Capsazepine Is a Novel Activator of the δ Subunit of the Human Epithelial Na+ Channel*
Capsazepine Is a Novel Activator of the δ Subunit of the Human Epithelial Na+ Channel*
复制标题
DOI：
10.1074/jbc.m408929200
复制
发表时间：
2004-10
影响因子：
4.8
通讯作者：
H. Yamamura;S. Ugawa;T. Ueda;M. Nagao;S. Shimada
中科院分区：
文献类型：
--
作者：
H. Yamamura;S. Ugawa;T. Ueda;M. Nagao;S. Shimada
阿米洛利敏感性上皮Na+通道（ENaC）调节Na+进入细胞和跨上皮的稳态。到目前为止，已经分离出哺乳动物ENaC的四个同源亚基，并将其表示为α、β、γ和δ。然而，除了作为ENaC抑制剂的阿米洛利和苯扎米尔之外，作用于ENaC的化学试剂在很大程度上是未知的。特别是，目前还没有已知的对ENaCδ具有选择性的激动剂，ENaCδ主要在脑中表达。在这里，我们证明辣椒平，瞬时受体电位香草酸亚家族1的竞争性拮抗剂，增强在爪蟾卵母细胞中表达的人ENaCδβγ（hENaCδβγ）异源多聚体的活性。在hENaCδβγ表达的卵母细胞中，辣椒平（≥1 μm）可显著增强-60 mV保持电位下的内向电流，而阿米洛利（100 μm）可基本消除辣椒平诱导的内向电流。辣椒平对内向电流的刺激作用呈浓度依赖性，EC 50值为8 μm。无论是应用其他香草素化合物（辣椒素，树脂毒素，和olvanil），也不是结构上相关的化合物（多巴胺）调制的内向电流。尽管辣椒平也显著激活hENaCδ同聚体，但出乎意料的是，辣椒平对hENaCα没有影响，并导致hENaCαβγ电流轻微降低。总之，辣椒平作用于ENaCδ并与质子一起作用。其他测试的香草素没有任何效果。这些发现确定辣椒平是第一个已知的ENaCδ的化学激活剂。
The amiloride-sensitive epithelial Na+ channel (ENaC) regulates Na+ homeostasis into cells and across epithelia. So far, four homologous subunits of mammalian ENaC have been isolated and are denoted as α, β, γ, and δ. The chemical agents acting on ENaC are, however, largely unknown, except for amiloride and benzamil as ENaC inhibitors. In particular, there are no agonists currently known that are selective for ENaCδ, which is mainly expressed in the brain. Here we demonstrate that capsazepine, a competitive antagonist for transient receptor potential vanilloid subfamily 1, potentiates the activity of human ENaCδβγ (hENaCδβγ) heteromultimer expressed in Xenopus oocytes. The inward currents at a holding potential of –60 mV in hENaCδβγ-expressing oocytes were markedly enhanced by the application of capsazepine (≥1 μm), and the capsazepine-induced current was mostly abolished by the addition of 100 μm amiloride. The stimulatory effects of capsazepine on the inward current were concentration-dependent with an EC50 value of 8 μm. Neither the application of other vanilloid compounds (capsaicin, resiniferatoxin, and olvanil) nor a structurally related compound (dopamine) modulated the inward current. Although hENaCδ homomer was also significantly activated by capsazepine, unexpectedly, capsazepine had no effect on hENaCα and caused a slight decrease on the hENaCαβγ current. In conclusion, capsazepine acts on ENaCδ and acts together with protons. Other vanilloids tested do not have any effect. These findings identify capsazepine as the first known chemical activator of ENaCδ.