关键词： c-Jun   ATF2   ATF3   p38   JNK   GnRH  

摘要： Induction of c-Jun and c-Fos, partners that comprise the AP1 transcription factor, is critical for GnRH regulation of FSH beta gene expression. The signaling pathways that are necessary for regulation of AP1 in the gonadotrope cell are not known. Here, we investigate the mechanism of c-Jun induction by GnRH, the sole regulator of c-Jun in the gonadotrope. We identify that GnRH phosphorylates ATF2 via p38 and JNK, the same pathways responsible for GnRH induction of c-Jun. Upon phosphorylation, ATF2 binds the CRE element within the c-Jun proximal promoter and interacts with NFY. Functional ATF2 is necessary for both GnRH induction of c-Jun and FSH beta. Taken together, these studies elucidate the specificity of c-Jun induction by GnRH in the gonadotrope by demonstrating GnRH activation of the p38 and JNK signaling pathways that lead to phosphorylation of ATF2, providing critical insight into GnRH regulation of its target gene, the gonadotropin subunit FSH beta. (C) 2012 Elsevier Ireland Ltd. All rights reserved.

关键词： activating transcription factor 4 (ATF4)   histone acetylation   histone code   histone methylation   nutrient sensing  

摘要： Amino acid deprivation of mammalian cells triggers several signalling pathways, the AAR (amino acid response), that results in transcriptional activation. For the ASNS (asparagine synthetase) and ATF3 (activating transcription factor 3) genes, increased transcription occurs in conjunction with recruitment of ATF4 to the gene. In HepG2 cells, analysis of the ASNS and ATF3 genes during AAR activation revealed increases in histone H3K4me3 (histone 3 trimethylated Lys(4)) and H4Ac (acetylated histone 4) levels, marks associated with active transcription, but a concurrent loss of total H3 protein near the promoter. The dynamic nature of AAR-regulated transcription was illustrated by a decline in ASNS transcription activity within minutes after removal of the AAR stress and a return to basal levels by 2 h. Reversal of ASNS transcription occurred in parallel with decreased promoter-associated H4Ac and ATF4 binding. However, the reduction in histone H3 and increase in H3K4me3 were not reversed. In yeast, persistence of H3K4me3 has been proposed to be a 'memory' mark of gene activity that alters the responsiveness of the gene, but the time course and magnitude of ASNS induction was unaffected when cells were challenged with a second round of AAR activation. The results of the present study document changes in gene-associated nucleosome abundance and histone modifications in response to amino-acid-dependent transcription.

关键词： Excitotoxicity   Neuroprotection   Plasminogen   Tissue-type plasminogen activator  

摘要： The release of the serine proteinase tissue-type plasminogen activator (tPA) from cerebral cortical neurons has a neuroprotective effect in the ischemic brain. Because excitotoxicity is a basic mechanism of ischemia-induced cell death, here we investigated the effect of tPA on excitotoxin-induced neuronal death. We report that genetic overexpression of neuronal tPA or treatment with recombinant tPA renders neurons resistant to the harmful effects of an excitotoxic injury in vitro and in vivo. We found that at concentrations found in the ischemic brain, tPA interacts with synaptic but not extrasynaptic NMDARs. This effect is independent of tPA's proteolytic properties and leads to a rapid and transient phosphorylation of the extracellular signal regulated kinases 1/2 (ERK 1/2), with ERK 1/2-mediated activation of the cAMP response element binding protein (CREB) and induction of the neuroprotective CREB-regulated activating transcription factor 3 (Atf3). In line with these observations, Atf3 down-regulation abrogates the protective effect of tPA against excitotoxin-induced neuronal death. Our data indicate that tPA preferentially activates synaptic NMDARs via a plasminogen-independent mechanism turning on a cell signaling pathway that protects neurons from the deleterious effects of excitotoxicity. Published by Elsevier Inc.

关键词： hemin   HK-2 renal proximal tubular cell   microarray   ATF3   siRNA  

摘要： Objective: To identify gene expression changes and the role of activating transcription factor 3 (ATF3) in hemin toxicity in renal tubular epithelial cells, then elucidate molecular mechanisms of hemin toxicity on renal tubular epithelial cells. Methods: An oligo array comprising 35,035 genes was used to compare differential gene expression in hemin-treated and non-treated HK-2 cells (human renal proximal tubular epithelial cells), and the role of ATF3 in hemin toxicity was assessed using siRNA technique. Results: A total of 128 mRNAs were at least twofold up-regulated and 101 mRNAs were at least twofold down-regulated after hemin treatment. Expression levels of ATF3, heat shock protein 70, c-fos, and c-jun were remarkably increased. Hemin also suppressed nuclear factor-kappa B inhibitor alpha, beta-2 adrenergic receptor, and interleukin-6 mRNA amounts more than twofold. We further demonstrated the protective role of ATF3 in hemin cytotoxicity. Conclusions: The data suggest that hemin caused multiple changes of gene expression in HK-2 cells, and ATF3 protects against hemin cytotoxicity.

关键词： coffee intake   insulin signaling pathway   ATF3   SOCS3  

摘要： Lipopolysaccharide (LPS) triggers innate immunity mainly via TLR4 signaling. ATF3 is a negative regulator of TLR4 signaling. HMGB1 plays a critical role in the final step of sepsis. However, the mechanisms of ATF3 and the role of HMGB1 in regulating innate immunity-induced sepsis are incompletely understood. In this study, we found that serum HMGB1 levels were 10-fold higher in patients with sepsis than normal controls. We further demonstrated that ATF3 gene knockout in mice subjected to LPS-induced endotoxemia correlates with an increase in the mortality rate and the elevated expression of IL-6, TNF-alpha, NO, MCP-1, and HMGB1 in the lung tissues or serum. The biochemical effects of ATF3 were observed in in vitro macrophages and blocked by ATF3 siRNA treatment. We have also shown that adeno-associated virus-mediated ATF3 gene transfer protected ATF3 knockout mice from LPS-induced mortality. In addition, ATF3 knockdown increased LPS-induced release of HMGB1. In conclusion, upregulation of ATF3 contributes to the reduced release of inflammatory molecules, especially HMGB1, which induced lung injury and increased the survival rate of mice after LPS challenge. Therefore, suppressing LPS-induced inflammation with ATF3 induction or ATF3 mimetics may be an important strategy for sepsis therapy.

关键词： ATF3   Stat3 phosphorylation   p53 expression   skin cancer cell  

摘要： Aim: ATF3, a member of the ATF/CREB family of transcription factors, has been found to be selectively induced by calcineurin/NFAT inhibition and to enhance keratinocyte tumor formation, although the precise role of ATF3 in human skin cancer and possible mechanisms remain unknown. Methods: In this study, clinical analysis of 30 skin cancer patients and 30 normal donors revealed that ATF3 was accumulated in skin cancer tissues. Functional assays demonstrated that ATF3 significantly promoted skin cancer cell proliferation. Results: Mechanically, ATF3 activated Stat3 phosphorylation in skin cancer cell through regulation of p53 expression. Moreover, the promotion effect of ATF3 on skin cancer cell proliferation was dependent on the p53-Stat3 signaling cascade. Conclusion: Together, the results indicate that ATF3 might promote skin cancer cell proliferation and enhance skin keratinocyte tumor development through inhibiting p53 expression and then activating Stat3 phosphorylation.

关键词： COX-2   肝星状细胞   Atf3   Serpinb2   Pgk1   Thra  

摘要： 目的 研究靶向COX-2shRNA对大鼠HSC-T6COX-2的抑制作用，观察Atf3、Serpinb2、Pgk1、Thra基因表达的影响，进一步探讨COX-2shRNA抑制HSC增殖的作用机制。 方法 实验将HSC-T6分为三组，空白对照组（以PBS液替代质粒），空载体组（未插入目的基因的DNA片段，HK质粒组）及转染组（pYr-1.1-hU6-EGFP-COX-2shRNA1组），利用LipofectamineTM2000将质粒转染入大鼠肝星状细胞，在荧光显微镜下观察其转染效率，然后提取转染后24h，48h，72h各组细胞中RNA，应用RT-PCR技术检测各组各时间段COX-2、Atf3、Serpinb2、Pgk1、Thra基因表达情况。 结果 1、荧光显微镜下观察结果：COX-2shRNA1转染大鼠肝星状细胞后24h、48h、72h，荧光显微镜下观察，转染成功的细胞质中可见绿色的荧光，转染效率均可达70%以上，空白组与空载体组细胞质中未见绿色荧光。 2、转染后COX-2表达的影响：应用RT-PCR方法检测转染后24h、48h、72h转染组COX-2mRNA的表达都低于空白对照组和空载体组（P<0.05），其中以72h抑制最为明显，空白对照组和空载体组无沉默效应。 3、转染后Atf3、Serpinb2、Thra表达的影响：应用RT-PCR方法检测转染后24h、48h、72h转染组Atf3、Serpinb2mRNA的表达都低于空白对照组和空载体组（P<0.05），其中以72h抑制最为明显，空白对照组和空载体组无沉默效应。 4、转染后Pgk1表达的影响：应用RT-PCR方法检测转染后24h转染组Pgk1mRNA的表达与空白对照组和空载体组之间无差异（P﹥0.05），48h、72h低于空白对照组和空载体组（P<0.05），以72h抑制最为明显，空白对照组和空载体组无沉默效应。 结论 1.靶向COX-2shRNA转染入大鼠HSC-T6可沉默HSC中COX-2的表达。 2.靶向COX-2shRNA可以下调HSC增殖相关基因Serpinb2的表达。 3.靶向COX-2shRNA可以下调HSC脂肪代谢相关基因Pgk1、Thra的表达。 4.靶向COX-2shRNA抑制HSC增殖可能通过调节Serpinb2、Pgk1、Thra等基因的表达起作用。

关键词： 前列腺癌   双联苄化合物   蛋白酶体   自噬性死亡   ATF3  

摘要： 前列腺癌(prostate cancer, PCa)是欧美国家老年男性最常见的恶性肿瘤,其死亡率仅次于肺癌。虽然我国前列腺癌的发病率明显低于西方国家,但随着人口老龄化、饮食结构的改变等,我国前列腺癌发病率,特别是晚期前列腺癌的发病率呈显著上升趋势。据预计10年后,前列腺癌在我国的发病率可能会超过60-70/10万,已成为威胁我国老年男性健康的恶性疾病之一。 前列腺癌是激素依赖性肿瘤,因此内分泌治疗是治疗前列腺癌的首选标准方案。然而绝大多数前列腺癌患者经内分泌治疗1-2年后易发展为激素难治性前列腺癌(Hormone Refractory Prostate Cancer,HRPC),对雄激素撤除不敏感,抵抗凋亡并伴随侵袭转移,预后差,死亡率高,目前临床尚无有效的治疗方法。由于HRPC的演变是复杂的多因素、多信号途径参与的过程,其机制尚不完全清楚,因此寻找有效的治疗靶点及机制,产生多种途径的协同效应,是治疗前列腺癌的有效策略之一。 第一部分地钱素M抑制蛋白酶体的活性,诱导细胞内质网应激和凋亡 泛素-蛋白酶体系统(Ubiquitin-proteasome system, UPS)是真核生物细胞内重要的蛋白质质量控制体系之一。UPS通过将小分子蛋白泛素与靶蛋白的赖氨酸残基共价结合,从而将其泛素化。泛素标记的蛋白被蛋白酶体特异性地识别并迅速降解。UPS通常降解受损变性蛋白、短寿命的调控蛋白等,对于细胞周期运转、凋亡与分化、信号转导等生理过程起着重要的调控作用。恶性肿瘤细胞内蛋白代谢紊乱,蛋白酶体活性升高,UPS调节失衡,使得肿瘤细胞更加依赖UPS,以维持细胞内稳态。因此,肿瘤细胞对蛋白酶体抑制剂更加敏感,蛋白酶体也成为肿瘤治疗的新靶点,开发针对UPS的抑制剂在肿瘤治疗中具有广阔的前景,而天然化合物以其独特的结构、多样的生物学活性更是备受关注。 双联苄(Bisbibenzyls)是苔藓植物中分离得到的一类大环多酚类化合物,因联苄之间的连接方式不同、取代基不同而具有结构新颖、多样的特点,具有抗真菌、抗炎、抗肿瘤等多种生物活性。本课题组前期研究发现双联苄类化合物地钱素M(Marchantin M,Mar)显著抑制前列腺癌细胞的增殖、促进其凋亡。由于地钱素M的结构与茶多酚的功能区域相似,而茶多酚已被证明是蛋白酶体的不可逆抑制剂。我们推测地钱素M可能具有抑制蛋白酶体活性的功能。为此,我们研究了地钱素M对重组纯化的20S蛋白酶体、前列腺癌细胞内蛋白酶体活性的影响,并对其生物学效应进行了分析,取得了以下研究结果： 一、地钱素M显著抑制蛋白酶体活性,是新的可逆性蛋白酶体抑制剂 1.地钱素M显著抑制蛋白酶体胰凝乳样蛋白酶(ChT-L)和肽基谷氨酰多肽解酶(PGPH)活性。Mar显著抑制重组纯化的20S蛋白酶体中ChT-L和PGPH活性,呈剂量依赖性。其半数抑制率分别为6.99和5.33μM。但不影响胰蛋白酶样活性。细胞实验表明,地钱素M对激素非依赖性前列腺癌PC3,DU145细胞和激素依赖性前列腺癌LNCaP细胞内26S蛋白酶体显示同样的抑制作用,且呈时间和剂量依赖性。表达差异谱基因芯片数据显示,地钱素M并不影响UPS途径中各组分的基因表达。 2.地钱素M是新的可逆性蛋白酶体抑制剂。通过Autodock vina软件分析发现,地钱素M能与蛋白酶体的β1(PGPH)和β5(ChT-L)亚基结合。二者主要依靠氢键、疏水键等非共价键相互作用,其自由能分别为：-7.4kcal/mol和-6.5kcal/mol。林-贝氏双倒数作图法表明,地钱素M对蛋白酶体的抑制呈现较典型的非竞争性抑制的方式。上述结果表明,地钱素M是一种新的蛋白酶体可逆的抑制剂。 3.地钱素M抑制蛋白酶体活性,导致前列腺癌细胞内多泛素化蛋白累积,且呈时间、剂量依赖性。 二、地钱素M抑制蛋白酶体活性,导致内质网相关蛋白降解途径(ERAD)受阻,诱导内质网应激和细胞凋亡 1.地钱素M介导的蛋白酶体抑制,抑制ERAD,诱导内质网应激。地钱素M处理前列腺癌细胞后,导致经ERAD降解的蛋白如突变蛋白CFTRAF508、SPCA4在内质网堆积；电镜下观察到内质网肿胀,激光共聚焦结果显示高浓度的地钱素M可引起内质网空泡化；Western blotting结果表明,内质网伴侣蛋白GRP78表达显著上调、PERK及其下游eIF2α磷酸化水平升高；定量PCR分析显示应激分子***4及其靶基因ATF3表达显著增加；IRE1激活并剪接XBP1的mRNA,激活XBP1。上述结果表明,地钱素M抑制蛋白酶体活性导致内质网内未折叠或错误折叠的蛋白累积,诱导内质网应激。 2.地钱素M诱导前列腺癌细胞凋亡。地钱素M呈剂量依赖性抑制激素依赖