Martín Pedro, Moncada Melisa, Enrique Nicolás, Asuaje Agustín, Valdez Capuccino Juan Manuel, Gonzalez Carlos, Milesi Verónica
GINFIV-CONICET-Grupo de Investigación en Fisiología Vascular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calles 47 y 115, La Plata, 1900, Argentina.
Pflugers Arch. 2014 Sep;466(9):1779-92. doi: 10.1007/s00424-013-1422-x. Epub 2013 Dec 28.
Arachidonic acid (AA) is a polyunsaturated fatty acid involved in a complex network of cell signaling. It is well known that this fatty acid can directly modulate several cellular target structures, among them, ion channels. We explored the effects of AA on high conductance Ca(2+)- and voltage-dependent K(+) channel (BKCa) in vascular smooth muscle cells (VSMCs) where the presence of β1-subunit was functionally demonstrated by lithocholic acid activation. Using patch-clamp technique, we show at the single channel level that 10 μM AA increases the open probability (Po) of BKCa channels tenfold, mainly by a reduction of closed dwell times. AA also induces a left-shift in Po versus voltage curves without modifying their steepness. Furthermore, AA accelerates the kinetics of the voltage channel activation by a fourfold reduction in latencies to first channel opening. When AA was tested on BKCa channel expressed in HEK cells with or without the β1-subunit, activation only occurs in presence of the modulatory subunit. These results contribute to highlight the molecular mechanism of AA-dependent BKCa activation. We conclude that AA itself selectively activates the β1-associated BKCa channel, destabilizing its closed state probably by interacting with the β1-subunit, without modifying the channel voltage sensitivity. Since BKCa channels physiologically contribute to regulation of VSMCs contractility and blood pressure, we used the whole-cell configuration to show that AA is able to activate these channels, inducing significant cell hyperpolarization that can lead to VSMCs relaxation.
花生四烯酸（AA）是一种参与复杂细胞信号网络的多不饱和脂肪酸。众所周知，这种脂肪酸可以直接调节多种细胞靶结构，其中包括离子通道。我们探讨了AA对血管平滑肌细胞（VSMC）中高电导钙依赖性和电压依赖性钾通道（BKCa）的影响，在这些细胞中，石胆酸激活在功能上证明了β1亚基的存在。使用膜片钳技术，我们在单通道水平上表明，10 μM AA可使BKCa通道的开放概率（Po）增加10倍，主要是通过减少关闭停留时间实现的。AA还会使Po与电压曲线向左移动，而不改变其斜率。此外，AA通过将首次通道开放的延迟时间缩短四倍，加速了电压通道激活的动力学。当在有或没有β1亚基的HEK细胞中表达的BKCa通道上测试AA时，激活仅在存在调节亚基的情况下发生。这些结果有助于突出AA依赖性BKCa激活的分子机制。我们得出结论，AA本身选择性激活与β-1相关的BKCa通道，可能通过与β1亚基相互作用使其关闭状态不稳定，而不改变通道电压敏感性。由于BKCa通道在生理上有助于调节VSMC的收缩性和血压，我们使用全细胞配置来表明AA能够激活这些通道，诱导显著的细胞超极化，从而导致VSMC舒张。
