The long activations of α2 glycine channels can be described by a mechanism with reaction intermediates ("flip").
The long activations of α2 glycine channels can be described by a mechanism with reaction intermediates ("flip").
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DOI：
10.1085/jgp.201010521
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发表时间：
2011-02
期刊：
影响因子：
--
通讯作者：
Sivilotti LG
中科院分区：
文献类型：
--
作者：
Krashia P;Lape R;Lodesani F;Colquhoun D;Sivilotti LG
α-2甘氨酸受体(GlyR)亚单位在胚胎神经元中含量丰富，在成人神经系统中被α-1取代。同聚体α2通道的单通道活性不同于含有α1的GlyRs通道，因为即使在最低的甘氨酸浓度(20µM)下，开放概率高的长(>；300-ms)组中也会出现开放(POpen；0.96；细胞附着记录，HEK表达的通道)。开口组内的关闭时间间隔主要是5-10微米S的短关闭。开口组中缺乏浓度依赖性，这表明它们代表单一的激活，在低浓度下被非常长的关闭时间分开。几个假定的机制是通过最大化整个打开和关闭时间序列的可能性，以及准确的错过事件允许(程序hjcfit)来适应的。在几种甘氨酸浓度下获得的记录被同时拟合。不同方案的充分性是通过它们不仅预测单通道数据的准确性，而且还预测由甘氨酸快速施加到外部斑块引起的宏观反应的时间过程和浓度依赖来判断的。只有在活化过程中加入反应中间体的方案才能充分描述数据，最好的方案是具有两个结合位置和一个开放状态的翻转机制。与这一机制的拟合表明，对于α2通道，开放速率常数非常快，∼130,000 S−1，与成熟突触中的受体α1βGlyRs相似，但估计的真实平均开放时间长20倍(约3ms)。α2的翻转步骤效率和结合亲和力低于α1β通道，但总体效果相似。正如我们先前对α1同源受体所显示的那样，在α2甘氨酸通道中，当五聚体中的五个假定结合位点被甘氨酸占据时，最大的开放是实现的。
The α2 glycine receptor (GlyR) subunit, abundant in embryonic neurons, is replaced by α1 in the adult nervous system. The single-channel activity of homomeric α2 channels differs from that of α1-containing GlyRs, as even at the lowest glycine concentration (20 µM), openings occurred in long (>300-ms) groups with high open probability (Popen; 0.96; cell-attached recordings, HEK-expressed channels). Shut-time intervals within groups of openings were dominated by short shuttings of 5–10 µs. The lack of concentration dependence in the groups of openings suggests that they represent single activations, separated by very long shut times at low concentrations. Several putative mechanisms were fitted by maximizing the likelihood of the entire sequence of open and shut times, with exact missed-events allowance (program hjcfit). Records obtained at several glycine concentrations were fitted simultaneously. The adequacy of the different schemes was judged by the accuracy with which they predicted not only single-channel data but also the time course and concentration dependence of macroscopic responses elicited by rapid glycine applications to outside-out patches. The data were adequately described only with schemes incorporating a reaction intermediate in the activation, and the best was a flip mechanism with two binding sites and one open state. Fits with this mechanism showed that for α2 channels, the opening rate constant is very fast, ∼130,000 s−1, much as for α1β GlyRs (the receptor in mature synapses), but the estimated true mean open time is 20 times longer (around 3 ms). The efficacy for the flipping step and the binding affinity were lower for α2 than for α1β channels, but the overall efficacies were similar. As we previously showed for α1 homomeric receptors, in α2 glycine channels, maximum Popen is achieved when fewer than all five of the putative binding sites in the pentamer are occupied by glycine.
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影响因子：
5.3
作者：
Beato, M;Groot-Kormelink, PJ;Sivilotti, LG
通讯作者：
Sivilotti, LG
影响因子：
5.5
作者：
Lape, Remigijus;Krashia, Paraskevi;Sivilotti, Lucia G.
通讯作者：
Sivilotti, Lucia G.
影响因子：
3.5
作者：
AKAGI, H;HIRAI, K;HISHINUMA, F
通讯作者：
HISHINUMA, F
影响因子：
5.5
作者：
COLQUHOUN, D;JONAS, P;SAKMANN, B
通讯作者：
SAKMANN, B
DOI：
10.1085/jgp.20028530
发表时间：
2002-05
期刊：
The Journal of general physiology
影响因子：
--
作者：
Beato M;Groot-Kormelink PJ;Colquhoun D;Sivilotti LG
通讯作者：
Sivilotti LG