A unique voltage sensor sensitizes the potassium channel AKT2 to phosphoregulation.
A unique voltage sensor sensitizes the potassium channel AKT2 to phosphoregulation.
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DOI：
10.1085/jgp.200509413
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发表时间：
2005-12
期刊：
影响因子：
--
通讯作者：
Dreyer I
中科院分区：
文献类型：
--
作者：
Michard E;Lacombe B;Porée F;Mueller-Roeber B;Sentenac H;Thibaud JB;Dreyer I
在来自模式植物拟南芥的所有电压门控 K+ 通道中，弱整流 K+ 通道（Kweak 通道）AKT2 显示出独特的门控特性。 AKT2 特别受磷酸化调节：当非磷酸化 AKT2 充当内向整流钾通道时； AKT2 的磷酸化通过将其激活阈值移至远正值 (>200 mV) 来消除内向整流，使其仅在正电压 +100 mV 时关闭。因此，以其磷酸化形式，AKT2 在整个生理电压范围内被锁定在开放状态。为了了解这种独特门控行为的分子基础，我们在 AKT2 和传统的内向整流通道 KAT1 之间生成了嵌合体。孔从 KAT1 到 AKT2 的转移改变了通道的渗透特性。然而，门控特性未受影响，这表明 AKT2 的孔区域并不是造成独特的 Kweak 门控的原因。相反，S4 中的一个赖氨酸残基在所有 Kweak 通道中高度保守，但在其他植物 K+ 通道中不存在，通过定点诱变方法被精确定位。用丝氨酸或天冬氨酸取代赖氨酸消除了“开锁”特性，并将 AKT2 转变为内向整流通道。有趣的是，突变体 AKT2-K197S 的磷酸调节似乎与 Kin 通道 KAT1 的磷酸调节相似：正如通过模拟磷酸化和去磷酸化状态所表明的，磷酸化诱导 AKT2-K197S 的激活阈值移动约 +50 mV。我们得出结论，赖氨酸残基 K197 使 AKT2 对磷酸调节敏感。 AKT2 中磷酸化诱导的活化能降低比 K197S 突变体大约 6 kT。据讨论，AKT2 对磷酸化的这种超敏反应使细胞具有建立钾梯度并有效利用它的多功能性。
Among all voltage-gated K+ channels from the model plant Arabidopsis thaliana, the weakly rectifying K+ channel (Kweak channel) AKT2 displays unique gating properties. AKT2 is exceptionally regulated by phosphorylation: when nonphosphorylated AKT2 behaves as an inward-rectifying potassium channel; phosphorylation of AKT2 abolishes inward rectification by shifting its activation threshold far positive (>200 mV) so that it closes only at voltages positive of +100 mV. In its phosphorylated form, AKT2 is thus locked in the open state in the entire physiological voltage range. To understand the molecular grounds of this unique gating behavior, we generated chimeras between AKT2 and the conventional inward-rectifying channel KAT1. The transfer of the pore from KAT1 to AKT2 altered the permeation properties of the channel. However, the gating properties were unaffected, suggesting that the pore region of AKT2 is not responsible for the unique Kweak gating. Instead, a lysine residue in S4, highly conserved among all Kweak channels but absent from other plant K+ channels, was pinpointed in a site-directed mutagenesis approach. Substitution of the lysine by serine or aspartate abolished the “open-lock” characteristic and converted AKT2 into an inward-rectifying channel. Interestingly, phosphoregulation of the mutant AKT2-K197S appeared to be similar to that of the Kin channel KAT1: as suggested by mimicking the phosphorylated and dephosphorylated states, phosphorylation induced a shift of the activation threshold of AKT2-K197S by about +50 mV. We conclude that the lysine residue K197 sensitizes AKT2 to phosphoregulation. The phosphorylation-induced reduction of the activation energy in AKT2 is ∼6 kT larger than in the K197S mutant. It is discussed that this hypersensitive response of AKT2 to phosphorylation equips a cell with the versatility to establish a potassium gradient and to make efficient use of it.
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影响因子：
4.8
作者：
CAO, YW;CRAWFORD, NM;SCHROEDER, JI
通讯作者：
SCHROEDER, JI
影响因子：
11.6
作者：
Chérel, I;Michard, E;Thibaud, JB
通讯作者：
Thibaud, JB
影响因子：
11.6
作者：
Lacombe, B;Pilot, G;Thibaud, JB
通讯作者：
Thibaud, JB
DOI：
10.1073/pnas.93.15.8123
发表时间：
1996-07-23
影响因子：
11.1
作者：
Becker, D;Dreyer, I;Hedrich, R
通讯作者：
Hedrich, R
影响因子：
4.3
作者：
Deeken, R;Geiger, D;Hedrich, R
通讯作者：
Hedrich, R