Kamynina E, Debonneville C, Bens M, Vandewalle A, Staub O
Institute of Pharmacology and Toxicology, University of Lausanne, 1005 Lausanne, Switzerland.
FASEB J. 2001 Jan;15(1):204-214. doi: 10.1096/fj.00-0191com.
Liddle's syndrome is a form of inherited hypertension linked to mutations in the genes encoding the epithelial Na+ channel (ENaC). These mutations alter or delete PY motifs involved in protein-protein interactions with a ubiquitin-protein ligase, Nedd4. Here we show that Na+ transporting cells, derived from mouse cortical collecting duct, express two Nedd4 proteins with different structural organization and characteristics of ENaC regulation: 1) the classical Nedd4 (herein referred to as Nedd4-1) containing one amino-terminal C2, three WW, and one HECT-ubiquitin protein ligase domain and 2) a novel Nedd4 protein (Nedd4-2), homologous to Xenopus Nedd4 and comprising four WW, one HECT, yet lacking a C2 domain. Nedd4-2, but not Nedd4-1, inhibits ENaC activity when coexpressed in Xenopus oocytes and this property correlates with the ability to bind to ENaC, as only Nedd4-2 coimmunoprecipitates with ENaC. Furthermore, this interaction depends on the presence of at least one PY motif in the ENaC complex and on WW domains 3 and 4 in Nedd4-2. Thus, these results suggest that the novel suppressor protein Nedd4-2 is the regulator of ENaC and hence a potential susceptibility gene for arterial hypertension.
利德尔综合征是一种遗传性高血压，与编码上皮钠通道（ENaC）的基因突变有关。这些突变改变或删除了与泛素蛋白连接酶Nedd4进行蛋白质-蛋白质相互作用的PY基序。在此我们表明，从小鼠皮质集合管衍生的钠转运细胞表达两种具有不同结构组织和ENaC调节特性的Nedd4蛋白：1）经典的Nedd4（在此称为Nedd4-1），包含一个氨基末端C2结构域、三个WW结构域和一个HECT泛素蛋白连接酶结构域；2）一种新的Nedd4蛋白（Nedd4-2），与非洲爪蟾Nedd4同源，包含四个WW结构域、一个HECT结构域，但缺乏C2结构域。当在非洲爪蟾卵母细胞中共表达时，Nedd4-2而非Nedd4-1抑制ENaC活性，并且这种特性与结合ENaC的能力相关联，因为只有Nedd4-2能与ENaC进行共免疫沉淀。此外，这种相互作用取决于ENaC复合物中至少一个PY基序的存在以及Nedd4-2中的WW结构域3和4。因此，这些结果表明新的抑制蛋白Nedd4-2是ENaC的调节因子，因此是动脉高血压的一个潜在易感基因。
