BAG3 蛋白Ser187磷酸化位点定点突变促进FRO细胞迁移和侵袭

Bcl-2相关抗凋亡蛋白3（Bcl-2 associated athanogene 3,BAG3）是BAG家族的重要成员,调节肿瘤细胞的黏附、迁移和侵袭,促进恶性肿瘤的复发和转移。我们的前期工作证明,PKCδ可催化BAG3的Ser187位点磷酸化。本文研究BAG3蛋白磷酸化修饰对甲状腺癌FRO 细胞迁移、侵袭的影响及其可能机制。通过定点突变的方法,将BAG3蛋白的187位丝氨酸突变为天冬氨酸（S187D）模拟磷酸化,或者将丝氨酸突变为丙氨酸（S187A）抵抗磷酸化,从而间接推测BAG3蛋白Ser187位点磷酸化对FRO细胞迁移、侵袭的影响。 FRO细胞转染野生型BAG3、模拟磷酸化型BAG3、阻碍磷酸化型BAG3,通过划痕愈合实验和Transwell转移小室实验,观察BAG3蛋白磷酸化对FRO细胞迁移、侵袭的影响。进一步通过PKC激活剂和抑制剂,研究BAG3蛋白磷酸化对FRO细胞迁移、侵袭影响的机制。 结果显示,FRO BAG3-S187D模拟磷酸化组细胞在培养24 h、48 h时,划痕愈合率分别达到35%和80%。Transwell及三维Matrigel转移小室实验显示,平均每个视野穿膜细胞数分别达到180和350个,与对照组相比,差异有统计学意义（P<0.05）。PKC激活剂TPA及抑制剂Rottelerin处理FRO WT-BAG3细胞,24 h愈合率分别为40% 和15%,48 h划痕愈合率分别为55%和18%,Transwell穿膜细胞数分别为240和70个,与对照组细胞相比,差异显著（P<0.05）。本研究提示,BAG3蛋白Ser187磷酸化修饰,可促进甲状腺癌FRO细胞迁移、侵袭,其机制可能与PKC信号通路有关。     

粗糙脉孢菌转录因子LAH-3参与渗透压调控

【目的】通过构建转录因子lah-3基因缺失突变体,研究lah-3基因缺失突变体菌株的渗透压表型,进而探究lah-3基因在渗透压调控中的作用。【方法】采用同源基因重组敲除技术构建lah-3基因缺失突变体。用4%NaCl和1 mol/L Sorbitol进行渗透压处理。利用Northern blot检测渗透压应答基因的表达。利用Westhern blot检测LAH-3蛋白磷酸化修饰水平,OS-2蛋白的表达水平及其磷酸化修饰水平。【结果】在转录因子lah-3基因缺失突变体中,渗透压应答基因gcy-1、stl-1以及pck-1的表达水平都明显降低,而且在渗透压刺激下,LAH-3蛋白磷酸化修饰水平升高。LAH-3的磷酸化修饰不受OS-2调控。lah-3基因的缺失既不影响OS-2蛋白的表达水平,也不影响其在渗透压刺激后的磷酸化修饰。【结论】粗糙脉孢菌中转录因子LAH-3参与调控渗透压应答基因的转录,但其响应过程不依赖于OS-2 MAPK信号通路。     

细胞基质Ⅰ型胶原通过调控β-catenin促进头颈鳞癌细胞转移和增殖

为探讨细胞基质Ⅰ型胶原(Col-Ⅰ)对头颈鳞癌细胞转移和增殖能力的影响,以头颈鳞癌细胞株为对象,运用transwell小室检查细胞的体外迁移能力,用倒置显微镜成像系统检测细胞的运动速度和扩散能力,Western blotting或/和免疫细胞荧光染色检测细胞表面黏附分子E-cadherin的表达和β-catenin的细胞定位,采用MTT以及PCNA的表达水平评价细胞增殖.结果显示,Col-Ⅰ能够促进头颈鳞癌细胞迁移、提高细胞运动速度、加快细胞扩散,其可能机制是通过上调β-连环蛋白磷酸化,从而下调黏附蛋白E-cadherin的表达.Col-Ⅰ还能促进头颈鳞癌细胞的增殖,其可能机制是增加β-catenin的核移位,提高细胞周期蛋白D1(cyclin D1)表达.研究结果表明,Col-Ⅰ通过上调β-catenin磷酸化水平,以及促进β-catenin核移位,从而增强头颈鳞癌细胞的转移和增殖能力.     

积雪草对转染TGF-β1基因的大鼠肾小球系膜细胞Smad 2/3、Smad 7和胶原蛋白Ⅳ表达的影响

目的：通过细胞转基因技术,获得稳定表达转化生长因子β1（TGF-β1）的系膜细胞（MC）克隆,观察积雪草（CA）对Smad 2/3、Smad 7和胶原蛋白1V表达及Smad 2/3磷酸化的影响。方法：采用脂质体的方法将TGF-β1表达质粒转入MC细胞,采用G418筛选并建立稳定表达TGF-β1的细胞株。将MC细胞株分为3组：对照组（未转染TGFβ1的MC+RPMI 1640+10%正常大鼠血清）,TGF-β1转染组（稳定表达TGF-β1的MC+RPMI 1640+10%正常大鼠血清）,积雪草（CA）组：稳定表达TGF-β1的MC+RPMI 1640+10%含高浓度CA的大鼠血清。实验重复5次。ELISA法检测各组培养上清中TGF-β1和胶原Ⅳ的含量;RT-PCR方法检测各组细胞TGF-β1、Smad 2/3、Smad 7的mRNA表达水平;Western印迹法检测各组细胞TGF-β1、Smad 2/3、p-Smad 2/3、Smad 7、胶原Ⅳ的蛋白质水平。结果：TGF-β1转染组细胞上清液中的TGF-β1和胶原蛋白Ⅳ水平显著升高,积雪草能显著降低TGF-β1和胶原蛋白Ⅳ水平;TGF-β1转染组细胞中TGF-β1、Smad 2/3的mRNA和蛋白质表达水平及Smad 2/3的磷酸化水平均显著升高,而CA可显著降低MC细胞中TGF-β1、Smad 2/3的mRNA和蛋白质表达水平及Smad 2/3的磷酸化水平;TGF-β1转染组细胞中的Smad 7 mRNA水平显著降低,而CA能使Smad 7的mRNA水平显著升高。结论：稳定表达TGF-β1的MC细胞能激活TGFβ1/Smad信号通路,并引起胶原蛋白Ⅳ表达增加,而CA通过抑制此通路的激活,进而抑制胶原蛋白Ⅳ的表达而减缓糖尿病肾病（DN）的发生。     

ANGPTL8调控糖代谢作用机制研究

探讨ANGPTL8在胰岛素作用下对人肝细胞糖代谢影响及可能的作用机制。利用尾静脉水动力转染证实在小鼠肝脏过表达ANGPTL8可提高进食期糖耐受;在Hep G2细胞中利用q PCR检测进食的主要调控因素胰岛素、葡萄糖等对ANGPTL8表达影响,发现单独的葡萄糖或胰岛素对ANGPTL8表达影响不明显,而葡萄糖和胰岛素组合可显著促进ANGPTL8表达;利用Western blotting分析在ANGPTL8敲除(ANGPTL8-/-)和ANGPTL8稳定过表达(ANGPTL8++)的Hep G2细胞中胰岛素介导PI3K/AKT信号通路蛋白及其蛋白磷酸化表达差异,结果显示ANGPTL8可上调胰岛素介导的AKT信号通路中AKT、GSK-3β、Fox O1蛋白磷酸化;PAS染色分析ANGPTL8可促进胰岛素介导的糖原合成。     

糖原合酶激酶-3β与帕金森病的发生及治疗

糖原合酶激酶-3β（glycogen synthase kinase-3β,GSK-3β）是调控糖 原代谢的主要激酶.它可以使多种底物蛋白磷酸化,参与调节细胞增殖、细胞分化和细胞凋亡.最 近研究表明,GSK-3β与帕金森病发生密切相关. 在帕金森病研究模型中,GSK-3β活性增高,诱导多巴胺能神经元凋亡;而GSK-3β活性被抑制时,tau蛋白磷酸化减少,α共核蛋白表达降低,神经元得到保护.因此,GSK-3 β可能成为帕金森病治疗的新靶点.     

利用碱性磷酸酶初步判定二维电泳中蛋白质磷酸化修饰

磷酸化是蛋白质最重要的翻译后修饰形式之一.以二维电泳为基础的蛋白质组学是发现蛋白磷酸化状态改变的有效途径. 本文介绍了在用于二维电泳的蛋白样品制备过程中,利用小牛肠碱性磷酸酶成功去除蛋白质上磷酸基团的过程. 该技术将去磷酸化作用和蛋白质组学手段联系在一起,为蛋白质磷酸化修饰的初步判定提供了简便、经济、切实可行的方法.     

Messl的结构分析和功能研究

Messl是新近鉴定的STE20家族的蛋白激酶.对Messl的基因表达和蛋白功能进行研究,发现其mRNA在鼠组织中广泛分布,但在不同细胞系中表达显著不同;结构分析表明,MeSSl蛋白N端是保守的STE20样激酶催化区,C端是高度亲水的酸性调节区,包含多个潜在的丝氨酸/苏氨酸磷酸化调节位点.哺乳动物细胞表达的MeSSl对MBP显示出激酶活性,并发生自主磷酸化.essl可被砷酸盐应激激活,但丝裂原EGF刺激无活化效应.表明Messl可能在蛋白磷酸化的早期过程中发挥作用,介导细胞对严重应激刺激引起的特异性反应.     

稳定表达小鼠CD40L的NIH3T3细胞系的建立及其在B细胞培养和激活中的应用

该研究构建小鼠CD40L真核表达重组质粒pcDNA3.1-mCD40L,通过电转法将重组质粒转至NIH3T3细胞中。利用G418对转染后细胞进行压力筛选,获得稳定转染细胞株。提取稳定转染细胞株RNA,通过RT-PCR法检测Neo基因的mRNA表达情况。分离稳定转染细胞上清,利用ELISA法检测小鼠CD40L蛋白水平的表达情况。RT-PCR结果显示,Neo基因能够在稳定转染细胞中表达,ELISA结果显示,获得的稳定转染细胞株NIH3T3-mCD40L细胞上清中CD40L的表达量高达1.286 ng/mL。进一步活性研究表明,该细胞系能够在体外与IL-2和IL-21共同作用培养B细胞至14天,并刺激B细胞产生特异性抗体。该细胞系的成功构建,为利用体外B细胞分离培养和活化法分离特异性单克隆抗体奠定了良好的基础。     

带Myc标签的人B55α真核表达载体的构建及其生物学功能

目的:构建带有Myc标签的人B55α真核表达载体,获得Myc-B55α融合蛋白,并初步检测其生物学功能。方法:以本实验室保存的乳腺文库为模板,采用PCR技术扩增出B55α编码序列,将其插入p XJ-40-myc载体,Western印迹检测其表达情况;将重组质粒与空载体分别转染人胚肾293T细胞,通过Western印迹检测B55α蛋白表达水平及其对AKT磷酸化的影响;免疫共沉淀实验检测B55α与AKT是否存在相互作用。结果:双酶切和测序结果表明Myc-B55α真核表达质粒构建成功;Western印迹证实转染293T细胞后Myc-B55α融合蛋白获得表达,并可抑制AKT308的磷酸化;免疫共沉淀结果表明B55α与AKT存在相互作用。结论:构建了带Myc标签的人B55α真核表达载体,为进一步研究B55α在蛋白磷酸化修饰功能中的作用奠定了基础。     

Inhibition of mTORC1 induces loss of E-cadherin through AKT/GSK-3β signaling-mediated upregulation of E-cadherin repressor complexes in non-small cell lung cancer cells

Background

mTOR, which can form mTOR Complex 1 (mTORC1) or mTOR Complex 2 (mTORC2) depending on its binding partners, is frequently deregulated in the pulmonary neoplastic conditions and interstitial lung diseases of the patients treated with rapalogs. In this study, we investigated the relationship between mTOR signaling and epithelial mesenchymal transition (EMT) by dissecting mTOR pathways.

Methods

Components of mTOR signaling pathway were silenced by shRNA in a panel of non-small cell lung cancer cell lines and protein expression of epithelial and mesenchymal markers were evaluated by immunoblotting and immunocytochemistry. mRNA level of the E-cadherin repressor complexes were evaluated by qRT-PCR.

Results

IGF-1 treatment decreased expression of the E-cadherin and rapamycin increased its expression, suggesting hyperactivation of mTOR signaling relates to the loss of E-cadherin. Genetic ablation of rapamycin-insensitive companion of mTOR (Rictor), a component of mTORC2, did not influence E-cadherin expression, whereas genetic ablation of regulatory-associated protein of mTOR (Raptor), a component of mTORC1, led to a decrease in E-cadherin expression at the mRNA level. Increased phosphorylation of AKT at Ser473 and GSK-3β at Ser9 were observed in the Raptor-silenced NSCLC cells. Of the E-cadherin repressor complexes tested, Snail, Zeb2, and Twist1 mRNAs were elevated in raptor-silenced A549 cells, and Zeb2 and Twist1 mRNAs were elevated in Raptor-silenced H2009 cells. These findings were recapitulated by treatment with the GSK-3β inhibitor, LiCl. Raptor knockdown A549 cells showed increased expression of N-cadherin and vimentin with mesenchymal phenotypic changes.

Conclusions

In conclusion, selective inhibition of mTORC1 leads to hyperactivation of the AKT/GSK-3β pathway, inducing E-cadherin repressor complexes and EMT. These findings imply the existence of a feedback inhibition loop of mTORC1 onto mTORC2 that plays a role in the homeostasis of E-cadherin expression and EMT, requiring caution in the clinical use of rapalog and selective mTORC1 inhibitors.     

TGF-β1 induces human alveolar epithelial to mesenchymal cell transition (EMT)

Background

Fibroblastic foci are characteristic features in lung parenchyma of patients with idiopathic pulmonary fibrosis (IPF). They comprise aggregates of mesenchymal cells which underlie sites of unresolved epithelial injury and are associated with progression of fibrosis. However, the cellular origins of these mesenchymal phenotypes remain unclear. We examined whether the potent fibrogenic cytokine TGF-β1 could induce epithelial mesenchymal transition (EMT) in the human alveolar epithelial cell line, A549, and investigated the signaling pathway of TGF-β1-mediated EMT.

Methods

A549 cells were examined for evidence of EMT after treatment with TGF-β1. EMT was assessed by: morphology under phase-contrast microscopy; Western analysis of cell lysates for expression of mesenchymal phenotypic markers including fibronectin EDA (Fn-EDA), and expression of epithelial phenotypic markers including E-cadherin (E-cad). Markers of fibrogenesis, including collagens and connective tissue growth factor (CTGF) were also evaluated by measuring mRNA level using RT-PCR, and protein by immunofluorescence or Western blotting. Signaling pathways for EMT were characterized by Western analysis of cell lysates using monoclonal antibodies to detect phosphorylated Erk1/2 and Smad2 after TGF-β1 treatment in the presence or absence of MEK inhibitors. The role of Smad2 in TGF-β1-mediated EMT was investigated using siRNA.

Results

The data showed that TGF-β1, but not TNF-α or IL-1β, induced A549 cells with an alveolar epithelial type II cell phenotype to undergo EMT in a time-and concentration-dependent manner. The process of EMT was accompanied by morphological alteration and expression of the fibroblast phenotypic markers Fn-EDA and vimentin, concomitant with a downregulation of the epithelial phenotype marker E-cad. Furthermore, cells that had undergone EMT showed enhanced expression of markers of fibrogenesis including collagens type I and III and CTGF. MMP-2 expression was also evidenced. TGF-β1-induced EMT occurred through phosphorylation of Smad2 and was inhibited by Smad2 gene silencing; MEK inhibitors failed to attenuate either EMT-associated Smad2 phosphorylation or the observed phenotypic changes.

Conclusion

Our study shows that TGF-β1 induces A549 alveolar epithelial cells to undergo EMT via Smad2 activation. Our data support the concept of EMT in lung epithelial cells, and suggest the need for further studies to investigate the phenomenon.