A transporter in the endoplasmic reticulum of Schizosaccharomyces pombe cells mediates zinc storage and differentially affects transition metal tolerance.
The cation diffusion facilitator (CDF) family represents a class of ubiquitous metal transporters. Inactivation of a CDF in Schizosaccharomyces pombe, Zhf, causes drastically different effects on the tolerance toward various metals. A deletion mutant is Zn(2+)/Co(2+)-hypersensitive yet displays significantly enhanced Cd(2+) and Ni(2+) tolerance. Accumulation of zinc, cobalt, and cadmium is reduced in mutant cells. Non-vacuolar zinc content, as measured by analytical electron microscopy, is lower in zhf(-) cells compared with wild-type cells in the presence of elevated Zn(2+) concentrations. The protective effect against cadmium toxicity is independent of the phytochelatin detoxification pathway. Phytochelatin synthase-deficient cells show extremely enhanced (about 200-fold) cadmium tolerance when zhf is disrupted. Immunogold labeling indicates endoplasmic reticulum (ER) localization of Zhf. Electron spectroscopic imaging shows that accumulation of zinc coincides with Zhf localization, demonstrating a major role of the ER for metal storage and the involvement of Zhf in cellular zinc homeostasis. Also, these observations indicate that Cd(2+) ions exert their toxic effects on cellular metabolism in the ER rather than in the cytosol.
Clemens
Stephan
S
Leibniz-Institut für Pflanzenbiochemie, Weinberg 3, 06120 Halle/Saale, Germany. sclemens@ipb-halle.de
Bloss
Tanja
T
Vess
Christoph
C
Neumann
Dieter
D
Nies
Dietrich H
DH
Zur Nieden
Uta
U
D002104:Cadmium / Q000378:metabolism; D003035:Cobalt / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000302:isolation & purification* / Q000378:metabolism; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D012568:Schizosaccharomyces / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000302:isolation & purification* / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
D026901:Membrane Transport Proteins; D029702:Schizosaccharomyces pombe Proteins; C459607:Zhf1 protein, S pombe; D002104:Cadmium; D003035:Cobalt; D015032:Zinc