Phosphorylation of the A-kinase-anchoring protein Yotiao contributes to protein kinase A regulation of a heart potassium channel
Phosphorylation of the A-kinase-anchoring protein Yotiao contributes to protein kinase A regulation of a heart potassium channel
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DOI：
10.1074/jbc.m505191200
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发表时间：
2005-09-09
影响因子：
4.8
通讯作者：
Kass, RS
中科院分区：
文献类型：
--
作者：
Chen, L;Kurokawa, J;Kass, RS
交感神经系统对心脏的调节是应激和运动生理反应的基础，需要多个下游分子靶点的协调磷酸化，包括I-Ks(缓慢激活钾电流)通道。交感神经系统刺激增加细胞内cAMP，对cAMP的靶向调控在很大程度上是由不同的支架或锚定蛋白指导的。肌条蛋白是一种A-激酶锚定蛋白(AKAP)，它将依赖于环磷酸腺苷的蛋白激酶(PKA)和蛋白磷酸酶1募集到I-Ks通道的羧基末端，形成分子复合体，控制其磷酸化状态，对交感神经系统刺激引起的心脏细胞反应至关重要。在这里，我们报告说，油条本身是PKA磷酸化的底物，我们发现了油条氨基末端(N-T)残基(Ser-43)，它是PKA磷酸化的，响应于β-肾上腺素能受体的刺激。Ala取代Ser-43可阻断N-T油条的PKA磷酸化，并显著降低野生型和假磷酸化的I-Ks通道对cAMP的功能反应，但不能阻止KCNQ1的PKA磷酸化及其与油条的结合。这些结果首次表明，PKA对AKAP的磷酸化在离子通道蛋白的功能调节中起关键作用，并且在肌条对I-Ks通道的磷酸化后变构调节中起着关键作用。
Regulation of the heart by the sympathetic nervous system, fundamental to the physiological response to stress and exercise, requires coordinated phosphorylation of multiple downstream molecular targets, including the I-Ks (slowly activating potassium current) channel. Sympathetic nervous system stimulation increases intracellular cAMP for which targeted regulation is directed in large part by distinct scaffold or anchoring proteins. Yotiao is an A-kinase-anchoring protein (AKAP) that recruits the cyclic AMP-dependent protein kinase (protein kinase A (PKA)) and protein phosphatase 1 to the carboxyl terminus of the I-Ks channel to form a molecular complex and control its phosphorylation state, crucial to the cardiac cellular response to sympathetic nervous system stimulation. Here we report that Yotiao itself is a substrate for PKA phosphorylation, and we identify a Yotiao amino-terminal (N-T) residue (Ser-43) that is PKA-phosphorylated in response to beta-adrenergic receptor stimulation. The replacement of Ser-43 by Ala ablates the PKA phosphorylation of N-T Yotiao and markedly diminishes the functional response of the wild type and pseudo-phosphorylated I-Ks channel to cAMP but neither prevents the PKA phosphorylation of KCNQ1 nor its binding to Yotiao. These results suggest, for the first time, a critical role for the PKA phosphorylation of an AKAP in the functional regulation of an ion channel protein and postphosphorylation allosteric modulation of the I-Ks channel by Yotiao.