Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc
Many excitatory synapses contain high levels of mobile zinc within glutamatergic vesicles. Although synaptic zinc and glutamate are coreleased, it is controversial whether zinc diffuses away from the release site or whether it remains bound to presynaptic membranes or proteins after its release. To...
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| Idioma: | en_US |
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National Academy of Sciences (U.S.)
2016
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| Acesso em linha: | http://hdl.handle.net/1721.1/100585 https://orcid.org/0000-0002-2693-4982 https://orcid.org/0000-0002-1577-2420 https://orcid.org/0000-0002-5910-6948 |
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| author | Anderson, Charles T. Radford, Robert J. Zhang, Daniel Y. Apfel, Ulf-Peter Lippard, Stephen J. Tzounopoulos, Thanos Zastrow, Melissa |
| author2 | Massachusetts Institute of Technology. Department of Chemistry |
| author_facet | Massachusetts Institute of Technology. Department of Chemistry Anderson, Charles T. Radford, Robert J. Zhang, Daniel Y. Apfel, Ulf-Peter Lippard, Stephen J. Tzounopoulos, Thanos Zastrow, Melissa |
| author_sort | Anderson, Charles T. |
| collection | MIT |
| description | Many excitatory synapses contain high levels of mobile zinc within glutamatergic vesicles. Although synaptic zinc and glutamate are coreleased, it is controversial whether zinc diffuses away from the release site or whether it remains bound to presynaptic membranes or proteins after its release. To study zinc transmission and quantify zinc levels, we required a high-affinity rapid zinc chelator as well as an extracellular ratiometric fluorescent zinc sensor. We demonstrate that tricine, considered a preferred chelator for studying the role of synaptic zinc, is unable to efficiently prevent zinc from binding low-nanomolar zinc-binding sites, such as the high-affinity zinc-binding site found in NMDA receptors (NMDARs). Here, we used ZX1, which has a 1 nM zinc dissociation constant and second-order rate constant for binding zinc that is 200-fold higher than those for tricine and CaEDTA. We find that synaptic zinc is phasically released during action potentials. In response to short trains of presynaptic stimulation, synaptic zinc diffuses beyond the synaptic cleft where it inhibits extrasynaptic NMDARs. During higher rates of presynaptic stimulation, released glutamate activates additional extrasynaptic NMDARs that are not reached by synaptically released zinc, but which are inhibited by ambient, tonic levels of nonsynaptic zinc. By performing a ratiometric evaluation of extracellular zinc levels in the dorsal cochlear nucleus, we determined the tonic zinc levels to be low nanomolar. These results demonstrate a physiological role for endogenous synaptic as well as tonic zinc in inhibiting extrasynaptic NMDARs and thereby fine tuning neuronal excitability and signaling. |
| first_indexed | 2024-09-23T10:43:39Z |
| format | Article |
| id | mit-1721.1/100585 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T10:43:39Z |
| publishDate | 2016 |
| publisher | National Academy of Sciences (U.S.) |
| record_format | dspace |
| spelling | mit-1721.1/1005852022-09-30T22:36:17Z Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc Anderson, Charles T. Radford, Robert J. Zhang, Daniel Y. Apfel, Ulf-Peter Lippard, Stephen J. Tzounopoulos, Thanos Zastrow, Melissa Massachusetts Institute of Technology. Department of Chemistry Radford, Robert J. Zastrow, Melissa Zhang, Daniel Y. Apfel, Ulf-Peter Lippard, Stephen J. Many excitatory synapses contain high levels of mobile zinc within glutamatergic vesicles. Although synaptic zinc and glutamate are coreleased, it is controversial whether zinc diffuses away from the release site or whether it remains bound to presynaptic membranes or proteins after its release. To study zinc transmission and quantify zinc levels, we required a high-affinity rapid zinc chelator as well as an extracellular ratiometric fluorescent zinc sensor. We demonstrate that tricine, considered a preferred chelator for studying the role of synaptic zinc, is unable to efficiently prevent zinc from binding low-nanomolar zinc-binding sites, such as the high-affinity zinc-binding site found in NMDA receptors (NMDARs). Here, we used ZX1, which has a 1 nM zinc dissociation constant and second-order rate constant for binding zinc that is 200-fold higher than those for tricine and CaEDTA. We find that synaptic zinc is phasically released during action potentials. In response to short trains of presynaptic stimulation, synaptic zinc diffuses beyond the synaptic cleft where it inhibits extrasynaptic NMDARs. During higher rates of presynaptic stimulation, released glutamate activates additional extrasynaptic NMDARs that are not reached by synaptically released zinc, but which are inhibited by ambient, tonic levels of nonsynaptic zinc. By performing a ratiometric evaluation of extracellular zinc levels in the dorsal cochlear nucleus, we determined the tonic zinc levels to be low nanomolar. These results demonstrate a physiological role for endogenous synaptic as well as tonic zinc in inhibiting extrasynaptic NMDARs and thereby fine tuning neuronal excitability and signaling. National Institutes of Health (U.S.) (Grant R01-GM065519) 2016-01-04T18:10:03Z 2016-01-04T18:10:03Z 2015-05 2015-02 Article http://purl.org/eprint/type/JournalArticle 0027-8424 1091-6490 http://hdl.handle.net/1721.1/100585 Anderson, Charles T., Robert J. Radford, Melissa L. Zastrow, Daniel Y. Zhang, Ulf-Peter Apfel, Stephen J. Lippard, and Thanos Tzounopoulos. “Modulation of Extrasynaptic NMDA Receptors by Synaptic and Tonic Zinc.” Proc Natl Acad Sci USA 112, no. 20 (May 6, 2015): E2705–E2714. https://orcid.org/0000-0002-2693-4982 https://orcid.org/0000-0002-1577-2420 https://orcid.org/0000-0002-5910-6948 en_US http://dx.doi.org/10.1073/pnas.1503348112 Proceedings of the National Academy of Sciences Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf National Academy of Sciences (U.S.) American Meteorological Society |
| spellingShingle | Anderson, Charles T. Radford, Robert J. Zhang, Daniel Y. Apfel, Ulf-Peter Lippard, Stephen J. Tzounopoulos, Thanos Zastrow, Melissa Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc |
| title | Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc |
| title_full | Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc |
| title_fullStr | Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc |
| title_full_unstemmed | Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc |
| title_short | Modulation of extrasynaptic NMDA receptors by synaptic and tonic zinc |
| title_sort | modulation of extrasynaptic nmda receptors by synaptic and tonic zinc |
| url | http://hdl.handle.net/1721.1/100585 https://orcid.org/0000-0002-2693-4982 https://orcid.org/0000-0002-1577-2420 https://orcid.org/0000-0002-5910-6948 |
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