Thromboxane A2 receptor and MaxiK-channel intimate interaction supports channel trans-inhibition independent of G-protein activation
Thromboxane A2 receptor and MaxiK-channel intimate interaction supports channel trans-inhibition independent of G-protein activation
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DOI：
10.1073/pnas.1002685107
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发表时间：
2010-11-02
影响因子：
11.1
通讯作者：
Toro, Ligia
中科院分区：
文献类型：
--
作者：
Li, Min;Tanaka, Yoshio;Toro, Ligia
大电导电压激活钾通道和钙激活钾通道（MaxiK、BK(Ca)）因维持大脑和冠状动脉张力以及与血管舒张剂 β-肾上腺素能受体的联系而闻名。然而，MaxiK 通道如何与平衡血管收缩受体相关联尚不清楚。在这里，我们证明血管加压性血栓素 A2 受体 (TP) 可以与 MaxiK 通道紧密耦合并抑制 MaxiK 通道。受体及其激动剂反式激活会独立于 G 蛋白激活而抑制 MaxiK。这种非常规机制得到了独立证据的支持：(i) 即使 G 蛋白活性受到抑制，血栓素 A2 模拟物 U46619 也会抑制 MaxiK 电流； (ii) MaxiK 和 TP 在物理上联系并表现出高度接近； (iii) Forster 共振能量转移发生在荧光标记的 MaxiK 和 TP 之间，支持直接相互作用。 MaxiK-TP紧密相互作用的分子机制涉及受体的第一胞内环和C末端，并且涉及MaxiK通道的电压传感传导盒。此外，在人冠状动脉和大鼠主动脉中给出了 MaxiK-TP 物理相互作用的生理学证据，并通过确认 TP 在 U46619 诱导的人冠状动脉 MaxiK 抑制中的作用（与拮抗剂 SQ29,548 一起）。我们认为，血管收缩剂 TP 受体和 MaxiK 通道直接相互作用促进了不依赖 G 蛋白的 TP 对 MaxiK 反式抑制，从而促进血管收缩。
Large conductance voltage- and calcium-activated potassium channels (MaxiK, BK(Ca)) are well known for sustaining cerebral and coronary arterial tone and for their linkage to vasodilator beta-adrenergic receptors. However, how MaxiK channels are linked to counterbalancing vasoconstrictor receptors is unknown. Here, we show that vasopressive thromboxane A2 receptors (TP) can intimately couple with and inhibit MaxiK channels. Activation of the receptor with its agonist trans-inhibits MaxiK independently of G-protein activation. This unconventional mechanism is supported by independent lines of evidence: (i) inhibition of MaxiK current by thromboxane A2 mimetic, U46619, occurs even when G-protein activity is suppressed; (ii) MaxiK and TP physically associate and display a high degree of proximity; and (iii) Forster resonance energy transfer occurs between fluorescently labeled MaxiK and TP, supporting a direct interaction. The molecular mechanism of MaxiK-TP intimate interaction involves the receptor's first intracellular loop and C terminus, and it entails the voltage-sensing conduction cassette of MaxiK channel. Further, physiological evidence of MaxiK-TP physical interaction is given in human coronaries and rat aorta, and by confirming TP role (with antagonist SQ29,548) in the U46619-induced MaxiK inhibition in human coronaries. We propose that vasoconstrictor TP receptor and MaxiK-channel direct interaction facilitates G-protein-independent TP to MaxiK trans-inhibition, which would promote vasoconstriction.