Regulation by interleukin 2 of interleukin 2 receptors and gamma-interferon synthesis by human thymocytes: augmentation of interleukin 2 receptors by interleukin 2

The role of interleukin 2 (IL 2) on the expression of IL 2 receptors and on the synthesis of gamma-interferon (gamma-IFN) by human thymocytes was investigated. Human thymocytes isolated from specimens obtained during cardiac surgery of infants and children were induced with one or all of the following agents: IL 2, concanavalin A (Con A), and 12-O-tetradecanoylphorbol 13-acetate (TPA). The expression of IL 2 receptors and gamma-IFN titers were determined. The results indicate that thymocytes cultured in complete medium do not express receptors for IL 2, nor did IL 2 by itself induce the expression of IL 2 receptors. Con A induced the expression of IL 2 receptors by a moderate number of the thymocyte population and induced the synthesis of low amounts of gamma-IFN. Preincubation of thymocytes with TPA increased the response to Con A; both the number of thymocytes expressing receptors and the synthesis of gamma-IFN were increased. Addition of IL 2 to these cultures further augmented the expression of IL 2 receptors and gamma-IFN synthesis and resulted in the optimal expression of IL 2 receptors and maximal gamma-IFN synthesis. The expression of IL 2 receptors could be detected within 24 hr and preceded the induction of proliferation; it was therefore probably not due to the clonal expansion of a population of receptor-bearing thymocytes. Conversely, inhibition of IL 2 synthesis with dexamethasone (Dex) by thymocytes activated with Con A, or inhibition of the function of IL 2 receptors by anti-Tac, resulted in a decrease in the number of IL 2 receptor-bearing thymocytes activated with Con A, or inhibition of the function of IL 2 receptors by anti-Tac, resulted in a decrease in the number of IL 2 receptor-bearing thymocytes and of gamma-IFN synthesis. Thymocytes activated with TPA and Con A were more resistant to the inhibitory effects of Dex on the expression of IL 2 receptors than thymocytes activated with Con A alone. Maximal inhibition of the expression of IL 2 receptors and of gamma-IFN synthesis was achieved as a result of the synergistic effect of anti-Tac with Dex. Therefore, when IL 2 was prevented from binding to the receptors, and IL 2 synthesis was inhibited, the number of thymocytes expressing IL 2 receptors was sharply reduced and gamma-IFN synthesis was markedly inhibited.(ABSTRACT TRUNCATED AT 400 WORDS)     

Polycystin-2 (TRPP2) Regulation by Ca2+ Is Effected and Diversified by Actin-Binding Proteins

Calcium regulation of Ca²⁺-permeable ion channels is an important mechanism in the control of cell function. Polycystin-2 (PC2, TRPP2), a member of the transient receptor potential superfamily, is a nonselective cation channel with Ca²⁺ permeability. The molecular mechanisms associated with PC2 regulation by Ca²⁺ remain ill-defined. We recently demonstrated that PC2 from human syncytiotrophoblast (PC2_hst) but not the in vitro translated protein (PC2_iv), functionally responds to changes in intracellular (cis) Ca²⁺. In this study we determined the regulatory effect(s) of Ca²⁺-sensitive and -insensitive actin-binding proteins (ABPs) on PC2_iv channel function in a lipid bilayer system. The actin-bundling protein α-actinin increased PC2_iv channel function in the presence of cis Ca²⁺, although instead was inhibitory in its absence. Conversely, filamin that shares actin-binding domains with α-actinin had a strong inhibitory effect on PC2_iv channel function in the presence, but no effect in the absence of cis Ca²⁺. Gelsolin stimulated PC2_iv channel function in the presence, but not the absence of cis Ca²⁺. In contrast, profilin that shares actin-binding domains with gelsolin, significantly increased PC2_iv channel function both in the presence and absence of Ca²⁺. The distinct effect(s) of the ABPs on PC2_iv channel function demonstrate that Ca²⁺ regulation of PC2 is actually mediated by direct interaction(s) with structural elements of the actin cytoskeleton. These data indicate that specific ABP-PC2 complexes would confer distinct Ca²⁺-sensitive properties to the channel providing functional diversity to the cytoskeletal control of transient receptor potential channel regulation.     

Nitroxide-Stimulated H2O2 Decomposition by Peroxidases and Pseudoperoxidases

Many copper and iron complexes can be reduced by O^-₂ as well as by H₂O₂. According to the rates of reduction and the concentration of O^-₂ and H₂O₂, the metal complexes may serve either as catalyst of O^-₂ dismutation or as catalysts of the reaction between O^-₂ and H₂O₂ to form OH' radical (Haber-Weiss reaction). Various factors which influence whether metal complexes protect the biological systems from superoxide toxicity or enhance it are discussed.     

Photoproduction of H2 and NADPH2 by polyurethane-immobilized cyanobacteria

Summary Cyanobacterial cells were grown in polyurethane foams (polyester or polyvinyl types). Chlorogloea fritschii, Nostoc muscorum and Mastigocladus laminosus remained immobilized in the foams and were used for continuous photoproduction of H₂ from ascorbate with methyl viologen (MV) and hydrogenase or Pt catalysts, for periods in excess of 9 days. Foam-immobilized N. muscorum continuously photoreduced exogenous NADP for at least 24 h in the presence of Fd-NADP reductase with ascorbate as electron donor.     

Nitroxide-Stimulated H2O2 Decomposition by Peroxidases and Pseudoperoxidases

Nitroxide free radicals interact with Hb/metHb, Mb/metMb and with peroxidases/phenols to induce a catalase-like conversion of H₂O₂ to O₂ (catalatic activity), without being substantially consumed in the process. The mechanism of this reaction is postulated to involve a one-electron oxidation of the nitroxide to the immonium oxene, which then reacts further to release oxygen and the nitroxide. An involvement of the immonium oxene in the reaction mechanism is consistent with ferryl heme reduction by nitroxides and a detection of the reduced nitroxide when the reaction mixture is supplemented with the two-electron reductant sodium borohydride. The nitroxide-induced catalatic activity is completely inhibited when the reaction mixture is supplemented with glutathione. Nitroxides suppress free radical formation by hydroperoxide-activated heme proteins, as inferred from their inhibition of the spin-trapping of glutathionyl radicals. H₂O₂ decomposition and a suppression of reactive free radical formation by heme proteins appears to be an antioxidant activity of nitroxides, which is distinct from their previously reported superoxide dismutating activity and which may be a factor in their protective action in models of cardiac reperfusion injury.     

Regulation of tyrosinase by tetrahydropteridines and H2O2

Recently two alternative mechanisms have been put forward for the inhibition of tyrosinase by 6R-l-erythro 5,6,7,8-tetrahydrobiopterin (6BH(4)). Initially allosteric uncompetitive inhibition was demonstrated due to 1:1 binding of 10(-6)M 6BH(4) to a specific domain 28 amino acids away from the Cu(A) active site of the enzyme. Alternatively it was then shown that 10(-3)M 6BH(4) inhibit the reaction by the reduction of the product dopaquinone back to l-dopa. In the study presented herein we have used two structural analogues of 6BH(4) (i.e., 6,7-(R,S)-dimethyl tetrahydrobiopterin and 6-(R,S)-tetrahydromonapterin) confirming classical uncompetitive inhibition due to specific binding of the pyrimidine ring of the pterin moiety to the regulatory domain on tyrosinase. Under these conditions there was no reduction of l-dopaquinone back to l-dopa by both cofactor analogues. Inhibition of tyrosinase by 6BH(4) occurs in the concentration range of 10(-6)M after preactivation with l-tyrosine and this mechanism uncouples the enzyme reaction producing H(2)O(2) from O(2). Moreover, a direct oxidation of 6BH(4) to 7,8-dihydrobiopterin by tyrosinase in the absence of the substrate l-tyrosine was demonstrated. The enzyme was activated by low concentrations of H(2)O(2) (<0.3 x 10(-3)M), but deactivated at concentrations in the range 0.5-5.0 x 10(-3)M. In summary, our results confirm a major role for 6BH(4) in the regulation of human pigmentation.     

Effects of phosphorylation by CAK on cyclin binding by CDC2 and CDK2.

The cyclin-dependent protein kinases (CDKs) are activated by association with cyclins and by phosphorylation at a conserved threonine residue by the CDK-activating kinase (CAK). We have studied the binding of various human CDK and cyclin subunits in vitro, using purified proteins derived from baculovirus-infected insect cells. We find that most CDK-cyclin complexes known to exist in human cells (CDC2-cyclin B, CDK2-cyclin A, and CDK2-cyclin E) form with high affinity in the absence of phosphorylation or other cellular components. One complex (CDC2-cyclin A) forms with high affinity only after CAK-mediated phosphorylation of CDC2 at the activating threonine residue. CDC2 does not bind with high affinity to cyclin E in vitro, even after phosphorylation of the CDC2 subunit. Thus, phosphorylation is of varying importance in the formation of high-affinity CDK-cyclin complexes.     

Casein kinase 2 inactivation by Mg2+, Mn2+ and Co2+ ions

In order to elucidate the relationship between hypertension and hypertrophy in the production of heat shock proteins, we studied the induction of the HSP72 synthesis by the heart and gracilis muscles of normo (WKY) and hypertensive (SHR) rats subjected to hyperthermia (42°C±0.5 for 15 min). Two age groups were investigated in each strain: young (2 months, with developing cardiac hypertrophy) and old (18 months, with fully developed chronic cardiac hypertrophy). The gracilis muscle never developed hypertrophy, independently of hypertension or aging. 72 kDa inducible protein was determined by Western blot analysis using a specific monoclonal antibody. We also used a commercial standard, loaded on each blot, to quantitate densitometrically the signal.The heart of young SHR responds to heat shock more than their normotensive age-matched control (298.8±24.7% vs 88.3 ±8.5%, p<0.001). This response is not maintained during aging as we did not find any significant difference between normo-and hypertensive old rats after exposure to hyperthermia (43.6±5.3% vs 65.3±10.4%).Unlike the heart, the gracilis muscle shows a basal spontaneous HSP72 synthesis in both the SHR (71.4±10.8%) and WKY (40.6±11.7%) animals. There was a significant increase in HSP72 synthesis in the gracilis muscle of young SHR with respect to their control (186.2±18.7% vs 115.8±9.9%, p<0.02) which was maintained also during aging (171.9±17.3% vs 95.2±10.5%, p<0.01).In conclusion, these data show that hypertension results in an increased synthesis of HSP72 both in cardiac and gracilis muscle in response to heat shock. This abnormal response is attenuated by aging in the heart but not in the gracilis muscle. Thus, the abnormality seems to be independent from hypertrophy and linked to genetic determination of the disease.     

Stereospecific 2'-amination and 2'-chlorination of adenosine by Actinomadura in the biosynthesis of 2'-amino-2'-deoxyadenosine and 2'-chloro-2'-deoxycoformycin

2'-Amino-2'-deoxyadenosine and 2'-chloro-2'-deoxycoformycin (2'-CldCF) are two nucleoside antibiotics produced by Actinomadura. The biosynthesis of these two nucleoside antibiotics has been studied by the addition of [U-14C]adenosine with or without unlabeled adenine to cultures of Actinomadura. By this experimental approach, it is possible to demonstrate that adenosine is the direct precursor for the biosynthesis of 2'-amino-2'-deoxyadenosine and 2'-CldCF. These conclusions are based on the observation that the percentage distribution of 14C in the aglyconic and pentofuranosyl moieties of 2'-amino-2'-deoxyadenosine and 2'-CldCF were similar to the distribution of 14C in the adenine and ribosyl moieties of the [U-14C]adenosine (i.e., 48:52) added to cultures of Actinomadura. Experimentally, the percentage distribution of 14C in the (i) adenine:2-amino-2-deoxy-beta-D-ribofuranose of 2'-amino-2'-deoxyadenosine is 51:49; (ii) 8-(R)-3,6,7,8-tetrahydroimidazo[4,5-d]-[1,3-diazepin-8-o1]:2 -chloro-2- beta-D-ribofuranose of 2'-CldCF is 45:55; and (iii) adenine:ribose of the adenosine isolated from the RNA of Actinomadura is 42:58. Further proof that adenosine is the direct precursor for the biosynthesis 2'-amino-2'-deoxyadenosine and 2'-CldCF was demonstrated by the addition of 75 mumol of unlabeled adenine together with [U-14C]adenosine to nucleoside-producing cultures of Actinomadura. The percentage distribution of 14C in the aglycon and the sugar moieties of 2'-amino-2'-deoxyadenosine and 2'-CldCF were 46:54 and 47:53, respectively; the percentage distribution of 14C in the adenine and ribose moieties of the adenosine isolated from the RNA of Actinomadura was 51:49. These data show that the hydroxyl on C-2' of the ribosyl moiety of adenosine undergoes a replacement by a 2'-amino or a 2'-chloro group to form 2'-amino-2'-deoxyadenosine or 2'-CldCF with retention of stereconfiguration at C-2'. Finally, Actinomadura can utilize inorganic chloride from the medium as demonstrated by the isolation of [36Cl]2'-CldCF following the addition of [36Cl]chloride to the culture medium. Mechanisms for the regioselective modification of the C-2' hydroxyl group and stereospecific insertion of the amino and chloro groups are discussed.     

Bio-synthesis of PGD2 and TXB2 by rabbit blood monocytes

A method for the preparation of a highly purified sample of rabbit blood monocytes is described. The metabolism of arachidonic acid (AA) in these cells was studied. Mononuclear cells were prepared by centrifugation on Ficoll-Paque gradients and the monocytes were obtained by further centrifugation and adherence onto plastic culture dishes. These procedures provided a preparation which contained 95% monocytes (non-specific esterase positive). Incubation of [1-14C]-AA with these cells produced four major metabolites which were separated by TLC; these corresponded to prostaglandin (PG) D2, thromboxane (TX) B2, 12-hydroxyheptadecatrienoic acid (HHT) and 12-/15-hydroxyeicosatetraenoic acid (HETE). A minor product which co-migrated with PGE2 was also detected but neither 6-keto-PGF1 alpha nor PGF2 alpha were detected. Also, there was no evidence of the formation of 5-lipoxygenase products (5-HETE and LTB4) by rabbit monocytes with or without calcium-ionophore A23187-stimulation. The production of PGD2, TXB2 and PGE2 was further confirmed by analyzing [3H]-AA metabolites using high-performance liquid chromatography (HPLC) with tritiated standards as references. The biosynthesis of these compounds from endogenous substrate in A23187-stimulated monocytes was confirmed by specific radioimmunoassays with or without prior HPLC separation. The synthesis of immunoreactive LTB4 and LTC4 by A23187-stimulated cells was also monitored and found to be relatively low. The synthesis of PGD2, TXB2 and PGE2 from both exogenous and endogenous substrate was suppressed by treatment of the monocytes with indomethacin (10(-6) M).     

Nuclear extracellular signal-regulated kinase 1 and 2 translocation is mediated by casein kinase 2 and accelerated by autophosphorylation

The extracellular signal-regulated kinases (ERK) 1 and 2 (ERK1/2) are members of the mitogen-activated protein kinase [MAPK] family. Upon stimulation, these kinases translocate from the cytoplasm to the nucleus, where they induce physiological processes such as proliferation and differentiation. The mechanism of translocation of this kinase involves phosphorylation of two Ser residues within a nuclear translocation signal (NTS), which allows binding to importin7 and a subsequent penetration via nuclear pores. Here we show that the phosphorylation of both Ser residues is mediated mainly by casein kinase 2 (CK2) and that active ERK may assist in the phosphorylation of the N-terminal Ser. We also demonstrate that the phosphorylation is dependent on the release of ERK from cytoplasmic anchoring proteins. Crystal structure of the phosphomimetic ERK revealed that the NTS phosphorylation creates an acidic patch in ERK. Our model is that in resting cells ERK is bound to cytoplasmic anchors, which prevent its NTS phosphorylation. Upon stimulation, phosphorylation of the ERK TEY domain releases ERK and allows phosphorylation of its NTS by CK2 and active ERK to generate a negatively charged patch in ERK, binding to importin 7 and nuclear translocation. These results provide an important role of CK2 in regulating nuclear ERK activities.     

白介素-2受体及其介导的信号转导

白介素２（ＩＬ－２）是一种重要的调控免疫系统细胞增殖和分化的细胞因子。其生物活性的发挥是通过与细胞表面白介素－２受体（ＩＬ－２Ｒ）结合,继而激活胞质内多种非受体型蛋白质酪氨酸激酶（ＰＴＫ）,进一步启动３种主要信号转导途径：控制基因转录的Ｊａｋ－ＳＴＡ...     

Differential regulation of Cdc2 and Cdk2 by RINGO and cyclins.

Cyclin-dependent kinases (Cdks) are key regulators of the eukaryotic cell division cycle. Cdk1 (Cdc2) and Cdk2 should be bound to regulatory subunits named cyclins as well as phosphorylated on a conserved Thr located in the T-loop for full enzymatic activity. Cdc2- and Cdk2-cyclin complexes can be inactivated by phosphorylation on the catalytic cleft-located Thr-14 and Tyr-15 residues or by association with inhibitory subunits such as p21(Cip1). We have recently identified a novel Cdc2 regulator named RINGO that plays an important role in the meiotic cell cycle of Xenopus oocytes. RINGO can bind and activate Cdc2 but has no sequence homology to cyclins. Here we report that, in contrast with Cdc2- cyclin complexes, the phosphorylation of Thr-161 is not required for full activation of Cdc2 by RINGO. We also show that RINGO can directly stimulate the kinase activity of Cdk2 independently of Thr-160 phosphorylation. Moreover, RINGO-bound Cdc2 and Cdk2 are both less susceptible to inhibition by p21(Cip1), whereas the Thr-14/Tyr-15 kinase Myt1 can negatively regulate the activity of Cdc2-RINGO with reduced efficiency. Our results indicate that Cdk-RINGO complexes may be active under conditions in which cyclin-bound Cdks are inhibited and can therefore play different regulatory roles.     

Production of NO, N2O and N2 by extracted soil bacteria, regulation by NO2(-) and O2 concentrations.

The oxygen control of denitrification and its emission of NO/N2O/N2 was investigated by incubation of Nycodenz-extracted soil bacteria in an incubation robot which monitors O2, NO, N2O and N2 concentrations (in He+O2 atmosphere). Two consecutive incubations were undertaken to determine (1) the regulation of denitrification by O2 and NO2(-) during respiratory O2 depletion and (2) the effects of re-exposure to O2 of cultures with fully expressed denitrification proteome. Early denitrification was only detected (as NO and N2O) at 相似文献   

Downregulation of ClC-2 by JAK2

JAK2 (Janus kinase-2) is activated by cell shrinkage and may thus participate in cell volume regulation. Cell volume regulatory ion channels include the small conductance Cl(-) channels ClC-2. The present study thus explored whether JAK2 influences ClC-2 activity. To this end, ClC-2 was expressed in Xenopus oocytes with or without wild type JAK2, active (V617F)JAK2 or inactive (K882E)JAK2 and the Cl(-) channel activity determined by dual electrode voltage clamp. Expression of ClC-2 was followed by a marked increase of cell membrane conductance. The conductance was significantly decreased following coexpression of JAK2 or (V617F)JAK2, but not by coexpression of (K882E)JAK2. Exposure of the oocytes expressing ClC-2 together with (V617F)JAK2 to the JAK2 inhibitor AG490 (40 μM) resulted in a gradual increase of the conductance. According to chemiluminescence JAK2 decreased the channel protein abundance in the cell membrane. The decline of conductance in ClC-2 and (V617F)JAK2 coexpressing oocytes following inhibition of channel protein insertion by brefeldin A (5 μM) was similar in oocytes expressing ClC-2 with (V617F)JAK2 and oocytes expressing ClC-2 alone, indicating that (V617F)JAK2 might slow channel protein insertion into rather than accelerating channel protein retrieval from the cell membrane. In conclusion, JAK2 down-regulates ClC-2 activity and thus counteracts Cl(-) exit, an effect which may impact on cell volume regulation.     

Magnetic field-induced Ca2+ intake by mesenchymal stem cells is mediated by intracellular Zn2+ and accompanied by a Zn2+ influx

Chronic exposure to magnetic fields (MFs) has a diverse range of effects on biological systems but definitive molecular mechanisms of the interaction remain largely unknown. One of the most frequently reported effects of MF exposure is an elevated concentration of intracellular Ca²⁺ through disputed pathways. Other prominent effects include increased oxidative stress and upregulation of neural markers through EGFR activation in stem cells. Further characterization of cascades triggered by MF exposure is hindered by the phenotype diversity of biological models used in the literature. In an attempt to reveal more mechanistic data in this field, we combined the most commonly used biological model and MF parameters with the most commonly reported effects of MFs.Based on clues from the pathways previously defined as sensitive to MFs (EGFR and Zn²⁺-binding enzymes), the roles of different types of channels (voltage gated Ca²⁺ channels, NMDA receptors, TRP channels) were inquired in the effects of 50 Hz MFs on bone marrow-derived mesenchymal stem cells. We report that, an influx of Zn²⁺ accompanies MF-induced Ca²⁺ intake, which is only attenuated by the broad-range inhibitor of TRP channels and store-operated Ca²⁺ entry (SOCE), 2-Aminoethoxydiphenyl borate (2-APB) among other blockers (memantine, nifedipine, ethosuximide and gabapentin). Interestingly, cation influx completely disappears when intracellular Zn²⁺ is chelated. Our results rule out voltage gated Ca²⁺ channels as a gateway to MF-induced Ca²⁺ intake and suggest Zn²⁺-related channels as a new focus in the field.     

Co2+, Cu2+, and Zn2+ accumulation by cyanobacterium Spirulina platensis

The Spirulina platensis biomass was characterized for its metal accumulation as a function of pH, external metal concentration, equilibrium isotherms, kinetics, effect of co-ions under free (living cells, lyophilized, and oven-dried) and immobilized (Ca-alginate and polyacrylamide gel) conditions. The maximum metal biosorption by S. platensis biomass was observed at pH 6.0 with free and immobilized biomass. The studies on equilibrium isotherm experiments showed highest maximum metal loading by living cells (181.0 +/- 13.1 mg Co(2+)/g, 272.1 +/- 29.4 mg Cu(2+)/g and 250.3 +/- 26.4 mg Zn(2+)/g) followed by lyophilized (79.7 +/- 9.6 mg Co(2+)/g, 250.0 +/- 22.4 mg Cu(2+)/g and 111.2 +/- 9.8 mg Zn(2+)/g) and oven-dried (25.9 +/- 1.9 mg Co(2+)/g, 160.0 +/- 14.2 mg Cu(2+)/g and 35.1 +/- 2.7 mg Zn(2+)/g) biomass of S. platensis on a dry weight basis. The polyacrylamide gel (PAG) immobilization of lyophilized biomass found to be superior over Ca-alginate (Ca-Alg) and did not interfere with the S. platensis biomass biosorption capacity, yielding 25% of metal loading after PAG entrapment. The time-dependent metal biosorption in both the free and immobilized form revealed existence of two phases involving an initial rapid phase (which lasted for 1-2 min) contributing 63-77% of total biosorption, followed by a slower phase that continued for 2 h. The metal elution studies conducted using various reagents showed more than 90% elution with mineral acids, calcium salts, and Na(2)EDTA with free (lyophilized or oven-dried) as well as immobilized biomass. The experiments conducted to examine the suitability of PAG-immobilized S. platensis biomass over multiple cycles of Co(2+), Cu(2+), and Zn(2+) sorption and elution showed that the same PAG cubes can be reused for at least seven cycles with high efficiency.     

Degradation of 2-bromo-, 2-chloro- and 2-fluorobenzoate by Pseudomonas putida CLB 250

Abstract Pseudomonas putida strain CLB 250 (DSM 5232) utilized 2-bromo-, 2-chloro- and 2-fluorobenzoate as sole source of carbon and energy. Degradation is suggested to be initiated by a dioxygenase liberating halide in the first catabolic step. After decarboxylation and rearomatization catechol is produced as a central metabolite which is degraded via the ortho-pathway. After inhibition of ring cleavage activities with 3-chlorocatechol, 2-chlorobenzoate was transformed to catechol in nearly stoichiometric amounts. Other ortho -substituted benzoates like anthranilate and 2-methoxybenzoate seem to be metabolized via the same route.