NEDD4-2 (neural precursor cell expressed, developmentally down-regulated 4-2) negatively regulates TGF-ß (transforming growth factor-β) signalling by inducing ubiquitin-mediated degradation of Smad2 and TGF-β type I receptor
NEDD4-2 (neural precursor cell expressed, developmentally down-regulated 4-2) negatively regulates TGF-ß (transforming growth factor-β) signalling by inducing ubiquitin-mediated degradation of Smad2 and TGF-β type I receptor
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DOI：
10.1042/bj20040738
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发表时间：
2005-03-15
影响因子：
4.1
通讯作者：
Imamura, T
中科院分区：
文献类型：
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作者：
Kuratomi, G;Komuro, A;Imamura, T
抑制性Smad，Smad7，是转化生长因子-β超家族信号的有效抑制因子。通过与激活的I型受体结合，它阻止了R-Smads(受体调节的Smads)的激活。为了鉴定Smad7途径的新成分，我们以Smad7为诱饵进行酵母双杂交筛选，确定NEDD4-2(神经前体细胞表达，发育下调的4-2)是Smad7的直接结合伙伴。NEDD4-2在结构上类似于SMurf(Smad泛素调节因子)1和2，这两个先前被认为是R-Smads和TGF-β超家族受体的E3泛素连接酶。NEDD4-2的功能类似于蓝精灵I和2，因为它通过Smad7与转化生长因子-βI型受体结合，并诱导其泛素依赖的降解。此外，NEDD4-2以配体依赖的方式与转化生长因子-β特异性R-Smads结合，诱导Smad2的降解，但不诱导Smad3的降解。然而，与SMurf2相比，NEDD4-2未能诱导SnoN(Ski相关新蛋白N)的泛素化，尽管NEDD4-2通过Smad2与SnoN的结合比SMurf2更强。我们进一步表明，过表达的NEDD4-2可以阻止由转化生长因子-β和骨形态发生蛋白诱导的转录活性，而通过siRNA(小干扰RNA)沉默NEDD4-2基因可以增强对转化生长因子-β超家族细胞因子的反应性。这些数据表明，NEDD4-2是蓝精灵样C2-WW-Hect(WW是Trp-Trp，Hect与E6-附件蛋白同源)型E3泛素连接酶的成员，该连接酶通过与蓝精灵使用的相似但不完全相同的机制对转化生长因子-β超家族信号进行负向调节。
Inhibitory Smad, Smad7, is a potent inhibitor of TGF-beta (transforming growth factor-beta) superfamily signalling. By binding to activated type I receptors, it prevents the activation of R-Smads (receptor-regulated Smads). To identify new components of the Smad pathway, we performed yeast two-hybrid screening using Smad7 as bait, and identified NEDD4-2 (neural precursor cell expressed, developmentally down-regulated 4-2) as a direct binding partner of Smad7. NEDD4-2 is structurally similar to Smurfs (Smad ubiquitin regulatory factors) 1 and 2, which were identified previously as E3 ubiquitin ligases for R-Smads and TGF-beta superfamily receptors. NEDD4-2 functions like Smurfs I and 2 in that it associates with TGF-beta type I receptor via Smad7, and induces its ubiquitin-dependent degradation. Moreover, NEDD4-2 bound to TGF-beta-specific R-Smads, Smads 2 and 3, in a ligand-dependent manner, and induced degradation of Smad2, but not Smad3. However, in contrast with Smurf2, NEDD4-2 failed to induce ubiquitination of SnoN (Ski-related novel protein N), although NEDD4-2 bound to SnoN via Smad2 more strongly than Smurf2. We showed further that overexpressed NEDD4-2 prevents transcriptional activity induced by TGF-beta and BMP, whereas silencing of the NEDD4-2 gene by siRNA (small interfering RNA) resulted in enhancement of the responsiveness to TGF-beta superfamily cytokines. These data suggest that NEDD4-2 is a member of the Smurf-like C2-WW-HECT (WW is Trp-Trp and HECT is homologous to the E6-accessory protein) type E3 ubiquitin ligases, which negatively regulate TGF-beta superfamily signalling through similar, but not identical, mechanisms to those used by Smurfs.