Evaluation and Comparison of Ion Permeation and Agonist Selectivities for N-Methyl- -Aspartate Receptor Channels with Different Subunit Compositions in Bilayer Lipid Membranes Based on Integrated Single-Channel Currents
| Autor: | Masaki Wakabayashi, Shigeo Uchino, Ayumi Hirano, Masao Sugawara, Sadayo Nakajima-Iijima |
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| Rok vydání: | 2000 |
| Předmět: |
Agonist
N-Methylaspartate medicine.drug_class Lipid Bilayers Biophysics Analytical chemistry Glutamic Acid CHO Cells Receptors N-Methyl-D-Aspartate Biochemistry Permeability Cricetinae Excitatory Amino Acid Agonists medicine Animals Lipid bilayer Receptor Molecular Biology Dose-Response Relationship Drug Chemistry Chinese hamster ovary cell Cell Biology Electrophysiology Evaluation Studies as Topic Glycine NMDA receptor lipids (amino acids peptides and proteins) Selectivity Signal Transduction |
| Zdroj: | Analytical Biochemistry. 283:258-265 |
| ISSN: | 0003-2697 |
| DOI: | 10.1006/abio.2000.4650 |
| Popis: | To quantify the ion-permeation ability of the recombinant epsilon1-4/zeta1 channel activated by agonists, the magnitude of agonist-induced integrated single-channel currents for the epsilon2-4/zeta1 N-methyl-d-aspartate (NMDA) channels in bilayer lipid membranes (BLMs) was evaluated electrochemically based on the single-channel recordings. The recombinant epsilon2-4/zeta1 channels were purified from Chinese hamster ovary cells expressing each channel and incorporated in BLMs formed by the tip-dip method. Three typical agonists, l-glutamate, NMDA, and (2S, 3R, 4S) isomer of 2-(carboxycyclopropyl)glycine (l-CCG-IV), were investigated at a concentration of 50 microM. The magnitude of l-glutamate-induced integrated current was found to depend on the epsilon-subunit composition and to increase in the order of epsilon2/zeta1 > epsilon1/zeta1 approximately epsilon4/zeta1 > epsilon3/zeta1, which differs from that of the reported binding affinities (EC(50)) between l-glutamate and each channel type. On the other hand, the magnitude of the integrated currents induced by NMDA and l-CCG-IV did not vary among the four channel types. The order of agonist selectivity toward the epsilon2-4/zeta1 channels in terms of the magnitude of the integrated current was l-glutamate > l-CCG-IV approximately NMDA for the epsilon2/zeta1 channel, l-CCG-IV > NMDA > l-glutamate for the epsilon3/zeta1 channel, and l-CCG-IV approximately l-glutamate > NMDA for the epsilon4/zeta1 channel, suggesting that the agonist selectivity also depends on the epsilon-subunit composition. The present study shows that each epsilon1-4/zeta1 channel has its own ability of ion permeation, i.e., its own signal transduction ability, which is not parallel to its binding ability. |
| Databáze: | OpenAIRE |
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