胶质细胞系源性神经营养因子促进大鼠中脑多巴胺能神经元存活与分化的机制

目的探讨胶质细胞系源性神经营养因子（GDNF）促进中脑多巴胺（DA）能神经元存活和分化过程中,磷脂酰肌醇3激酶（P13K）信号通路和丝裂原活化蛋白激酶（MAPK）信号通路的可能作用.方法生后大鼠中脑脑片培养,并依培养基内加入的不同物质分为空白对照组、GDNF组、PI3K通路阻断组、MAPK通路阻断组.培养6 d后,进行酪氨酸羟化酶（TH）免疫组织化学染色,光镜观察,计算机辅助图像分析,统计学处理;同时用Western blotting方法检测脑片中TH的表达.结果GDNF组TH表达阳性神经元的形状更趋向成熟,其TH表达阳性神经元的密度、胞体大小和TH的表达水平均显著高于空白对照组;P13K通路阻断组TH表达阳性神经元几乎消失,其TH表达水平显著低于GDNF组而与空白对照组无显著差别;MAPK通路阻断组TH表达阳性神经元的密度及TH表达水平与GDNF组无显著区别,但TH表达阳性神经元胞体显著小于GDNF组.结论P13K通路参与介导GDNF对DA能神经元的促存活作用,而MAPK通路参与介导其促形态学分化作用.     

Akt、ERK1/2活化在脑源性神经营养因子促血管新生中的作用

目的： 探讨脑源性神经营养因子(BDNF) 促进血管新生的作用及其参与的信号通路,为抗肿瘤血管生成的研究提供新的实验依据。 方法: 以人脐静脉内皮细胞为对象,采用Western 印迹方法检测细胞内磷酸化Akt、ERK1/2蛋白质的表达； 采用Transwell小室迁移实验、管腔形成实验评价体外内皮细胞血管新生的能力，MTT法检测内皮细胞增殖 活性，FITC-Annexin-Ⅴ/PI双染流式细胞术分析细胞凋亡。 结果: BDNF以时间依赖性方式激活PI3K/Akt 和MEK1/ERK信号通路。分别应用PI3K激酶抑制剂Ly294002、 MEK1激酶抑制剂PD98059可以明显阻断BDNF对PI3K/Akt、MEK1/ERK信号通路的激活。100 μg/L 的BDNF体 外促内皮细胞血管新生能力与 25 μg/L 血管内皮生长因子（VEGF）相当， 其中BDNF诱导的细胞迁移分 别被Ly294002和PD98059阻断，其抑制率分别约为74%和36%；同样，Ly294002、PD98059可部分阻断BDNF诱 导的小管形成效应，其阻断率分别约57%和37%；而BDNF的促增殖效应仅被PD98059拮抗，抑制凋亡效应仅受Ly294002影响。 结论: BDNF在体外有促血管新生的作用。PI3K/Akt 和MEK1/ERK信号通路以不同机制共同调节这一过程,其中PI3K/Akt信号通路起着更为重要的调节作用。     

Bcl-2和Bad参与GDNF协同雌二醇对多巴胺能神经细胞的保护作用

目的:研究GDNF和雌二醇(E2)联合使用对6-羟基多巴胺(6-OHDA)所致的多巴胺能神经细胞损伤的影响并探讨其作用的机制。方法:新生2~3 d的雄性SD大鼠行常规中脑脑片培养,6-OHDA诱导损伤,脑片分为8组:正常对照组、溶剂对照组、E2组、Wortmannin(PI3-K特异性阻断剂)+E2组、GDNF组、Wortmannin+GDNF组、GDNF+E2组、Wortmannin+GDNF+E2组。免疫荧光染色观察黑质致密部(SNc)酪氨酸羟化酶(TH)的表达情况;Western Blot检测各组脑片中Bcl-2及Bad的表达。结果:免疫荧光染色结果显示,在GDNF+E2组,TH的表达比单用GDNF或E2时显著升高,差异有统计学意义(P<0.05);阻断PI3-K/Akt信号通路后,TH的表达与未阻断组相比降低,差异有统计学意义(P<0.05)。Western Blot检测结果显示,在GDNF+E2组,Bcl-2的表达比单用GDNF或E2时升高,而Bad的表达比单用GDNF或E2时降低,差异均有统计学意义(P<0.05);阻断PI3-K/Akt信号通路后,Bcl-2的表达与未阻断组相比降低,而Bad的表达是升高的,差异有统计学意义(P<0.05)。结论:GDNF和E2联合使用对6-OHDA所致的黑质多巴胺能神经细胞损伤有保护作用,其机制可能是通过调节凋亡相关蛋白Bcl-2和Bad的表达变化实现的。     

NGF促进神经细胞生长发育的信号通路及与哮喘发病的关系

神经生长因子(NGF)作为第一个被发现的神经营养因子,具有促进神经细胞存活和生长发育的作用。NGF结合酪氨酸受体TrkA,引起胞内四条信号通路:Ras/Raf/Erk蛋白激酶通路,磷脂酰肌醇-3激酶(PI3-K)/Akt激酶通路,磷脂酶c(PLC-γ)通路以及SNT。NGF的另一个受体P75神经营养因子受体(P75NTR)的信号通路仍不是十分清楚,但可与TrkA协同作用,也可单独作用促进神经细胞的存活或凋亡。另外,NGF介导下TrkA的信号通路与哮喘的发病之间有着密切的联系。本文主要就NGF与TrkA和P75NTR蛋白结合后,胞内传导系统及尚待研究解决的问题进行综述。     

Ras／Raf／MEK／Erk通路调控细胞功能的机制

Ras/Raf/MEK/Erk信号传递通路为近年来细胞信号转导方面最活跃的研究领域。很多研究表明该通路具有调控细胞增殖,分化等功能,但其如何发挥这些功能一直为人们所关注。大量的研究报道说明该通路行使不同功能与其组成成员的活化程度以及不同的效应因子如p21cip1表达紧密相关。     

大黄酸哌嗪雌酚酮抑制人成骨样MG-63细胞分泌IL-6分子机制的研究

目的探讨大黄酸哌嗪雌酚酮(rhein-piperizinyl-estrone,命名为LC)调节人成骨样MG-63细胞分泌IL-6的分子机制。方法在原工作基础上,选择兼有2种雌激素受体(estrogen receptor,ER)亚型表达的人成骨样MG-63细胞为研究模型,采用ELISA、RT-PCR及荧光素酶报告基因检测、小RNA干扰及免疫印迹等技术,探讨LC对人成骨细胞产生的骨吸收调节因子IL-6表达的作用及作用机制。结果 LC可抑制MG-63细胞IL-6表达和IL-6基因启动子的转录活性,该作用可被纯ER阻断剂ICI182,780完全阻断,应用小RNA干扰技术进一步证实LC对成骨细胞IL-6产生的抑制作用是由ERα和ERβ共同介导的。PD98059(MEK1/2抑制剂)和Wortmannin(PI3K抑制剂)可分别阻断LC诱导的成骨细胞ERK和Akt的活化作用。结论 LC抑制成骨细胞产生IL-6是经ER途径、由ERα和ERβ共同介导的,LC还可通过活化Ras/MEK/ERK和PI3K/Akt信号通路对成骨细胞发挥作用。     

白细胞介素-6信号通路在银屑病发病机制中的研究进展

银屑病是一种病因不明的自身免疫性炎症性多基因遗传的皮肤疾病,其病理变化的形成需要多种信号通路和细胞因子的共同参与.近年来关于银屑病相关细胞因子信号转导通路及细胞调控信号的研究受到广泛关注,其中IL-6触发的三条途径,包括Ras/Raf/MEK/ERK途径、PI3K/AKt途径和JAK/STAT途径,共同促进银屑病角质形成细胞增殖、炎症反应及血管生成等病理变化;下面针对IL-6信号通路在银屑病发病机制中的研究进展做一综述.     

bFGF对卵巢癌CAOV3细胞Bcl-2、Bcl-xl、Bax、Bad表达的影响

目的研究bFGF调控卵巢癌CAOV3凋亡的信号通路及对Bcl-2、Bcl-xl、Bax、Bad表达的影响。方法无血清饥饿诱导细胞凋亡。分为饥饿对照、bFGF、bFGF PD98059、bFGF Wortmannin组。流式细胞术、DNA Ladder检测细胞凋亡;Western印迹法检测ERK、PKB、Bad活性以及Bcl-2、Bax表达,RT- PCR检测Bcl-2、Bcl-xl mRNA变化。结果bFGF促进p-ERK、p-PKB、p-Bad、Bcl-2表达,抑制Bax表达及饥饿诱导的细胞凋亡。激酶抑制剂PD98059可抑制bFGF对ERK、Bcl-2、Bax的调节作用,Wortmannin可抑制bFGF对PKB、Bad、Bax的调控作用,二者均可阻断bFGF对凋亡的抑制作用。bFGF对Bcl-xl表达无影响。结论bFGF可能通过激活MEK/ERK、P13K/PKB信号途径通路调节Bcl-2、Bax、Bad表达,抑制饥饿诱导的卵巢癌CAOV3细胞凋亡。     

转化生长因子β1促进骨髓间充质干细胞Snail表达的信号转导通路

目的 探讨细胞外信号调节激酶1/2(ERK1/2)和磷脂酰肌醇3-激酶(PI3K)-Akt信号转导通路在转化生长因子β1(TGF-β1)引起骨髓间充质干细胞(BMSCs)Snail表达改变中的调控作用. 方法 采用密度梯度离心结合贴壁法分离、培养大鼠BMSCs,用免疫荧光法对培养第3代的细胞进行鉴定.应用Western blotting检测TGF-β1对p-ERK1/2及p-Akt表达的影响,以不同浓度ERK特异性抑制剂(PD98059)或PI3K通路特异性抑制剂(Wortmannin)干预后检测BMSCs ERK、Akt磷酸化水平变化,确定PD98059和Wortmannin分别抑制Snail诱导的BMSCs ERK和Akt磷酸化的有效浓度,进而用RT-PCR、Western blotting技术证实TGF-β1诱导骨髓间充质干细胞Snail mRNA及蛋白表达的影响. 结果 密度梯度离心结合贴壁法能有效分离、纯化大鼠BMSCs,免疫荧光检测显示,培养的细胞CD29、CD44表达阳性,而CD34、CD45表达阴性;Western blotting分析显示,TGF-β1作用6h后BMSCs p-Akt和p-ERK水平较对照组明显增高;Wortmannin和PD98059可分别以剂量依赖性抑制BMSCs p-Akt和p-ERK水平;可有效抑制TGF-β1诱导的BMSCs ERK及Akt的磷酸化,PD98059和Wortmannin相应浓度分别为30 μmol/L和40 nmol/L.PD98059(30 μmol/L)、Wortmannin(40 nmol/L)明显抑制了TGF-β1诱导的Snail mRNA及蛋白水平,而两者联合应用对骨髓间充质干细胞Snail mRNA及蛋白表达的抑制作用具有协同作用,与对照组相比,差异有统计学意义(P<0.05). 结论 TGF-β1能促进BMSCs的Snail的转录及蛋白的表达,且ERK1/2及PI3K转导通路的激活在此过程中具有调控作用.     

内源性IL-8诱导卵巢癌细胞对顺铂与紫杉醇产生耐药的机制研究

目的探讨内源性IL-8诱导卵巢癌细胞对顺铂和紫杉醇产生耐药的机制及相关信号转导通路。方法在原有工作基础上,以2种人卵巢癌细胞系A2780(不分泌IL-8,对顺铂、紫杉醇敏感)和SKOV-3(高分泌IL-8,对顺铂、紫杉醇耐药)为研究模型,分别将正义(sense,ss)IL-8基因或反义(antisense,as)IL-8基因稳定转染至A2780细胞或SKOV3细胞,应用MTT法、Caspase-3活性测定、RT-PCR及Western blot技术等观察内源性IL-8是否影响卵巢癌细胞对顺铂和紫杉醇的敏感性,并对其作用的机制和可能的信号传导通路进行研究。结果 1)内源性过表达IL-8可诱导A2780细胞对顺铂和紫杉醇产生耐药,而抑制IL-8表达可恢复SKOV3细胞对顺铂和紫杉醇的敏感性,IL-8诱导的卵巢癌细胞化疗耐药是通过降低Caspase-3活性来实现的;2)内源性过表达IL-8可上调A2780细胞的耐药相关基因MDR1和凋亡抑制基因Bcl-2、Bcl-xL及XIAP的表达,而抑制IL-8表达可使上述基因的表达明显降低;3)Wortmannin(PI3K抑制剂)和PD98059(MEK1/2抑制剂)能分别阻断IL-8诱导下卵巢癌细胞的Akt和ERK活化及化疗耐药作用。结论 IL-8诱导的卵巢癌细胞化疗耐药可能与其上调耐药相关基因MDR1和凋亡抑制基因Bcl-2、Bcl-xL及XIAP的表达以及活化Raf/MEK/ERK和PI3K/Akt信号通路相关,提示调节IL-8表达或其相关信号通路可能是治疗耐药性卵巢癌的一种良好策略。     

CD19 signal transduction in normal human B cells: linkage to downstream pathways requires phosphatidylinositol 3-kinase, protein kinase C and Ca2+

CD19 is required for normal antibody responses in mice. We have shown that CD19 enhances the activation of extracellular signal-regulated kinase (ERK) 2 by membrane (m) IgM but otherwise little is known of CD19 signaling in primary human cells. We now ask which pathways link CD19 with ERK2 in human tonsillar B cells. In analyses of signaling intermediates, the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin partially suppressed the release of Ca2+ induced by coligation of CD19 and mIgM but the selective PKC inhibitor bisindolylmaleimide I (BIM-I) did not. The Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, BIM-I and wortmannin each had only a small effect on ERK2 activation induced by surface IgM alone but blocked the enhancement of that activation by CD1 9/mIgM coligation. To analyze the mitogen-activated protein kinase (MAPK) cascade, we measured activation of Raf, MAPK- or ERK kinase (MEK) 1 and ERK2. CD19 consistently enhanced activation of ERK2 and MEK1. However, synergistic activation of Raf was variably observed. In subpopulation analyses, synergistic activation of Raf1 was consistently observed in the IgDlow but not in the IgDhigh cells. Thus, in normal human B cells, PI3K is upstream of the Ca2+ response while PI3K, Ca2+ release and protein kinase C are all required for ERK2 activation, and CD19 enhances the MAPK cascade at multiple levels, depending on the state of differentiation.     

Targets of p56(lck) activity in immature thymoblasts: stimulation of the Ras/Raf/MAPK pathway

Previous studies suggest that p56(lck) activity influences thymocyte development at a stage prior to TCR alphabeta expression. Transgenic mice that express high levels of p56(lck) activity during thymopoiesis develop thymic lymphomas consisting of cells with immature surface phenotypes. We have utilized cell lines derived from lck-induced thymic tumors to define biochemical pathways regulated by p56(lck) activity in immature thymocytes. Here we report that components of the Ras/Raf/MAPK pathway are constitutively activated in these lck-transformed immature thymoblasts. p56(lck) utilizes Shc and Grb2 adaptors to mediate activation of p21(ras) in the thymoblast lines by promoting tyrosine phosphorylation of the Shc protein and constitutive interaction between Shc and Grb2. The putative guanine nucleotide exchange factor p95(vav) is also maintained in constitutively tyrosine phosphorylated form as a result of elevated Lck activity. One target of activated Ras, the Raf-1 kinase, is hyperphosphorylated and downstream targets of activated Raf- 1, Erk1 and Erk2, are hyperphosphorylated and activated in Lck- transformed thymocytes. Forskolin treatment reverses Raf-1 hyperphosphorylation in the cells and inhibits proliferation by blocking G1/S transition. In contrast, conventional protein tyrosine kinase inhibitors block proliferation by arresting Lck thymoblasts at G2/M. Lck-mediated stimulation of the Ras/Raf/MAPK pathway is also required to maintain cell viability by preventing programmed cell death. In summary, p56(lck) activity stimulates G1/S transition in immature thymoblasts and maintains cell viability via transduction of constitutive activation signals downstream to components of the Ras/Raf/MAPK pathway.      

Interplay of T-cell receptor and interleukin-2 signalling in V��2V��2 T-cell cytotoxicity

Human peripheral blood Vγ2Vδ2 T cells are important for host defence and tumour immunity. Their unusual T‐cell receptor (TCR) recognizes small molecule phosphoantigens; stimulated cells produce inflammatory cytokines and are potently cytotoxic for a variety of tumours. However, molecular mechanisms linking phosphoantigen stimulation and cytotoxicity are incompletely understood. We know that isopentenyl pyrophosphate (IPP) activates mitogen‐activated protein kinase kinase/extracellular signal‐regulated kinase (MEK/Erk) and phosphoinositide 3‐kinase (PI‐3K)/Akt pathways; specific inhibition of Erk or Akt significantly impairs the functional response to IPP. We now show that interleukin‐2 also activates MEK/Erk and PI‐3K/Akt pathways but on its own, fails to induce cytokine expression or cytotoxicity. Hence, MEK/Erk and PI‐3K/Akt activation are necessary but not sufficient to induce effector responses in Vγ2Vδ2 T cells and a TCR‐dependent signal is still required for tumour cell killing. Cyclosporin A, an inhibitor of calcineurin, blocked calcium‐dependent nuclear translocation of nuclear factor of activated T cell (NFAT) and significantly reduced IPP‐induced cytokine production, degranulation and cytotoxicity. The IPP‐induced calcium mobilization and NFAT translocation were necessary to activate Vγ2Vδ2 effector functions; interleukin‐2, acting on the MEK/Erk pathway, regulated the strength of these responses. The TCR has a specific role in Vγ2Vδ2 T‐cell killing of tumour cells, which is distinct from its role in triggering cellular proliferation in response to phosphoantigens.     

Developmental regulation of neuronal K(Ca) channels by TGFbeta1: an essential role for PI3 kinase signaling and membrane insertion

TGFbeta1 is a target-derived factor responsible for the developmental expression of large-conductance Ca(2+)-activated K(+) (K(Ca)) channels in ciliary neurons of the chick ciliary ganglion. The acute effects of TGFbeta1 on K(Ca) channels are mediated by posttranslational events and require activation of the MAP kinase Erk. Here we show that TGFbeta1 evokes robust phosphorylation of Akt/PKB, a protein kinase dependent on the products of phosphatidylinositol 3-OH kinase (PI3K). TGFbeta1-evoked stimulation of K(Ca) channels is blocked by the PI3K inhibitors wortmannin and LY294002. These drugs also inhibit TGFbeta1 effects on Akt/PKB phosphorylation but have no effect on TGFbeta1-evoked Erk activation. Application of the MEK1 inhibitor PD98059 blocked TGFbeta1 effects on Erk but had no effect on Akt/PKB phosphorylation. These results indicate that PI3K and Erk represent parallel signaling cascades activated by TGFbeta1 in ciliary neurons. The effects of TGFbeta1 on functional expression of K(Ca) are blocked by the microtubule inhibitors colchicine and nocodazole, by botulinum toxins A and E, and by brefeldin-A, an agent that disrupts the Golgi apparatus. These data indicate that translocation of a membrane protein, possibly Slowpoke (SLO), is required for the acute posttranslational effects of TGFbeta1 on K(Ca) channels. Confocal immunofluorescence studies with three different SLO antisera showed robust expression of SLO in multiple intracellular compartments of embryonic day 9-13 ciliary neurons, including the cell nucleus. These data suggest that TGFbeta1 evokes insertion of SLO channels into the plasma membrane as a result of signaling cascades that entail activation of Erk and PI3K.     

Role of Ras/Raf/MEK/ERK signaling in physiological hematopoiesis and leukemia development

Recent research on hematological malignancies has shown that malignant cells often co-opt physiological pathways to promote their growth and development. Bone marrow homeostasis requires a fine balance between cellular differentiation and self-renewal; cell survival and apoptosis; and cellular proliferation and senescence. The Ras/Raf/MEK/ERK pathway has been shown to be important in regulating these biological functions. Moreover, the Ras/Raf/MEK/ERK pathway has been estimated to be mutated in 30% of all cancers, thus making it the focus of many scientific studies which have lead to a deeper understanding of cancer development and help to elucidate potential weaknesses that can be targeted by pharmacological agents [1]. In this review, we specifically focus on the role of this pathway in physiological hematopoiesis and how augmentation of the pathway may lead to hematopoietic malignancies. We also discuss the challenges and success of targeting this pathway.