Nuclear localization signal-independent and importin/karyopherin-independent nuclear import of β-catenin
Nuclear localization signal-independent and importin/karyopherin-independent nuclear import of β-catenin
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DOI：
10.1016/s0960-9822(98)70082-x
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发表时间：
1998-02-12
期刊：
影响因子：
9.2
通讯作者：
Gumbiner, BM
中科院分区：
文献类型：
--
作者：
Fagotto, F;Glück, U;Gumbiner, BM
背景：控制特定蛋白质的核定位是调节许多信号转导途径的重要机制。在Wnt信号通路激活后，β-连环蛋白定位于细胞核中并与TCF/LEF-1（T细胞因子/淋巴细胞增强因子-1）转录因子相互作用，触发下游基因的激活。β-连环蛋白没有核定位序列（NLS）。尽管已有报道β-连环蛋白可以通过与TCF/LEF-1结合而背驮到细胞核中，但有证据表明其在体内的输入不依赖于TCF/LEF-1。因此，β-连环蛋白核定位的机制仍有待建立。结果：我们分析了β-连环蛋白核进口在体外试验中使用透化细胞。β-连环蛋白在没有其它胞质因子的情况下特异性地停靠在核膜上。对接不受NLS肽的抑制，并且不需要输入蛋白/核转运蛋白（经典NLS底物的受体）。相反，对接被输入蛋白-β/β-核转运蛋白特异性竞争，表明β-连环蛋白和输入蛋白-β/β-核转运蛋白都与共同的核孔组分相互作用。β-连环蛋白的核转位是能量依赖性的，并且被不可水解的GTP类似物和Ran GTP酶的显性负突变形式抑制。胞浆制剂含有β-catenin输入的抑制活性，不同于importin-beta/beta-karyopherin的竞争，并可能参与生理调节pathway.Conclusions：β-catenin是通过直接结合到核孔机制，类似于importin-beta/beta-karyopherin或其他importin-beta样输入因子，如transportin。这些发现为β-连环蛋白如何在没有NLS的情况下定位于细胞核并且独立于其与TCF/LEF-1的相互作用提供了解释。这是一个新的和不寻常的机制，核输入的信号转导蛋白。β-连环蛋白输入活性的存在下，正常的胞质溶胶的缺乏表明，其进口可能是由Wnt信号通路的上游事件进行调节。(C)当前生物有限公司
Background: Control of the nuclear localization of specific proteins is an important mechanism for regulating many signal transduction pathways. Upon activation of the Wnt signaling pathway, beta-catenin localizes into the nucleus and interacts with TCF/LEF-1 (T-cell factor/lymphocyte enhancer factor-1) transcription factors, triggering activation of downstream genes, The role of regulated nuclear localization in beta-catenin signaling is still unclear. beta-catenin has no nuclear localization sequence (NLS). Although it has been reported that beta-catenin can piggyback into the nucleus by binding to TCF/LEF-1, there is evidence that its import is independent of TCF/LEF-1 in vivo. Therefore, the mechanism for beta-catenin nuclear localization remains to be established.Results: We have analyzed beta-catenin nuclear import in an in vitro assay using permeabilized cells. beta-catenin docks specifically onto the nuclear envelope in the absence of other cytosolic factors. Docking is not inhibited by an NLS peptide and does not require importins/karyopherins, the receptors for classical NLS substrates, Rather, docking is specifically competed by importin-beta/beta-karyopherin, indicating that beta-catenin and importin-beta/beta-karyopherin both interact with common nuclear pore components. Nuclear translocation of beta-catenin is energy dependent and is inhibited by nonhydrolyzable GTP analogs and by a dominant-negative mutant form of the Ran GTPase. Cytosol preparations contain inhibitory activities for beta-catenin import that ale distinct from the competition by importin-beta/beta-karyopherin and may be involved in the physiological regulation of the pathway.Conclusions: beta-catenin is imported into the nucleus by binding directly to the nuclear pore machinery, similar to importin-beta/beta-karyopherin or other importin-beta-like import factors, such as transportin. These findings provide an explanation for how beta-catenin localizes to the nucleus without an NLS and independently of its interaction with TCF/LEF-1. This is a new and unusual mechanism for the nuclear import of a signal transduction protein. The lack of beta-catenin import activity in the presence of normal cytosol suggests that its import may be regulated by upstream events in the Wnt signaling pathway. (C) Current Biology Ltd.