Reduced axonal surface expression and phosphoinositide sensitivity in K(v)7 channels disrupts their function to inhibit neuronal excitability in Kcnq2 epileptic encephalopathy.
Reduced axonal surface expression and phosphoinositide sensitivity in K(v)7 channels disrupts their function to inhibit neuronal excitability in Kcnq2 epileptic encephalopathy.
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DOI：
10.1016/j.nbd.2018.07.004
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发表时间：
2018-10
影响因子：
6.1
通讯作者：
Chung HJ
中科院分区：
文献类型：
--
作者：
Kim EC;Zhang J;Pang W;Wang S;Lee KY;Cavaretta JP;Walters J;Procko E;Tsai NP;Chung HJ
神经元Kv7/KCNQ通道是由Kv7.2/KCNQ2和Kv7.3/KCNQ3亚基组成的电压门控钾通道。它们在轴突膜富集，能有效抑制神经元的兴奋性。Kv7.2的新生和遗传显性突变导致以耐药癫痫发作和深度精神运动延迟为特征的早发性癫痫性脑病。然而，它们的确切致病机制仍然难以捉摸。在这里，我们研究了导致Kv7.2钙调素（CaM）结合螺旋A和B突变的癫痫性脑病。我们发现，位于CaM接触位点外周的R333W、K526N和R532W突变降低了异质通道轴突表面的表达，尽管只有R333W突变降低了CaM与Kv7.2的结合。这些突变还改变了磷脂酰肌醇4,5-二磷酸（PIP2）的门控调节，揭示了新的PIP2结合残基。虽然这些突变破坏了Kv7的功能以抑制兴奋性，但在表达Kv7.2-R532W的神经元中观察到高兴奋性，表现出严重的电压依赖性激活损伤。螺旋B中CaM接触位点的M518V突变严重降低了Kv7通道的CaM结合、K+电流和轴突表面表达，从而导致Kv7通道的大部分缺陷。有趣的是，M518V突变诱导泛素化和加速蛋白酶体依赖的Kv7.2降解，而Kv7.3的存在阻止了这种降解。Kv7.2-M518V的表达增加了神经元的死亡。总之，我们的研究结果表明，Kv7.2螺旋A和B的癫痫性脑病突变通过破坏Kv7.2与CaM的结合和/或PIP2的调节，导致Kv7的异常表达和功能。我们认为这种多重Kv7通道缺陷可能对神经元的兴奋性和健康产生更严重的影响，从而可能是Kcnq2癫痫性脑病的致病机制。
Neuronal Kv7/KCNQ channels are voltage-gated potassium channels composed of Kv7.2/KCNQ2 and Kv7.3/KCNQ3 subunits. Enriched at the axonal membrane, they potently suppress neuronal excitability. De novo and inherited dominant mutations in Kv7.2 cause early onset epileptic encephalopathy characterized by drug resistant seizures and profound psychomotor delay. However, their precise pathogenic mechanisms remain elusive. Here, we investigated selected epileptic encephalopathy causing mutations in calmodulin (CaM)-binding helices A and B of Kv7.2. We discovered that R333W, K526N, and R532W mutations located peripheral to CaM contact sites decreased axonal surface expression of heteromeric channels although only R333W mutation reduced CaM binding to Kv7.2. These mutations also altered gating modulation by phosphatidylinositol 4,5-bisphosphate (PIP2), revealing novel PIP2 binding residues. While these mutations disrupted Kv7 function to suppress excitability, hyperexcitability was observed in neurons expressing Kv7.2-R532W that displayed severe impairment in voltage-dependent activation. The M518V mutation at the CaM contact site in helix B caused most defects in Kv7 channels by severely reducing their CaM binding, K+ currents, and axonal surface expression. Interestingly, the M518V mutation induced ubiquitination and accelerated proteasome-dependent degradation of Kv7.2, whereas the presence of Kv7.3 blocked this degradation. Furthermore, expression of Kv7.2-M518V increased neuronal death. Together, our results demonstrate that epileptic encephalopathy mutations in helices A and B of Kv7.2 cause abnormal Kv7 expression and function by disrupting Kv7.2 binding to CaM and/or modulation by PIP2. We propose that such multiple Kv7 channel defects could exert more severe impacts on neuronal excitability and health, and thus serve as pathogenic mechanisms underlying Kcnq2 epileptic encephalopathy.
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影响因子：
3.7
作者：
Cavaretta JP;Sherer KR;Lee KY;Kim EH;Issema RS;Chung HJ
通讯作者：
Chung HJ
DOI：
10.1073/pnas.211431298
发表时间：
2001-10-09
影响因子：
11.1
作者：
Dedek, K;Kunath, B;Steinlein, OK
通讯作者：
Steinlein, OK
影响因子：
30.8
作者：
Charlier, C;Singh, NA;Leppert, M
通讯作者：
Leppert, M
影响因子：
3.7
作者：
Coan AC;Campos BM;Yasuda CL;Kubota BY;Bergo FP;Guerreiro CA;Cendes F
通讯作者：
Cendes F
影响因子：
56.9
作者：
Biervert, C;Schroeder, BC;Steinlein, OK
通讯作者：
Steinlein, OK