Subunit-specific Interactions of Cyanide with the N-Methyl-d-aspartate Receptor*
- From the Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
Abstract
Cyanide can potentiateN-methyl-d-aspartate receptor-mediated physiological responses in neurons. Here we show that this phenomenon may be attributable to a subunit-specific chemical modification of the receptor directly by the toxin.N-Methyl-d-aspartate (30 μm)-induced whole cell responses in mature (22–29 daysin vitro) rat cortical neurons were potentiated nearly 2-fold by a 3–5-min treatment with 2 mm potassium cyanide, as did a similar treatment with 4 mm dithiothreitol. A 1-min incubation with the thiol oxidant 5,5′-dithiobis(2-nitrobenzoic acid) (0.5 mm) readily reversed the potentiation induced by either cyanide or dithiothreitol. Cyanide did not increase further currents previously potentiated by dithiothreitol nor was it able to potentiate responses during brief co-application with the agonist. Transient expression studies in Chinese hamster ovary cells with wild-type and mutated recombinantN-methyl-d-aspartate subunits (NR) demonstrated that cyanide selectively potentiated NR1/NR2A receptors, presumably via the chemical reduction of NR2A. In contrast, currents mediated by NR1/NR2B receptors were somewhat diminished by the metabolic inhibitor. Some of the effects of cyanide on NR1/NR2B receptors may be mediated by the formation of a thiocyanate adduct with a cysteine residue located in NR1. Cyanide thus is able to distinguish chemically between two different N-methyl-d-aspartate receptor subtypes and produce diametrically opposing functional effects.
Footnotes
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↵* This work was supported in part by National Institutes of Health Grant NS29365 (to E. A.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ Supported by National Institutes of Health Training Grant NS07391.
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↵§ To whom correspondence should be addressed: Dept. of Neurobiology, University of Pittsburgh School of Medicine, E1456-BST, 3500 Terrace St., Pittsburgh, PA 15261. Tel.: 412-648-9434; Fax: 412-648--1441; E-mail: redox+{at}pitt.edu.
- Abbreviations:
- NMDA
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N-methyl-d-aspartate
- NR
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NMDA receptor subunit
- KCN
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potassium cyanide
- CHO
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Chinese hamster ovary
- DTT
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dithiothreitol
- DTNB
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5,5′-dithiobis(2-nitrobenzoic acid)
- TPEN
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N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine
- DIV
-
days in vitro
- PCR
-
polymerase chain reaction.
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- Received December 23, 1997.
- Revision received June 10, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
