Transforming growth factor beta stimulates the human immunodeficiency virus 1 enhancer and requires NF-kappaB activity

HIV Expression in Infected T Cell Clones

The principal barrier to an HIV-1 cure is the persistence of infected cells harboring replication-competent proviruses despite antiretroviral therapy (ART). HIV-1 transcriptional suppression, referred to as viral latency, is foremost among persistence determinants, as it allows infected cells to evade the cytopathic effects of virion production and killing by cytotoxic T lymphocytes (CTL) and other immune factors. HIV-1 persistence is also governed by cellular proliferation, an innate and essential capacity of CD4+ T cells that both sustains cell populations over time and enables a robust directed response to immunological threats. However, when HIV-1 infects CD4+ T cells, this capacity for proliferation can enable surreptitious HIV-1 propagation without the deleterious effects of viral gene expression in latently infected cells. Over time on ART, the HIV-1 reservoir is shaped by both persistence determinants, with selective forces most often favoring clonally expanded infected cell populations harboring transcriptionally quiescent proviruses. Moreover, if HIV latency is incomplete or sporadically reversed in clonal infected cell populations that are replenished faster than they are depleted, such populations could both persist indefinitely and contribute to low-level persistent viremia during ART and viremic rebound if treatment is withdrawn. In this review, select genetic, epigenetic, cellular, and immunological determinants of viral transcriptional suppression and clonal expansion of HIV-1 reservoir T cells, interdependencies among these determinants, and implications for HIV-1 persistence will be presented and discussed.

Regulation of HIV-1 transcription

Human immunodeficiency virus type-1 (HIV-1) is a highly pathogenic lentivirus that requires transcription of its provirus genome for completion of the viral life cycle and the production of progeny virions. Since the first genetic analysis of HIV-1 in 1985, much has been learned about the transcriptional regulation of the HIV-1 genome in infected cells. It has been demonstrated that HIV-1 transcription depends on a varied and complex interaction of host cell transcription factors with the viral long terminal repeat (LTR) promoter. The regulatory elements within the LTR interact with constitutive and inducible transcription factors to direct the assembly of a stable transcription complex that stimulates multiple rounds of transcription by RNA polymerase II (RNAPII). However, the majority of these transcripts terminate prematurely in the absence of the virally encoded trans-activator protein Tat, which stimulates HIV-1 transcription elongation by interacting with a stem-loop RNA element (TAR) formed at the extreme 5' end of all viral transcripts. The Tat-TAR interaction recruits a cellular kinase into the initiation-elongation complex that alters the elongation properties of RNAPII during its transit through TAR. This review summarizes our current knowledge and understanding of the regulation of HIV-1 transcription in infected cells and highlights the important contributions human lentivirus gene regulation has made to our general understanding of the transcription process.

PubAngioGen: a database and knowledge for angiogenesis and related diseases

Angiogenesis is the process of generating new blood vessels based on existing ones, which is involved in many diseases including cancers, cardiovascular diseases and diabetes mellitus. Recently, great efforts have been made to explore the mechanisms of angiogenesis in various diseases and many angiogenic factors have been discovered as therapeutic targets in anti- or pro-angiogenic drug development. However, the resulted information is sparsely distributed and no systematical summarization has been made. In order to integrate these related results and facilitate the researches for the community, we conducted manual text-mining from published literature and built a database named as PubAngioGen (http://www.megabionet.org/aspd/). Our online application displays a comprehensive network for exploring the connection between angiogenesis and diseases at multilevels including protein–protein interaction, drug-target, disease-gene and signaling pathways among various cells and animal models recorded through text-mining. To enlarge the scope of the PubAngioGen application, our database also links to other common resources including STRING, DrugBank and OMIM databases, which will facilitate understanding the underlying molecular mechanisms of angiogenesis and drug development in clinical therapy.

The expression of HIV-1 Vpu in monocytes causes increased secretion of TGF-β that activates profibrogenic genes in hepatic stellate cells

There is faster progression to fibrosis in persons with liver injury who are also infected with HIV. Other reports have suggested that HIV can directly infect and activate stellate cells, and the viral Tat and gp160 proteins also induce profibrogenic factors from peripheral blood mononuclear cells (PBMCs). We tested the role of HIV-1 Vpu accessory protein in promoting profibrogenic activation of hepatic stellate cells. Human stellate LX2 cells were cocultured with human monocytic U937 cells stably expressing the Vpu protein or latently infected U1 cells knocked down for Vpu expression, LX2 cells were also cultured with the supernatants from these cells. The expression of profibrogenic markers was evaluated in LX2 cells usingquantitative reverse transcription polymerase chain reaction (qRT-PCR),western blotting, immunofluorescence,flow cytometry and ELISA were used to confirm and quantitate protein expression. Monocytic cells expressing Vpu increased the expression of profibrogenic markers in LX2 cells. The culture supernatants of these cells contained increased levels of transforming growth factor beta (TGF-β), which correlated with increased activity of the AP-1 transcription factor. Antibodies against TGF-β or a TGF-β receptor inhibitor (SB431452) reversed Vpu-mediated profibrogenic activation of LX2 cells, suggesting that TGF-β mediated these effects. The cytokine macrophage migration inhibitory factor (MIF) attenuated Vpu-mediated TGF-β secretion and profibrogenic effects on LX2 cells. Besides its other roles in pathogenesis, Vpu is likely to contribute to hepatic fibrosis through this hitherto unknown mechanism.

Expression analysis of immune response genes in fish epithelial cells following ranavirus infection

Ranaviruses (family Iridoviridae) are a growing threat to fish and amphibian populations worldwide. The immune response to ranavirus infection has been studied in amphibians, but little is known about the responses elicited in piscine hosts. In this study, the immune response and apoptosis induced by ranaviruses were investigated in fish epithelial cells. Epithelioma papulosum cyprini (EPC) cells were infected with four different viral isolates: epizootic haematopoietic necrosis virus (EHNV), frog virus 3 (FV3), European catfish virus (ECV) and doctor fish virus (DFV). Quantitative real-time PCR (qPCR) assays were developed to measure the mRNA expression of immune response genes during ranavirus infection. The target genes included tumour necrosis factor α (TNF-α), interleukin-1β (IL-1β), β2-microglobulin (β2M), interleukin-10 (IL-10) and transforming growth factor β (TGF-β). All ranaviruses elicited changes in immune gene expression. EHNV and FV3 caused a strong pro-inflammatory response with an increase in the expression of both IL-1β and TNF-α, whereas ECV and DFV evoked transient up-regulation of regulatory cytokine TGF-β. Additionally, all viral isolates induced increased β2M expression as well as apoptosis in the EPC cells. Our results indicate that epithelial cells can serve as an in vitro model for studying the mechanisms of immune response in the piscine host in the first stages of ranavirus infection.

Arc of a vicious circle: pathways activated by Mycobacterium tuberculosis that target the HIV-1 long terminal repeat

In this review, we examine how a subset of signal transduction cascades initiated by Mycobacterium tuberculosis (Mtb) infection modulates transcription mediated by the human immunodeficiency virus type 1 long terminal repeat (HIV-1 LTR). We describe two distinct phases of signaling that target transcription factors known to bind the HIV-1 LTR, and thus drive viral transcription and replication, in cells of the Mtb-infected host. First, Mtb-derived molecules, including cell wall components and DNA, interact with a number of host pattern recognition receptors. Second, cytokines and chemokines secreted in response to Mtb infection initiate signal transduction cascades through their cognate receptors. Given the variation in cell wall components among distinct clinical Mtb strains, the initial pattern recognition receptor interaction leading to direct LTR activation and differential cytokine and chemokine production is likely to be an important aspect of Mtb strain-specific regulation of HIV-1 transcription and replication. Improved understanding of these molecular mechanisms in the context of bacterial and host genetics should provide key insights into the accelerated viral replication and disease progression characteristic of HIV/TB coinfection.

Stromal down-regulation of macrophage CD4/CCR5 expression and NF-κB activation mediates HIV-1 non-permissiveness in intestinal macrophages

Tissue macrophages are derived exclusively from blood monocytes, which as monocyte-derived macrophages support HIV-1 replication. However, among human tissue macrophages only intestinal macrophages are non-permissive to HIV-1, suggesting that the unique microenvironment in human intestinal mucosa renders lamina propria macrophages non-permissive to HIV-1. We investigated this hypothesis using blood monocytes and intestinal extracellular matrix (stroma)-conditioned media (S-CM) to model the exposure of newly recruited monocytes and resident macrophages to lamina propria stroma, where the cells take up residence in the intestinal mucosa. Exposure of monocytes to S-CM blocked up-regulation of CD4 and CCR5 expression during monocyte differentiation into macrophages and inhibited productive HIV-1 infection in differentiated macrophages. Importantly, exposure of monocyte-derived macrophages simultaneously to S-CM and HIV-1 also inhibited viral replication, and sorted CD4⁺ intestinal macrophages, a proportion of which expressed CCR5⁺, did not support HIV-1 replication, indicating that the non-permissiveness to HIV-1 was not due to reduced receptor expression alone. Consistent with this conclusion, S-CM also potently inhibited replication of HIV-1 pseudotyped with vesicular stomatitis virus glycoprotein, which provides CD4/CCR5-independent entry. Neutralization of TGF-β in S-CM and recombinant TGF-β studies showed that stromal TGF-β inhibited macrophage nuclear translocation of NF-κB and HIV-1 replication. Thus, the profound inability of intestinal macrophages to support productive HIV-1 infection is likely the consequence of microenvironmental down-regulation of macrophage HIV-1 receptor/coreceptor expression and NF-κB activation.

Human intestinal macrophages, unlike lymphoid tissue macrophages, brain microglia and genital (vaginal) macrophages, are profoundly incapable of supporting productive HIV-1 infection. Intriguingly, all macrophages are derived exclusively from blood monocytes, which are HIV-1 permissive after differentiation into monocyte-derived macrophages. Therefore, the unique non-permissiveness of intestinal macrophages to HIV-1 must be conferred by the intestinal mucosal microenvironment. Here we report that intestinal stroma potently blocked up-regulation of HIV-1 receptor/coreceptor CD4 and CCR5 expression during monocyte differentiation into macrophages and macrophage nuclear translocation of NF-κB, which is a critical requirement for HIV-1 transcription. These two mechanisms work collaboratively to render intestinal macrophages non-permissive to HIV-1. Harnessing this natural antiviral defense may provide a novel strategy to exploit for the prevention of infection in HIV-1 permissive cells.

Modulation of NFAT-dependent gene expression by the RhoA signaling pathway in T cells

We have reported previously that p115Rho guanine nucleotide exchange factor, its upstream activator Galpha13, and its effector RhoA are able to inhibit HIV-1 replication. Here, we show that RhoA is able to inhibit HIV-1 gene expression through the NFAT-binding site in the HIV long-terminal repeat. Constitutively active NFAT counteracts the inhibitory activity of RhoA, and inhibition of NFAT activation also inhibits HIV-1 gene expression. We have shown further that RhoA inhibits NFAT-dependent transcription and IL-2 production in human T cells. RhoA does not inhibit nuclear localization of NFAT but rather, inhibits its transcriptional activity. In addition, RhoA decreases the level of acetylated histone H3, but not NFAT occupancy, at the IL-2 promoter. These data suggest that activation of RhoA can modulate IL-2 gene expression by inhibiting the transcriptional activity of NFAT and chromatin structure at the IL-2 promoter during T cell activation.

Interleukin-15 but not interleukin-7 abrogates vaccine-induced decrease in virus level in simian immunodeficiency virus mac251-infected macaques

The loss of CD4(+) T cells and the impairment of CD8(+) T cell function in HIV infection suggest that pharmacological treatment with IL-7 and IL-15, cytokines that increase the homeostatic proliferation of T cells and improve effector function, may be beneficial. However, these cytokines could also have a detrimental effect in HIV-1-infected individuals, because both cytokines increase HIV replication in vitro. We assessed the impact of IL-7 and IL-15 treatment on viral replication and the immunogenicity of live poxvirus vaccines in SIV(mac251)-infected macaques (Macaca mulatta). Neither cytokine augmented the frequency of vaccine-expanded CD4(+) or CD8(+) memory T cells, clonal recruitment to the SIV-specific CD8(+) T cell pool, or CD8(+) T cell function. Vaccination alone transiently decreased the viral set point following antiretroviral therapy suspension. IL-15 induced massive proliferation of CD4(+) effector T cells and abrogated the ability of vaccination to decrease set point viremia. In contrast, IL-7 neither augmented nor decreased the vaccine effect and was associated with a decrease in TGF-beta expression. These results underscore the importance of testing immunomodulatory approaches in vivo to assess potential risks and benefits for HIV-1-infected individuals.

Influence of RANTES, SDF-1 and TGF-beta levels on the value of interleukin-7 as a predictor of virological response in HIV-1-infected patients receiving double boosted protease inhibitor-based therapy

OBJECTIVES

Interleukin-7 (IL-7), RANTES (regulated on activation, normal T cell expressed and secreted), stromal cell-derived factor-1 (SDF-1) and transforming growth factor-beta (TGF-beta) appear to share certain biological properties in vitro and all are involved in HIV-1 disease progression. Our earlier observations indicated that IL-7 levels decrease upon CD4 T-cell recovery and represent a new, independent predictor of virological response. Here, we examine associations among circulating levels of IL-7, RANTES, SDF-1 and TGF-beta in hopes of gaining insight into their contribution to the predictive value of IL-7.

METHODS

Levels of IL-7, RANTES, SDF-1 and TGF-beta, and immune and viral parameters were assessed in HIV-1-infected patients.

RESULTS

Cross-sectional (n=148) and longitudinal (n=36) analyses showed that levels of IL-7, but not RANTES, SDF-1 or TGF-beta, were increased in HIV-1-infected adults compared with those of healthy controls. In the cross-sectional study, levels of IL-7 were correlated with RANTES (r=0.31, P=0.002) and TGF-beta (r=0.53, P<0.001) but not with SDF-1 (r=0.12, P=0.22), and these associations were more pronounced in patients with CD4 T-cell counts >200 cells/microL. In contrast to IL-7, levels of RANTES, SDF-1 and TGF-beta were not correlated with CD4 T-cell counts. Longitudinal analysis revealed a marked decline in IL-7 levels accompanied by an increase in CD4 T-cell count following antiretroviral therapy (ART), but no changes in RANTES, SDF-1 or TGF-beta levels. Multivariate regression analysis showed no influence of baseline RANTES, SDF-1 or TGF-beta levels on the value of IL-7 as a predictor of virological response at 48 weeks.

CONCLUSIONS

Collectively, these results indicate that changes in IL-7 levels did not induce changes in RANTES, SDF-1 or TGF-beta. Furthermore, they indicate that RANTES, SDF-1 or TGF-beta levels do not explain the predictor value of IL-7 in patients receiving ART.

Role of cytokines and chemokines in the regulation of innate immunity and HIV infection

The earliest defense against microbial infection is represented by the responses of the innate (or natural) immune system, that also profoundly regulates the adaptive (or acquired) T- and B-cell immune responses. Activation of the innate immune system is primed by microbial invasion in response to conserved structures present in large groups of microorganisms (LPS, peptidoglycan, double-stranded RNA), and is finely tuned by different cell types (including dendritic cells, macrophages, natural killer cells, natural killer T cells, and gammadelta T cells). In addition, several soluble factors (complement components, defensins, mannose-binding lectins, interferons, cytokines and chemokines) can play a major role in the regulation of both the innate and adaptive immunity. In this review, we will briefly overview the regulation of some cellular subsets of the innate immune system particularly involved in human immunodeficiency virus (HIV) infection and then focus our attention on those cytokines and chemokines whose levels of expression are more profoundly affected by HIV infection and that, conversely, can modulate virus infection and replication.

Cell-type-dependent effect of transforming growth factor beta, a major cytokine in breast milk, on human immunodeficiency virus type 1 infection of mammary epithelial MCF-7 cells or macrophages

Breastfeeding plays a substantial role in mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1). Mammary epithelial cells, as well as macrophages and lymphocytes, are thought to serve as sources of the virus in breast milk. Soluble factors in breast milk exert various biological functions, including immune tolerance or immune modulation, and may influence milk-borne infection with HIV-1. In this study we show that transforming growth factor beta (TGF-beta), a major cytokine in breast milk, inhibited HIV-1 infection of mammary epithelial MCF-7 cells but enhanced that of macrophages. TGF-beta downregulated the HIV-1 long terminal repeat (LTR) promoter in MCF-7 cells but upregulated it in macrophages. Stimulation with TGF-beta suppressed NF-kappaB binding to the HIV-1 LTR in MCF-7 cells, at least in part by downregulating induced IkappaB kinase expression. Cell type-dependent effects of TGF-beta on HIV-1 expression may play a role in milk-borne infection with HIV-1.

Increased plasma transforming growth factor-beta1 is associated with disease progression in HIV-1-infected patients

Transforming growth factor-beta(1) (TGF-beta(1)) is a pleiotropic cytokine with a variety of effects on a wide range of cells in the immune system. Evidence suggests that TGF-beta(1) is also involved in the pathogenesis of human immunodeficiency virus type 1 infections. The aim of this study was to explore possible relationships between circulating TGF-beta(1) and immune as well as clinical HIV infection parameters with special impact on disease progression. TGF-beta(1) concentrations were measured by ELISA in the plasma of 66 patients in different stages of HIV infection and 20 healthy controls. HIV infection resulted in a significant increase of plasma TGF-beta(1) concentration compared to healthy individuals (11.4 +/- 6.8 vs. 6.1 +/- 1.5 ng/mL, p < 0.01). TGF-beta(1) values showed a significant negative correlation with CD4 cells count (r = -0.42, p = 0.001), as well as with CD8 cells count (r = -0.031, p < 0.05). Moreover, patients with the symptomatic phase of HIV infection presented an almost twofold increase of plasma TGF-beta(1) concentration in comparison to asymptomatic patients and healthy individuals. Our results demonstrate the relationship between TGF-beta(1) concentrations and HIV infection advancement with marked elevation in the late stages of the disease. These findings support in vitro observations suggesting an important, immunosuppressive role of TGF-beta(1) in HIV infection pathogenesis.

Basic fibroblast growth factor (bFGF) and its receptor expression (bek and flg) In bone marrow stroma of murine AIDS

Murine acquired immunodeficiency disease (MAIDS) induced by LPBM5 MuLV is characterized by a late-stage lymphoma and hematopoietic cytopenias similar to those observed in human AIDS. The pathogenesis of MAIDS-related lymphoma/cytopenia is unknown but it has been postulated to involve a defective marrow microenvironment or stroma. The basic Fibroblast Growth Factor (bFGF) of stromal origin is an important stimulator for hematopoietic progenitors of several lineages. Long-term bone marrow cultures (LTBMCs) were established and pure stromal cell cultures were used for in vitro infection hematopoietic reconstitution studies. Reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze bFGF gene expression in stromal cells derived from either viral-infected marrow or uninfected marrow. RT-PCR analysis showed a 40% reduction in the expression of bFGF transcript expression from viral-infected stromal cells, however, the levels of bek and flg bFGF receptors remained unchanged indicating virus-infection only inhibited bFGF gene expression in stromal cells. Viral infection was associated with a progressive decrease in bFGF transcript expression 35% of control at day 7, 50% of control at day 14 and 60% of control at day 21 compared to the mock-infected cultures. In addition, for bek and flg the transcript expression in, in vitro-infected primary cultures were comparable to the mock-infected cultures and remained essentially unchanged throughout culture period. Western blot analysis revealed viral-infected stromal cells produced a 45% decrease in bFGF protein production. Reduction of bFGF protein was confirmed by indirect immunofluorescent staining. We report MuLV infection reduces bFGF transcript expression but not its surface-receptors (bek and flg) in infected stromal cells. Impaired hematopoiesis consistently exhibited from MuLV-infected stromal cultures was restored by exogenous bFGF; therefore, bFGF was responsible in restoration of normal marrow stromal support function. These results suggest a role for bFGF deficiency in the pathogenesis of MAIDS-related marrow failure.

Secretion of cytokines and growth factors as a general cause of constitutive NFkappaB activation in cancer

The constitutive activation of nuclear factor kappaB (NFkappaB) helps a variety of tumors to resist apoptosis and desensitizes them to chemotherapy, but the causes are still largely unknown. We have analysed this phenomenon in eight mutant cell lines derived from human 293 cells, selected for NFkappaB-dependent expression of a marker gene, and also in seven tumor-derived cell lines. Conditioned media from all of these cells stimulated the activation of NFkappaB (up to 30-fold) in indicator cells carrying an NFkappaB-responsive reporter. Therefore, secretion of extracellular factors as the cause of constitutive activation seems to be general. The mRNAs encoding several different cytokines and growth factors were greatly overexpressed in the tumor and mutant cells. The pattern of overexpression was distinct in each cell line, indicating that the phenomenon is complex. Two secreted factors whose roles in the constitutive activation of NFkappaB are not well defined were investigated further as pure proteins: transforming growth factor beta2 (TGFbeta2) and fibroblast growth factor 5 (FGF5) were both highly expressed in some mutant clones and tumor cell lines, each activated NFkappaB alone, and the combination was synergistic. Our data indicate that a group of different factors, expressed at abnormally high levels, can contribute singly and synergistically to the constitutive activation of NFkappaB in all of the mutant and tumor cell lines we studied. Since several NFkappaB target genes encode secreted proteins that induce NFkappaB, autocrine loops are likely to be ubiquitously important in the constitutive activation of NFkappaB in cancer. We provide the first evidence of the general, complex, and synergistic activation of NFkappaB in tumor and mutant cell lines through the action of secreted factors and suggest that the same explanation is likely for the constitutive activation of NFkappaB in cancers.

Bile salts regulate intestinal epithelial cell migration by nuclear factor-kappa B-induced expression of transforming growth factor-beta

BACKGROUND

Mucosal restitution is an important repair modality in the gastrointestinal tract. We have shown that taurodeoxycholate increases intestinal epithelial cell migration by increasing TGF-beta expression, and that the transcription factor NF-kappa B regulates TDCA induced cell migration after injury. The objectives of this study were to determine if this is a property shared by other bile salts or an effect specific to TDCA, and to determine if NF-kappa B regulates TGF-beta expression.

STUDY DESIGN

Studies were conducted in IEC-6 cells. Cell migration was examined using an in vitro model. TGF-beta protein and mRNA expression was determined by ELISA and Northern blot analysis. Sequence-specific NF-kappa B binding activity was measured by gel shift assays.

RESULTS

Taurocholate and deoxycholate at physiologic concentrations significantly increased intestinal epithelial cell migration 6 hours after wounding (p < 0.01), and was associated with a significant increase in specific NF-kappa B binding activity. Inhibition of NF-kappa B activity significantly inhibited cell migration during restitution and resulted in a significant decrease in TGF-beta mRNA expression and protein expression.

CONCLUSIONS

We conclude that bile salts at physiologic conditions increase cell migration after injury, an effect regulated by NF-kappa B. Further, NF-kappa B elicits TGF-beta gene transcription during cell migration. These data support a physiologic role of bile salts in the maintenance of intestinal mucosal integrity.

A role of the TATA box and the general co-activator hTAF(II)130/135 in promoter-specific trans-activation by simian virus 40 small t antigen

The small t antigen (st-ag) of simian virus 40 can exert pleiotropic effects on biological processes such as DNA replication, cell cycle progression and gene expression. One possible mode of achieving these effects is through stimulation of NFkappaB-responsive genes encoding growth factors, cytokines, transcription factors and cell cycle regulatory proteins. Indeed, a previous study has shown that st-ag enhanced NFkappaB-mediated transcription. This study demonstrates that promoters possessing a consensus TATA box (i.e. TATAAAAG) in the context of either NFkappaB- or Sp1-binding sites are trans-activated by st-ag. Overexpressing the general transcription factor hTAF(II)130/135, but not hTAF(II)28 or hTAF(II)80, stimulated the activity of promoters in a consensus TATA box-dependent mode. Converting the consensus TATA motif into a non-consensus TATA box strongly impaired activation by st-ag and hTAF(II)130/135. Conversely, mutating a non-consensus TATA motif into the consensus TATA box rendered the mutated promoter inducible by st-ag and hTAF(II)130/135. Mutation of the TATA box had no effect on TNFalpha- or RelA/p65-mediated induction of NFkappaB-responsive promoters, indicating a specific st-ag effect on hTAF(II)130/135. St-ag stimulated the intrinsic transcriptional activity of hTAF(II)130/135. Substitutions in the conserved HPDKGG motif in the N-terminal region or a mutation that impaired the interaction with protein phosphatase 2A abrogated the ability of st-ag to activate hTAF(II)130/135-mediated transcription. These results indicate that trans-activation of promoters by st-ag may depend on a consensus TATA motif and suggest that such promoters recruit the general transcription factor hTAF(II)130/135.

IKK beta plays an essential role in the phosphorylation of RelA/p65 on serine 536 induced by lipopolysaccharide

Activation of the I kappa B kinase (IKK) complex by LPS induces phosphorylation and degradation of I kappa B alpha, leading to the nuclear translocation of NF-kappa B. Although it is essential for NF-kappa B activation, emerging evidence has indicated that the nuclear translocation of NF-kappa B is not sufficient to activate NF-kappa B-dependent transcription. Here, we reported that LPS induced the phosphorylation of the p65 trans-activation domain on serine 536 in monocytes/macrophages. Using mouse embryonic fibroblasts lacking either IKK alpha or IKK beta, we found that IKK beta played an essential role in LPS-induced p65 phosphorylation on serine 536, while IKK alpha was partially required for the p65 phosphorylation. The LPS-induced p65 phosphorylation on serine 536 was independent of the phosphatidylinositol 3'-kinase/Akt signaling pathway. Furthermore, we found that the phosphorylation on serine 536 increased the p65 transcription activity. In summary, our results demonstrate that IKK beta plays an essential role in the LPS-induced p65 phosphorylation on serine 536, which may represent a mechanism to regulate the NF-kappa B transcription activity by LPS.

Transforming growth factor-beta -Smad signaling pathway cooperates with NF-kappa B to mediate nontypeable Haemophilus influenzae-induced MUC2 mucin transcription

Transforming growth factor-beta (TGF-beta) and related factors are multifunctional cytokines that regulate diverse cellular processes, including proliferation, differentiation, apoptosis, and immune response. The involvement of TGF-beta receptor-mediated signaling in bacteria-induced up-regulation of mucin, a primary innate defensive response for mammalian airways, however, still remains unknown. Here, we report that the bacterium nontypeable Haemophilus influenzae (NTHi), an important human respiratory pathogen, utilizes the TGF-beta-Smad signaling pathway together with the TLR2-MyD88-TAK1-NIK-IKKbeta/gamma-IkappaBalpha pathway to mediate NF-kappaB-dependent MUC2 mucin transcription. The NTHi-induced TGF-beta receptor Type II phosphorylation occurred at as early as 5 min. Pretreatment of NTHi with TGF-beta neutralization antibody reduced up-regulation of MUC2 transcription. Moreover, functional cooperation of NF-kappaB p65/p50 with Smad3/4 appears to positively mediate NF-kappaB-dependent MUC2 transcription. These data are the first to demonstrate the involvement of TGF-beta receptor-mediated signaling in bacteria-induced up-regulation of mucin transcription, bring insights into the novel role of TGF-beta signaling in bacterial pathogenesis, and may lead to new therapeutic intervention of NTHi infections.

c-Myc sensitizes cells to tumor necrosis factor-mediated apoptosis by inhibiting nuclear factor kappa B transactivation

Nuclear factor kappaB (NF-kappaB) plays a key role in suppression of tumor necrosis factor (TNF)-mediated apoptosis by inducing a variety of anti-apoptotic genes. Expression of c-Myc has been shown to sensitize cells to TNF-mediated apoptosis by inhibiting NF-kappaB activation. However, the precise step in the NF-kappaB signaling pathway and apoptosis modified by c-Myc has not been identified. Using the inducible c-MycER system and c-Myc null fibroblasts, we found that expression of c-Myc inhibited NF-kappaB activation by interfering with RelA/p65 transactivation but not nuclear translocation of NF-kappaB. Activation of c-Myc promoted TNF-induced release of cytochrome c from mitochondria to the cytosol because of the inhibition of NF-kappaB. Furthermore, we found that NF-kappaB-inducible gene A1 was attenuated by expression of c-Myc and that the restoration of A1 expression suppressed c-Myc-induced TNF sensitization. Our results elucidate the molecular mechanisms by which c-Myc increases cell susceptibility to TNF-mediated apoptosis, indicating that c-Myc may exhibit its pro-apoptotic activities by repression of cell survival genes.

Interaction between TGFbeta signaling proteins and C/EBP controls basal and Tat-mediated transcription of HIV-1 LTR in astrocytes

Signal transduction pathways induced by cytokines can modulate the level of HIV-1 gene transcription and replication in a variety of cells including those from the central nervous system. Here, we investigated the effect of TGFbeta-1 signaling the factors, including Smads, on transcription of the viral LTR in human astrocytic cells. Ectopic expression of Smad-3 increased activity of the viral promoter, while its partner protein, Smad-4, caused a slight decrease in viral gene transcription. Further, Smad-4 was able to suppress transcriptional activation of the LTR by Smad-3 as well as by C/EBPbeta, another activator of LTR transcription in these cells. Results from promoter deletion experiments identified the C/EBP-binding site, which is positioned between nucleotides -114 and -102 as one of the targets for Smad-mediated regulation of the LTR. Band-shift studies showed inhibition of C/EBP binding to its target DNA in protein extract from cells overexpressing Smad-3 and Smad-4. Results from GST pull-down assay and combined immunoprecipitation/Western blot of protein extracts from human astrocytes verified the association of Smad-3 and Smad-4 with C/EBPbeta, suggesting that interaction of C/EBPbeta with Smad-3 and Smad-4 may have a negative impact upon C/EBPbeta-mediated activation of the LTR. Interestingly, Smad-4 showed no inhibitory effect on viral gene transcription in cells expressing Tat protein. However, in the presence of Smad-3, expression of Smad-4 exerted a negative effect on Tat-mediated activation of the LTR promoter. These observations pointed to the functional interplay between viral and cellular proteins in modulating LTR transcription.

Cytokine receptor common beta subunit-mediated STAT5 activation confers NF-kappa B activation in murine proB cell line Ba/F3 cells

The cytokine receptor common beta subunit (beta(c)) transmits intracellular signals upon binding ligand such as granulocyte-macrophage colony-stimulating factor or interleukin-3 (IL-3); however, transcriptional regulation under the control of signaling events downstream of the beta(c) is not fully understood. Using murine Ba/F3 cells, here we demonstrate that the beta(c)-mediated signals stimulate NF-kappa B-driven gene expression of not only the reporter construct but also endogenous target genes such as IL-6. Analyzing the effects of several inhibitors or mutant receptors revealed that this NF-kappa B activation is mediated neither by MEK/ERK/MAPK nor by the phosphatidylinositol 3-kinase pathway but by STAT5. Overexpression experiments of the wild-type or constitutive active form of STAT5 further confirmed this notion. In addition, STAT5-dependent NF-kappa B activation is mediated not through an inducible nuclear translocation but via up-regulation of both DNA binding activity and transactivation potential of NF-kappa B. Furthermore, we also show that as yet undefined humoral factor(s) may be involved in this NF-kappa B activation process. Taken together, we may propose that cytokine receptor-mediated STAT5 activation and expression of its target genes culminates in a unique mode of NF-kappa B activation and gene expression.

Mullerian-inhibiting substance regulates NF-kappa B signaling in the prostate in vitro and in vivo

Mullerian-inhibiting substance (MIS) is a member of the transforming growth factor beta superfamily, a class of molecules that regulates growth, differentiation, and apoptosis in many cells. MIS type II receptor in the Mullerian duct is temporally and spatially regulated during development and becomes restricted to the most caudal ends that fuse to form the prostatic utricle. In this article, we have demonstrated MIS type II receptor expression in the normal prostate, human prostate cancer cell lines, and tissue derived from patients with prostate adenocarcinomas. MIS induced NF-kappaB DNA binding activity and selectively up-regulated the immediate early gene IEX-1S in both androgen-dependent and independent human prostate cancer cells in vitro. Dominant negative IkappaBalpha expression ablated both MIS-induced increase of IEX-1S mRNA and inhibition of growth, indicating that activation of NF-kappaB signaling was required for these processes. Androgen also induced NF-kappaB DNA binding activity in prostate cancer cells but without induction of IEX-1S mRNA, suggesting that MIS-mediated increase in IEX-1S was independent of androgen-mediated signaling. Administration of MIS to male mice induced IEX-1S mRNA in the prostate in vivo, suggesting that MIS may function as an endogenous hormonal regulator of NF-kappaB signaling and growth in the prostate gland.

Transforming growth factor-beta signal transduction in epithelial cells

Transforming growth factor (TGF)-beta is a natural and potent growth inhibitor of a variety of cell types, including epithelial, endothelial, and hematopoietic cells. The ability of TGF-beta to potently inhibit the growth of many solid tumors of epithelial origin, including breast and colon carcinomas, is of particular interest. However, many solid tumor cells become refractory to the growth inhibitory effects of TGF-beta due to defects in TGF-beta signaling pathways. In addition, TGF-beta may stimulate the invasiveness of tumor cells via the paracrine effects of TGF-beta. Accordingly, in order to develop more effective anticancer therapeutics, it is necessary to determine the TGF-beta signal transduction pathways underlying the growth inhibitory effects and other cellular effects of TGF-beta in normal epithelial cells. Thus far, two primary signaling cascades downstream of the TGF-beta receptors have been elucidated, the Sma and mothers against decapentaplegic homologues and the Ras/mitogen-activated protein kinase pathways. The major objective of this review is to summarize TGF-beta signaling in epithelial cells, focusing on recent advances involving the Sma and mothers against decapentaplegic homologues and Ras/mitogen-activated protein kinase pathways. This review is particularly timely in that it provides a comprehensive summary of both signal transduction mechanisms and the cell cycle effects of TGF-beta.

Nef triggers a transcriptional program in T cells imitating single-signal T cell activation and inducing HIV virulence mediators

Gene expression profiling was used to explore the role of Nef in HIV. Nef induces a transcriptional program in T cells that is 97% identical to that of anti-CD3 T cell activation. This program is inhibited in the presence of cyclosporin. A requirement for TCR zeta and ZAP-70 is demonstrated for formation of the complete profile. Among eight factors particular to the anti-CD3 activation profile are IL16 and YY1, negative regulators of HIV transcription. In contrast, Nef exclusively upregulates factors positively regulating HIV, including Tat-SF1, U1 SNRNP, and IRF-2. New genes associated with Nef include CDK9, the induction of which enhances Tat function. Thus, Nef acts as a master switch early in the viral life cycle, forcing an environment conducive to dynamic viral production.

Activation of nuclear factor kappaB at the onset of ossification of the spinal ligaments

We examined the correlation between the activation of nuclear factor kappaB (NFkappaB), stimulated by environmental factors involving cytokines and growth factors in ligament cells, and the onset of ossification of the spinal ligaments (OSL) or diffuse idiopathic skeletal hyperostosis (DISH). Aseptic samples were taken carefully from non-ossified sites during surgery (75 patients). We carried out preliminary hematoxylin and eosin and toluidine blue staining, using five portions of each specimen, and excluded samples containing chondrocytic, osteoblastic, or inflammatory cells (n = 25). We used specimens from the remaining 50 patients (35 men and 15 women, ranging in age from 45-81 years); average age, 59.5 years (18 nuchal ligament specimens, and 32 yellow ligament specimens). OSL or DISH had occurred in 25 patients, 20 patients were in the non-OSL group (8 with cervical spondylotic myelopathy, and 12 with lumbar canal stenosis), and the remaining 5 samples were collected from patients with injury. For culture study, we used portions of the 14 largest samples from the above 50 patients. We extracted nuclear proteins and cytoplasmic proteins from non-ossified spinal ligaments in 50 patients and detected p65RelA/NFkappaB by Western blotting. Tumor necrosis factor-alpha (TNF alpha), interleukin 1beta (IL-1beta), platelet-derived growth factor BB (PDGF-BB) and transforming growth factor-beta1 (TGF-beta1) in cytoplasm were quantified by enzyme-linked immunosorbent assays (ELISA). Cultured cells from the 14 samples were then stimulated with 10, 100, 250, or 500 ng/ml of recombinant human (rh)PDGF-B or TGFbeta1. A control experiment was performed without rhPDGF-BB or TGFbeta1 stimulation. Alkaline phosphatase (ALP) activity was standardized by the DNA content of the cells. The number of NFkappaB-positive samples was significantly higher in patients with OSL or DISH than in non-OSL patients. This tendency was obvious in the case of OSL or DISH with non-insulin-dependent diabetes mellitus (NIDDM). In OSL and in DISH patients, significantly greater amounts of PDGF-BB and TGFbeta1 were seen in ligament cells than in non-OSL patients (P < 0.05). There was a positive correlation between the detection of p65RelA/NFkappaB band and the content of PDGF-BB and TGFbeta1 in ligament cells (P < 0.05). ALP activity tended to be higher in cells in the OSL group not receiving any other treatment. Our results indicate the possibility that NFkappaB, stimulated by environmental factors involving PDGF-BB and TGFbeta1 in ligament cells, influences the osteoblastic differentiation of undifferentiated mesenchymal cells.

Interaction and functional cooperation of NF-kappa B with Smads. Transcriptional regulation of the junB promoter

The transforming growth factor-beta (TGF-beta) family of cytokines regulates diverse cellular processes through control of the expression of target genes. Smad proteins are a recently identified family of signal transducers for members of the TGF-beta family. Smads act as transcriptional regulators through binding to DNA and interacting with a variety of transcription factors. Here, we identified a kappaB site as a TGF-beta-responsive region in the 3'-downstream junB promoter region. We also demonstrate that kappaB sites alone are sufficient to mediate immediate transcriptional activation by TGF-beta. Transactivation of kappaB sites by TGF-beta requires an intact NF-kappaB pathway, cooperates with known activators of this pathway, and is mediated by Smad family members. Furthermore, we show that Smad3 interacts with p52 in vivo. These data expand the model in which Smad proteins undergo multiple interactions with several transcription factors that could induce either activation or repression of gene expression.

Bone morphogenetic proteins and retinoic acid induce human endogenous retrovirus HERV-K expression in NT2D1 human embryonal carcinoma cells

Expression of the HERV-K human endogenous retrovirus is very low in normal and tumor tissue, but is readily detected in testicular germ cell tumors (TGCT). NT2D1 human embryonal carcinoma cells represent in vitro models for the stem cells of TGCT, and can be differentiated by treatment with bone morphogenetic proteins (BMP) or retinoic acid (RA). In a search for BMP target genes in NT2D1 cells, HERV-K was identified as an early BMP and RA target. It was shown that HERV-K expression was induced upon treatment of NT2D1 cells with BMP or with RA, but not with activin or transforming growth factor (TGF)-beta. Induction of HERV-K expression was rapid but transient, with transcripts becoming undetectable in differentiated NT2D1 cultures. Thus NT2D1 cells provide a suitable in vitro system for the study of the factors controlling HERV-K expression during cellular differentiation, which may play a role in HERV-K expression in TGCT.

Repression of transforming-growth-factor-beta-mediated transcription by nuclear factor kappaB

Activation of transforming growth factor-beta (TGF-beta) and activin receptors leads to phosphorylation of Sma- and Mad-related protein 2 (Smad2) and Smad3, which function as transcription factors to regulate gene expression. Smad7 is a regulatory protein which is able to inhibit TGF-beta and activin signalling in a negative-feedback loop, mediated by a direct regulation by Smad3 and Smad4 via a Smad-binding element (SBE) in the Smad7 promoter. Interestingly, we found that the Smad7 promoter was also regulated by nuclear factor kappaB (NF-kappaB), a transcription factor which plays an important role in inflammation and the immune response. Expression of NF-kappaB p65 subunit was able to inhibit the Smad7 promoter activity, and this inhibition could be reversed by co-expression of IkappaB, an inhibitor of NF-kappaB. In addition, the inhibitory activity of p65 was observed in a minimal promoter that contained only the Smad7 SBE and a TATA box, without any consensus NF-kappaB binding site. This inhibitory effect appeared to be common to other TGF-beta- and activin-responsive promoters, since p65 also inhibited the forkhead-activin-signal-transducer-2-mediated activation of a Xenopus Mix.2 promoter, as well as the Smad3-mediated activation of 3TP-lux which contains PMA-responsive elements and a plasminogen-activator-inhibitor-1 promoter. Activation of endogenous NF-kappaB by tumour necrosis factor-alpha (TNF-alpha) was also able to inhibit the Smad7 promoter in human embryonic kidney 293 cells. In human hepatoma HepG2 cells, TNF-alpha was able to inhibit TGF-beta- and activin-mediated transcriptional activation. Furthermore, overexpression of the transcription co-activator p300 could abrogate the inhibitory effect of NF-kappaB on the Smad7 promoter. Taken together, these data have indicated a novel mode of crosstalk between the Smad and the NF-kappaB signalling cascades at the transcriptional level by competing for a limiting pool of transcription co-activators.

Modulation of susceptibility to HIV-1 infection by the cytotoxic T lymphocyte antigen 4 costimulatory molecule

CD4 T cells activated in vitro by anti-CD3/28-coated beads are resistant to infection by CC chemokine receptor 5 (CCR5)-dependent HIV-1 isolates. In vivo, antigen-presenting cells (APCs) activate CD4 T cells in part by signaling through the T cell receptor and CD28, yet cells stimulated in this manner are susceptible to HIV-1 infection. We show that cytotoxic T lymphocyte antigen 4 (CTLA-4) engagement counteracts the CD28 antiviral effects, and that the ratio of CTLA-4 to CD28 engagement determines the susceptibility of HIV-1 infection. Furthermore, unopposed CTLA-4 signaling provided by CD28 blockade promotes vigorous HIV-1 replication, despite minimal T cell proliferation. Finally, CTLA-4 antibodies decrease the susceptibility of antigen-activated CD4 T cells to HIV, suggesting a potential approach to prevent or limit viral spread in HIV-1-infected individuals.

Schnurri interacts with Mad in a Dpp-dependent manner

BACKGROUND

Decapentaplegic (Dpp) is a member of the transforming growth factor-beta superfamily. Dpp governs various developmental processes in Drosophila through the transcriptional regulation of a variety of genes. Signals of Dpp are transmitted from the cell membrane to the nucleus by Medea and Mad, both belonging to the Smad protein family. Mad was shown to bind to the Dpp-responsive element in genes such as vestigial, labial, and Ultrabithorax. The DNA binding affinity of Smad proteins is relatively low, and requires other nuclear factor(s) to form stable DNA binding complexes. schnurri (shn) was identified as a candidate gene acting downstream of Dpp receptors, but its relevance to Mad has remained unknown.

RESULTS

We characterized the biochemical functions of Shn. Shn forms homo-oligomers. Shn is localized in the nucleus, and is likely to have multiple nuclear localizing signals. Finally, we found that Shn interacts with Mad in a Dpp-dependent manner.

CONCLUSIONS

The present results argue that Shn may act as a nuclear component of the Dpp signalling pathway through direct interaction with Mad.

A mechanism of suppression of TGF-beta/SMAD signaling by NF-kappa B/RelA

A number of pathogenic and proinflammatory stimuli, and the transforming growth factor-beta (TGF-beta) exert opposing activities in cellular and immune responses. Here we show that the RelA subunit of nuclear factor kappaB (NF-kappaB/RelA) is necessary for the inhibition of TGF-beta-induced phosphorylation, nuclear translocation, and DNA binding of SMAD signaling complexes by tumor necrosis factor-alpha (TNF-alpha). The antagonism is mediated through up-regulation of Smad7 synthesis and induction of stable associations between ligand-activated TGF-beta receptors and inhibitory Smad7. Down-regulation of endogenous Smad7 by expression of antisense mRNA releases TGF-beta/SMAD-induced transcriptional responses from suppression by cytokine-activated NF-kappaB/RelA. Following stimulation with bacterial lipopolysaccharide (LPS), or the proinflammatory cytokines TNF-alpha and interleukin-1beta (IL-1beta, NF-kappaB/RelA induces Smad7 synthesis through activation of Smad7 gene transcription. These results suggest a mechanism of suppression of TGF-beta/SMAD signaling by opposing stimuli mediated through the activation of inhibitory Smad7 by NF-kappaB/RelA.

A mechanism of suppression of TGF–β/SMAD signaling by NF-κB/RelA

A number of pathogenic and proinflammatory stimuli, and the transforming growth factor-β (TGF-β) exert opposing activities in cellular and immune responses. Here we show that the RelA subunit of nuclear factor κB (NF-κB/RelA) is necessary for the inhibition of TGF-β-induced phosphorylation, nuclear translocation, and DNA binding of SMAD signaling complexes by tumor necrosis factor-α (TNF-α). The antagonism is mediated through up-regulation of Smad7 synthesis and induction of stable associations between ligand-activated TGF-β receptors and inhibitory Smad7. Down-regulation of endogenous Smad7 by expression of antisense mRNA releases TGF-β/SMAD-induced transcriptional responses from suppression by cytokine-activated NF-κB/RelA. Following stimulation with bacterial lipopolysaccharide (LPS), or the proinflammatory cytokines TNF-α and interleukin-1β (IL-1β, NF-κB/RelA induces Smad7 synthesis through activation of Smad7 gene transcription. These results suggest a mechanism of suppression of TGF-β/SMAD signaling by opposing stimuli mediated through the activation of inhibitory Smad7 by NF-κB/RelA.

Transcriptional regulation of fibronectin gene by phorbol myristate acetate in hepatoma cells: a negative role for NF-kappaB

The transcriptional regulation of the fibronectin (FN) gene in hepatoma cells by phorbol myristate acetate (PMA) was investigated. PMA increased the synthesis and mRNA levels of FN and its promoter activity in Hep3B hepatoma cells. The PMA-induced activation of FN expression was blocked by a protein kinase C (PKC) inhibitor and did not require a new protein synthesis. Deletion analysis revealed that the sequence between positions -69 and +136 of the FN gene was responsible for the PMA induction. Two PMA-inducible nuclear protein complexes were found to bind to a putative NF-kappaB site at -41 and were identified as a p65/p50 heterodimer and a p50/50 homodimer of NF-kappaB family. Mutations in the -41 NF-kappaB site, however, did not block the PMA induction of the FN promoter but rather enhanced it. Overexpression of p65 increased the FN promoter activity. While overexpression of p50 alone did not affect the promoter activity, it decreased the p65-induced activation of the FN promoter. Mutations in the -41 NF-kappaB site attenuated the p50-mediated suppression of the p65 transactivation of the FN promoter. Deletion of the sequence between +1 and +136 decreased the basal and PMA-induced activities of the FN promoter. This study shows that PMA induces the transcription of the FN gene in hepatoma cells via the PKC pathway. The DNA sequence between +1 and +136 is responsible, at least in part, for the PMA-induced activation of the FN gene, while the -41 NF-kappaB binding site plays as a negative regulatory element for it. In addition, this study is the first to show a role for NF-kappaB p65 in the transcriptional activation of the FN gene.

TGF-beta1 regulation of dendritic cells

Dendritic cells (DCs) represent antigen-presenting cell (APC) populations in lymphoid and nonlymphoid organs which are considered to play key roles in the initiation of antigen-specific T-cell proliferation. According to current knowledge, the net outcome of T-cell immune responses seems to be significantly influenced by the activation stage of antigen-presenting DCs. Several studies have shown that transforming growth factor-beta 1 (TGF-beta1) inhibits in vitro activation and maturation of DCs. TGF-beta1 inhibits upregulation of critical T-cell costimulatory molecules on the surface of DCs and reduces the antigen-presenting capacity of DCs. Thus, in addition to direct inhibitory effects of TGF-beta1 on effector T lymphocytes, inhibitory effects of TGF-beta1 at the level of APCs may critically contribute to previously characterized immunosuppressive effects of TGF-beta1. In contrast to these negative regulatory effects of TGF-beta1 on function and maturation of lymphoid tissue type DCs, certain subpopulations of immature DCs in nonlymphoid tissues are positively regulated by TGF-beta1 signaling. In particular, epithelial-associated DC populations seem to critically require TGF-beta1 stimulation for development and function. Recent studies established that TGF-beta1 stimulation is absolutely required for the development of epithelial Langerhans cells (LCs) in vitro and in vivo. Furthermore, TGF-beta1 seems to enhance antigen processing and costimulatory functions of epithelial LCs.

A 23-bp sequence element from human neurotropic JC virus is responsive to NF-kappa B subunits

The regulatory region of the human neurotropic JC virus (JCV) is composed of several cis-acting motifs that confer cell type specificity to viral gene transcription and enable the viral promoters to respond to extracellular stimuli. For example, the bidirectional 98-bp tandem repeat sequences, positioned between the JCV early and late genes, were shown to be responsible for basal and activated levels of viral gene transcription in central nervous system (CNS) cells. Additionally, the NF-kappaB site located approximately 75 bp from the repeats on the early side of the viral genome was also found to influence both levels of viral transcription. Recently, we isolated a novel JCV variant, JCV(Phila-1), from a clinical specimen that contains a 23-bp sequence element (23-bpse) within its promoter-enhancer region. Here we demonstrate that this element is responsive to an extracellular stimulatory factor, such as phorbol 12-myristate 13-acetate (PMA), and can augment the basal levels of the viral early and to a lesser degree late promoter activities in cells derived from the CNS. The 23-bpse, by associating with nuclear proteins present in uninduced cells, forms a 40-kDa DNA-protein complex. Although no direct correlation between transcriptional enhancement of the JCV promoter by PMA treatment and the level of the 40-kDa DNA-protein complex was observed, results from site-directed mutagenesis indicated that formation of this complex is critical for the transcriptional activation of the viral promoter by PMA. These observations suggested that transcriptional enhancement of the JCV promoter activity upon PMA treatment may be an indirect event and mediated by an intermediary factor(s). In this respect, we demonstrated that overexpression of the inducible NF-kappaB subunits, p50 and p65, enhanced transcriptional activity of the JCV promoter through the 23-bp region with no evidence for their direct association with the 23-bpse DNA. Of importance, the p50/p65-induced JCV promoter activity requires the nucleotide sequences within the 23-bpse that are critical for the assembly of the 40-kDa DNA-protein complex. Thus, it is likely that the NF-kappaB subunits, by recruiting the cellular factors such as those associated with the 40-kDa DNA-protein complex, influence the basal level of the viral gene transcription. The implications of these findings with respect to regulation of viral and cellular genomes by extracellular stimuli and NF-kappaB pathway are discussed.

Dopamine stimulates expression of the human immunodeficiency virus type 1 via NF-kappaB in cells of the immune system

Recent studies have reported that lymphocytes produce, transport and bind dopamine present in plasma. However, the action of dopamine on HIV-1 gene expression in cells of the immune system has not yet been examined. Here, we have investigated the regulation of HIV-1 expression by dopamine in Jurkat T cells and in primary blood mononuclear cells (PBMC). HIV-1 replication was increased by dopamine, which correlated with the increased levels of HIV-1 transactivation. Our transient expression data revealed that dopamine stimulated transcription through the NF-kappaB element present in the long terminal repeat. The importance of NF-kappaB sites was confirmed by using vectors containing wild-type or mutant kappaB sites in a heterologous promoter. Consistent with the role of NF-kappaB in mediating dopamine responsiveness, the proteasome inhibitor MG132 abolished dopamine-induced transcriptional activation. We further explored the effect of dopamine in the presence of phorbol esters or tumor necrosis factor-alpha (TNF-alpha) known to activate NF-kappaB. The combination of dopamine and TNF-alpha led to a stimulation of HIV-1 transcription and replication. However, in contrast with TNF-alpha, dopamine treatment did not affect NF-kappaB DNA binding activity nor the concentrations of p50, p65 and IkappaB-alpha proteins, which suggests a distinct NF-kappaB activation mechanism. These results reveal a new link between the dopamine system, cytokine signaling pathway and regulation of gene expression via the involvement of NF-kappaB in T cells and PBMC.

Profile of transforming growth factor-beta 1 in patients with dengue haemorrhagic fever

The pathogenesis of dengue haemorrhagic fever (DHF) is incompletely understood but it has been suggested that various cytokines may have a role in the process. In this study the profile of the cytokine Transforming Growth Factor-beta 1 (TGF-beta1) was investigated in the sera of 79 patients with various grades of dengue illness and in 21 normal healthy controls. Also, TGF-beta1-specific mRNA was examined in their peripheral blood mononuclear cells (PBMC). The results showed that neither TGF-beta1 protein nor its mRNA were detected in healthy controls. In dengue patients, the TGF-beta1 protein and its mRNA were detected in 96%. However, among the patient groups, the levels of TGF-beta1 were lowest in patients with dengue fever (DF; mean value 315 +/- 95 pg/ml) and were highest in patients with DHF grade IV (mean value 1350 +/- 280 pg/ml; P = < 0. 001). The cytokine appeared during the first four days of illness (304 +/- 90 pg/ml) and gradually increased, reaching peak levels (1050 +/- 215 pg/ml) after the 9th day of the illness. Thus TGF-beta1 in the sera and TGF-beta1-mRNA in the PBMC were present in most of the patients with dengue (96%) but the cytokine levels were highest during the later periods of illness and in patients with DHF grade IV, suggesting a possible role of TGF-beta1 in the pathogenesis of DHF.

TGF-beta induces fibronectin synthesis through a c-Jun N-terminal kinase-dependent, Smad4-independent pathway

Transforming growth factor-beta (TGF-beta) exerts its effects on cell proliferation, differentiation and migration in part through its modulation of extracellular matrix components, such as fibronectin and plasminogen activator inhibitor-1 (PAI-1). Although the SMAD family of proteins recently has been shown to be a key participant in TGF-beta signaling, other signaling pathways have also been shown to be activated by TGF-beta. We report here that c-Jun N-terminal kinase (JNK), a member of the MAP kinase family, is activated in response to TGF-beta in the human fibrosarcoma HT1080-derived cell line BAHgpt. Stable expression of dominant-negative forms of JNK1 and MKK4, an upstream activator of JNK, results in loss of TGF-beta-stimulated fibronectin mRNA and protein induction, while having little effect on TGF-beta-induced levels of PAI-1. The human fibronectin promoter contains three CRE elements, one of which has been shown to bind a c-Jun-ATF-2 heterodimer. Utilizing a GAL4 fusion trans-reporting system, we demonstrate a decrease in transactivating potential of GAL4-c-Jun and GAL4-ATF-2 in dominant-negative JNK1- and MKK4-expressing cells. Finally, we show that TGF-beta-induced fibronectin synthesis is independent of Smad4. These results demonstrate that TGF-beta-mediated fibronectin induction requires activation of JNK which in turn modulates the activity of c-Jun and ATF-2 in a Smad4independent manner.

TGF-beta-induced phosphorylation of Smad3 regulates its interaction with coactivator p300/CREB-binding protein

Smads are intermediate effector proteins that transduce the TGF-beta signal from the plasma membrane to the nucleus, where they participate in transactivation of downstream target genes. We have shown previously that coactivators p300/CREB-binding protein are involved in TGF-beta-mediated transactivation of two Cdk inhibitor genes, p21 and p15. Here we examined the possibility that Smads function to regulate transcription by directly interacting with p300/CREB-binding protein. We show that Smad3 can interact with a C-terminal fragment of p300 in a temporal and phosphorylation-dependent manner. TGF-beta-mediated phosphorylation of Smad3 potentiates the association between Smad3 and p300, likely because of an induced conformational change that removes the autoinhibitory interaction between the N- and C-terminal domains of Smad3. Consistent with a role for p300 in the transcription regulation of multiple genes, overexpression of a Smad3 C-terminal fragment causes a general squelching effect on multiple TGF-beta-responsive reporter constructs. The adenoviral oncoprotein E1A can partially block Smad-dependent transcriptional activation by directly competing for binding to p300. Taken together, these findings define a new role for phosphorylation of Smad3: in addition to facilitating complex formation with Smad4 and promoting nuclear translocation, the phosphorylation-induced conformational change of Smad3 modulates its interaction with coactivators, leading to transcriptional regulation.