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Subunit-specific redox modulation of NMDA receptors expressed in Xenopus oocytes
A Omerovic1, S J Chen, J P Leonard
1Department of Biological Sciences, University of Illinois at Chicago 60607, USA.
Abstract:
We have examined the effects of oxidizing and reducing agents on a number of subtypes of N-methyl-D-aspartate (NMDA) receptors expressed in Xenopus oocytes. Oocytes were injected with cRNA for the zeta 1 subunit from mouse to express homomeric receptors or with zeta 1 in combination with either epsilon 1, epsilon 2, epsilon 3 or epsilon 4 subunits to express heteromeric receptors. All heteromeric combinations resulted in receptors that were affected by the redox reagents, dithiothreitol (DTT) and 5-5-dithio-bis-2-nitrobenzoic acid (DTNB). However, the effects on the small currents from homomeric receptors were quite variable. The zeta 1/epsilon 3 combination showed a greater enhancement by DTT than any of the other combinations. All four receptors expressed showed both a component of persistent potentiation and a slowly reversible component. The reversible component was largest for zeta 1/epsilon 3. Additional experiments were done with S-nitrosocysteine (SNOC), a nitric oxide donor that may affect NMDA receptors by oxidation. SNOC had transient effects on the four heteromeric subunit combinations. The different sensitivities of particular subunit combinations may have pharmacological and clinical significance.
Insights
Oxidizing and reducing agents impact N-methyl-D-aspartate (NMDA) receptor subtypes differently. Specific subunit combinations, like zeta 1/epsilon 3, show unique sensitivities, suggesting potential clinical applications for NMDA receptor modulation.
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- N-methyl-D-aspartate (NMDA) receptors are crucial ion channels involved in synaptic plasticity and neurological disorders.
- The functional properties of NMDA receptors are modulated by various cellular mechanisms, including redox signaling.
- Understanding NMDA receptor subunit composition is key to deciphering their physiological and pathological roles.
Purpose of the Study:
- To investigate the impact of oxidizing and reducing agents on different NMDA receptor subunit combinations.
- To characterize the redox sensitivity of homomeric and heteromeric NMDA receptors expressed in Xenopus oocytes.
- To explore the potential pharmacological significance of differential subunit sensitivity to redox agents.
Main Methods:
- Expression of various NMDA receptor subunit combinations (homomeric zeta 1 and heteromeric zeta 1 with epsilon 1, 2, 3, or 4) in Xenopus oocytes.
- Electrophysiological recordings to assess receptor function and response to redox reagents.
- Application of dithiothreitol (DTT), 5,5-dithio-bis-2-nitrobenzoic acid (DTNB), and S-nitrosocysteine (SNOC) to evaluate redox modulation.
Main Results:
- All tested heteromeric NMDA receptor combinations were sensitive to the redox reagents DTT and DTNB.
- The zeta 1/epsilon 3 subunit combination exhibited the greatest enhancement by DTT and the largest slowly reversible component.
- S-nitrosocysteine (SNOC) produced transient effects on the four heteromeric subunit combinations, indicating diverse responses to nitric oxide donors.
Conclusions:
- NMDA receptor subunit composition dictates sensitivity to redox modulation.
- Specific subunit interactions influence potentiation and reversibility, with zeta 1/epsilon 3 showing distinct characteristics.
- Differential redox sensitivity of NMDA receptor subtypes holds potential for targeted pharmacological interventions.