Specific sites within the ligand-binding domain and ion channel linkers modulate NMDA receptor gating.
Specific sites within the ligand-binding domain and ion channel linkers modulate NMDA receptor gating.
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DOI：
10.1523/jneurosci.5382-09.2010
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发表时间：
2010-09-01
期刊：
影响因子：
--
通讯作者：
Wollmuth LP
中科院分区：
文献类型：
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作者：
Talukder I;Borker P;Wollmuth LP
NMDA受体中的门控起始于胞外配体结合结构域（LBD），并最终通过三个接头S1-M1、M3-S2和S2-M4传播至离子通道。M3-S2直接将LBD运动耦合到通道门控中，但是S1-M1和S2-M4对整个门控过程的功能和结构贡献是未知的。用大体积半胱氨酸反应性试剂扫描NMDA受体S1-M1和S2-M4中及其周围的取代半胱氨酸，鉴定出许多显示谷氨酸激活和漏电流增强的位置。如由MK 801（一种开放通道阻断剂）索引的，这种增强是由于开放概率的增加，这是对具有单通道记录的位置子集的解释。这种通过S1-M1或S2-M4起作用的门控效应的大小取决于NMDAR的内在门控特性，在固有低开放概率GluN 2C-中比在较高开放概率GluN 2A-亚基中更有效。对于大多数这些增强的位置，我们建议，门控的改变产生的接触界面的空间不稳定，其中紧密并列的接触合作伙伴是必要的有效的通道关闭。因此，我们的研究结果表明，NMDA受体S1-M1和S2-M4连接器是动态的门控过程中，可以调节这一过程的整体能量。此外，这些结果概念化了通过非竞争性和亚基特异性作用模式药理学靶向接头的机制以及可能的结构框架。
Gating in the NMDA receptor is initiated in the extracellular ligand-binding domain (LBD) and is ultimately propagated via three linkers—S1-M1, M3-S2 and S2-M4—to the ion channel. M3-S2 directly couples LBD movements into channel gating, but the functional and structural contributions of S1-M1 and S2-M4 to the overall gating process are unknown. A scan of substituted cysteines in and around the NMDA receptor S1-M1 and S2-M4 with a bulky cysteine-reactive reagent identified numerous positions that showed potentiation of glutamate-activated as well as leak currents. As indexed by MK801, an open channel blocker, this potentiation was due to an increase in open probability, an interpretation confirmed for a subset of positions with single channel recordings. The magnitude of this gating effect, acting through S1-M1 or S2-M4, was dependent on the intrinsic gating properties of the NMDARs, being more effective in the inherently low open probability GluN2C- than the higher open probability GluN2A- subunit containing receptors. For the majority of these potentiation positions, we propose that alteration of gating arises from steric destabilization of contact interfaces where close apposition of the contacting partners is necessary for efficient channel closure. Our results therefore indicate that the NMDA receptor S1-M1 and S2-M4 linkers are dynamic during gating and can modulate the overall energetics of this process. Furthermore, the results conceptualize a mechanistic, as well as a possible structural, framework for pharmacologically targeting the linkers through non-competitive and subunit-specific modes of action.