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![[優(yōu)秀文章推薦] 中科院揭示細(xì)胞核內(nèi)Net1調(diào)控TGF-β信號(hào)轉(zhuǎn)導(dǎo)機(jī)制]()
Net1分別作為鳥核苷酸交換因子和適配體蛋白,整合了Wnt/β-catenin和Nodal/Smad2信號(hào)通路
Nodal是TGF-β超家族成員之一,在脊椎動(dòng)物胚胎中內(nèi)胚層誘導(dǎo)、神經(jīng)圖式形成、原腸運(yùn)動(dòng)、內(nèi)臟器官左右不對(duì)稱等發(fā)育過(guò)程中具有廣泛而重要的作用。中國(guó)科學(xué)院動(dòng)物研究所王強(qiáng)研究員領(lǐng)導(dǎo)的研究組主要從事TGF-β家族跨膜信號(hào)轉(zhuǎn)導(dǎo)通路在胚胎早期發(fā)育及組織器官形成中的調(diào)控機(jī)制研究。他們?cè)谠c期斑馬魚胚胎中系統(tǒng)鑒定了Nodal/Smad2信號(hào)的靶基因,其中包括鳥核苷酸交換因子Net1(J Biol Chem. 2011)。Net1蛋白主要位于細(xì)胞核,少量位于細(xì)胞質(zhì),在多種腫瘤細(xì)胞中高表達(dá),通過(guò)激活小G蛋白R(shí)hoA促進(jìn)腫瘤細(xì)胞侵襲和轉(zhuǎn)移。王強(qiáng)研究組的前期研究發(fā)現(xiàn),斑馬魚的net1是MBT前后最早表達(dá)的合子基因之一,特異表達(dá)于預(yù)定背部組織中心。Net1通過(guò)激活RhoA家族的G蛋白,干擾PAK1二聚體的形成,激活PAK1激酶活性,從而磷酸化β-catenin 675位絲氨酸,抑制β-catenin與組蛋白去乙酰化酶HDAC結(jié)合,促進(jìn)Wnt靶基因轉(zhuǎn)錄,在胚胎背部軸建立過(guò)程中發(fā)揮重要作用(Cell Research. 2017)。然而,目前對(duì)于細(xì)胞核內(nèi)Net1的功能還所知甚少!
![[優(yōu)秀文章推薦] 中科院揭示細(xì)胞核內(nèi)Net1調(diào)控TGF-β信號(hào)轉(zhuǎn)導(dǎo)機(jī)制-1]()
Net1 promotes Nodal signal downstream of or parallel to Smad2
TGF-β/Nodal靶基因可以反饋調(diào)控信號(hào)通路。例如TGF-β信號(hào)通路激活2小時(shí),可以顯著增加SnoN 的轉(zhuǎn)錄;另一方面,SnoN可以抑制Smad2及Smad3的磷酸化及Smad復(fù)合體與DNA結(jié)合,是TGF-β信號(hào)通路的抑制因子。因此,做為TGF-β/Nodal信號(hào)通路的靶基因,Net1可能參與了TGF-β信號(hào)通路的調(diào)控。王強(qiáng)研究組的研究發(fā)現(xiàn),在胚胎及哺乳動(dòng)物細(xì)胞中敲低net1后,抑制了TGF-β/Nodal信號(hào)活性,致使中內(nèi)胚層及其衍生器官的形成產(chǎn)生嚴(yán)重缺陷。進(jìn)一步的研究表明,與Net1鳥核苷酸交換因子活性無(wú)關(guān),定位于細(xì)胞核內(nèi)的Net1通過(guò)與Smad2結(jié)合,增強(qiáng)Smad2招募組蛋白乙;竝300的能力,促進(jìn)胚胎中內(nèi)胚層的形成。因此,在脊椎動(dòng)物早期胚胎發(fā)育過(guò)程中,Net1分別做為鳥核苷酸交換因子和適配體蛋白,整合了Wnt/β-catenin和Nodal/Smad2兩種極為重要的信號(hào)通路,在體軸建立和中內(nèi)胚層形成過(guò)程中扮演了關(guān)鍵的角色。鑒于TGF-β、Wnt及Net1在腫瘤細(xì)胞增殖、侵襲和轉(zhuǎn)移中的重要作用,這項(xiàng)研究結(jié)果還為了解相關(guān)腫瘤發(fā)生發(fā)展機(jī)制及腫瘤診治方面開拓了新的思路!
![[優(yōu)秀文章推薦] 中科院揭示細(xì)胞核內(nèi)Net1調(diào)控TGF-β信號(hào)轉(zhuǎn)導(dǎo)機(jī)制-2]()
Net1 increases the affinity of Smad2 for p300
Net1 is a well-characterized oncoprotein with RhoA-specific GEF activity. Oncogenic Net1 lacking the first 145 amino acids is present in the cytosol and contributes to the efficient activation of RhoA and the formation of actin stress fibers in a number of tumor cell types. Meanwhile, wild-type Net1 is predominantly localized in the nucleus at steady state due to its N-terminal nuclear localization sequences, where the function of nuclear Net1 has not been fully determined. Here, we find that zebrafish net1 is expressed specifically in mesendoderm precursors during gastrulation. Endogenous Net1 is located in the nucleus during early embryonic development. Gain- and loss-of-function experiments in zebrafish embryos and mammalian cells demonstrate that, regardless of its GEF activity, nuclear Net1 is critical for zebrafish mesendoderm formation and Nodal/Smad2 signal transduction. Detailed analyses of protein interactions reveal that Net1 associates with Smad2 in the nucleus in a GEF-independent manner, and then promotes Smad2 activation by enhancing recruitment of p300 to the transcriptional complex. These findings describe a novel genetic mechanism by which nuclear Net1 facilitates Smad2 transcriptional activity to guide mesendoderm development. |