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Copper-dependent trafficking of the Ctr4-Ctr5 copper transporting complex.
Raphaël Ioannoni1, Jude Beaudoin, Alexandre Mercier
1Département de Biochimie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Canada.
Plos One
|August 10, 2010
Summary
Copper uptake in yeast involves the Ctr4-Ctr5 complex. This complex is internalized when copper levels are high and recycled when levels decrease, regulating cell surface protein numbers.
Area of Science:
- Cell biology
- Molecular biology
- Biochemistry
Background:
- Copper uptake in *Schizosaccharomyces pombe* is mediated by the heteromeric Ctr4-Ctr5 complex.
- Differential subcellular localization of Ctr4 and Ctr5 is crucial for regulating cell surface protein levels.
Purpose of the Study:
- To investigate the in vivo protein-protein interactions of the Ctr4-Ctr5 complex.
- To analyze the dynamic behavior of the Ctr4-Ctr5 complex in response to varying copper concentrations.
Main Methods:
- Developed a bimolecular fluorescence complementation (BiFC) assay in *S. pombe*.
- Utilized Venus fluorescent protein fragments (VN and VC) fused to Ctr4 and Ctr5.
- Observed protein localization and complex formation at the plasma membrane.
Main Results:
- Co-expression of Ctr4 and Ctr5 fusion proteins confirmed their interaction and localization at the plasma membrane under copper-limited conditions.
- The Ctr4-Ctr5 complex requires a stoichiometry of two Ctr4 molecules to one Ctr5 molecule.
- Copper-induced internalization of the Ctr4-Ctr5 complex was observed upon exposure to high copper levels.
- Internalized complexes reappeared at the plasma membrane when copper levels were reduced, independent of new protein synthesis.
Conclusions:
- The heteromeric Ctr4-Ctr5 complex undergoes copper-dependent internalization and recycling.
- This dynamic regulation fine-tunes the availability of copper transporters at the cell surface based on environmental copper levels.
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