Copper-inducible transcription: regulation by metal- and oxidative stress-responsive pathways.
Although copper is an essential metal, it is capable of catalyzing the formation of reactive oxygen species that can cause intracellular oxidative damage. We investigated the hypothesis that metal- and oxidative stress-responsive signal transduction pathways mediate the cellular and molecular responses associated with copper exposure. Transient transfection assays using COS-7 cells and mouse metallothionein-I (MT-I) or rat NAD(P)H:oxidoreductase 1-based reporter genes demonstrate that copper activates transcription via metal and antioxidant response elements. Concomitant with copper exposures is a decrease in the level of total glutathione and an increase in oxidized glutathione. Depletion of glutathione, before copper exposure, increases metal- and oxidative stress-inducible transcription and cytotoxicity. Pretreatment with the reactive oxygen scavengers aspirin or vitamin E provides partial protection against copper toxicity and reduces inducible transcription. Experiments using signal transduction inhibitors and a metal transcription factor (MTF)-1 null cell line demonstrate that copper-inducible MT-I transcription is regulated by protein kinase C and mitogen-activated protein kinase signaling pathways and requires MTF-1. The results of these studies indicate that copper activates transcription through both metal- and oxidative stress-responsive signal transduction pathways.
Nicholas School of Environement and Earth Sciences, Duke University, Durham, NC 27708-0328, USA.
Michael D
MD
Mattie
Jonathan H
JH
Freedman
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D019556:COS Cells; D002522:Chlorocebus aethiops; D003300:Copper / Q000494:pharmacology*; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D017930:Genes, Reporter / Q000235:genetics; D005978:Glutathione / Q000172:deficiency / Q000378:metabolism; D008668:Metallothionein / Q000235:genetics; D008670:Metals / Q000494:pharmacology*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics; D018384:Oxidative Stress / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D020218:Response Elements / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects* / Q000502:physiology; D014162:Transfection; D000097809:Transcription Factor MTF-1
D000975:Antioxidants; D003300:Copper; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D005978:Glutathione; D008668:Metallothionein; D008670:Metals; D020928:Mitogen-Activated Protein Kinases; D009247:NADH, NADPH Oxidoreductases; D011493:Protein Kinase C; D014157:Transcription Factors; D000097809:Transcription Factor MTF-1