PMID:11792622

Citation	St Croix, CM, Wasserloos, KJ, Dineley, KE, Reynolds, IJ, Levitan, ES and Pitt, BR (2002) Nitric oxide-induced changes in intracellular zinc homeostasis are mediated by metallothionein/thionein. Am. J. Physiol. Lung Cell Mol. Physiol. 282:L185-92
Abstract	We hypothesized that metallothionein (MT), a cysteine-rich protein with a strong affinity for Zn(2+), plays a role in nitric oxide (NO) signaling events via sequestration or release of Zn(2+) by the unique thiolate clusters of the protein. Exposing mouse lung fibroblasts (MLF) to the NO donor S-nitrosocysteine resulted in 20-30% increases in fluorescence of the Zn(2+)-specific fluorophore Zinquin that were rapidly reversed by the Zn(2+) chelator N,N,N',N'-tetrakis-(2-pyridylmethyl)ethylenediamine. The absence of a NO-mediated increase in labile Zn(2+) in MLF from MT knockouts and its restoration after MT complementation by adenoviral gene transfer inferred a critical role for MT in the regulation of Zn(2+) homeostasis by NO. Additional data obtained in sheep pulmonary artery endothelial cells suggested a role for the apo form of MT, thionein (T), as a Zn(2+)-binding protein in intact cells, as overexpression of MT caused inhibition of NO-induced changes in labile Zn(2+) that were reversed by Zn(2+) supplementation. Furthermore, fluorescence-resonance energy-transfer data showed that overexpression of green fluorescent protein-modified MT prevented NO-induced conformational changes, which are indicative of Zn(2+) release from thiolate clusters. This effect was restored by Zn(2+) supplementation. Collectively, these data show that MT mediates NO-induced changes in intracellular Zn(2+) and suggest that the ratio of MT to T can regulate Zn(2+) homeostasis in response to nitrosative stress.
Links	PubMed Online version:10.1152/ajplung.00267.2001
Keywords	Animals; Cells, Cultured; Chelating Agents/pharmacology; Cysteine/analogs & derivatives; Cysteine/pharmacology; Endothelium, Vascular/cytology; Endothelium, Vascular/metabolism; Ergothioneine/metabolism; Ethylenediamines/pharmacology; Female; Fibroblasts/cytology; Fibroblasts/metabolism; Fluorescent Dyes; Gene Expression/physiology; Homeostasis/physiology; Lung/cytology; Lung/metabolism; Male; Metallothionein/genetics; Metallothionein/metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide/metabolism; Nitric Oxide Donors/pharmacology; Pulmonary Artery/cytology; Quinolones; S-Nitrosothiols/pharmacology; Sheep; Spectrometry, Fluorescence; Tosyl Compounds; Zinc/metabolism; Zinc/pharmacology
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