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XB-ART-50456
Am J Physiol Lung Cell Mol Physiol 2014 Oct 15;3078:L609-17. doi: 10.1152/ajplung.00126.2014.
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Regulation of epithelial sodium channels in urokinase plasminogen activator deficiency.

Chen Z , Zhao R , Zhao M , Liang X , Bhattarai D , Dhiman R , Shetty S , Idell S , Ji HL .


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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 γ 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.

???displayArticle.pubmedLink??? 25172911
???displayArticle.pmcLink??? PMC4200389
???displayArticle.link??? Am J Physiol Lung Cell Mol Physiol
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Species referenced: Xenopus laevis
Genes referenced: akt1 camp mapk1 plg

References [+] :
Ahn, Cloning and functional expression of the mouse epithelial sodium channel. 1999, Pubmed, Xenbase