstrated that Ctr5 is an integral membrane protein, which is required for properly localizing Ctr4 to the plasma membrane in S. pombe cells (39). Once copper ions are transported by the Ctr4-Ctr5 complex into the cells, they are presumably taken by putative copper chaperones, which are yet uncharacterized at the molecular level (41). A hallmark of the ctr4 ϩ and ctr5 ϩ genes is the fact that they are transcriptionally regulated according to copper need (40,42).…”

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Ctr6, a Vacuolar Membrane Copper Transporter inSchizosaccharomyces pombe

Bellemare

Shaner²,

Morano³

et al. 2002

Journal of Biological Chemistry

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Aerobic organisms possess efficient systems for the transport of copper. This involves transporters that mediate the passage of copper across biological membranes to reach essential intracellular copper-requiring enzymes. In this report, we identify a new copper transporter in Schizosaccharomyces pombe, encoded by the ctr6 ؉ gene. The transcription of ctr6 ؉ is induced under copper-limiting conditions. This regulation is mediated by the cis-acting promoter element CuSE (copper-signaling element) through the copper-sensing transcription factor Cuf1. An S. pombe strain bearing a disrupted ctr6⌬ allele displays a strong reduction of copper,zinc superoxide dismutase activity. When the ctr6؉ gene is overexpressed from the thiamine-inducible nmt1 ؉ promoter, the cells are unable to grow on medium containing exogenous copper. Surprisingly, this copper-sensitive growth phenotype is not due to an increase of copper uptake at the cell surface. Instead, copper delivery across the plasma membrane is reduced. Consistently, this results in repressing ctr4 ؉ gene expression. By using a functional ctr6 ؉ epitope-tagged allele expressed under the control of its own promoter, we localize the Ctr6 protein on the membrane of vacuoles. Furthermore, we demonstrate that Ctr6 is an integral membrane protein that can trimerize. Moreover, we show that Ctr6 harbors a putative copper-binding Met-X-His-Cys-X-Met-X-Met motif in the amino terminus, which is essential for its function. Our findings suggest that under conditions in which copper is scarce, Ctr6 is required as a means to mobilize stored copper from the vacuole to the cytosol.

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Regulatory Responses to Copper Ions in Fungi

Cited by 4 publications

References 0 publications

Copper Distributed by Atx1 Is Available to Copper Amine Oxidase 1 in Schizosaccharomyces pombe

Copper Distributed by Atx1 Is Available to Copper Amine Oxidase 1 in Schizosaccharomyces pombe

The Schizosaccharomyces pombe Pccs Protein Functions in Both Copper Trafficking and Metal Detoxification Pathways

Ctr6, a Vacuolar Membrane Copper Transporter inSchizosaccharomyces pombe

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