Simplet/Fam53b is required for Wnt signal transduction by regulating β-catenin nuclear localization
Simplet/Fam53b is required for Wnt signal transduction by regulating β-catenin nuclear localization
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DOI：
10.1242/dev.108415
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发表时间：
2014-09-01
期刊：
影响因子：
4.6
通讯作者：
Antos, Christopher L.
中科院分区：
文献类型：
--
作者：
Kizil, Caghan;Kuechler, Beate;Antos, Christopher L.
典型β -连环蛋白依赖的Wnt信号转导在许多生物现象中都很重要，如细胞命运决定、细胞增殖、干细胞维持和前后轴形成。典型Wnt信号的标志是β -连环蛋白易位进入细胞核，在那里它激活基因转录。然而，调节-连环蛋白核定位的机制尚不清楚。我们发现Simplet/Fam53B （Smp）通过正向调节β -连环蛋白核定位是wnt信号转导所必需的。在斑马鱼胚胎中，smp的缺失阻断了两种β -连环蛋白依赖报告蛋白的活性和Wnt靶基因的表达，并阻止了β -连环蛋白的核积累。相反，smp的过表达增加了β -连环蛋白在体内和体外的核定位和转录活性。缺乏核定位信号或β -catenin相互作用域的突变体Smp蛋白的表达表明，Smp易位到细胞核中是体内β -catenin核定位和Wnt信号传导的必要条件。我们还提供证据表明哺乳动物Smp参与调节β -连环蛋白核定位：该蛋白与小鼠肠隐窝中β -连环蛋白依赖基因表达共定位；siRNA敲低Smp降低β -连环蛋白的核定位和转录活性；人SMP以剂量依赖的方式介导β -连环蛋白的转录活性；人类的SMP蛋白主要在细胞核中与人的-连环蛋白相互作用。因此，我们的研究结果确定了进化保守的SMP蛋白作为β -连环蛋白依赖性Wnt信号转导的调节剂。
Canonical beta-catenin-dependent Wnt signal transduction is important for several biological phenomena, such as cell fate determination, cell proliferation, stem cell maintenance and anterior-posterior axis formation. The hallmark of canonical Wnt signaling is the translocation of beta-catenin into the nucleus where it activates gene transcription. However, the mechanisms regulating beta-catenin nuclear localization are poorly understood. We show that Simplet/Fam53B (Smp) is required forWnt signaling by positively regulating beta-catenin nuclear localization. In the zebrafish embryo, the loss of smp blocks the activity of two beta-catenin-dependent reporters and the expression of Wnt target genes, and prevents nuclear accumulation of beta-catenin. Conversely, overexpression of smp increases beta-catenin nuclear localization and transcriptional activity in vitro and in vivo. Expression of mutant Smp proteins lacking either the nuclear localization signal or the beta-catenin interaction domain reveal that the translocation of Smp into the nucleus is essential for beta-catenin nuclear localization and Wnt signaling in vivo. We also provide evidence that mammalian Smp is involved in regulating beta-catenin nuclear localization: the protein colocalizes with beta-catenin-dependent gene expression in mouse intestinal crypts; siRNA knockdown of Smp reduces beta-catenin nuclear localization and transcriptional activity; human SMP mediates beta-catenin transcriptional activity in a dose-dependent manner; and the human SMP protein interacts with human beta-catenin primarily in the nucleus. Thus, our findings identify the evolutionary conserved SMP protein as a regulator of beta-catenin-dependent Wnt signal transduction.