关键词： Angiotensin   Signal transduction   ATF3   Left atrium  

摘要： The atria respond to various pathological stimuli including pressure and volume overload with remodeling and dilatation. Dilatation of the left atrium is associated with atrial fibrillation. The mechanisms involved in chamber-specific hypertrophy are largely unknown. Angiotensin II is hypothesized to take part in mediating this response. ATF3 is an immediate early gene found at the receiving end of multiple stress and growth stimuli. Here we characterize ATF3 as a direct target gene for angiotensin II. ATF3 expression is regulated by angiotensin receptor-mediated signaling in vivo and in vitro at the transcriptional level. ATF3 induction is mediated by cooperation between both the AT(1A) and AT(2) receptor subtypes. While AT(2)R blocker (PD123319) efficiently blocks ATF3 induction in response to angiotensin II injection, it results in an increase in blood pressure indicating that the effect of angiotensin II on ATF3 is independent of its effect on blood pressure. In contrast to adrenergic stimulation that induces ATF3 in all heart chambers, ATF3 induction in response to angiotensin II occurs primarily in the left chambers. We hypothesize that the activation of differential signaling pathways accounts for the chamber-specific induction of ATF3 expression in response to angiotensin II stimulation. Angiotensin II injection rapidly activates the EGFR-dependent pathways including ERK and PI3K-AKT in the left but not the right atrium. EGF receptor inhibitor (Gefitinib/Iressa) as well as the AKT inhibitor (Triciribine) significantly abrogates ATF3 induction by angiotensin II in the left chambers. Collectively, our data strongly place ATF3 as a unique nuclear protein target in response to angiotensin II stimulation in the atria. The spatial expression of ATF3 may add to the understanding of the signaling pathways involved in cardiac response to neuro-hormonal stimulation, and in particular to the understanding of left atrial-generated pathology such as atrial fibrillation.

关键词： ATF3   肿瘤   免疫调节   内分泌调节  

摘要： 活化转录因子（activating transcription factor 3，ATF3）属于适应性反应基因，作为ATF／cAMP效应元件的结合蛋白，参与细胞为适应内外环境变化所发生的应激反应。ATF3可以根据靶基因和细胞环境的不同，激活或抑制相关基因表达，具有广泛的转录调节作用，在细胞周期、免疫调节、内分泌调节和肿瘤发生的过程中扮演重要角色。

关键词： ATF3   detrusor   ganglia   growth   obstruction   p-c-Jun   urinary bladder  

摘要： Objective. Infravesical obstruction leads to growth of urinary bladder smooth-muscle cells. The ganglion cells innervating the bladder muscle also increase in size. Stretch of detrusor muscle cells rapidly activates c-Jun NH2-terminal kinase (JNK), which phosphorylates the transcription factor c-Jun, and stimulates the synthesis of the cotranscription factor ATF3. The aim of the study was to determine whether ATF3 and p-c-Jun were involved in growth of bladder smooth-muscle and ganglion cells. Material and methods. The urethra was partially obstructed in female rats. After 3 days or 10 weeks bladders were weighed, fixated and cut for immunohistochemistry to demonstrate ATF3 and p-c-Jun. Ganglia were processed separately. Unoperated and sham-operated rats were used as controls. Results. There was no ATF3 or p-c-Jun in control detrusor muscle. After 3 days of obstruction bladder weight had nearly doubled. Almost all nuclei in the detrusor showed immunofiuorescence for ATF3 and p-c-Jun. After 10 weeks bladder weight had increased 10-fold. Almost all detrusor nuclei still showed p-c-Jun, but few had ATF3 activity. In control ganglia there was no ATF3 and only faint nuclear p-c-Jun activity. After 3 days of obstruction the ganglion cells had increased in size and many nuclei showed intense immunofluorescence for ATF3 and p-c-Jun. After 10 weeks the ganglion cell size had increased further. There was no ATF3 activity and no more p-c-Jun than in control ganglia. Conclusion. ATF3 and p-c-Jun seem to be involved in the growth of the detrusor muscle and its motor innervation following infravesical outlet obstruction.

关键词： Breast cancer   Breast tumors   Mammary glands   Endocrine tumors   Genetically modified animals   DNA transcription   Mouse models   Gene expression  

摘要： Female transgenic mice that constitutively overexpress the transcription factor ATF3 in the basal epithelium of the mammary gland develop mammary carcinomas with high frequency, but only if allowed to mate and raise pups early in life. This transgenic mouse model system reproduces some features of human breast cancer in that about 20% of human breast tumor specimens exhibit overexpression of ATF3 in the tumor cells. The ATF3-induced mouse tumors are phenotypically similar to mammary tumors induced by overexpression of activating Wnt/beta-catenin pathway genes. We now show that the Wnt/beta-catenin pathway is indeed activated in ATF3-induced tumors. beta-catenin is transcriptionally up-regulated in the tumors, and high levels of nuclear beta-catenin are seen in tumor cells. A reporter gene for Wnt/beta-catenin pathway activity, TOPGAL, is up-regulated in the tumors and several downstream targets of Wnt signaling, including Ccnd1, Jun, Axin2 and Dkk4, are also expressed at higher levels in ATF3-induced tumors compared to mammary glands of transgenic females. Several positive-acting ligands for this pathway, including Wnt3, Wnt3a, Wnt7b, and Wnt5a, are significantly overexpressed in tumor tissue, and mRNA for Wnt3 is about 5-fold more abundant in transgenic mammary tissue than in non-transgenic mammary tissue. Two known transcriptional targets of ATF3, Snai1 and Snai2, are also overexpressed in the tumors, and Snail and Slug proteins are found to be located primarily in the nuclei of tumor cells. In vitro knockdown of Atf3 expression results in significant decreases in expression of Wnt7b, Tcf7, Snai2 and Jun, suggesting that these genes may be direct transcriptional targets of ATF3 protein. By chromatin immunoprecipitation analysis, both ATF3 and JUN proteins appear to bind to a particular subclass of AP-1 sites upstream of the transcriptional start sites of each of these genes.

关键词： Complementary antibody pairs   Hybridoma antibody screening   Biomarker   Akt2   ATF3   NAE beta   AlphaScreen  

摘要： The utility of antibody reagents for the detection of specific cellular targets for both research and diagnostic applications is widespread and continually expanding. Often it is useful to develop specific antibodies as reagent pairs that distinguish different epitopes of the target such that sandwich enzyme-linked immunosorbent assay can be used for selective and specific detection. However, the identification of pairing antibodies is often cumbersome and labor-intensive even with the use of designed peptide-specific epitopes as antigens. We have developed a robust and high-throughput method for identifying pairing complementary antibodies derived either from commercial sources or during a rabbit hybridoma monoclonal screening and selection process using protein A capture with the AlphaScreen bead-based assay format. We demonstrate the value and effectiveness of this assay with three protein targets: Akt2, ATF3, and NAE beta (the beta-subunit of the neddylation activation enzyme). (c) 2010 Elsevier Inc. All rights reserved.

关键词： ATF3   VSMCs   apoptosis   migration  

摘要： Activating transcription factor 3 (ATF3) is a member of the ATF/CREB (CAMP responsive element binding protein) family of transcription factors. The expression and the function of ATF3 in vascular smooth muscle cells (VSMCs) remain unknown. The aim of this work is to determine the expression and possible function of ATF3 in VSMCs. We found that VSMCs expressed ATF3, and expression of ATF3 in VSMCs was induced by a variety of stimuli including serum, angiotensin II, and H2O2. Knockdown of ATF3 induced apoptosis of VSMCs, caspase-3 cleavage, and cytochrome c release. The results suggest that ATF3 regulates survivability of VSMCs. Moreover, we found that overexpression of ATF3 promoted migration of VSMCs and induced expression of matrix metalloproteinase 1, 3, and 13. These results suggest that ATF3 plays a role in regulating migration of VSMCs. In addition, we found that the expression of ATF3 was upregulated in smooth muscle cells in the injured mouse femoral arteries compared with the uninjured control group. These results suggest that ATF3 is relevant to disease physiology. (C) 2011 IUBMB IUBMB Life, 63(1): 62-69, 2011

关键词： Copper   HNF4 alpha   HepG2 cell   Transcription   p53   Gene expression   ATF3  

摘要： Previous global transcriptome and interactome analyses of copper-treated HepG2 cells identified hepatocyte nuclear factor 4 alpha (HNF4 alpha) as a potential master regulator of copper-responsive transcription. Copper exposure caused a decrease in the expression of HNF4 alpha at both mRNA and protein levels, which was accompanied by a decrease in the level of HNF4 alpha binding to its consensus DNA binding sequence. qRT-PCR and RNAi studies demonstrated that changes in HNF4 alpha expression ultimately affected the expressions of its down-stream target genes. Analysis of upstream regulators of HNF4 alpha expression, including p53 and ATF3, showed that copper caused an increase in the steady-state levels of these proteins. These results support a model for copper-responsive transcription in which the metal affects ATF3 expression and stabilizes p53 resulting in the down-regulation of HNF4 alpha expression. In addition, copper may directly affect p53 protein levels. The suppression of HNF4 alpha activity may contribute to the molecular mechanisms underlying the physiological and toxicological consequences of copper toxicity in hepatic-derived cells. Published by Elsevier B.V.