Calmodulin Activation Limits the Rate of KCNQ2 K+ Channel Exit from the Endoplasmic Reticulum
Calmodulin Activation Limits the Rate of KCNQ2 K+ Channel Exit from the Endoplasmic Reticulum
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DOI：
10.1074/jbc.m109.019539
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发表时间：
2009-07-31
影响因子：
4.8
通讯作者：
Villarroel, Alvaro
中科院分区：
文献类型：
--
作者：
Alaimo, Alessandro;Gomez-Posada, Juan Camilo;Villarroel, Alvaro
钙调素（CaM）对蛋白质运输的潜在调节是一个尚待证实的新概念。我们认为KCNQ 2 K+通道的运输受CaM与C-末端A和B螺旋的结合调节。在这里，我们表明，L339 R突变的螺旋A，这是与人类良性新生儿惊厥，干扰钙调素结合KCNQ 2通道，并阻止其正确的运输到质膜。我们使用谷胱甘肽S-转移酶融合到螺旋A和B，以检查螺旋A（I340 A，I340 E，A343 D和R353 G）的这种和其他突变与钙调素的相互作用的影响。该过程似乎需要至少两个步骤;第一个涉及CaM与KCNQ 2的瞬时结合，第二个，复合物采用更稳定的“活性”构象，并且具有退出内质网的能力。值得注意的是，我们分析的突变主要影响复合物活性构型的稳定性，而单独的Ca 2+似乎影响初始结合步骤。来自该突变体集合的反应谱揭示了在哺乳动物细胞中采用活性构象和通道运输之间的强相关性。这些数据是完全一致的概念，结合到KCNQ 2的钙调素作为一个Ca 2+传感器，赋予Ca 2+依赖于运输的通道质膜和充分解释的要求，钙调素结合KCNQ 2功能。
The potential regulation of protein trafficking by calmodulin (CaM) is a novel concept that remains to be substantiated. We proposed that KCNQ2 K+ channel trafficking is regulated by CaM binding to the C-terminal A and B helices. Here we show that the L339R mutation in helix A, which is linked to human benign neonatal convulsions, perturbs CaM binding to KCNQ2 channels and prevents their correct trafficking to the plasma membrane. We used glutathione S-transferase fused to helices A and B to examine the impact of this and other mutations in helix A (I340A, I340E, A343D, and R353G) on the interaction with CaM. The process appears to require at least two steps; the first involves the transient association of CaM with KCNQ2, and in the second, the complex adopts an "active" conformation that is more stable and is that which confers the capacity to exit the endoplasmic reticulum. Significantly, the mutations that we have analyzed mainly affect the stability of the active configuration of the complex, whereas Ca2+ alone appears to affect the initial binding step. The spectrum of responses from this collection of mutants revealed a strong correlation between adopting the active conformation and channel trafficking in mammalian cells. These data are entirely consistent with the concept that CaM bound to KCNQ2 acts as a Ca2+ sensor, conferring Ca2+ dependence to the trafficking of the channel to the plasma membrane and fully explaining the requirement of CaM binding for KCNQ2 function.