Dada Laura A, Welch Lynn C, Zhou Guofei, Ben-Saadon Ronen, Ciechanover Aaron, Sznajder Jacob I
Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, United States.
Cell Signal. 2007 Sep;19(9):1893-8. doi: 10.1016/j.cellsig.2007.04.013. Epub 2007 May 5.
As a cellular adaptative response, hypoxia decreases Na,K-ATPase activity by triggering the endocytosis of its alpha(1) subunit in alveolar epithelial cells. Here, we present evidence that the ubiquitin conjugating system is important in the Na,K-ATPase endocytosis during hypoxia and that ubiquitination of Na,K-ATPase alpha(1) subunit occurs at the basolateral membrane. Endocytosis and ubiquitination were prevented when the Ser 18 in the PKC phosphorylation motif of the Na,K-ATPase alpha(1) subunit was mutated to an alanine, suggesting that phosphorylation at Ser-18 is required for ubiquitination. Mutation of the four lysines surrounding Ser 18 to arginine prevented Na,K-ATPase ubiquitination and endocytosis during hypoxia; however, only one of them was sufficient to restore hypoxia-induced endocytosis. We provide evidence that ubiquitination plays an important role in cellular adaptation to hypoxia by regulating Na,K-ATPase alpha(1)-subunit endocytosis.
作为一种细胞适应性反应，缺氧通过触发肺泡上皮细胞中Na，K - ATP酶α(1)亚基的内吞作用来降低其活性。在此，我们提供证据表明泛素结合系统在缺氧期间Na，K - ATP酶的内吞作用中起重要作用，并且Na，K - ATP酶α(1)亚基的泛素化发生在基底外侧膜。当Na，K - ATP酶α(1)亚基的PKC磷酸化基序中的丝氨酸18突变为丙氨酸时，内吞作用和泛素化被阻止，这表明丝氨酸18处的磷酸化是泛素化所必需的。将丝氨酸18周围的四个赖氨酸突变为精氨酸可防止缺氧期间Na，K - ATP酶的泛素化和内吞作用；然而，其中只有一个足以恢复缺氧诱导的内吞作用。我们提供证据表明，泛素化通过调节Na，K - ATP酶α(1)亚基的内吞作用在细胞对缺氧的适应中起重要作用。
