Lu Min, Echeverri Fernando, Kalabat Dalia, Laita Bianca, Dahan David S, Smith Raymond D, Xu Hong, Staszewski Lena, Yamamoto Jeff, Ling Jing, Hwang Nancy, Kimmich Rachel, Li Peter, Patron Erika, Keung Walter, Patron Andrew, Moyer Bryan D
Senomyx, Inc., San Diego, California 92121, USA.
J Biol Chem. 2008 May 2;283(18):11981-94. doi: 10.1074/jbc.M708001200. Epub 2008 Mar 6.
The epithelial sodium channel (ENaC), a heterotrimeric complex composed of alpha, beta, and gamma subunits, belongs to the ENaC/degenerin family of ion channels and forms the principal route for apical Na(+) entry in many reabsorbing epithelia. Although high affinity ENaC blockers, including amiloride and derivatives, have been described, potent and specific small molecule ENaC activators have not been reported. Here we describe compound S3969 that fully and reversibly activates human ENaC (hENaC) in an amiloride-sensitive and dose-dependent manner in heterologous cells. Mechanistically, S3969 increases hENaC open probability through interactions requiring the extracellular domain of the beta subunit. hENaC activation by S3969 did not require cleavage by the furin protease, indicating that nonproteolyzed channels can be opened. Function of alphabetaG37Sgamma hENaC, a channel defective in gating that leads to the salt-wasting disease pseudohypoaldosteronism type I, was rescued by S3969. Small molecule activation of hENaC may find application in alleviating human disease, including pseudohypoaldosteronism type I, hypotension, and neonatal respiratory distress syndrome, when improved Na(+) flux across epithelial membranes is clinically desirable.
上皮钠通道（ENaC）是一种由α、β和γ亚基组成的异源三聚体复合物，属于离子通道的ENaC/退化素家族，是许多重吸收上皮细胞顶端Na⁺进入的主要途径。尽管已经描述了包括氨氯地平和衍生物在内的高亲和力ENaC阻滞剂，但尚未报道有效且特异性的小分子ENaC激活剂。在此，我们描述了化合物S3969，它在异源细胞中以氨氯地平敏感且剂量依赖的方式完全且可逆地激活人ENaC（hENaC）。从机制上讲，S3969通过需要β亚基细胞外结构域的相互作用增加hENaC的开放概率。S3969对hENaC的激活不需要弗林蛋白酶切割，这表明未被蛋白水解的通道也可以被打开。S3969挽救了αβG37Sγ hENaC的功能，αβG37Sγ hENaC是一种门控缺陷的通道，可导致I型假性醛固酮减少症（一种失盐性疾病）。当临床上需要改善跨上皮膜的Na⁺通量时，hENaC的小分子激活可能在缓解人类疾病中找到应用，包括I型假性醛固酮减少症、低血压和新生儿呼吸窘迫综合征。
