Shimkets R A, Lifton R, Canessa C M
Department of Genetics, Yale University School of Medicine, New Haven, CT 06520-8026, USA.
Proc Natl Acad Sci U S A. 1998 Mar 17;95(6):3301-5. doi: 10.1073/pnas.95.6.3301.
The activity of the epithelial sodium channel (ENaC) in the distal nephron is regulated by an antidiuretic hormone, aldosterone, and insulin, but the molecular mechanisms that mediate these hormonal effects are mostly unknown. We have investigated whether aldosterone, insulin, or activation of protein kinases has an effect on the phosphorylation of the channel. Experiments were performed in an epithelial cell line generated by stable cotransfection of the three subunits (alpha, beta, and gamma) of ENaC. We found that beta and gamma, but not the alpha subunit, are phosphorylated in the basal state. Aldosterone, insulin, and protein kinases A and C increased phosphorylation of the beta and gamma subunits in their carboxyl termini, but none of these agents induced de novo phosphorylation of alpha subunits. Serines and threonines but not tyrosines were found to be phosphorylated. The results suggest that aldosterone, insulin, and protein kinases A and C modulate the activity of ENaC by phosphorylation of the carboxyl termini of the beta and gamma subunits.
远端肾单位上皮钠通道（ENaC）的活性受抗利尿激素、醛固酮和胰岛素调节，但介导这些激素作用的分子机制大多未知。我们研究了醛固酮、胰岛素或蛋白激酶的激活是否对该通道的磷酸化有影响。实验在通过稳定共转染ENaC的三个亚基（α、β和γ）产生的上皮细胞系中进行。我们发现，在基础状态下，β和γ亚基会发生磷酸化，而α亚基不会。醛固酮、胰岛素以及蛋白激酶A和C增加了β和γ亚基羧基末端的磷酸化，但这些试剂均未诱导α亚基的从头磷酸化。发现被磷酸化的是丝氨酸和苏氨酸，而非酪氨酸。结果表明，醛固酮、胰岛素以及蛋白激酶A和C通过β和γ亚基羧基末端的磷酸化来调节ENaC的活性。
