Fouladkou Fatemeh, Landry Tamara, Kawabe Hiroshi, Neeb Antje, Lu Chen, Brose Nils, Stambolic Vuk, Rotin Daniela
Hospital for Sick Children and Biochemistry Department, University of Toronto, MaRS-TMDT, 101 College Street, Toronto, Ontario M5G 1L7, Canada.
Proc Natl Acad Sci U S A. 2008 Jun 24;105(25):8585-90. doi: 10.1073/pnas.0803233105. Epub 2008 Jun 18.
PTEN is a tumor suppressor frequently mutated in cancer. Recent reports implicated Nedd4-1 as the E3 ubiquitin ligase for PTEN that regulates its stability and nuclear localization. We tested the physiological role of Nedd4-1 as a PTEN regulator by using cells and tissues derived from two independently generated strains of mice with their Nedd4-1 gene disrupted. PTEN stability and ubiquitination were indistinguishable between the wild-type and Nedd4-1-deficient cells, and an interaction between the two proteins could not be detected. Moreover, PTEN subcellular distribution, showing prominent cytoplasmic and nuclear staining, was independent of Nedd4-1 presence. Finally, activation of PKB/Akt, a major downstream target of cytoplasmic PTEN activity, and the ability of PTEN to transactivate the Rad51 promoter, a measure of its nuclear function, were unaffected by the loss of Nedd4-1. Taken together, our results fail to support a role for Nedd4-1 as the E3 ligase regulating PTEN stability and subcellular localization.
PTEN是一种在癌症中经常发生突变的肿瘤抑制因子。最近的报道表明Nedd4-1是PTEN的E3泛素连接酶，可调节其稳定性和核定位。我们通过使用来自两个独立生成的Nedd4-1基因被破坏的小鼠品系的细胞和组织，测试了Nedd4-1作为PTEN调节剂的生理作用。野生型细胞和Nedd4-1缺陷型细胞之间PTEN的稳定性和泛素化没有区别，并且未检测到这两种蛋白质之间的相互作用。此外，PTEN的亚细胞分布显示出明显的细胞质和细胞核染色，与Nedd4-1的存在无关。最后，细胞质PTEN活性的主要下游靶点PKB/Akt的激活以及PTEN反式激活Rad51启动子的能力（衡量其核功能的指标）不受Nedd4-1缺失的影响。综上所述，我们的结果不支持Nedd4-1作为调节PTEN稳定性和亚细胞定位的E3连接酶的作用。
