Polarized axonal surface expression of neuronal KCNQ potassium channels is regulated by calmodulin interaction with KCNQ2 subunit.
Polarized axonal surface expression of neuronal KCNQ potassium channels is regulated by calmodulin interaction with KCNQ2 subunit.
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DOI：
10.1371/journal.pone.0103655
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Chung HJ
中科院分区：
文献类型：
--
作者：
Cavaretta JP;Sherer KR;Lee KY;Kim EH;Issema RS;Chung HJ
由KCNQ 2和KCNQ 3亚基组成的KCNQ钾通道产生M电流，这是一种缓慢激活和非失活的电压依赖性钾电流，限制了动作电位的重复放电。KCNQ通道在轴突和轴突起始段的表面富集，是动作电位产生和调节的位点。它们在轴突表面的富集受到KCNQ 2羧基末端尾部突变的损害，导致良性家族性新生儿惊厥和肌震颤，这表明它们在轴突的正确表面分布和密度对于控制神经元兴奋性至关重要。然而，负责调节富集的KCNQ通道在神经元轴突的分子机制仍然难以捉摸。在这里，我们表明，富集的KCNQ通道在轴突表面的解离大鼠海马培养神经元的普遍存在的钙传感器钙调素调节。使用免疫细胞化学和分化簇4（CD 4）膜蛋白作为贩运报告，我们表明，融合KCNQ 2羧基末端尾巴是足够的靶向CD 4蛋白的轴突表面，而抑制钙调蛋白结合KCNQ 2废除轴突表面表达的CD 4融合蛋白保留在内质网。干扰钙调素与KCNQ 2的结合也会通过阻断异聚体KCNQ 2/KCNQ 3通道从内质网向轴突的运输而损害其在轴突表面的富集。一致的是，海马神经元的兴奋性是由野生型KCNQ 2的瞬时表达抑制，但不是突变KCNQ 2缺乏钙调素结合。此外，共表达的突变钙调素，它可以与KCNQ 2/KCNQ 3通道，但不是钙相互作用，减少，但不取消他们的富集在轴突表面，这表明载脂蛋白钙调素，但不是钙结合的钙调素是必要的，他们优先靶向轴突表面。这些发现共同揭示钙调蛋白作为一个重要的球员，调节贩运和丰富的KCNQ通道在神经元轴突。
KCNQ potassium channels composed of KCNQ2 and KCNQ3 subunits give rise to the M-current, a slow-activating and non-inactivating voltage-dependent potassium current that limits repetitive firing of action potentials. KCNQ channels are enriched at the surface of axons and axonal initial segments, the sites for action potential generation and modulation. Their enrichment at the axonal surface is impaired by mutations in KCNQ2 carboxy-terminal tail that cause benign familial neonatal convulsion and myokymia, suggesting that their correct surface distribution and density at the axon is crucial for control of neuronal excitability. However, the molecular mechanisms responsible for regulating enrichment of KCNQ channels at the neuronal axon remain elusive. Here, we show that enrichment of KCNQ channels at the axonal surface of dissociated rat hippocampal cultured neurons is regulated by ubiquitous calcium sensor calmodulin. Using immunocytochemistry and the cluster of differentiation 4 (CD4) membrane protein as a trafficking reporter, we demonstrate that fusion of KCNQ2 carboxy-terminal tail is sufficient to target CD4 protein to the axonal surface whereas inhibition of calmodulin binding to KCNQ2 abolishes axonal surface expression of CD4 fusion proteins by retaining them in the endoplasmic reticulum. Disruption of calmodulin binding to KCNQ2 also impairs enrichment of heteromeric KCNQ2/KCNQ3 channels at the axonal surface by blocking their trafficking from the endoplasmic reticulum to the axon. Consistently, hippocampal neuronal excitability is dampened by transient expression of wild-type KCNQ2 but not mutant KCNQ2 deficient in calmodulin binding. Furthermore, coexpression of mutant calmodulin, which can interact with KCNQ2/KCNQ3 channels but not calcium, reduces but does not abolish their enrichment at the axonal surface, suggesting that apo calmodulin but not calcium-bound calmodulin is necessary for their preferential targeting to the axonal surface. These findings collectively reveal calmodulin as a critical player that modulates trafficking and enrichment of KCNQ channels at the neuronal axon.
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DOI：
10.1523/jneurosci.5175-09.2010
发表时间：
2010-02-10
期刊：
The Journal of neuroscience : the official journal of the Society for Neuroscience
影响因子：
--
作者：
Bal M;Zhang J;Hernandez CC;Zaika O;Shapiro MS
通讯作者：
Shapiro MS
影响因子：
64.8
作者：
通讯作者：
--
影响因子：
4.8
作者：
Alaimo, Alessandro;Gomez-Posada, Juan Camilo;Villarroel, Alvaro
通讯作者：
Villarroel, Alvaro
影响因子：
9.9
作者：
Borgatti, R;Zucca, C;Bassi, MT
通讯作者：
Bassi, MT
DOI：
10.1073/pnas.090092797
发表时间：
2000-04-25
影响因子：
11.1
作者：
Cooper, EC;Aldape, KD;Jan, LY
通讯作者：
Jan, LY