Cloning, sequencing and partial functional characterization of the 5' region of the human p75 tumor necrosis factor receptor-encoding gene (TNF-R)

A 1887-bp region at the 5' flank of the human p75 tumor necrosis factor receptor (p75 TNF-R)-encoding gene was found to be active in driving expression of the luc (luciferase-encoding) reporter gene, suggesting that it contains the promoter for the receptor. Rather unexpectedly, a 1827-bp region at the 3' end of the first intron of the p75 TNF-R gene also displayed promoter activity. This activity may be artefactual, reflecting only the presence of an enhancer in this region; yet it also raises the possibility that p75 TNF-R is controlled by more than one promoter and that it encodes various forms of the receptor, or even other proteins. We present here the nucleotide sequences of the 5' flanking and intron regions. Possible implications for the transcriptional regulation of the p75 TNF-R gene are discussed.

Nck-interacting Ste20 kinase couples Eph receptors to c-Jun N-terminal kinase and integrin activation.

The mammalian Ste20 kinase Nck-interacting kinase (NIK) specifically activates the c-Jun amino-terminal kinase (JNK) mitogen-activated protein kinase module. NIK also binds the SH3 domains of the SH2/SH3 adapter protein Nck. To determine whether Nck functions as an adapter to couple NIK to a receptor tyrosine kinase signaling pathway, we determined whether NIK is activated by Eph receptors (EphR). EphRs constitute the largest family of receptor tyrosine kinases (RTK), and members of this family play important roles in patterning of the nervous and vascular systems. In this report, we show that NIK kinase activity is specifically increased in cells stimulated by two EphRs, EphB1 and EphB2. EphB1 kinase activity and phosphorylation of a juxtamembrane tyrosine (Y594), conserved in all Eph receptors, are both critical for NIK activation by EphB1. Although pY594 in the EphB1R has previously been shown to bind the SH2 domain of Nck, we found that stimulation of EphB1 and EphB2 led predominantly to a complex between NIK/Nck, p62(dok), RasGAP, and an unidentified 145-kDa tyrosine-phosphorylated protein. Tyrosine-phosphorylated p62(dok) most probably binds directly to the SH2 domain of Nck and RasGAP and indirectly to NIK bound to the SH3 domain of Nck. We found that NIK activation is also critical for coupling EphB1R to biological responses that include the activation of integrins and JNK by EphB1. Taken together, these findings support a model in which the recruitment of the Ste20 kinase NIK to phosphotyrosine-containing proteins by Nck is an important proximal step in the signaling cascade downstream of EphRs.

Nck recruitment to Eph receptor, EphB1/ELK, couples ligand activation to c-Jun kinase.

Eph family receptor tyrosine kinases signal axonal guidance, neuronal bundling, and angiogenesis; yet the signaling systems that couple these receptors to targeting and cell-cell assembly responses are incompletely defined. Functional links to regulators of cytoskeletal structure are anticipated based on receptor mediated cell-cell aggregation and migratory responses. We used two-hybrid interaction cloning to identify EphB1-interactive proteins. Six independent cDNAs encoding the SH2 domain of the adapter protein, Nck, were recovered in a screen of a murine embryonic library. We mapped the EphB1 subdomain that binds Nck and its Drosophila homologue, DOCK, to the juxtamembrane region. Within this subdomain, Tyr594 was required for Nck binding. In P19 embryonal carcinoma cells, activation of EphB1 (ELK) by its ligand, ephrin-B1/Fc, recruited Nck to native receptor complexes and activated c-Jun kinase (JNK/SAPK). Transient overexpression of mutant EphB1 receptors (Y594F) blocked Nck recruitment to EphB1, attenuated downstream JNK activation, and blocked cell attachment responses. These findings identify Nck as an important intermediary linking EphB1 signaling to JNK.

IL-9 and its receptor are predominantly involved in the pathogenesis of UC.

OBJECTIVE Several pathogenic roles attributed over the past two decades to either T helper (Th)1 or Th2 cells are increasingly becoming associated with interleukin (IL)-17 and most recently IL-9 signalling. However, the implication of IL-9 in IBD has not been addressed so far. DESIGN We investigated the expression of IL-9 and IL-9R by using peripheral blood, biopsies and surgical samples. We addressed the functional role of IL-9 signalling by analysis of downstream effector proteins. Using Caco-2 cell monolayers we followed the effect of IL-9 on wound healing. RESULTS IL-9 mRNA expression was significantly increased in inflamed samples from patients with UC as compared with controls. CD3(+) T cells were major IL-9-expressing cells and some polymorphonuclear leucocytes (PMN) also expressed IL-9. IL-9 was co-localised with the key Th9 transcription factors interferon regulatory factor 4 and PU.1. Systemically, IL-9 was abundantly produced by activated peripheral blood lymphocytes, whereas its receptor was overexpressed on gut resident and circulating PMN. IL-9 stimulation of the latter induced IL-8 production in a dose-dependent manner and rendered PMN resistant to apoptosis suggesting a functional role for IL-9R signalling in the propagation of gut inflammation. Furthermore, IL-9R was overexpressed on gut epithelial cells and IL-9 induced STAT5 activation in these cells. Moreover, IL-9 inhibited the growth of Caco-2 epithelial cell monolayers in wound healing experiments. CONCLUSIONS Our results provide evidence that IL-9 is predominantly involved in the pathogenesis of UC suggesting that targeting IL-9 might become a therapeutic option for patients with UC.

Inhibition of photosynthesis by high temperature in oak (Quercus pubescens L.) leaves grown under natural conditions closely correlates with a reversible heat-dependent reduction of the activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase

Inhibition of the net photosynthetic CO2 assimilation rate (Pn) by high temperature was examined in oak (Quercus pubescens L.) leaves grown under natural conditions. Combined measurements of gas exchange and chlorophyll (Chl) a fluorescence were employed to differentiate between inhibition originating from heat effects on components of the thylakoid membranes and that resulting from effects on photosynthetic carbon metabolism. Regardless of whether temperature was increased rapidly or gradually, Pn decreased with increasing leaf temperature and was more than 90% reduced at 45 °C as compared to 25 °C. Inhibition of Pn by heat stress did not result from reduced stomatal conductance (gs), as heat-induced reduction of gs was accompanied by an increase of the intercellular CO2 concentration (Ci). Chl a fluorescence measurements revealed that between 25 and 45 °C heat-dependent alterations of thylakoid-associated processes contributed only marginally, if at all, to the inhibition of Pn by heat stress, with photosystem II being remarkably well protected against thermal inactivation. The activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) decreased from about 90% at 25 °C to less than 30% at 45 °C. Heat stress did not affect Rubisco per se, since full activity could be restored by incubation with CO2 and Mg2+. Western-blot analysis of leaf extracts disclosed the presence of two Rubisco activase polypeptides, but heat stress did not alter the profile of the activase bands. Inhibition of Pn at high leaf temperature could be markedly reduced by artificially increasing Ci. A high Ci also stimulated photosynthetic electron transport and resulted in reduced non-photochemical fluorescence quenching. Recovery experiments showed that heat-dependent inhibition of Pn was largely, if not fully, reversible. The present results demonstrate that in Q. pubescens leaves the thylakoid membranes in general and photosynthetic electron transport in particular were well protected against heat-induced perturbations and that inhibition of Pn by high temperature closely correlated with a reversible heat-dependent reduction of the Rubisco activation state.

Association of long-term nicotine abstinence with normal metabotropic glutamate receptor-5 binding

BACKGROUND Nicotine addiction is a major public health problem and is associated with primary glutamatergic dysfunction. We recently showed marked global reductions in metabotropic glutamate receptor type 5 (mGluR5) binding in smokers and recent ex-smokers (average abstinence duration of 25 weeks). The goal of this study was to examine the role of mGluR5 downregulation in nicotine addiction by investigating a group of long-term ex-smokers (abstinence >1.5 years), and to explore associations between mGluR5 binding and relapse in recent ex-smokers. METHODS Images of mGluR5 receptor binding were acquired in 14 long-term ex-smokers, using positron emission tomography with radiolabeled [11C]ABP688, which binds to an allosteric site with high specificity. RESULTS Long-term ex-smokers and individuals who had never smoked showed no differences in mGluR5 binding in any of the brain regions examined. Long-term ex-smokers showed significantly higher mGluR5 binding than recent ex-smokers, most prominently in the frontal cortex (42%) and thalamus (57%). CONCLUSIONS Our findings suggest that downregulation of mGluR5 is a pathogenetic mechanism underlying nicotine dependence and the high relapse rate in individuals previously exposed to nicotine. Therefore, mGluR5 receptor binding appears to be an effective biomarker in smoking and a promising target for the discovery of novel medication for nicotine dependence and other substance-related disorders.

The role of metabotropic glutamate receptor 5 in the pathogenesis of mood disorders and addiction: combining preclinical evidence with human Positron Emission Tomography (PET) studies.

In the present review, we deliver an overview of the involvement of metabotropic glutamate receptor 5 (mGluR5) activity and density in pathological anxiety, mood disorders and addiction. Specifically, we will describe mGluR5 studies in humans that employed Positron Emission Tomography (PET) and combined the findings with preclinical animal research. This combined view of different methodological approaches-from basic neurobiological approaches to human studies-might give a more comprehensive and clinically relevant view of mGluR5 function in mental health than the view on preclinical data alone. We will also review the current research data on mGluR5 along the Research Domain Criteria (RDoC). Firstly, we found evidence of abnormal glutamate activity related to the positive and negative valence systems, which would suggest that antagonistic mGluR5 intervention has prominent anti-addictive, anti-depressive and anxiolytic effects. Secondly, there is evidence that mGluR5 plays an important role in systems for social functioning and the response to social stress. Finally, mGluR5's important role in sleep homeostasis suggests that this glutamate receptor may play an important role in RDoC's arousal and modulatory systems domain. Glutamate was previously mostly investigated in non-human studies, however initial human clinical PET research now also supports the hypothesis that, by mediating brain excitability, neuroplasticity and social cognition, abnormal metabotropic glutamate activity might predispose individuals to a broad range of psychiatric problems.

Reactions of CF3-enones with arenes under superelectrophilic activation: a pathway to trans-1,3-diaryl-1-CF3-indanes, new cannabinoid receptor ligands

4-Aryl-1,1,1-trifluorobut-3-en-2-ones ArCH[double bond, length as m-dash]CHCOCF3 (CF3-enones) react with arenes in excess of Brønsted superacids (TfOH, FSO3H) to give, stereoselectively, trans-1,3-diaryl-1-trifluoromethyl indanes in 35-85% yields. The reaction intermediates, the O-protonated ArCH[double bond, length as m-dash]CHC(OH(+))CF3 and the O,C-diprotonated ArHC(+)CH2C(OH(+))CF3 species, have been studied by means of (1)H, (13)C, (19)F NMR, and DFT calculations. Both types of the cations may participate in the reaction, depending on their electrophilicity and electron-donating properties of the arenes. The formation of CF3-indanes is a result of cascade reaction of protonated CF3-enones to form chemo-, regio- and stereoselectively three new C-C bonds. The obtained trans-1,3-diaryl-1-trifluoromethyl indanes were investigated as potential ligands for cannabinoid receptors CB1 and CB2 types. The most potent compound showed sub-micromolar affinity for both receptor subtypes with a 6-fold selectivity toward the CB2 receptor with no appreciable cytotoxicity toward SHSY5Y cells.

Discovery of Novel Adenosine Receptor Agonists That Exhibit Subtype Selectivity

A series of N6-bicyclic and N6-(2-hydroxy)cyclopentyl derivatives of adenosine were synthesized as novel A1R agonists and their A1R/A2R selectivity assessed using a simple yeast screening platform. We observed that the most selective, high potency ligands were achieved through N6-adamantyl substitution in combination with 5′-N-ethylcarboxamido or 5′-hydroxymethyl groups. In addition, we determined that 5′-(2-fluoro)thiophenyl derivatives all failed to generate a signaling response despite showing an interaction with the A1R. Some selected compounds were also tested on A1R and A3R in mammalian cells revealing that four of them are entirely A1R-selective agonists. By using in silico homology modeling and ligand docking, we provide insight into their mechanisms of recognition and activation of the A1R. We believe that given the broad tissue distribution, but contrasting signaling profiles, of adenosine receptor subtypes, these compounds might have therapeutic potential.

Downregulation of sphingosine 1-phosphate (S1P) receptor 1 by dexamethasone inhibits S1P-induced mesangial cell migration

Sphingosine 1-phosphate (S1P) is generated by sphingosine kinase (SK)-1 and -2 and acts mainly as an extracellular ligand at five specific receptors, denoted S1P1-5. After activation, S1P receptors regulate important processes in the progression of renal diseases, such as mesangial cell migration and survival. Previously, we showed that dexamethasone enhances SK-1 activity and S1P formation, which protected mesangial cells from stress-induced apoptosis. Here we demonstrate that dexamethasone treatment lowered S1P1 mRNA and protein expression levels in rat mesangial cells. This effect was abolished in the presence of the glucocorticoid receptor antagonist RU-486. In addition, in vivo studies showed that dexamethasone downregulated S1P1 expression in glomeruli isolated from mice treated with dexamethasone (10 mg/kg body weight). Functionally, we identified S1P1 as a key player mediating S1P-induced mesangial cell migration. We show that dexamethasone treatment significantly lowered S1P-induced migration of mesangial cells, which was again reversed in the presence of RU-486. In summary, we suggest that dexamethasone inhibits S1P-induced mesangial cell migration via downregulation of S1P1. Overall, these results demonstrate that dexamethasone has functional important effects on sphingolipid metabolism and action in renal mesangial cells.