アルファー7型ニコチン性ACh受容体(α7 nAChR) の内在性修飾因子を同定する目的で, Ly6Hに着目した。α7 nAChRのリガンド結合領域とグリシン受容体のイオンチャネル領域のキメラ受容体を構築し, Ly6Hの作用をパッチクランプ法により解析したところ, AChによる流入電流が抑制された。さらに, α7n AChRとNACHOおよびRic-3の3種のcDNAを共発現させ, 機能的α7 nAChRを形質膜上に安定発現する細胞株を作製した。この細胞でも, Ly6Hはリガンド誘発電流を抑制した。以上より, Ly6Hは, 形質膜上においてα7 nAChに作用し, 流入電流を抑制することが示された。
Alpha7-type nicotinic acetylcholine receptor (α7 nAChR) is a therapeutic target for various neurodegenerative and inflammatory conditions. To find a novel α7 nAChR modulator, we picked up Ly6H which is an endogenous protein with structural resemblance to a snake venom α-bungarotoxin. Chimeric receptor channel consisting of the ligand-binding domain of α7 nAChR and the channel domain of the glycine receptor was constructed. Electrophysiological analyses revealed that Ly6H reduced the magnitude of ACh-evoked currents. Next, we established stable cells expressing α7 nAChR, Ric-3 and NACHO, and ACh-induced currents were analyzed. The TARO cells (Triple Alpha7 Ric-3 NACHO cells) showed robust ligand-induced currents. Again, electrophysiological analyses revealed that expression of Ly6H in the TARO cells reduced the magnitude of α7-mediated currents. These results indicate that Ly6H directly binds to the extracellular domain of α7 nAChR and negatively modulates its channel activity.
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