Guo-Ping Zhou

Down-regulation of microRNA-223 promotes degranulation via the PI3K/Akt pathway by targeting IGF-1R in mast cells.

Background Mast cells play a central role in allergic and inflammatory disorders by inducing degranulation and inflammatory mediator release. Recent reports have shown that miRNAs play an important role in inflammatory response regulation. Therefore, the role of miR-223 in mast cells was investigated. Methods The expression of miR-223 was quantified by quantitative real-time polymerase chain reaction (qRT-PCR) in immunoglobulin E (IgE)-mediated mast cells. After successful miR-223 inhibition by transfection, degranulation was detected in IgE-mediated mast cells. The phosphorylation of IκB-α and Akt were examined using western blotting. NF-κB was tested using electrophoretic mobility shift assay. PI3K-inhibitor (LY294002) was used to investigate whether the PI3K/Akt pathway was essential for mast cell activation. The TargetScan database and a luciferase reporter system were used to identify whether insulin-like growth factor 1 receptor (IGF-1R) is a direct target of miR-223. Results MiR-223 expression was up-regulated in IgE-mediated mast cells, whereas its down-regulation promoted mast cell degranulation. Levels of IκB-α and Akt phosphorylation as well as NF-κB were increased in miR-223 inhibitor cells. LY294002 could block the PI3K/Akt signaling pathway and rescue the promotion caused by suppressing miR-223 in mast cells. IGF-1R was identified as a direct target of miR-223. Conclusions These findings suggest that down-regulation of miR-223 promotes degranulation via the PI3K/Akt pathway by targeting IGF-1R in mast cells.

Direct repression of the human IRF-3 promoter by E2F1

Interferon regulatory factor 3 (IRF-3) plays an important role in virus and double-stranded RNA-mediated induction of type I interferon and RANTES, DNA damage signaling, tumor suppression, and virus-induced apoptosis. However, cis elements or trans factors responsible for regulating IRF-3 expression remain largely unknown. Here we report that the transcription factor E2F1 negatively regulates the basal transcriptional activity of IRF-3 and deregulates IRF-3 expression at mRNA level. By transient transfection analysis, we demonstrate that the mutation of E2F-binding site results in a profound promotion of IRF-3 promoter activity. Overexpression of E2F1, but not a mutant E2F1, represses the IRF-3 promoter activity in reporter gene assays while knocking down of endogenous E2F1 by shRNA strategy results in enhanced IRF-3 promoter activity. Electrophoretic gel mobility shift assays and antibody competition assays confirm that E2F1 protein binds to the E2F consensus binding site in the IRF-3 promoter. Chromatin immunoprecipitation assays demonstrate that E2F1 interacts with the IRF-3 promoter in vivo. These results suggest that E2F1 negatively regulates IRF-3 transcription through binding to the E2F consensus binding site.

Promoter characterization and role of cAMP/PKA/CREB in the basal transcription of the mouse ORMDL3 gene.

Orosomucoid 1-like 3 (ORMDL3) gene was strongly linked with the development of asthma in genetic association studies, and its expression could be significantly induced by allergen in airway epithelial cells of mice. However, the expression mechanism of ORMDL3 was still unclear. Here we have identified and characterized the mouse ORMDL3 gene promoter. Deletion constructs of the 5′ flanking region were fused to a luciferase reporter gene. After transient transfection in mouse fibroblast cell line NIH3T3, a CRE (−27/−20) binding CREB was identified in the core promoter region. Deletion or mutation of the CRE consensus sequence resulted in a significant loss of the promoter activity. EMSA and ChIP assays demonstrated the binding of CREB to the core promoter. Knocking down endogenous CREB led to a reduction in ORMDL3 expression. Conversely, overexpression of CREB up-regulated ORMDL3 expression. Moreover, forskolin, a PKA activator, could facilitate the phosphorylation of CREB, which in turn heightens ORMDL3 expression. H-89, a PKA-specific inhibitor, could significantly inhibit ORMDL3 expression. This study delineates the characterization of mouse ORMDL3 gene promoter and shows signaling pathway cAMP/PKA/CREB plays an important role in regulating ORMDL3 expression, which will be helpful for future animal model studies regarding the regulation or function of ORMDL3 gene.

EGF-recruited JunD/c-fos complexes activate CD2AP gene promoter and suppress apoptosis in renal tubular epithelial cells

CD2-associated protein (CD2AP) plays a critical role in the maintenance of the kidney filtration barrier. In this study, we showed that epidermal growth factor (EGF) led to an increase of the CD2AP protein and mRNA in the human renal proximal tubular epithelial cell line HK-2 cells, which was due to the elevation of CD2AP promoter activity. Upon deletion and mutation analysis, electrophoretic mobility shift assays and chromatin immunoprecipitation, an AP-1-like element within CD2AP promoter was characterized, by which EGF recruited c-fos and JunD, two components of AP-1, to the human CD2AP gene promoter and suppressed angiotensin II-induced apoptosis in HK-2 cells. Specific siRNA was synthesized to knock down the human CD2AP gene in HK-2 cells. We found that CD2AP deficiency attenuated the inhibitory effects of EGF and predisposed the renal tubular epithelial cells to undergo angiotensin II-induced apoptosis. Furthermore, EGF-induced increases of CD2AP protein and mRNA expressions in HK-2 cells were significantly inhibited by the transfection of dominant negative JunD or c-fos vector, which was in parallel with a marked reduction of antiapoptotic effect of EGF. These results indicated that the antiapoptotic effect of EGF/CD2AP signal transduction was mediated by JunD and c-fos, at least partially. This study defined a new EGF/AP-1/CD2AP mediated cell-survival signaling, which might be useful to clarify the molecular mechanisms responsible for CD2AP associated kidney diseases.

CREB and Sp1 regulate the human CD2AP gene promoter activity in renal tubular epithelial cells.

The human CD2-associated protein (CD2AP) is involved in several molecular signaling pathways and is an important factor responsible for nephrotic syndrome. Here we report the identification of the transcription start point and promoter region of the human CD2AP gene in renal tubular epithelial cells. With luciferase assays and deletion analysis, we found that the region between -558 and -1bp ahead of the transcription start point is indispensable for the promoter activity of the human CD2AP gene. A CREB site and two Sp1 sites were essential for maintaining the basal transcriptional activity of the human CD2AP promoter. Overexpression of phosphorylated CREB and Sp1 transactivated the human CD2AP promoter, whereas small interfering RNA-mediated blockage of CREB and Sp1 genes expressions inhibited markedly its activity. These findings provide the first analysis of the human CD2AP gene promoter and demonstrate that not only CREB but also Sp1 plays a critical role in regulating basal CD2AP promoter activity in renal tubular epithelial cells.

Transcriptional control of human CD2AP expression: the role of Sp1 and Sp3

The CD2 associated protein (CD2AP) is characterized as a T-lymphocyte CD2 adapter protein and is found to be related to glomerulosclerosis, and CD2AP knockout mice develop a rapid onset nephrotic syndrome and die of renal failure. Here we report that the transcription factor Sp1 and Sp3 up-regulate the basal transcriptional activity of CD2AP and increase CD2AP expression at mRNA level. We show by Chromatin immunoprecipitation (ChIP) assay that Sp1 and Sp3 interact with the CD2AP promoter region in vivo. By transient transfection analysis we also demonstrate the mutations of Sp1/3 binding sites result in a profound reduction of CD2AP promoter activity. Overexpression of Sp1 and Sp3 transactivates the CD2AP promoter, whereas small interfering RNA-mediated (siRNA) blockage of Sp1 and Sp3 genes expressions inhibits markedly its activity. These results suggest that Sp1 and Sp3 play an important role in regulating CD2AP transcription through binding to the Sp1/3 binding sites.

Multimolecular complex of Par-4 and E2F1 binding to Smac promoter contributes to glutamate-induced apoptosis in human- bone mesenchymal stem cells.

Neural cells undergo glutamate-induced apoptosis in ischaemic brain tissue, in which prostate apoptosis response-4 gene (Par-4) is involved. Human-bone mesenchymal stem cells can be utilized as an effective therapy for ischemic brain injury. In this study, we found that glutamate could induce apoptosis in human-bone mesenchymal stem cells, accompanied by increased expression of Par-4 gene and Smac release from mitochondria. Repressing Par-4 expression attenuated the glutamate-induced apoptosis. Both Par-4 protein and E2F1 protein could bind to E2F1-binding BS3 site on Smac promoter and participated in the formation of a proteins-DNA complex. Moreover, in the complex, E2F1, not Par-4, was found to be directly bound to the Smac promoter, suggesting that Par-4 exerted indirectly its transcriptional control on the Smac gene though interacting with E2F1. Expression of full-length Par-4 in human-bone mesenchymal cells resulted in increased activity of the Smac promoter. In addition, the indirect transcripional regulation of Par-4 on Smac depended on its COOH terminus-mediated interaction between Par-4 and E2F1. We conclude that the formation of proteins–DNA complex, containing Par-4 protein, E2F1 protein and the Smac promoter, contributes to the pro-apoptotic effect on glutamate-treated human-bone mesenchymal stem cells.

All-Trans Retinoic Acid Modulates ORMDL3 Expression via Transcriptional Regulation

All-trans retinoic acid (ATRA) is an active metabolite of Vitamin A, it shows protective effects on asthma, including maintains airway epithelial integrity, inhibits asthma effector cells differentiation, modulates immune response, et al. However, the promoting effect of ATRA on Th2 response has restricted the clinical application of ATRA in asthma treatment. ORMDL3 is a candidate gene of childhood onset asthma, and high-transcript of ORMDL3 is associated with the development of asthma. Here we show that ATRA increases ORMDL3 production in vitro via inducing PKA-dependent CREB phosphorylation which in turn binds to the CRE element in promoter region of ORMDL3 and initiates ORMDL3 transcription. This finding is in consistent with the previous reports that ATRA could regulate target genes without the presence of retinoic acid response element (RARE) in promoter region but through other signals such as PKA/CREB. Nevertheless, in the present study, the traditional signal pathway of ATRA, retinoic acid receptor (RAR) signal transduction pathway, indirectly modulated ORMDL3 expression. RAR-α agonist (Am-80) increased ORMDL3 production even though there was no RARE in ORMDL3 promoter, introns or 3′-downstream region. Besides, the signal of RAR might differ from that of ATRA since Am-80 failed to induce CREB activation. In conclusion, our data indicate that ATRA facilitates ORMDL3 production probable through PKA/CREB, and this may be a starting point for more detailed mechanism researches on ATRA and asthma.

Characterization of a spliced variant of human IRF-3 promoter and its regulation by the transcription factor Sp1

Interferon regulatory factor 3 (IRF-3), an essential transcriptional regulator of the interferon genes, plays an important role in host defense against viral and microbial infection as well as in cell growth regulation. Promoter plays a crucial role in gene transcription. We have reported the characterization of the wide type of human IRF-3 promoter, but the characterization of the spliced variant of human IRF-3 Int2V1 promoter has not been systematically analyzed. To observe the spliced variant of human IRF-3 promoter, we have cloned the human IRF-3 gene promoter region containing 300 nucleotides upstream the transcription start site (TSS). Transient transfection of 5′ deleted promoter-reporter constructs and luciferase assay illustrated the region −159/−100 relative to the TSS is sufficient for full promoter activity. This region contains GATA1 and specific protein-1 (Sp1) transcription factor binding sites. Interestingly, mutation of this Sp1 site reduced the promoter activity by 50%. However, overexpression of Sp1 increased the transcription activity by 2.4-fold. These results indicated that the spliced variant of human IRF-3 gene core promoter was located within the region −159/−100 relative to the TSS. Sp1 transcription factor upregulates the spliced variant of human IRF-3 gene promoter.

Functional characterization of the regulatory region of human CD2-associated protein promoter in HEK 293 cells.

Background: The mRNA of CD2-associated protein (CD2AP) was found to be changed in glomerular diseases. The promoter plays an important role in the regulation of gene expression, but the characterization of the human CD2AP promoter has not been systematically analyzed in HEK 293 cells. Aims: To analyze in detail the promoter of human CD2AP in HEK 293 cells. Methods: The transcriptional initiation sites were identified by 5′ RACE. Promoter activities were detected by series deletion and mutational luciferase analyses. Results: Multiple transcriptional start sites were identified. Progressive deletion analysis from both 5′ and 3′ ends revealed two kinds of promoter activity. One basic promoter activity was located within 500 bp upstream of ATG. Fragments of further upstream 100 bp increased the promoter activity 5-fold. Two Sp1/Sp3 sites were in this region. Mutations of these two sites reduced the transcriptional activity by 50%. Sp1 increased the activity, whereas Sp3 decreased the activity. Deletion of 9 single nucleotide polymorphism sites and 3 Lmx1b sites did not change the transcriptional activity.Conclusion: Sp1/Sp3 binding sites play a critical role in the CD2AP regulation. These findings should facilitate studies on the clinical mutational and polymorphism analysis.