Department of Medicine.
Department of Computational and Systems Biology.
JCI Insight. 2023 Nov 8;8(21):e172051. doi: 10.1172/jci.insight.172051.
Epithelial Na+ channels (ENaCs) control extracellular fluid volume by facilitating Na+ absorption across transporting epithelia. In vitro studies showed that Cys-palmitoylation of the γENaC subunit is a major regulator of channel activity. We tested whether γ subunit palmitoylation sites are necessary for channel function in vivo by generating mice lacking the palmitoylated cysteines (γC33A,C41A) using CRISPR/Cas9 technology. ENaCs in dissected kidney tubules from γC33A,C41A mice had reduced open probability compared with wild-type (WT) littermates maintained on either standard or Na+-deficient diets. Male mutant mice also had higher aldosterone levels than WT littermates following Na+ restriction. However, γC33A,C41A mice did not have reduced amiloride-sensitive Na+ currents in the distal colon or benzamil-induced natriuresis compared to WT mice. We identified a second, larger conductance cation channel in the distal nephron with biophysical properties distinct from ENaC. The activity of this channel was higher in Na+-restricted γC33A,C41A versus WT mice and was blocked by benzamil, providing a possible compensatory mechanism for reduced prototypic ENaC function. We conclude that γ subunit palmitoylation sites are required for prototypic ENaC activity in vivo but are not necessary for amiloride/benzamil-sensitive Na+ transport in the distal nephron or colon.
上皮钠离子通道(ENaC)通过促进转运上皮细胞的钠离子吸收来控制细胞外液容量。体外研究表明,γENaC 亚基的半胱氨酸棕榈酰化是调节通道活性的主要因素。我们使用 CRISPR/Cas9 技术生成缺乏棕榈酰化半胱氨酸(γC33A、C41A)的小鼠,以测试 γ 亚基棕榈酰化位点是否对体内通道功能是必需的。与在标准或低钠饮食下维持的野生型(WT)同窝仔相比,从 γC33A、C41A 小鼠分离的肾脏小管中的 ENaC 的开放概率降低。雄性突变小鼠在限制钠后,醛固酮水平也高于 WT 同窝仔。然而,与 WT 小鼠相比,γC33A、C41A 小鼠的远端结肠中阿米洛利敏感的钠离子电流或苯并咪嗪诱导的排钠作用并没有减少。我们在远端肾单位中发现了第二个具有不同于 ENaC 的生理特性的较大电导阳离子通道。在受钠限制的 γC33A、C41A 与 WT 小鼠相比,该通道的活性更高,并且被苯并咪嗪阻断,这为减少典型 ENaC 功能提供了一种可能的补偿机制。我们得出结论,γ 亚基棕榈酰化位点是体内典型 ENaC 活性所必需的,但对远端肾单位或结肠中的阿米洛利/苯并咪嗪敏感的钠离子转运并非必需。
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