Volume-regulated anion channels serve as an auto/paracrine nucleotide release pathway in aortic endothelial cells.
Volume-regulated anion channels serve as an auto/paracrine nucleotide release pathway in aortic endothelial cells.
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体积调节的阴离子通道是主动脉内皮细胞中的自动/旁分泌核苷酸释放途径。
DOI：
10.1085/jgp.20028540
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发表时间：
2002-06
影响因子：
3.8
通讯作者：
Oike, Masahiro
中科院分区：
文献类型：
--
作者：
Hisadome, Kazunari;Koyama, Tetsuya;Kimura, Chiwaka;Droogmans, Guy;Ito, Yushi;Oike, Masahiro
机械应力会诱导各种细胞类型自动/旁分泌 ATP 释放，但这种释放背后的机制尚不清楚。在这里，我们发现牛主动脉内皮细胞（BAEC）中低渗应激（HTS）诱导的 ATP 释放是通过容量调节阴离子通道（VRAC）发生的。各种 VRAC 抑制剂，如格列本脲、维拉帕米、他莫昔芬和氟西汀，抑制 HTS 诱导的 ATP 释放，以及伴随的 Ca2+ 振荡和 NO 产生。然而，它们并不影响由外源施加的 ATP 诱导的 Ca2+ 振荡和 NO 产生。细胞外 ATP 以电压依赖性方式抑制 VRAC 电流：在负电位时不存在阻滞，在正电位时明显，但在高度去极化电位时减弱。这种现象可以用“渗透阻滞剂模型”来描述，其中 ATP 在 0 mV 下以 1.0 ± 0.5 mM 的亲和力与通道内电距离为 0.41 的位点结合。结合的 ATP 在中等正电位时会阻塞通道，但在去极化电位较高时会渗透到细胞质中。三磷酸核苷酸UTP、GTP和CTP以及腺嘌呤核苷酸ADP在亚毫摩尔浓度下对VRAC电流产生类似的电压依赖性抑制，这也可以用该模型来描述。然而，ADP 的抑制对电压不太敏感，而腺苷不影响 VRAC 电流，这表明核苷酸的负电荷对其抑制作用至关重要。高浓度细胞外ADP增强了低Cl-低渗溶液中VRAC电流的外向分量并将其反转电位转变为负电位的观察结果为VRAC的核苷酸通透性提供了更直接的证据。我们从这些观察中得出结论，VRAC 是一种核苷酸可渗透通道，它可能作为 BAEC 中 HTS 诱导的 ATP 释放的途径。
Mechanical stress induces auto/paracrine ATP release from various cell types, but the mechanisms underlying this release are not well understood. Here we show that the release of ATP induced by hypotonic stress (HTS) in bovine aortic endothelial cells (BAECs) occurs through volume-regulated anion channels (VRAC). Various VRAC inhibitors, such as glibenclamide, verapamil, tamoxifen, and fluoxetine, suppressed the HTS-induced release of ATP, as well as the concomitant Ca2+ oscillations and NO production. They did not, however, affect Ca2+ oscillations and NO production induced by exogenously applied ATP. Extracellular ATP inhibited VRAC currents in a voltage-dependent manner: block was absent at negative potentials and was manifest at positive potentials, but decreased at highly depolarized potentials. This phenomenon could be described with a “permeating blocker model,” in which ATP binds with an affinity of 1.0 ± 0.5 mM at 0 mV to a site at an electrical distance of 0.41 inside the channel. Bound ATP occludes the channel at moderate positive potentials, but permeates into the cytosol at more depolarized potentials. The triphosphate nucleotides UTP, GTP, and CTP, and the adenine nucleotide ADP, exerted a similar voltage-dependent inhibition of VRAC currents at submillimolar concentrations, which could also be described with this model. However, inhibition by ADP was less voltage sensitive, whereas adenosine did not affect VRAC currents, suggesting that the negative charges of the nucleotides are essential for their inhibitory action. The observation that high concentrations of extracellular ADP enhanced the outward component of the VRAC current in low Cl− hypotonic solution and shifted its reversal potential to negative potentials provides more direct evidence for the nucleotide permeability of VRAC. We conclude from these observations that VRAC is a nucleotide-permeable channel, which may serve as a pathway for HTS-induced ATP release in BAEC.