Malbert-Colas Laurence, Fay Michel, Cluzeaud Françoise, Blot-Chabaud Marcel, Farman Nicolette, Dhermy Didier, Lecomte Marie-Christine
INSERM Unité 409, Faculté de Médecine X. Bichat, BP416, 75870 Paris Cedex 18, France.
Pflugers Arch. 2003 Oct;447(1):35-43. doi: 10.1007/s00424-003-1152-6. Epub 2003 Aug 8.
Ubiquitination of proteins such as ion transporters appears to be an important process in the regulation of their membrane expression. Recently, using two-hybrid screening, we have selected a potential partner for the alpha-subunit of the amiloride-sensitive epithelial sodium channel (ENaC): the WWP1 protein, a ubiquitin ligase belonging to the Nedd4 family. To establish whether WWP1 is co-expressed with ENaC, we employed in situ hybridisation, immunohistochemistry and Western blotting to determine the expression of WWP1 in various tissues and cell lines, including those known to express ENaC. As expected, WWP1 was expressed, like ENaC, in the bronchiolar epithelium. However it was also present in the proximal colon and the proximal part of the nephron (where ENaC is not expressed) and absent in the distal parts of the nephron (where ENaC is expressed abundantly). These results suggest that other channels or transport proteins, containing specific domains, such as PY motifs, could be the targets for regulation by WWP1.
蛋白质（如离子转运体）的泛素化似乎是调节其膜表达的一个重要过程。最近，通过双杂交筛选，我们为氨氯地平敏感的上皮钠通道（ENaC）的α亚基选择了一个潜在的伙伴：WWP1蛋白，一种属于Nedd4家族的泛素连接酶。为了确定WWP1是否与ENaC共表达，我们采用原位杂交、免疫组织化学和蛋白质印迹法来测定WWP1在各种组织和细胞系中的表达，包括那些已知表达ENaC的组织和细胞系。正如预期的那样，WWP1与ENaC一样，在细支气管上皮中表达。然而，它也存在于近端结肠和肾单位的近端部分（ENaC在此处不表达），而在肾单位的远端部分（ENaC在此处大量表达）不存在。这些结果表明，其他含有特定结构域（如PY基序）的通道或转运蛋白可能是WWP1调节的靶点。
