Regulation of epithelial sodium channels in urokinase plasminogen activator deficiency
Regulation of epithelial sodium channels in urokinase plasminogen activator deficiency
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DOI：
10.1152/ajplung.00126.2014
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发表时间：
2014-10-15
影响因子：
4.9
通讯作者：
Ji, Hong-Long
中科院分区：
文献类型：
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作者：
Chen, Zaixing;Zhao, Runzhen;Ji, Hong-Long
上皮钠通道（ENaC）控制跨上皮盐和流体稳态。ENaC有助于极化、凋亡、上皮-间质转化等。纤溶蛋白酶在几乎所有这些过程中发挥关键作用，并由气道上皮精心制作。我们假设尿激酶样纤溶酶原激活物（uPA）调节气道上皮细胞中的ENaC功能，并在原代小鼠气管上皮细胞（MTE）中测试了这种可能性。在uPA缺陷细胞单层中，基础和cAMP激活的Na+流经ENaC均显著减少。ENaC活性的降低在基底外侧膜透化细胞中得到进一步证实。基底外侧膜Na+ -K+ -ATP酶活性的降低可能导致完整单层细胞ENaC功能的减弱。在uPA破坏的细胞中观察到功能障碍性液体消退。给予uPA和纤溶酶部分恢复ENaC活性和MTEs的液体重吸收。在uPA缺陷小鼠的细胞和肺中观察到ERK 1/2磷酸化，而不是Akt磷酸化。另一方面，与野生型对照相比，uPA敲除小鼠肺中γ ENaC的裂解显著抑制。然而，半胱天冬酶8的表达在野生型和uPA（-/-）小鼠之间没有差异。此外，uPA缺乏并不改变跨上皮阻力。总之，在MTEs中uPA调节ENaC的机制包括增加Na+ -K+ -ATP酶、蛋白水解和限制ERK 1/2磷酸化。我们首次证明ENaC可能作为uPA控制气道液体和上皮功能的生物物理特征的下游信号传导靶点。
Epithelial sodium channels (ENaC) govern transepithelial salt and fluid homeostasis. ENaC contributes to polarization, apoptosis, epithelial-mesenchymal transformation, etc. Fibrinolytic proteases play a crucial role in virtually all of these processes and are elaborated by the airway epithelium. We hypothesized that urokinase-like plasminogen activator (uPA) regulates ENaC function in airway epithelial cells and tested that possibility in primary murine tracheal epithelial cells (MTE). Both basal and cAMP-activated Na+ flow through ENaC were significantly reduced in monolayers of uPA-deficient cells. The reduction in ENaC activity was further confirmed in basolateral membrane-permeabilized cells. A decrease in the Na+ -K+ -ATPase activity in the basolateral membrane could contribute to the attenuation of ENaC function in intact monolayer cells. Dysfunctional fluid resolution was seen in uPA-disrupted cells. Administration of uPA and plasmin partially restores ENaC activity and fluid reabsorption by MTEs. ERK1/2, but not Akt, phosphorylation was observed in the cells and lungs of uPA-deficient mice. On the other hand, cleavage of gamma ENaC is significantly depressed in the lungs of uPA knockout mice vs. those of wild-type controls. Expression of caspase 8, however, did not differ between wild-type and uPA(-/-) mice. In addition, uPA deficiency did not alter transepithelial resistance. Taken together, the mechanisms for the regulation of ENaC by uPA in MTEs include augmentation of Na+ -K+ -ATPase, proteolysis, and restriction of ERK1/2 phosphorylation. We demonstrate for the first time that ENaC may serve as a downstream signaling target by which uPA controls the biophysical profiles of airway fluid and epithelial function.