Nucleoredoxin Sustains Wnt/β-Catenin Signaling by Retaining a Pool of Inactive Dishevelled Protein
Nucleoredoxin Sustains Wnt/β-Catenin Signaling by Retaining a Pool of Inactive Dishevelled Protein
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DOI：
10.1016/j.cub.2010.09.065
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发表时间：
2010-11-09
期刊：
影响因子：
9.2
通讯作者：
Miki, Hiroaki
中科院分区：
文献类型：
--
作者：
Funato, Yosuke;Terabayashi, Takeshi;Miki, Hiroaki
Wnt信号通路的一个重要组成部分DVI的过度表达经常与肿瘤相关[1，2]，因此必须严格控制DVI的蛋白水平才能维持Wnt信号而不会导致肿瘤。Kelch-like 12(KLHL12)针对DVI泛素化和降解[3]，表明其在避免异常DVI过度表达方面的潜在重要性。然而，KLHL12活性的调控机制仍然难以捉摸。我们在这里表明，核氧还蛋白(NRX)决定了DVI蛋白水平，这是通过对表现出骨骼和心血管缺陷的NRX-/-小鼠的分析揭示的。与先前报道的NRX抑制DVI功能一致[4]，Wnt/β-catenin信号在NRX-/-成骨细胞中被过度激活。然而，在高表达KLHL12的心肌细胞中，信号活性受到抑制。生化分析表明，在NRX-/-小鼠胚胎成纤维细胞中，DVI被加速的泛素化迅速降解，并且它们无法激活Wnt配体反应的Wnt/β-catenin信号。此外，利用纯化蛋白的实验表明，NRX可以将KLHL12从DVI中排出，并抑制泛素化。这些发现揭示了NRX的一项意想不到的功能，它保留了一个不活跃的DVI池，用于在Wnt刺激时强大地激活Wnt/β-catenin信号。
Overexpression of Dishevelled (DvI), an essential component of the Wnt signaling pathway, is frequently associated with tumors [1, 2], and thus the DvI protein level must be tightly controlled to sustain Wnt signaling without causing tumors. Kelch-like 12 (KLHL12) targets DvI for ubiquitination and degradation [3], suggesting its potential importance in avoiding aberrant DvI overexpression. However, the regulatory mechanism of the KLHL12 activity remained elusive. We show here that nucleoredoxin (NRX) determines the DvI protein level, which is revealed by analyses on NRX-/- mice showing skeletal and cardiovascular defects. Consistent with the previously reported DvI-inhibiting function of NRX [4], Wnt/beta-catenin signaling is hyperactivated in NRX-/- osteoblasts. However, the signal activity is suppressed in cardiac cells, where KLHL12 is highly expressed. Biochemical analyses reveal that DvI is rapidly degraded by accelerated ubiquitination in NRX-/- mouse embryonic fibroblasts, and they fail to activate Wnt/beta-catenin signaling in response to Wnt ligands. Moreover, experiments utilizing purified proteins show that NRX expels KLHL12 from DvI and inhibits ubiquitination. These findings reveal an unexpected function of NRX, retaining a pool of inactive DvI for robust activation of Wnt/beta-catenin signaling upon Wnt stimulation.