High NaCl-induced inhibition of PTG contributes to activation of NFAT5 through attenuation of the negative effect of SHP-1.
High NaCl-induced inhibition of PTG contributes to activation of NFAT5 through attenuation of the negative effect of SHP-1.
复制标题
DOI：
10.1152/ajprenal.00218.2013
复制
发表时间：
2013-08
期刊：
影响因子：
--
通讯作者：
Xiaoming Zhou;Hong Wang;M. Burg;J. Ferraris
中科院分区：
文献类型：
--
作者：
Xiaoming Zhou;Hong Wang;M. Burg;J. Ferraris
高 NaCl 激活转录因子 NFAT5 涉及磷酸化的变化。通过siRNA筛选，我们之前发现靶向糖原（PTG）的蛋白（PTG）是蛋白磷酸酶1（PP1）的调节亚基，有助于调节高氯化钠诱导的NFAT5转录活性。本研究探讨了所涉及的机制。我们发现高 NaCl 诱导的 PTG 抑制通过增加 NFAT5 反式激活活性、蛋白质丰度和核定位来提高 NFAT5 活性。 PTG 通过催化亚基 PP1γ 发挥作用。 PTG 与 PP1γ 物理结合，而 NaCl 会降低这种结合以及剩余的 PTG 相关 PP1γ 活性。高 NaCl 诱导的 p38、ERK 和 SHP-1 磷酸化有助于 NFAT5 的激活。 PTG 的敲除不影响 p38 或 ERK 的磷酸化。然而，PTG 和 PP1γ 与 SHP-1 结合，PTG 或 PP1γ 的敲低会增加高 NaCl 诱导的 SHP-1-S591 磷酸化，从而抑制 SHP-1。 SHP-1-S591 突变为丙氨酸（无法磷酸化），会增加 SHP-1 对 NFAT5 的抑制。因此，高NaCl会降低PTG和PP1γ对SHP-1的刺激作用，进而降低SHP-1对NFAT5的抑制作用。我们的发现增加了 PTG 的已知功能，此前人们仅认识到 PTG 的糖原活性。
Activation of the transcription factor NFAT5 by high NaCl involves changes in phosphorylation. By siRNA screening, we previously found that protein targeting to glycogen (PTG), a regulatory subunit of protein phosphatase1 (PP1), contributes to regulation of high NaCl-induced NFAT5 transcriptional activity. The present study addresses the mechanism involved. We find that high NaCl-induced inhibition of PTG elevates NFAT5 activity by increasing NFAT5 transactivating activity, protein abundance, and nuclear localization. PTG acts via a catalytic subunit PP1γ. PTG associates physically with PP1γ, and NaCl reduces both this association and remaining PTG-associated PP1γ activity. High NaCl-induced phosphorylation of p38, ERK, and SHP-1 contributes to activation of NFAT5. Knockdown of PTG does not affect phosphorylation of p38 or ERK. However, PTG and PP1γ bind to SHP-1, and knockdown of either PTG or PP1γ increases high NaCl-induced phosphorylation of SHP-1-S591, which inhibits SHP-1. Mutation of SHP-1-S591 to alanine, which cannot be phosphorylated, increases inhibition of NFAT5 by SHP-1. Thus high NaCl reduces the stimulatory effect of PTG and PP1γ on SHP-1, which in turn reduces the inhibitory effect of SHP-1 on NFAT5. Our findings add to the known functions of PTG, which was previously recognized only for its glycogenic activity.