Definition of cis-regulatory elements of the mouse interleukin-5 gene promoter. Involvement of nuclear factor of activated T cell-related factors in interleukin-5 expression

Kv1.3 channel blockade with the Vm24 scorpion toxin attenuates the CD4+ effector memory T cell response to TCR stimulation

BACKGROUND

In T cells, the Kv1.3 and the KCa3.1 potassium channels regulate the membrane potential and calcium homeostasis. Notably, during TEM cell activation, the number of Kv1.3 channels on the cell membrane dramatically increases. Kv1.3 blockade results in inhibition of Ca2+ signaling in TEM cells, thus eliciting an immunomodulatory effect. Among the naturally occurring peptides, the Vm24 toxin from the Mexican scorpion Vaejovis mexicanus is the most potent and selective Kv1.3 channel blocker known, which makes it a promissory candidate for its use in the clinic. We have shown that addition of Vm24 to TCR-activated human T cells inhibits CD25 expression, cell proliferation and reduces delayed-type hypersensitivity reactions in a chronic inflammation model. Here, we used the Vm24 toxin as a tool to investigate the molecular events that follow Kv1.3 blockade specifically on human CD4+ TEM cells as they are actively involved in inflammation and are key mediators of autoimmune diseases.

METHODS

We combined cell viability, activation, and multiplex cytokine assays with a proteomic analysis to identify the biological processes affected by Kv1.3 blockade on healthy donors CD4+ TEM cells, following TCR activation in the presence or absence of the Vm24 toxin.

RESULTS

The peptide completely blocked Kv1.3 channels currents without impairing TEM cell viability, and in response to TCR stimulation, it inhibited the expression of the activation markers CD25 and CD40L (but not that of CD69), as well as the secretion of the pro-inflammatory cytokines IFN-γ and TNF and the anti-inflammatory cytokines IL-4, IL-5, IL-9, IL-10, and IL-13. These results, in combination with data from the proteomic analysis, indicate that the biological processes most affected by the blockade of Kv1.3 channels in a T cell activation context were cytokine-cytokine receptor interaction, mRNA processing via spliceosome, response to unfolded proteins and intracellular vesicle transport, targeting the cell protein synthesis machinery.

CONCLUSIONS

The Vm24 toxin, a highly specific inhibitor of Kv1.3 channels allowed us to define downstream functions of the Kv1.3 channels in human CD4+ TEM lymphocytes. Blocking Kv1.3 channels profoundly affects the mRNA synthesis machinery, the unfolded protein response and the intracellular vesicle transport, impairing the synthesis and secretion of cytokines in response to TCR engagement, underscoring the role of Kv1.3 channels in regulating TEM lymphocyte function.

Dexamethasone inhibits inflammatory response via down regulation of AP-1 transcription factor in human lung epithelial cells

The production of inflammatory mediators by epithelial cells in inflammatory lung diseases may represent an important target for the anti-inflammatory effects of glucocorticoids. Activator protein-1 is a major activator of inflammatory genes and has been proposed as a target for inhibition by glucocorticoids. We have used human pulmonary type-II A549 cells to examine the effect of dexamethasone on the phorbol ester (PMA)/Lipopolysaccharide (LPS) induced pro-inflammatory cytokines and AP-1 factors. A549 cells were treated with and without PMA or LPS or dexamethasone and the cell viability and nitric oxide production was measured by MTT assay and Griess reagent respectively. Expression of pro-inflammatory cytokines and AP-1 factors mRNA were measured using semi quantitative RT-PCR. The PMA/LPS treated cells show significant 2-3 fold increase in the mRNA levels of pro-inflammatory cytokines (IL-1β, IL-2, IL-6, IL-8 and TNF-α), cyclo‑oxygenase-2 (COX-2) and specific AP-1 factors (c-Jun, c-Fos and Jun-D). Whereas, pretreatment of cells with dexamethasone significantly inhibited the LPS induced nitric oxide production and PMA/LPS induced mRNAs expression of above pro-inflammatory cytokines, COX-2 and AP-1 factors. Cells treated with dexamethasone alone at both the concentrations inhibit the mRNAs expression of IL-1β, IL-6 and TNF-α compared to control. Our study reveals that dexamethasone decreased the mRNAs expression of c-Jun and c-Fos available for AP-1 formation suggested that AP-1 is the probable key transcription factor involved in the anti-inflammatory activity of dexamethasone. This may be an important molecular mechanism of steroid action in asthma and other chronic inflammatory lung diseases which may be useful for treatment of lung inflammatory diseases.

Interleukin-5 and IL-5 receptor in health and diseases

While interleukin-5 (IL-5) is initially identified by its ability to support the growth and terminal differentiation of mouse B cells in vitro into antibody-secreting cells, recombinant IL-5 exerts pleiotropic activities on various target cells including B cells, eosinophils, and basophils. IL-5 is produced by both hematopoietic and non-hematopoietic cells including T cells, granulocytes, and natural helper cells. IL-5 exerts its effects for proliferation and differentiation via receptors that comprise an IL-5-specific α and common β-subunit. IL-5Rα expression in activated B cells is regulated by a complex of transcription factors including E12, E47, Sp1, c/EBPβ, and Oct2. IL-5 signals are transduced through JAK-STAT, Btk, and Ras/Raf-ERK signaling pathways and lead to maintenance of survival and functions of B cells and eosinophils. Overexpression of IL-5 in vivo significantly increases eosinophils and B cells in number, while mice lacking a functional gene for IL-5 or IL-5 receptor display a number of developmental and functional impairments in B cells and eosinophil lineages. In humans, the biologic effects of IL-5 are best characterized for eosinophils. The recent expansion in our understanding of eosinophil development and activation and pathogenesis of eosinophil-dependent inflammatory diseases has led to advance in therapeutic options. Intravenous administration of humanized anti-IL-5 monoclonal antibody reduces baseline bronchial mucosal eosinophils in mild asthma; providing important implications for strategies that inhibit the actions of IL-5 to treat asthma and other allergic diseases.

Glucocorticoids inhibit GATA-3 phosphorylation and activity in T cells

Glucocorticoid (GC) immunosuppression and anti-inflammatory action involve the regulation of several transcription factors (TFs). GCs inhibit the acute production of T-helper (Th) 1 and Th2 cytokines but ultimately favor a shift toward Th2 phenotype. GCs inhibit the transcriptional activity of T-bet Th1 TF by a transrepression mechanism. Here we analyze GC regulation of GATA-3, the master driver of Th2 differentiation. We found that GCs inhibit GATA-3 transcriptional activity. We demonstrate that this mechanism does not involve physical interaction between the glucocorticoid receptor (GR) and GATA-3 or reduction of GATA-3 binding to DNA, as described previously for T-bet. Instead, GCs inhibit GATA-3 activity by inhibition of p38 mitogen-activated protein kinase induced GATA-3 phosphorylation. GCs also inhibit GATA-3 mRNA and protein expression. Finally, GATA-3 inhibition affects the interleukin-5 gene, a central Th2 cytokine. The IC(50) of dexamethasone is 10 nM with a maximum effect at 100 nM. All inhibitory actions were blocked by the GR antagonist RU38486 (1 uM), proving the specificity of GR action. In view of the crucial role of GATA-3 in T-cell differentiation and inflammation, we propose that the mechanism of GATA-3 inhibition compared with that in T-bet may have relevant implications in understanding and modulating the anti-inflammatory and Th-regulatory properties of GCs.

Activating transcription factor 3 is a negative regulator of allergic pulmonary inflammation

We recently demonstrated the pivotal role of the transcription factor (TF) activating TF 3 (ATF3) in dampening inflammation. We demonstrate that ATF3 also ameliorates allergen-induced airway inflammation and hyperresponsiveness in a mouse model of human asthma. ATF3 expression was increased in the lungs of mice challenged with ovalbumin allergen, and this was associated with its recruitment to the promoters of genes encoding Th2-associated cytokines. ATF3-deficient mice developed significantly increased airway hyperresponsiveness, pulmonary eosinophilia, and enhanced chemokine and Th2 cytokine responses in lung tissue and in lung-derived CD4(+) lymphocytes. Although several TFs have been associated with enhanced inflammatory responses in the lung, ATF3 attenuates the inflammatory responses associated with allergic airway disease.

Cyclic AMP-induced chromatin changes support the NFATc-mediated recruitment of GATA-3 to the interleukin 5 promoter

Elevated intracellular cyclic AMP levels, which suppress the proliferation of naive T cells and type 1 T helper (Th1) cells are a property of T helper 2 (Th2) cells and regulatory T cells. While cyclic AMP signals interfere with the IL-2 promoter induction, they support the induction of Th2-type genes, in particular of il-5 gene. We show here that cyclic AMP signals support the generation of three inducible DNase I hypersensitive chromatin sites over the il-5 locus, including its promoter region. In addition, cyclic AMP signals enhance histone H3 acetylation at the IL-5 promoter and the concerted binding of GATA-3 and NFATc to the promoter. This is facilitated by direct protein-protein interactions involving the C-terminal Zn(2+)-finger of GATA-3 and the C-terminal region of the NFATc1 DNA binding domain. Because inhibition of NFATc binding to the IL-5 promoter in vivo also affects the binding of GATA-3, one may conclude that upon induction of Th2 effector cells NFATc recruits GATA-3 to Th2-type genes. These data demonstrate the functional importance of cyclic AMP signals for the interplay between GATA-3 and NFATc factors in the transcriptional control of lymphokine expression in Th2 effector cells.

Effect of 5-O-Methylhirsutanonol on nuclear factor-kappaB-dependent production of NO and expression of iNOS in lipopolysaccharide-induced RAW264.7 cells

Diarylheptanoids are known to have anti-inflammatory and anti-atherosclerotic activities in various cell types, including macrophages. 5- O-Methylhirsutanonol (5-MH) isolated from the leaves of Alnus japonica Steud exhibited the antioxidant activities on Cu (2+)- and AAPH-mediated low-density lipoprotein (LDL) oxidation in the thiobarbituric acid-reactive substances (TBARS) assay as well as the macrophage-mediated LDL oxidation. In the main study, we examined anti-inflammatory activities of 5- O-methylhirsutanonol (5-MH) on nuclear factor kappaB (NF-kappaB)-dependent nitric oxide (NO) production and expression of inducible nitric oxide synthease (iNOS) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. 5-MH inhibited NO production with an IC 50 value of 14.5 microM and expression of both iNOS protein and iNOS mRNA in a parallel dose-response manner. Then, expression of inflammation-associated genes, such as TNF-alpha, COX-2, and IL-1beta, was suppressed by 5-MH, as determined by reverse transcriptase polymerase chain reaction analysis. Moreover, 5-MH attenuated NF-kappaB activation by inhibition of hyperphosphorylation of IkappaB-alpha and its subsequent proteolytic degradation and p65 nuclear translocation, as well as preventing DNA-binding ability. In addition, 5-MH suppressed the mRNA expression of the gene reactive oxygen species (ROS) concerned in the regulation of NF-kappaB signaling.

Effects of diarylheptanoids on the tumor necrosis factor-alpha-induced expression of adhesion molecules in human umbilical vein endothelial cells

Atherosclerosis is a chronic inflammatory disease that is characterized by infiltration of mononuclear lymphocytes into the intima through the expression of adhesion molecules on the arterial wall. In the present study, we report the inhibitory effects of two diarylheptanoids, 5-O-methylhirsutanonol (1) and oregonin (2), isolated from the methanolic extracts of Alnus japonica leaves, on the expression of adhesion molecules in human umbilical vein endothelial cells (HUVECs). Compounds 1 and 2 inhibited tumor necrosis factor (TNF)-alpha-induced up-regulation of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), which also prevented adhesion of monocytes to HUVECs, and slightly suppressed the mRNA expression of the inflammation-associated gene interleukin-1beta (IL-1beta). A further study demonstrated the inhibitory effect of compound 1 on DNA-binding of nuclear factor kappaB (NF-kappaB) and on the phosphorylation and degradation of inhibitory factor kappaBalpha (IkappaBalpha) in TNF-alpha-stimulated HUVECs. These results indicate that compounds 1 and 2 may be useful in the prevention and treatment of atherosclerosis through attenuation of adhesion molecule expression by inhibition of NF-kappaB activation.

Eosinophilic inflammation: mechanisms regulating IL-5 transcription in human T lymphocytes

BACKGROUND

Interleukin (IL)-5 is a key regulator of eosinophilia in allergic inflammation and parasite infections but the mechanisms regulating IL-5 expression in activated human T lymphocytes are poorly understood. From studies on mouse cells, the activation protein (AP)-1 and GATA-3 sites in the proximal promoter region appear to be important in IL-5 regulation but the significance of an adjacent Ets/nuclear factor of activated T cell (NFAT) site has been less clear.

METHODS

Interleukin-5 transcriptional activity was measured by transfection of reporter genes into the human HSB-2 cells and normal T lymphocytes. Expression vectors encoding transcription factors were used for transactivation studies and IL-5 expression measured using reporter genes and mRNA levels. Transcription factor binding was shown with chromatin immunoprecipitation (ChIP).

RESULTS

HSB-2 cells showed high inducible expression of IL-5 mRNA. Mutation of reporter gene plasmids showed the Ets/NFAT site was of equal importance to the AP-1 and GATA-3 sites in regulating IL-5 transcription. Transactivation by Ets1 increased luciferase expression 15-fold, in the absence of stimulation, and AP-1 (c-Fos/c-Jun) and GATA-3 gave transactivations of 85-fold, and 100-fold, respectively. Synergistic interactions were demonstrated between Ets1, GATA-3 and AP-1. Dominant-negative AP-1 inhibited IL-5 transcription. Transactivation by GATA-3 and synergy between GATA-3, Ets1 and AP-1 were verified measuring IL-5 mRNA levels. Chromatin immunoprecipitation showed increased binding of Ets1 and GATA-3 to the IL-5 promoter after stimulation. The importance of the Ets1 site and of synergistic interactions between the three transcription factors were verified with primary human T cells.

CONCLUSION

Ets1, GATA-3 and AP-1 synergize to regulate IL-5 transcription in human T cells.

RAS2 regulates growth and pathogenesis in Fusarium graminearum

Fusarium graminearum is a ubiquitous pathogen of cereal crops, including wheat, barley, and maize. Diseases caused by F. graminearum are of particular concern because harvested grains frequently are contaminated with harmful mycotoxins such as deoxynivalenol (DON). In this study, we explored the role of Ras GTPases in pathogenesis. The genome of F. graminearum contains two putative Ras GTPase-encoding genes. The two genes (RAS1 and RAS2) showed different patterns of expression under different conditions of nutrient availability and in various mutant backgrounds. RAS2 was dispensable for survival but, when disrupted, caused a variety of morphological defects, including slower growth on solid media, delayed spore germination, and significant reductions in virulence on wheat heads and maize silks. Intracellular cAMP levels were not affected by deletion of RAS2 and exogenous treatment of the ras2 mutant with cAMP did not affect phenotypic abnormalities, thus indicating that RAS2 plays a minor or no role in cAMP signaling. However, phosphorylation of the mitogen-activated protein (MAP) kinase Gpmk1 and expression of a secreted lipase (FGL1) required for infection were reduced significantly in the ras2 mutant. Based on these observations, we hypothesize that RAS2 regulates growth and virulence in F. graminearum by regulating the Gpmk1 MAP kinase pathway.

UR-1505, a new salicylate, blocks T cell activation through nuclear factor of activated T cells

2-Hydroxy-4(-2,2,3,3,3-pentafluoropropoxy)-benzoic acid (UR-1505), a new molecule chemically related to salicylic acid, has immunomodulator properties and is currently under clinical development for treatment of atopic dermatitis. The present work describes the immunomodulatory profile of UR-1505. UR-1505 targets T cells, inhibiting their proliferation and cytokine production by blocking nuclear factor of activated T cells (NF-AT) DNA-binding activity. The effects of UR-1505 (100-300 microM) on T cell proliferation seems to be dependent on the stimulus, because UR-1505 inhibited CD3/CD28-induced T-cell proliferation, increased p27(KIP) levels, and induced G1/S cell arrest but, interestingly, did not inhibit the Janus tyrosine kinase/signal transducer and activator of transcription-induced T-cell proliferation. These data suggest that UR-1505 acts by means of a specific mechanism inhibiting T cell activation depending on T cell receptor signaling pathway. Furthermore, the antiproliferative effects of UR-1505 are not a consequence of decreased cell viability. In addition to the inhibition of T-cell proliferation, UR-1505 decreased, in a dose-dependent manner, the production of interleukin (IL)-5 and interferon (IFN)-gamma in activated T cells, and this effect was produced at the transcriptional level. Because T-cell proliferation and cytokine production were regulated through NF-AT, we examined the effect of UR-1505 on this transcription factor. According to its effect on IL-5 and IFN-gamma mRNA expression, UR-1505 specifically inhibited NF-AT DNA binding without effect on nuclear factor-kappaB and activator protein-1 activities. The effect of UR-1505 on NF-AT is not attributable to a blockade of nuclear import. In conclusion, UR-1505 is a new immunomodulator agent that specifically inhibits NF-AT activation. Because NF-AT regulates the transcription of most genes involved in lymphocyte activation, its selective inactivation results in both decreased T-cell proliferation and cytokine production.

The activated glucocorticoid receptor inhibits the transcription factor T-bet by direct protein-protein interaction

Glucocorticoids (GCs) immunosuppression acts via regulation of several transcription factors (TF), including activating protein (AP)-1, NF-kappaB, and NFAT. GCs inhibit Th1 cytokines and promote a shift toward Th2 differentiation. Th1 phenotype depends on TF T-bet. In this study, we examined GC regulation of T-bet. We found that GCs inhibit T-bet transcriptional activity. We show that glucocorticoid receptor (GR) physically interacts with T-bet both in transfected cell lines and in primary splenocyte cultures with endogenous GR and T-bet. This interaction also blocks GR-dependent transcription. We show both in vitro and in vivo at endogenous binding sites that the mechanism underlying T-bet inhibition further involves reduction of T-bet binding to DNA. Using specific mutations of GR, we demonstrate that the first zinc finger region of GR is required for T-bet inhibition. GCs additionally inhibit T-bet both at mRNA and protein expression levels, revealing another layer of GR action on T-bet. Finally, we examined the functional consequences of GR/T-bet interaction on IFN-gamma, showing that GCs inhibit transcriptional activity of T-bet on its promoter. In view of the crucial role of T-bet in T cell differentiation and inflammation, we propose that GR inhibitory interaction with T-bet may be an important mechanism underlying the immunosuppressive properties of GCs.

A role for Ets1, synergizing with AP-1 and GATA-3 in the regulation of IL-5 transcription in mouse Th2 lymphocytes

IL-5 is a key regulator of eosinophilic inflammation and is selectively expressed by antigen-activated Th2 lymphocytes. An important role for the proximal AP-1 and GATA sites in regulating IL-5 transcription is generally accepted but the significance of an adjacent Ets/NFAT site has remained unclear. We have investigated its role using the mouse Th2 clone D10.G4.1. Transcription of IL-5 reporter gene plasmids could be induced in D10 cells by phorbol myristate acetate/cyclic adenosine monophosphate (PMA/cAMP) stimulation and significantly further enhanced by activation of the mitogen-activated protein (MAP) kinase pathways. Strong induction of IL-5 mRNA was also induced by PMA/cAMP. Mutagenesis showed that the Ets/NFAT site is of critical importance along with the AP-1 and GATA sites in regulating IL-5 transcription stimulated by PMA/cAMP and MAP kinase activation. Transactivation was used to investigate the transcription factors which could function at the three sites and possible synergistic interactions. AP-1 (c-Fos/c-Jun) strongly induced IL-5 transcription and dominant negative AP-1 constructs confirmed that AP-1 plays an important role in regulating IL-5 expression. Ets1, unlike other members of the Ets/NFAT family, synergized strongly with AP-1 suggesting that Ets1 is the family member which functions at the Ets/NFAT site. AP-1/Ets1 transactivation also stimulated IL-5 mRNA expression. Ets1 binding to the proximal promoter region, demonstrated by chromatin immunoprecipitation, was stimulated by PMA/cAMP. The absolute dependence on the binding sites for Ets1, AP-1 and GATA-3 together with the strong synergy between Ets1 and AP-1 suggest close cooperative interactions between the three transcription factors in the regulation of IL-5 expression in mouse T cells.

The hematopoietic transcription factor PU.1 regulates RANK gene expression in myeloid progenitors

Osteoclasts are bone resorbing cells of hematopoietic origin. The hematopoietic transcription factor PU.1 is critical for osteoclastogenesis; however, the molecular mechanisms of PU.1-regulated osteoclastogenesis have not been explored. Here, we present evidence that the receptor activator of nuclear factor kappaB (RANK) gene that has been shown to be crucial for osteoclastogenesis is a transcriptional target of PU.1. The PU.1-/- progenitor cells failed to express the RANK gene and reconstitution of PU.1 in these cells induced RANK expression. Treatment of the PU.1 reconstituted cells with M-CSF and RANKL further augmented the RANK gene expression. To explore the regulatory mechanism of the RANK gene expression by PU.1, we have cloned the human RANK promoter. Transient transfection assays have revealed that the 2.2-kb RANK promoter was functional in a monocyte line RAW264.7, whereas co-transfection of PU.1 transactivated the RANK promoter in HeLa cells. Taken together, these results suggest that PU.1 regulates the RANK gene transcription and this may represent one of the key roles of PU.1 in osteoclast differentiation.

Characterization of the first nonmammalian T2 cytokine gene cluster: the cluster contains functional single-copy genes for IL-3, IL-4, IL-13, and GM-CSF, a gene for IL-5 that appears to be a pseudogene, and a gene encoding another cytokinelike transcript, KK34

A genomics approach based on the conservation of synteny was used to develop a bacterial artificial chromosome (BAC) contig across the chicken T2 cytokine gene cluster. Sequencing of representative BACs showed that the chicken genome encodes genes for the homologs of mammalian interleukin-3 (IL-3), IL-4, IL-5, IL-13, and granulocyte-macrophage colony-stimulating factor (GM-CSF). These sequences represent the first T2 cytokines found outside of mammals, and their location demonstrates that the T2 cluster is ancient (at least 300 million years old). Four of these genes (IL-3, IL-4, IL-13, and GM-CSF) are expressed at the mRNA level and can be expressed as recombinant protein. In contrast to the other four genes, the chicken IL-5 (ChIL-5) gene we sequenced lacks a recognizable promoter and regulatory sequences in the predicted 3'-untranslated region (3'-UTR). Further, there is no evidence for its expression at the mRNA level. We, therefore, hypothesize that it is a pseudogene. Genomic analysis revealed that a recently characterized cytokinelike transcript, KK34, not identified in our initial analysis of the BAC sequence, is also encoded in this cluster. This gene may represent a duplication of an ancestral IL-5 gene and may encode the functional homolog of IL-5 in the chicken.

Granulocyte-macrophage colony-stimulating factor enhancer activation requires cooperation between NFAT and AP-1 elements and is associated with extensive nucleosome reorganization

The human granulocyte-macrophage colony-stimulating factor (GM-CSF) gene is activated by an NFAT-dependent enhancer forming an inducible DNase I hypersensitive (DH) site. The enhancer core comprising the DH site contains the GM330 and GM420 elements that bind NFAT and AP-1 cooperatively. Here we demonstrate that both elements are essential for enhancer activity and that Sp1 and AML1 sites in the enhancer become occupied in vivo only after activation. Chromatin structure analysis revealed that the GM-CSF enhancer core elements are divided between two adjacent nucleosomes that become destabilized and highly accessible after activation. Inducible chromatin reorganization was not restricted to the enhancer core but extended across a 3-kb domain of mobilized nucleosomes, within which the nucleosome repeat length was compressed from approximately 185 to 150 bp. The GM420 element is a high-affinity site that binds NFAT independently of AP-1 but depends on the linked AP-1 site for enhancer function. Nevertheless, just the NFAT motif from the GM420 element was sufficient to form a DH site within chromatin even in the absence of the AP-1 site. Hence, NFAT has the potential to cooperate with other transcription factors by promoting chromatin remodelling and increasing accessibility at inducible regulatory elements.

Transcriptional Regulation of Human CD5: Important Role of Ets Transcription Factors in CD5 Expression in T Cells

CD5 is a surface receptor constitutively expressed on thymocytes and mature T and B-1a cells. CD5 expression is tightly regulated during T and B cell development and activation processes. In this study we shown that the constitutive expression of CD5 on human T cells correlates with the presence of a DNase I-hypersensitive (DH) site at the 5'-flanking region of CD5. Human CD5 is a TATA-less gene for which 5'-RACE analysis shows multiple transcriptional start sites, the most frequent of which locates within an initiator sequence. Luciferase reporter assays indicate that a 282-bp region upstream of the initiation ATG displays full promoter activity in human T cells. Two conserved Ets-binding sites (at positions -239 and -185) were identified as functionally relevant to CD5 expression by site-directed mutagenesis, EMSAs, and cotransfection experiments. A possible contribution of Sp1 (-115 and -95), c-Myb (-177), and AP-1-like (-151) motifs was also detected. Further DH site analyses revealed an inducible DH site 10 kb upstream of the human CD5 gene in both T and B CD5(+) cells. Interestingly, a 140-bp sequence showing high homology with a murine inducible enhancer is found within that site. The data presented indicate that the 5'-flanking region of human CD5 is transcriptionally active in T cells, and that Ets transcription factors in conjunction with other regulatory elements are responsible for constitutive and tissue-specific CD5 expression.

Dexamethasone inhibits IL-12p40 production in lipopolysaccharide-stimulated human monocytic cells by down-regulating the activity of c-Jun N-terminal kinase, the activation protein-1, and NF-kappa B transcription factors

IL-12 plays a critical role in the development of cell-mediated immune responses and in the pathogenesis of inflammatory and autoimmune disorders. Dexamethasone (DXM), an anti-inflammatory glucocorticoid, has been shown to inhibit IL-12p40 production in LPS-stimulated monocytic cells. In this study, we investigated the molecular mechanism by which DXM inhibits IL-12p40 production by studying the role of the mitogen-activated protein kinases (MAPKs), and the key transcription factors involved in human IL-12p40 production in LPS-stimulated monocytic cells. A role for c-Jun N-terminal kinase (JNK) MAPK in LPS-induced IL-12p40 regulation in a promonocytic THP-1/CD14 cell line was demonstrated by using specific inhibitors of JNK activation, SP600125 and a dominant-negative stress-activated protein/extracellular signal-regulated kinase kinase-1 mutant. To identify transcription factors regulating IL-12p40 gene transcription, extensive deletion analyses of the IL-12p40 promoter was performed. The results revealed the involvement of a sequence encompassing the AP-1-binding site, in addition to that of NF-kappaB. The role of AP-1 in IL-12p40 transcription was confirmed by using antisense c-fos and c-jun oligonucleotides. Studies conducted to understand the regulation of AP-1 and NF-kappaB activation by JNK MAPK revealed that both DXM and SP600125 inhibited IL-12p40 gene transcription by inhibiting the activation of AP-1 and NF-kappaB transcription factors as revealed by luciferase reporter and gel mobility shift assays. Taken together, our results suggest that DXM may inhibit IL-12p40 production in LPS-stimulated human monocytic cells by down-regulating the activation of JNK MAPK, the AP-1, and NF-kappaB transcription factors.

Protein kinase A regulates GATA-3-dependent activation of IL-5 gene expression in Th2 cells

Treatment of Th cells with compounds that elevate cAMP levels augments Th2-type lymphokine expression, in particular the synthesis of IL-5. Using primary murine CD4(+) T lymphocytes, we show in this study that inhibition of protein kinase A (PKA) activity in Th2 effector cells impairs IL-5 synthesis, whereas the expression of PKA catalytic subunit alpha enhances IL-5 synthesis in Th0 cells. In addition, we observed by coexpression of PKA catalytic subunit and GATA-3 in Th1 cells that the stimulatory effect of PKA is dependent on GATA-3 activity. These data demonstrate that activation of PKA in Th effector cells induces the IL-5 gene expression in a GATA-3-dependent manner.

Specific activation of human interleukin-5 depends on de novo synthesis of an AP-1 complex

It is clear from the biology of eosinophilia that a specific regulatory mechanism must exist. Because interleukin-5 (IL5) is the key regulatory cytokine, it follows that a gene-specific control of IL5 expression must exist that differs even from closely related cytokines such as IL4. Two features of IL5 induction make it unique compared with other cytokines; first, induction by cyclic adenosine monophosphate (cAMP), which inhibits other T-cell-derived cytokines, and second, sensitivity to protein synthesis inhibitors, which have no effect on other cytokines. This study has utilized the activation of different transcription factors by different stimuli in a human T-cell line to study the role of conserved lymphokine element 0 (CLE0) in the specific induction of IL5. In unstimulated cells the ubiquitous Oct-1 binds to CLE0. Stimulation induces de novo synthesis of the AP-1 members JunD and Fra-2, which bind to CLE0. The amount of IL5 produced correlates with the production of the AP-1 complex, suggesting a key role in IL5 expression. The formation of the AP-1 complex is essential, but the rate-limiting step is the synthesis of AP-1, especially Fra-2. This provides an explanation for the sensitivity of IL5 to protein synthesis inhibitors and a mechanism for the specific induction of IL5 compared with other cytokines.

Transcriptional regulation of the IL-5 gene in peripheral T cells of asthmatic patients

Mechanisms that underlie the regulation of IL-5 gene expression in human peripheral T cells remain incompletely defined because of the low efficiency of transfection of plasmid constructs into non-transformed T cells. To elucidate the cellular and molecular mechanisms of IL-5 production, concanavalin A (ConA)-stimulated blastocytes derived from peripheral blood lymphocytes of asthmatic patients were employed in this study. Transcriptional activity of the synthetic human IL-5 promoter in ConA-stimulated blastocytes correlated with the production of IL-5. Deletion analysis of the reporter gene showed that the cis-regulatory element located at - 119 to - 80 is critical for inducible IL-5 promoter activity. Electrophoretic mobility shift assay revealed that an oligonucleotide probe corresponding to the element (- 119 to - 90) gave two specific bands. The slower migrating band was absolutely dependent on stimulation and was composed of a co-operative complex of the transcription factors, nuclear factor of activated T cells (NFAT) and activating protein-1 (AP-1). The faster migrating band was also inducible and was identified as AP-1-less NFAT. Mutation of either the NFAT or AP-1 element abrogated the slower migrating band and at the same time abolished transcriptional activity of the human IL-5 promoter/enhancer gene. Cyclosporin A equivalently suppressed DNA-binding activity of the composite NFAT/AP-1 site, promoter activity and protein production of IL-5. In conclusion, these data suggests that the composite NFAT/AP-1 binding element (- 115 to - 100) plays a crucial role in IL-5 synthesis by peripheral T cells of asthmatic patients.

The role of Ras in T lymphocyte activation

Ras plays an important role in T cell signal transduction through multiple pathways. Here, we demonstrate that, upon stimulation, increasing Ras activity partially substitutes for calcium-mediated signals leading to IL-2 induction. The increase of Ras activity renders Jurkat cells the resistant to cyclosporin A (CsA) through increasing calcineurin activity. Coincidentally, the inducible binding of NIL-2 to a negative-regulatory element in the IL-2 promoter becomes less sensitive to CsA in the cells with increasing Ras activity. The dose of CsA required for inhibition of IL-2 induction in the cells with increased Ras activity remains similar to the concentration of CsA needed for the suppression of NFAT activation in control cells. The results suggest that Ras regulates calcium/calcineurin signalling during T cell activation and the existence of new immune-related target(s) for CsA action at the posttranscriptional level.

rVista for comparative sequence-based discovery of functional transcription factor binding sites

Identifying transcriptional regulatory elements represents a significant challenge in annotating the genomes of higher vertebrates. We have developed a computational tool, rVista, for high-throughput discovery of cis-regulatory elements that combines clustering of predicted transcription factor binding sites (TFBSs) and the analysis of interspecies sequence conservation to maximize the identification of functional sites. To assess the ability of rVista to discover true positive TFBSs while minimizing the prediction of false positives, we analyzed the distribution of several TFBSs across 1 Mb of the well-annotated cytokine gene cluster (Hs5q31; Mm11). Because a large number of AP-1, NFAT, and GATA-3 sites have been experimentally identified in this interval, we focused our analysis on the distribution of all binding sites specific for these transcription factors. The exploitation of the orthologous human-mouse dataset resulted in the elimination of > 95% of the approximately 58,000 binding sites predicted on analysis of the human sequence alone, whereas it identified 88% of the experimentally verified binding sites in this region.

Physical and functional interaction between GATA-3 and Smad3 allows TGF-beta regulation of GATA target genes

BACKGROUND

Members of the GATA family of zinc finger transcription factors are genetically controlled "master" regulators of development in the hematopoietic and nervous systems. Whether GATA factors also serve to integrate epigenetic signals on target promoters is, however, unknown. The transforming growth factor-beta (TGF-beta) superfamily is a large group of phylogenetically conserved secreted factors controlling cell proliferation, differentiation, migration, and survival in multiple tissues.

RESULTS

GATA-3, a key regulator of T helper cell development, was found to directly interact with Smad3, an intracellular signal transducer of TGF-beta. Complex formation required a central region in GATA-3 and the N-terminal domain of Smad3. GATA-3 mediated recruitment of Smad3 to GATA binding sites independently of Smad3 binding to DNA, and the two factors cooperated synergistically to regulate transcription from the IL-5 promoter in a TGF-beta-dependent manner. Treatment of T helper cells with TGF-beta promoted the formation of an endogenous Smad3/GATA-3 nuclear complex and stimulated production of the Th2 cytokine IL-10 in a Smad3- and GATA-3-dependent manner.

CONCLUSIONS

Although Smad proteins are known to interact with a number of general transcription factors, these are insufficient to explain the tissue-specific biology of TGF-beta proteins. Through its interaction with Smad3, GATA-3 is able to integrate a genetic program of cell differentiation with an extracellular signal, providing a molecular framework for the effects of TGF-beta on the development and function of specific subsets of immune cells and possibly other cell types.

Requirement of two NFATc4 transactivation domains for CBP potentiation

Recruitment of the coactivator CREB-binding protein (CBP) to transcription factors is important for gene expression. Various regions of CBP such as the KIX and CH3 domains have been shown to interact with numerous transcription factors. The NFAT group of transcription factors is involved in multiple biological processes. NFATc4/NFAT3 has been proposed to play an important role in heart hypertrophy, adipocyte differentiation, and learning and memory. We demonstrate here that two transactivation domains, located at the NH(2) and COOH termini of NFATc4, are critical for interacting with CBP. Each transactivation domain interacts with a distinct region of the CBP protein (the KIX and CH3 domains). Binding of CBP potentiates NFATc4-mediated transcription activity. Both transactivation domains of NFATc4 are required for CBP function. Removal of either NFATc4 transactivation domain abolishes CBP potentiation. Conversely, mutation of the KIX or CH3 domain prevents CBP-mediated potentiation of NFATc4 transcription activation. These data demonstrate that formation of a functional NFATc4.CBP transcription complex requires interactions at two distinct sites.

Dexamethasone inhibits the binding of nuclear factors to the IL-5 promoter in human CD4 T cells

BACKGROUND

IL-5 is produced by the T(H)2 subset of CD4(+) T lymphocytes and is necessary for the eosinophilia typical of allergic conditions. Glucocorticoids such as dexamethasone are highly effective inhibitors of eosinophilic inflammation, and one of their effects is inhibition of IL-5 gene expression.

OBJECTIVE

We wished to examine the effect of dexamethasone on the binding of nuclear factors from primary human CD4(+) T lymphocytes to the RE-I and RE-II positively acting regulatory elements of the IL-5 promoter.

METHODS

CD4(+) T cells, purified from PBMCs by magnetic bead separation, were activated with anti-CD3 antibody and phorbol myristate acetate. Nuclear extracts were tested in electrophoretic mobility shift assays with probes based on RE-I and RE-II.

RESULTS

In extracts from activated cells, the RE-II region of the promoter formed a complex that was shown by supershift assay to contain NFATc. This complex was abolished by treatment of the cells with dexamethasone before activation and was weak or absent in unactivated cells. By contrast, binding to the RE-I region and to the GATA-3 site within RE-I was observed in resting cells and was not affected by activation or treatment with dexamethasone.

CONCLUSION

Dexamethasone inhibits the inducible binding of factors to the RE-II region but does not affect the constitutive binding to the RE-I region. Characterization of such molecular effects of glucocorticoids could enable the development of specific inhibitors of IL-5 expression that lack the side effects of glucocorticoids.

Binding of octamer factors to the murine IL-5 CLE0 in primary T-cells and a T-cell line

Interleukin-5 (IL-5) is an inducible T-cell derived cytokine with remarkable specificity for the eosinophil lineage. It is controlled at the level of transcription and regulation of the gene is an obvious target for therapy of eosinophil-dependent allergic disorders such as asthma, eczema and rhinitis. Using a T-cell line and primary T-cells we have shown for the first time that the Oct1 and Oct2 transcription factors combine to form a complex with the functionally critical murine IL-5 cis-regulatory element, conserved lymphokine element 0 (CLE0), and contribute to positive regulation of the gene. These results show the increasingly important role of octamer factors in regulation of the IL-5 gene.

Ras biochemistry and farnesyl transferase inhibitors: a literature survey

Over the last decades, knowledge on the genetic defects involved in tumor formation and growth has increased rapidly. This has launched the development of novel anticancer agents, interfering with the proteins encoded by the identified mutated genes. One gene of particular interest is ras, which is found mutated at high frequency in a number of malignancies. The Ras protein is involved in signal transduction: it passes on stimuli from extracellular factors to the cell nucleus, thereby changing the expression of a number of growth regulating genes. Mutated Ras proteins remain longer in their active form than normal Ras proteins, resulting in an overstimulation of the proliferative pathway. In order to function, Ras proteins must undergo a series of post-translational modifications, the most important of which is farnesylation. Inhibition of Ras can be accomplished through inhibition of farnesyl transferase, the enzyme responsible for this modification. With this aim, a number of agents, designated farnesyl transferase inhibitors (FTIs), have been developed that possess antineoplastic activity. Several of them have recently entered clinical trials. Even though clinical testing is still at an early stage, antitumor activity has been observed. At the same time, knowledge on the biochemical mechanisms through which these drugs exert their activity is expanding. Apart from Ras, they also target other cellular proteins that require farnesylation to become activated, e.g. RhoB. Inhibition of the farnesylation of RhoB results in growth blockade of the exposed tumor cells as well as an increase in the rate of apoptosis. In conclusion, FTIs present a promising class of anticancer agents, acting through biochemical modulation of the tumor cells.

The role of NF-AT transcription factors in T cell activation and differentiation

The family of genuine NF-AT transcription factors consists of four members (NF-AT1 [or NF-ATp], NF-AT2 [or NF-ATc], NF-AT3 and NF-AT4 [or NF-ATx]) which are characterized by a highly conserved DNA binding domain (is designated as Rel similarity domain) and a calcineurin binding domain. The binding of the Ca(2+)-dependent phosphatase calcineurin to this region controls the nuclear import and exit of NF-ATs. This review deals (1) with the structure of NF-AT proteins, (2) the DNA binding of NF-AT factors and their interaction with AP-1, (3) NF-AT target genes, (4) signalling pathways leading to NF-AT activation: the role of protein kinases and calcineurin, (5) the nuclear entry and exit of NF-AT factors, (6) transcriptional transactivation by NF-AT factors, (7) the structure and expression of the chromosomal NF-AT2 gene, and (8) NF-AT factors in Th cell differentiation. The experimental data presented and discussed in the review show that NF-AT factors are major players in the control of T cell activation and differentiation and, in all likelihood, also of the cell cycle and apoptosis of T lymphocytes.

Cloning, characterization, and tissue distribution of mouse phosphodiesterase 7A1

We have cloned a cDNA representing mouse phosphodiesterases (PDE) 7A1. The open reading frame encodes a protein of 482 amino acids with a predicted molecular mass of 55417. Like human PDE7A variants, mouse PDE7A1 and A2 are 5' splice variants from a common gene. The distinct N-terminal sequence of mouse PDE7A1 is highly homologous to the corresponding sequence of human PDE7A1 with a similarity of 98% but not to that of mouse PDE7A2 (with a similarity of 12%), and is more hydrophilic than that of mouse PDE7A2. Mouse PDE7A1 expressed in SF9 cells has been compared with human PDE7A1 under identical conditions. Mouse PDE7A1 has a Km for cAMP of 0.2 microM, an optimal pH of 7.5, an IC(50) value of 14 microM for 3-isobutyl-1-methylxanthine (IBMX), and is dependent on Mg(2+) for activity. All these characteristics are very similar to those of human PDE7A1. In mice, PDE7A1 is expressed in tissues of the immune system (lymph node, thymus, spleen, and blood leukocyte), testis, brain, kidney and lung but not in skeletal muscle, heart, embryo, or liver, while PDE7A2 is expressed in skeletal muscle, heart, embryo, and kidney, but not in the other tissues. This tissue distribution profile is very similar to that in humans, and hence suggests that PDE7A1 and 7A2 might play a similar role in different species.

GATA-3 induces T helper cell type 2 (Th2) cytokine expression and chromatin remodeling in committed Th1 cells

Committed T helper type 1 (Th1) and Th2 effector cells, resulting from chronic antigenic stimulation in interleukin (IL)-12 and IL-4, are implicated in the pathology of autoimmune and allergic diseases. Committed Th1 cells cannot be induced to change their cytokine profiles in response to antigenic stimulation and Th2 cytokine-inducing conditions. Here, we report that ectopic expression of GATA-3 induced Th2-specific cytokine expression not only in developing Th1 cells but also in otherwise irreversibly committed Th1 cells and a Th1 clone, HDK1. Moreover, cAMP, an inhibitor of cytokine production by Th1 cells, markedly augmented Th2 cytokine production in GATA-3-expressing Th1 cells. Ectopic expression of GATA-3 in developing Th1 cells, but not in Th1 clone HDK1, induced endogenous GATA-3, suggesting an autoregulatory mechanism for maintenance of GATA-3 expression in Th2 cells. Structure-function analyses of GATA-3 revealed that the NH(2)-terminal transactivation domain and the COOH-terminal zinc finger domain of GATA-3 were critical, whereas the NH(2)-terminal zinc finger domain was dispensable for the induction of IL-4. Both zinc fingers, however, were required for IL-5 induction. A Th2-specific DNaseI-hypersensitive site of the IL-4 locus was detected in GATA-3-expressing Th1 cells. Thus, GATA-3 can change the phenotype of committed Th1 cells, previously considered to be irreversible.

The duration of nuclear residence of NFAT determines the pattern of cytokine expression in human SCID T cells

The expression of cytokine genes and other inducible genes is crucially dependent on the pattern and duration of signal transduction events that activate transcription factor binding to DNA. Two infant patients with SCID and a severe defect in T cell activation displayed an aberrant regulation of the transcription factor NFAT. Whereas the expression levels of the NFAT family members NFAT1, -2, and -4 were normal in the patients' T cells, dephosphorylation and nuclear translocation of these NFAT proteins occurred very transiently and incompletely upon stimulation. Only after inhibition of nuclear export with leptomycin B were we able to demonstrate a modest degree of nuclear translocation in the patients' T cells. This transient activation of NFAT was not sufficient to induce the expression of several cytokines, including IL-2, IL-3, IL-4, and IFN-gamma, whereas mRNA levels for macrophage inflammatory protein-1alpha, GM-CSF, and IL-13 were only moderately reduced. By limiting the time of NFAT activation in normal control cells using the calcineurin inhibitor cyclosporin A, we were able to mimic the cytokine expression pattern in SCID T cells, suggesting that the expression of different cytokine genes is differentially regulated by the duration of NFAT residence in the nucleus.

Y-24180, an antagonist of platelet-activating factor, suppresses interleukin 5 production in cultured murine th(2)cells and human peripheral blood mononuclear cells

Interleukin (IL)-5 has been shown to play an essential role in the pathogenesis of airway inflammation. We investigated the effect of 4-(2-chlorophenyl)-2-[2-(4-isobutylphenyl)ethyl]-6, 9-dimethyl-6 H -thieno[3,2- f ][1,2,4]triazolo[4,3- a][1,4]diazepine (Y-24180), an antagonist of platelet-activating factor (PAF), on the production of IL-5 in cultured D10.G4.1 cells, a murine Th(2)clone, and human peripheral blood mononuclear cells (PBMC). As a result, Y-24180 was found to suppress both the mRNA expression of IL-5 and the subsequent secretion of this cytokine in antigen-stimulated D10.G4.1 cells. Y-24180 also suppressed the production of IL-4, another Th(2)type cytokine, at the level of mRNA expression, however, it hardly affected the mRNA expression for IL-6 or IL-10, thus indicating it to have a selective action against IL-5 and IL-4. The suppressive effect of Y-24180 on the secretion of IL-5 by human PBMC was more potent than that of WEB2086, which is another PAF-antagonist. These results suggest that Y-24180 suppresses IL-5 production through a common pathway which also affects the production of IL-4, even though the mechanism remains to be elucidated as to whether the PAF-antagonistic actions are involved or not.

DNase I footprinting of the human interleukin-5 gene promoter

A characteristic feature of allergic asthma is the overexpression of the T helper type 2 (Th2) cytokines interleukin-4 (IL-4), IL-5 and IL-13 by T lymphocytes. Of these cytokines, IL-5 is critical for the growth, survival and recruitment of eosinophils which are thought to be responsible for the tissue damage observed in asthmatic airways. The expression of human IL-5 is primarily regulated at the transcriptional level; however, little is known about the mechanisms that control its transcription. Using nuclear extracts from allergen-specific human T-cell clones we have performed DNase I footprinting of the human IL-5 promoter in order to establish sites occupied by transcription factors. We show footprints covering the conserved lymphokine element 0 ¿(CLE0) -60 to -44 base pairs (bp) and GATA (-73 to -62 bp) elements, which have previously been identified to be important in the regulation of the murine IL-5 promoter. We also describe a footprint covering a considerably extended Octamer binding site (-249 to -217 bp), which encompasses two hitherto unidentified CCAAT/enhancer binding protein consensus binding sites. We have also identified a previously unknown Ets binding site (-274 to -264 bp). These novel data on the regions of the human IL-5 promoter that are bound by transcription factors should allow dissection of the regulatory mechanisms involved in the transcription of IL-5 in the T-helper lymphocytes of asthmatics.

Role of nuclear factor of activated T cells (NFAT) in the expression of interleukin-5 and other cytokines involved in the regulation of hemopoetic cells

NFAT (nuclear factor of activated T cells) is a transcription factor that plays a role in the regulation of various cytokines, including those involved in the regulation of hemopoetic cells such as granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-4 (IL4), interleukin-3 (IL3), interleukin-13 (IL13) and interleukin-5 (IL5). In this report we provide a summary of the various locations in the promoters of each of these cytokines where NFAT has been shown or suggested to bind, and at which sites NFAT has been shown to be involved in transcriptional regulation. We also provide experimental data to show that the binding of NFAT to the nucleotides GAA at positions -113 to -111 of the human IL5 promoter is associated with functional activity in human T cells.

The activity of the human interleukin-5 conserved lymphokine element 0 is regulated by octamer factors in human cells

Interleukin-5 (IL-5) controls the development of eosinophilia and contributes to a number of disease states including asthma. Expression of IL-5 is inducible under tight transcriptional regulation. This requires the contribution of several promoter elements; however, the conserved lymphokine element 0 (CLE0) in particular, is essential for expression of IL-5. In this study, we report the nuclear factors which regulate human IL-5 CLE0 activity in the human cell line PER-117. Using specific antibodies, we identified the transcriptional factors Oct-1 and Oct-2 binding to the 5' region of the CLE0 element. The involvement of Oct factors with CLE0 has not been reported previously in any of the lymphokines. In addition, the CLE0 element also appeared to complex with the transcriptional activator AP-1, consisting of the family members Jun D and Fra-2. We observed the binding of Oct-1 to be constitutive in comparison to Oct-2 and AP-1, both of which were induced in response to cell activation by PMA/A23187. Although the interaction of all three factors with CLE0 was closely linked and overlapping, residues critical to their binding were identified. We demonstrate, using site-directed mutagenesis and cotransfection experiments, that the CLE0 element is indispensable for IL-5 promoter activity and that Octamer factors contribute to the positive regulation of the hIL-5 gene.

Multiple NF-ATc Isoforms with Individual Transcriptional Properties Are Synthesized in T Lymphocytes

The transcription factor NF-ATc that controls gene expression in T lymphocytes and embryonic cardiac cells is expressed in three prominent isoforms. This is due to alternative splice/polyadenylation events that lead to the predominant synthesis of two long isoforms in naive T cells and a shorter NF-ATc isoform in effector T cells. Whereas the previously described isoform NF-ATc/A contains a relatively short C terminus, the longer isoforms, B and C, span extra C-terminal peptides of 128 and 246 aa, respectively. We show here that in addition to the strong N-terminal trans-activation domain, TAD-A, which is common to all three NF-ATc isoforms, NF-ATc/C contains a second trans-activation domain, TAD-B, in its C-terminal peptide. Various stimuli of T cells that induce the activity of TAD-A also enhance the activity of TAD-B, but, unlike TAD-A, TAD-B remains unphosphorylated by protein from 12-O-tetradecanoyl 12-phorbol 13-acetate-stimulated T cells. The shorter C-terminal peptide of isoform NF-ATc/B exerts a suppressive transcriptional effect. These properties of NF-ATc/B and -C might be of importance for gene regulation in naive T lymphocytes in which NF-ATc/B and -C are predominantly synthesized.

Recognition of NFATp/AP-1 composite elements within genes induced upon the activation of immune cells

Composite elements are regulatory modules of promoters or enhancers that consist of binding sites of two different but synergizing transcription factors. A well-studied example is nuclear factors of activated T-cell (NFAT) sites which are composite elements of a NFATp/c and an activating protein 1 (AP-1) binding site. We have developed a computational approach to identify potential NFAT target genes which (a) comprises an improved method to scan for individual NFAT composite elements; (b) considers positional effects relative to transcription start sites; and (c) involves cluster analysis of potential NFAT composite elements. All three steps progressively helpX?ed to discriminate T-cell-specific promoter sequences against other functional regions (coding and intronic sequences) of the same genes, against promoters of muscle-specific genes or against random sequences. Using this approach, we identified potential NFAT composite elements in promoters of cytokine genes and their receptors as well as in promoters of genes for AP-1 family members, Ca2+-binding proteins and some other components of the regulatory network operating in activated T-cells and other immune cells. The method developed can be adapted to characterize and identify other composite elements as well. The program for recognition NFAT composite elements is available through the World Wide Web (http://compel.bionet.nsc.ru/FunSite/CompelScan. html and http://transfac.gbf.de/dbsearch/funsitep/s _comp.html).

Characterization of the mouse interleukin-5 promoter in a mouse TH2 T cell clone

The proximal mouse IL-5 promoter was examined using a mouse TH2 clone stimulated through the T cell receptor using anti-CD3 monoclonal antibody. DNase I protection defined four protein binding regions [IL-5RE-A, -69/-45; -B, (-90/-76); -C, (-154/-130); and -D (-176/-157)]. Stimulation-dependent binding, which was seen in the IL-5RE-B, -D regions and the 5' end of tIL-5RE-A, did not require new protein synthesis inhibitor during cell activation. EMSA using probes targeted to the IL-5RE-B, -C, -D regions demonstrated the multimeric nature of the bound proteins. By transfection analysis using a series of truncated IL-5 promoter-luciferase constructs, IL-5RE-C and -D contributed little to constitutive or inducible activity. The CLE0 site in the IL-5RE-A region contributed to full transcriptional activity but was not sufficient to mediate full activity. Full stimulation-dependent activity required the IL-5RE-B region and/or the GATA site (-70/-60).

Characterisation of inducible DNase I hypersensitive sites flanking the human interleukin-5 gene

Interleukin-5 (IL-5) production is necessary for eosinophilia associated with allergic conditions and parasitic infection. IL-5 mRNA is transiently expressed by activated T-lymphocytes. In this report, we have analysed DNA regulatory regions associated with inducible IL-5 expression in the human HSB-2 T-cell line. Only low levels of transcriptional activity were induced in cells transfected with up to 1.2 kb of DNA upstream of the IL-5 gene. DNase I hypersensitivity analysis was employed to identify additional regulatory sequences located outside this region. Two hypersensitivity sites (HS) were identified, one 2.5 kb 5' and the other 1.6 kb 3' from the gene, that were induced on activation of HSB-2 cells by stimuli that induced IL-5 expression. The 5' site, but not the 3' site, was found in primary human T-cells. The presence of the 5' HS did not always coincide with IL-5 expression. Inclusion of the region encompassing the 5' HS in promoter studies mediated a moderate increase in transcriptional activity, suggesting that enhancer elements essential for induction of maximal IL-5 transcription reside at a greater distance from the IL-5 gene.

Carboxyl-Terminal 15-Amino Acid Sequence of NFATx1 Is Possibly Created by Tissue-Specific Splicing and Is Essential for Transactivation Activity in T Cells

NFAT regulates transcription of a number of cytokine and other immunoregulatory genes. We have isolated NFATx, which is one of four members of the NFAT family of transcription factors and is preferentially expressed in the thymus and peripheral blood leukocytes, and an isoform of NFATx, NFATx1. Here we provide evidence showing that 15 amino acids in the carboxyl-terminal end of NFATx1 are required for its maximum transactivation activity in Jurkat T cells. A fusion between these 15 amino acids and the GAL4 DNA binding domain was capable of transactivating reporters driven by the GAL4 DNA binding site. Interestingly, this 15-amino acid transactivation sequence is well conserved in NFAT family proteins, although the sequences contiguous to the carboxyl-terminal regions of the NFAT family are much less conserved. We also report three additional isoforms of NFATx, designated NFATx2, NFATx3, and NFATx4. This transactivation sequence is altered by tissue-specific alternative splicing in newly isolated NFATx isoforms, resulting in lower transactivation activity in Jurkat T cells. NFATx1 is expressed predominantly in the thymus and peripheral blood leukocyte, while the skeletal muscle expressed primarily NFATx2. In Jurkat cells, transcription from the NFAT site of the IL-2 promoter is activated strongly by NFATx1 but only weakly by NFATx2. These data demonstrate that the 15-amino acid sequence of NFATx1 is a major transactivation sequence required for induction of genes by NFATx1 in T cells and possibly regulates NFAT activity through tissue-specific alternative splicing.

Retarded thymic involution and massive germinal center formation in NF-ATp-deficient mice

NF-ATp and NF-ATc are the most prominent nuclear NF-AT transcription factors in peripheral T lymphocytes. After T cell activation both factors bind to and control the promoters and enhancers of numerous lymphokine and receptor ligand genes. In order to define a specific role for NF-ATp in vivo we have inactivated the NF-ATp gene by gene targeting in mice. We show that NF-ATp deficiency leads to the accumulation of peripheral T cells with a "preactivated" phenotype, enhanced immune responses of T cells after secondary stimulation in vitro and severe defects in the proper termination of antigen responses, as shown by a reduced deletion of superantigen-reactive CD4+ T cells. These alterations in the function of the immune system are correlated with drastic changes in the morphology of lymphoid organs. Approximately 25 % of NF-ATp-deficient mice older than 6 months develop large germinal centers in the spleen and peripheral lymph nodes. In addition, they exhibit a pronounced retardation in the involution of the thymus. The thymus of these NF-ATp-deficient mice exhibits large cortical areas typical for newborn mice and a massive infiltration of IgM+/ IgD+ B lymphocytes. Contrary to the T lymphocytes from IL-2-deficient mice which develop a phenotype similar to the NF-ATp-/- mice, NF-ATp-/- T cells do not show obvious defects in Fas-mediated apoptosis. This might indicate defects in other types of programmed cell death which are controlled by the activity of NF-ATp.

Inhibition of phosphodiesterase type IV suppresses human immunodeficiency virus type 1 replication and cytokine production in primary T cells: involvement of NF-kappaB and NFAT

Rolipram, a phosphosdiesterase type IV-specific inhibitor, prevented p24 antigen release from anti-CD3-activated human immunodeficiency virus (HIV)-infected T cells and CD4(+)-cell depletion associated with viral replication in a dose-responsive manner but minimally inhibited T-cell proliferation. Moreover, rolipram reduced the production of tumor necrosis factor alpha (TNF-alpha) and interleukin-10 (IL-10) by HIV-infected T cells. The transcriptional ability of a luciferase reporter gene under control of the HIV long terminal repeat, induced by phorbol myristic acetate plus ionomycin or by TNF-alpha, in primary T and Jurkat cells was also inhibited by rolipram. Rolipram inhibited NF-kappaB and NFAT activation induced by T-cell activation in Jurkat and primary T cells, as measured by transient transfection of reporter genes and electrophoretic mobility shift assays. Exogenous addition of TNF-alpha in the presence of rolipram restored NF-kappaB but not NFAT activation or p24 release. Addition of dibutyryl-cyclic AMP (dBcAMP) mimicked the effects of rolipram on p24 antigen release, NF-kappaB activation, and TNF-alpha secretion, but it did not affect NFAT activation or IL-10 production. The protein kinase A inhibitor KT5720 prevented the inhibition of TNF-alpha secretion but not that of HIV type 1 (HIV-1) replication caused by rolipram. Our data indicate that blockade of phosphodiesterase type IV could be of benefit against HIV-1 disease by modulating cytokine secretion and transcriptional regulation of HIV replication, and they suggest an important role of NFAT in HIV replication in primary T cells. Some of those activities cannot be ascribed solely to its ability to increase cAMP.

Histamine affects interleukin-4, interleukin-5, and interferon-gamma production by human T cell clones from the airways and blood

High levels of histamine can be found in the airways of asthma patients. This study describes the effects of histamine on anti-CD3-induced production of IL-4, IL-5, and IFN-gamma by T cell clones from subjects with allergic asthma and healthy subjects. T cell clones were obtained from bronchoalveolar lavage (BAL) fluid and blood. The number of clones tested, and the percentage of clones in which histamine inhibited or enhanced cytokine production by more than 25%, were as follows: IL-4, 47, 8.5%, and 4.3%; IL-5, 43, 14%, and 30%; and IFN-gamma, 52, 40%, and 15%. Inhibition of IL-5 and IFN-gamma production was reversed by IL-2. The enhancement of IFN-gamma production was associated with an enhancement of both IL-2 production and proliferation. In 21% of the clones a combined effect consisting of inhibition of IFN-gamma production and enhancement of IL-5 production was found. This response was reversed by H2-receptor antagonists and was significantly associated with a histamine-induced increase in intracellular levels of cAMP. The role of cAMP in mediating the histamine effects was supported by the observations that the beta2-agonist salbutamol had effects similar to histamine and that high concentrations of PGE2 mimicked the inhibitory effects of histamine. Clones from BAL fluid and blood showed similar responses, as did clones from patients with asthma and from control subjects. The enhancement of IFN-gamma production by histamine, however, was found only in clones from healthy subjects. The results warrant further investigations on the role of cAMP in the regulation of cytokine production.

Biological and molecular characteristics of interleukin-5 and its receptor

Interleukin-5 (IL5) is a T cell-derived cytokine involved in the pathogenesis of atopic diseases. It specifically controls the production, the activation and the localization of Eosinophils. The Eosinophils are the major cause of tissue damage resulting in the symptoms of asthma and related allergic disorders. T cells purified from bronchoalveolar lavage and peripheral blood of asthmatics secrete elevated amount of IL5. Therefore IL5 emerges to be an attractive target for the generation of new anti-allergic drugs. Agents which inhibit either the production or the activity of IL5 could be expected to ameliorate the pathological effects of the allergic response. A better understanding of the biology of IL5 and the regulation of its expression is, however, a prerequisite for the development of new therapeutic agents. This review covers the major biological, molecular and structural aspects of IL5 research since the identification of this cytokine ten years ago.

Regulation of the cAMP cascade, gene expression and immune function by cannabinoid receptors

The objective of this article is to discuss the putative role of cannabinoid receptors in immune modulation by cannabinoid compounds. The primary focus is on the signal transduction events that are initiated following ligand binding to cannabinoid receptors and how these events lead to detrimental effects on the normal responsiveness of immunocompetent cells. Toward this end, signalling events are traced from the cannabinoid receptor to the transcription factors which are adversely regulated in the presence of cannabinoid compounds during leukocyte activation. Moreover, this aberrant regulation of transcription factors is discussed in the context of altered gene expression and the impact this has on leukocyte function. Lastly, an important goal of this article is to dispel a long standing myth that the cyclic adenosine 3':5'-monophosphate (cAMP) cascade is a negative regulatory pathway for immunocompetent cells. This chapter examines two major immunologic cell-types which are well established as exhibiting altered function following cannabinoid treatment, helper T-cells and the macrophage. Not discussed are the effects of cannabinoids on B-cell function. This is primarily due to the rather refractory nature of B-cells to inhibition by cannabinoids in spite of the fact that this cell-type expresses functional cannabinoid receptors [Schatz, A.R., Koh, W.S., Kaminski, N.E., 1993. Delta9-tetrahydrocannabinol selectively inhibits T-cell dependent humoral immune responses through direct inhibition of accessory T-cell function. Immunopharmacol., 26, pp. 129-137.]. One cautionary note, although the focus of this article is on cannabinoid receptor mediated signalling events, immune modulation by cannabinoid compounds is likely multi-factorial presumably involving receptor as well as receptor-nonrelated events. Effects on leukocytes by cannabinoids which are believed to be mediated by receptor-nonrelated events are outside the scope of this paper and will not be discussed. One last introductory point is that even though their is presumably little overlap in the genes which are regulated by cannabinoids in leukocytes as compared to other cell-types (e.g., neural cells), the major signalling pathways involved in cellular regulation are ubiquitous. With that in mind, it is likely that their is a considerable amount of similarity in the signalling pathways regulated by cannabinoids in cell-types of different lineage, given that they express cannabinoid receptors. In this context, signalling events observed in leukocytes can provide important insight into which genes may be modulated by cannabinoid in other cell types.

Characterization of cis-Regulatory Elements and Nuclear Factors Conferring Th2-Specific Expression of the IL-5 Gene: A Role for a GATA-Binding Protein

Expression of the IL-5 gene is restricted to the Th2 subset of helper T cells. We have previously defined four cis-regulatory elements of the IL-5 promoter responding to PMA and cAMP in EL-4 cells. We now report that the 1.2-kb region of the IL-5 promoter directs expression of the IL-5 gene in a Th2 clone but not a Th1 clone, indicating that transcription from the IL-5 promoter is Th2 specific. For the functioning of the IL-5 promoter in a Th2 clone, IL-5C and IL-5CLE0 were critical. IL-5CLE0 interacted with both constitutive and inducible nuclear factors (designated NFIL-5CLE0), which existed in both Th1 and Th2 clones, whereas IL-5C interacted with a constitutive nuclear factor (designated NFIL-5C), which was found only in Th2 but not in Th1 clones. Th2 specificity of NFIL-5C was also confirmed using in vitro-differentiated Th1 and Th2 cells derived from TCR-transgenic mice. The sequence for NFIL-5C binding bears homology with GATA-binding sites. The NFIL-5C complex was supershifted by an anti-GATA-3 Ab and inhibited by an oligonucleotide containing GATA-binding sites. We showed preferential expression of GATA-3 in Th2 cells. Finally, we demonstrated that in vitro-translated GATA-3 bound to IL-5C and overexpression of GATA-3 augmented stimulation-dependent IL-5 promoter activity in EL-4 cells. Taken together, our results provide evidence that GATA-related factors may be involved in Th2-specific expression of the IL-5 gene.

Distinct NFAT Family Proteins Are Involved in the Nuclear NFAT-DNA Binding Complexes from Human Thymocyte Subsets

The nuclear factor of activated T cells (NFAT) is involved in the transcriptional induction of cytokine and other immunoregulatory genes during an immune response. Among four distinct NFAT family members identified to date, mRNAs of NFAT1, NFATc, and NFATx are expressed in the thymus. Here, we report the distribution of these three NFAT family members in human fetal thymocyte subsets and in peripheral mature T cells. We show that NFATx mRNA was expressed in all T lymphocyte subsets tested and was highest in CD4+CD8+ double positive (DP) thymocytes. Conversely, NFAT1 mRNA was preferentially expressed in the mature CD4+ single positive (SP) populations. NFATc mRNA was present at low levels in all subsets but strongly induced upon treatment with phorbol ester and calcium ionophore. Interestingly, we detected NFAT-DNA binding complexes in DP thymocytes, albeit at lower levels than in CD4 SP cells. Corresponding to the mRNA expression, we observed that NFATx was responsible for the NFAT-DNA binding in DP thymocytes. Moreover, this DNA binding was inhibited by cyclosporin A, indicating that NFATx nuclear translocation was regulated by the calcineurin phosphatase in DP thymocytes. For the CD4 SP populations, NFAT1 and NFATc, and to some extent NFATx, were responsible for the NFAT-DNA binding complexes. These results indicate that NFAT family members are differentially regulated during the development of T cells, and that NFATx may play a distinct role in calcineurin-dependent signaling in DP thymocytes.