Activation of protein kinase C augments T-type Ca2+ channel activity without changing channel surface density
Activation of protein kinase C augments T-type Ca2+ channel activity without changing channel surface density
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DOI：
10.1113/jphysiol.2006.117440
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发表时间：
2006-12-01
影响因子：
5.5
通讯作者：
Lee, Jung-Ha
中科院分区：
文献类型：
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作者：
Park, Jin-Yong;Kang, Ho-Won;Lee, Jung-Ha
T 型 Ca2+ 通道在许多细胞过程中发挥着重要作用。最近，我们报道了佛波醇12-肉豆蔻酸13-乙酸酯（PMA）有效增强了非洲爪蟾卵母细胞中重建的Ca(v)3.2 T型通道的电流振幅。在这里，我们比较了 PMA 对 Ca(v)3.1、Ca(v)3.2 和 Ca(v)3.3 通道活性的调节，并研究了其潜在机制。 PMA 增强了三种 T 型通道亚型的电流幅度，但倍数刺激和时间进程不同。 4α-PMA（PMA 的一种无活性立体异构体）并未模仿这种增强效应，但通过与蛋白激酶 C (PKC) 抑制剂预孵育而消除了这种增强效应，表明 PMA 通过激活卵母细胞 PKC 增强了 T 型通道电流。当内皮素受体 A 型与爪蟾卵母细胞系统中的 Ca(v)3.1 共表达时，内皮素可模拟 PKC 对 Ca(v)3.1 通道活性的刺激作用。药理学研究结合荧光成像表明，Ca(v)3.1 T 型通道的表面密度并未因 PKC 的激活而发生显着变化。使用嵌合通道将 PKC 对 Ca(v)3.1 的影响定位于细胞质 II-III 环，其中 Ca(v)3.1 的各个细胞质环被 Ca(v)2.1 的细胞质环取代。
T-type Ca2+ channels play essential roles in numerous cellular processes. Recently, we reported that phorbol-12-myristate-13-acetate (PMA) potently enhanced the current amplitude of Ca(v)3.2 T-type channels reconstituted in Xenopus oocytes. Here, we have compared PMA modulation of the activities of Ca(v)3.1, Ca(v)3.2 and Ca(v)3.3 channels, and have investigated the underlying mechanism. PMA augmented the current amplitudes of the three T-type channel isoforms, but the fold stimulations and time courses differed. The augmentation effects were not mimicked by 4 alpha-PMA, an inactive stereoisomer of PMA, but were abolished by preincubation with protein kinase C (PKC) inhibitors, indicating that PMA augmented T-type channel currents via activation of oocyte PKC. The stimulation effect on Ca(v)3.1 channel activity by PKC was mimicked by endothelin when endothelin receptor type A was coexpressed with Ca(v)3.1 in the Xenopus oocyte system. Pharmacological studies combined with fluorescence imaging revealed that the surface density of Ca(v)3.1 T-type channels was not significantly changed by activation of PKC. The PKC effect on Ca(v)3.1 was localized to the cytoplasmic II-III loop using chimeric channels with individual cytoplasmic loops of Ca(v)3.1 replaced by those of Ca(v)2.1.