KA-AMPA-ゲートグルタミン酸受容体チャネルのCa2+透過性は,サブユニット組成に依存する
M Hollmann1, M Hartley, S Heinemann
1Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037.
まとめ
非NMDA受容体は,典型的には単価イオンを通過し,特定のサブユニット (GluR1,GluR3) が存在すると,カルシウムを伝導することができます. この発見は,グルタミン酸が,これらの非NMDA受容体を通して,カルシウムに依存するイベントを活性化することを示唆しています.
科学分野:
- 神経科学は神経科学である.
- 分子生物学は分子生物学である.
- バイオケミストリー バイオケミストリー
背景:
- イオンチャネル結合グルタミン酸受容体は,神経細胞の信号伝達に不可欠です.
- NMDA受容体と非NMDA受容体は2つの主要なクラスです.
- 伝統的に,非NMDA受容体は単価イオンのみを伝導すると考えられていた.
研究 の 目的:
- 非NMDA受容体チャネルの二価イオンへの浸透性を調査する.
- 特定のグルタミン酸受容体のサブユニットがイオン透過性に影響するかどうかを判断する.
- 非NMDA受容体がカルシウム流入を媒介する可能性を調査する.
主な方法:
- Xenopus卵細胞におけるグルタミン酸受容体サブユニット (GluR1,GluR2,GluR3) の発現.
- カイン酸 (KA) とアルファ-アミノ-3-ヒドロキシ-5-メチル-4-イソクサゾールプロピオニン酸 (AMPA) をゲート付きチャネルに適用する.
- 生理学的静止電位におけるイオン電流,特にカルシウム電流の測定.
主要な成果:
- GluR1,GluR3,またはGluR1+GluR3を発現する卵細胞は,KAとAMPAの刺激により,内側へのカルシウム電流を示した.
- GluR1+GluR2またはGluR3+GluR2を発現する卵細胞は,カルシウム浸透性を示しませんでした.
- GluR2サブユニットの存在は,カルシウムイオン伝導性を防ぐように見える.
結論:
- 非NMDA受容体サブユニットの特定の組み合わせ (特にGluR2が欠けているもの) は,カルシウムイオンを誘導することができる.
- 非NMDA受容体のグルタミン酸活性化により,これらの特定のサブユニットを発現するニューロンにカルシウムが流入する可能性があります.
- この非NMDA受容体を通るカルシウムの流入は,細胞内カルシウム依存的イベントを誘発する可能性があります.
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