14-3-3 Mediates Phosphorylation-Dependent Inhibition of the Interaction between the Ubiquitin E3 Ligase Nedd4-2 and Epithelial Na+ Channels

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• 作者：Kazunori Nagaki ; Hisao Yamamura ; Shoichi Shimada ; Taro Saito ; Shin-ichi Hisanaga ; Masato Taoka ; Toshiaki Isobe ; and Tohru Ichimura
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：May 30, 2006
• 年：2006
• 卷：45
• 期：21
• 页码：6733 - 6740
• 全文大小：281K
• 年卷期：v.45,no.21(May 30, 2006)
• ISSN：1520-4995

文摘

Although recent studies show that the 14-3-3 protein is a negative regulator of ubiquitin E3protein ligases, the molecular mechanism remains largely unknown. We previously demonstrated that14-3-3 specifically binds one of the E3 enzymes, Nedd4-2 (a human gene product of KIAA0439, termedhNedd4-2), which can be phosphorylated by serum glucocorticoid-inducible protein kinase 1 (SGK1);this binding protects the phosphorylated/inactive hNedd4-2 from phosphatase-catalyzed dephosphorylation[Ichimura, T., et al. (2005) J. Biol. Chem. 280, 13187-13194]. Here we report an additional mechanismof 14-3-3-mediated regulation of hNedd4-2. Using surface plasmon resonance spectrometry, we showthat 14-3-3 inhibits the interaction between the WW domains of hNedd4-2 and the PY motif of the epithelialNa⁺ channel, ENaC. The inhibition was dose-dependent and was dependent on SGK1-catalyzedphosphorylation of Ser468 located between the WW domains. Importantly, a mutant of hNedd4-2, whichcan be phosphorylated by SGK1 but cannot bind 14-3-3, reduced SGK1-mediated stimulation of the ENaC-induced current in Xenopus laevis oocytes. In addition, 14-3-3 had similar effects on hNedd4-2 that hadbeen phosphorylated by cAMP-dependent protein kinase (PKA). Our results, together with the recentfinding on 14-3-3/parkin interactions [Sato, S., et al. (2006) EMBO J. 25, 211-221], suggest that 14-3-3suppresses ubiquitin E3 ligase activities by inhibiting the formation of the enzyme/substrate complex.