A lysine residue from an extracellular turret switches the ion preference in a Cav3 T-Type channel from calcium to sodium ions.
A lysine residue from an extracellular turret switches the ion preference in a Cav3 T-Type channel from calcium to sodium ions.
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DOI：
10.1016/j.jbc.2022.102621
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发表时间：
2022-12
影响因子：
4.8
通讯作者：
Spafford, J. David
中科院分区：
文献类型：
--
作者：
Guan, Wendy;Orellana, Kaidy G.;Stephens, Robert F.;Zhorov, Boris S.;Spafford, J. David
大池蜗牛Cav 3 T型钙通道具有5个酸性残基EE（D）DD的选择性过滤环。具有外显子12 b或12 a的剪接变体跨越孔模块的结构域II中的外螺旋IIS 5和膜下降孔螺旋IIP 1（IIS 5-P1）之间的细胞外环，分别具有钙选择性或主导钠渗透性。在这里，我们使用AlphaFold 2神经网络软件来预测外显子12 a中的赖氨酸残基是盐桥连到天冬氨酸残基的，该天冬氨酸残基紧邻选择性过滤器中第二结构域谷氨酸的C末端。外显子12 b具有类似的折叠，但用丙氨酸残基代替外显子12 a中的赖氨酸。我们表达具有突变的外显子Ala-12 b-Lys和Lys-12 a-Ala的LCav 3通道，并证明它们分别将离子偏好切换为高钠渗透性和钙选择性。我们提出，在钙选择性变体中，结构域II选择性过滤谷氨酸和天冬氨酸之间螯合的钙离子在钙渗透过程中被传入的钙离子敲除，而钠离子被排斥。天冬氨酸被钠渗透变体中的赖氨酸残基中和，允许钠渗透通过四个带负电荷的残基的选择性过滤环，类似于选择性过滤器中具有四个谷氨酸的原核钠通道。无脊椎动物LCav 3通道的进化适应突出了结构域II外孔中一个关键的、普遍存在的天冬氨酸（“钙信标”）的参与，作为通过真核生物Cav 1、Cav 2和Cav 3通道对钠离子的钙离子偏好的决定性因素。
Cav3 T-type calcium channels from great pond snail Lymnaea stagnalis have a selectivity-filter ring of five acidic residues, EE(D)DD. Splice variants with exons 12b or 12a spanning the extracellular loop between the outer helix IIS5 and membrane-descending pore helix IIP1 (IIS5-P1) in Domain II of the pore module possess calcium selectivity or dominant sodium permeability, respectively. Here, we use AlphaFold2 neural network software to predict that a lysine residue in exon 12a is salt-bridged to the aspartate residue immediately C terminal to the second-domain glutamate in the selectivity filter. Exon 12b has a similar folding but with an alanine residue in place of lysine in exon 12a. We express LCav3 channels with mutated exons Ala-12b-Lys and Lys-12a-Ala and demonstrate that they switch the ion preference to high sodium permeability and calcium selectivity, respectively. We propose that in the calcium-selective variants, a calcium ion chelated between Domain II selectivity-filter glutamate and aspartate is knocked-out by the incoming calcium ion in the process of calcium permeation, whereas sodium ions are repelled. The aspartate is neutralized by the lysine residue in the sodium-permeant variants, allowing for sodium permeation through the selectivity-filter ring of four negatively charged residues akin to the prokaryotic sodium channels with four glutamates in the selectivity filter. The evolutionary adaptation in invertebrate LCav3 channels highlight the involvement of a key, ubiquitous aspartate, “a calcium beacon” of sorts in the outer pore of Domain II, as determinative for the calcium ion preference over sodium ions through eukaryotic Cav1, Cav2, and Cav3 channels.
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DOI：
10.1007/s00249-009-0574-2
发表时间：
2010-04-01
影响因子：
2
作者：
Cheng, Ricky C. K.;Tikhonov, Denis B.;Zhorov, Boris S.
通讯作者：
Zhorov, Boris S.
影响因子：
1.2
作者：
Senatore, Adriano;Boone, Adrienne N.;Spafford, J. David
通讯作者：
Spafford, J. David
影响因子：
--
作者：
Vinogradova, Irina;Cook, Alan;Holden-Dye, Lindy
通讯作者：
Holden-Dye, Lindy
影响因子：
5.5
作者：
FATT, P;GINSBORG, BL
通讯作者：
GINSBORG, BL
DOI：
10.1073/pnas.1309452110
发表时间：
2013-07-09
影响因子：
11.1
作者：
Chakrabarti, Nilmadhab;Ing, Christopher;Pomes, Regis
通讯作者：
Pomes, Regis