Abstract
Zinc has been known for many years to inhibit apoptosis but the mechanism remains unclear. Originally thought to inhibit an apoptotic endonuclease, zinc has subsequently been shown to inhibit steps earlier in the pathway. Since many additional steps in apoptosis have now been defined, we have re-evaluated the steps inhibited by zinc. In response to activation of the chemical-mediated death pathway by anisomycin, 0.3 mM zinc inhibited Bax and Bak activation, cytochrome c release, and all of the subsequent steps in apoptosis. In the receptor-mediated death pathway initiated by Fas or tumor necrosis factor, 3 mM zinc was required to inhibit apoptosis as judged by inhibition of caspase 3 activity and DNA digestion, but it failed to inhibit cytochrome c release, activation of Bax and Bak, or upstream signaling events in this pathway. These results are consistent with zinc selectively inhibiting activation of BH3-only proteins required in the chemical pathway but inhibiting downstream caspase activation in the death-receptor pathway.
MeSH terms
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Anisomycin / pharmacology
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Apoptosis / drug effects
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Apoptosis / physiology*
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Caspase Inhibitors
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Caspases / metabolism
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Cycloheximide / pharmacology
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Cytochromes c / metabolism*
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DNA Fragmentation / drug effects
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DNA Fragmentation / physiology
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Feedback, Physiological / drug effects
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Feedback, Physiological / physiology
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Humans
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Jurkat Cells
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Membrane Proteins / drug effects
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Membrane Proteins / metabolism*
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Protein Synthesis Inhibitors / pharmacology
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Proto-Oncogene Proteins / drug effects
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins c-bcl-2*
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Receptors, Tumor Necrosis Factor / drug effects
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Receptors, Tumor Necrosis Factor / metabolism
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Signal Transduction / drug effects
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Signal Transduction / physiology
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Tumor Necrosis Factor-alpha / pharmacology
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Zinc / metabolism*
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Zinc / pharmacology
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bcl-2 Homologous Antagonist-Killer Protein
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bcl-2-Associated X Protein
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fas Receptor / drug effects
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fas Receptor / metabolism*
Substances
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BAK1 protein, human
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BAX protein, human
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Caspase Inhibitors
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Membrane Proteins
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Protein Synthesis Inhibitors
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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Receptors, Tumor Necrosis Factor
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Tumor Necrosis Factor-alpha
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bcl-2 Homologous Antagonist-Killer Protein
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bcl-2-Associated X Protein
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fas Receptor
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Anisomycin
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Cytochromes c
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Cycloheximide
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Caspases
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Zinc