Gene transcription through activation of G-protein-coupled chemoattractant receptors

Receptors for leukocyte chemoattractants, including chemokines, are traditionally considered to be responsible for the activation of special leukocyte functions such as chemotaxis, degranulation, and the release of superoxide anions. Recently, these G-protein-coupled serpentine receptors have been found to transduce signals leading to gene transcription and translation in leukocytes. Transcription factors, such as NF kappa B and AP-1, are activated upon stimulation of the cells with several chemoattractants at physiologically relevant concentrations. Activation of transcription factors through these receptors involves G-protein coupling and the activation of protein kinases. The underlying signaling pathways appear to be different from those utilized by TNF-alpha, a better characterized cytokine that induces the transcription of immediate-early genes. Chemoattractants stimulate the expression of several inflammatory cytokines and chemokines, which in turn may activate their respective receptors and initiate an autocrine regulatory mechanism for persistent cytokine and chemokine gene expression.

Some features of information properties of holographic recording media based on a photoconducting carbazolyl-containing oligomer doped with an organic electron acceptor

Unusual multimodal kinetics of diffraction efficiency in the cycle of hologram recording and erasing were observed in the recording media for the holographic photothermoplastic technique. It was shown that this effect is caused by competition between the simultaneous development of regular and random "frosty" surface reliefs of the photoconducting polymer film during the hologram development. The mechanism explaining the decrease of the maximal diffraction efficiency as compared to its calculated value is discussed.

[Using AELTIS-synchro-02 device in the therapy of chronic bacterial prostatitis]

The treatment of chronic bacterial prostatitis combined antibacterial drugs and physiotherapy (low-energy laser radiation, electrostimulation of the prostate). Treatment of chronic bacterial prostatitis with medication and complex two-channel bio-synchronized electrolaser therapy with application of the unit AELTIS-synchro-02 raises efficacy of treatment with chronic bacterial prostatitis due to combined effect of antibacterial drugs and bacteriostatic and immunomodulating actions of the physical factors applied. These normalize microcirculation in the region of the prostatic gland, improve a draining function of the prostatic ducts, allows achievement of good results in 88.2% patients.

[Technical aspects of laparoscopic cholecystectomy in umbilical hernia]

There were analyzed the results of laparoscopic cholecystectomy performance in 1230 patients, in 60 (4.7%) of whom--with simultant intervention for concurrent umbilical hernia. The expediency of simultant operation performance was caused by exclusion of the concurrent disease progressing, the reduction of the temporary disablement duration and by the shortage of the treatment expenses. The management of postoperative period is similar both in simultant treatment and in conventional performance of laparoscopic cholecystectomy.

[Chemoattractants of Distyostelium discoideum (Protozoa: Sarcomastigophora, Eumycetozoa)]

The authors summarize data on interaction of protozoan Dictyostelium discoideum with folia acid and cyclic adenozinmonophosphate as chemoattractants. These substances play role of antagonists in the life cycle of Dictyostelium discoideum: one disperses cells in space and another gathers them into groups forming and organism. Analysis of interaction between Dictyostelium discoideum and environment allows to reveal that Deictyosteliceae has unique mechanism of adaptation of shortage of feeding resource--forming of multicellular organism with functional differentiation of cells. This mechanism could be found at different hierarchical levels of living organisms.

Gene induction by coagulation factor Xa is mediated by activation of protease-activated receptor 1

Cell signaling by coagulation factor Xa (Xa) contributes to pro-inflammatory responses in vivo. This study characterizes the signaling mechanism of Xa in a HeLa cell line that expresses protease-activated receptor 1 (PAR-1) but not PAR-2, -3, or -4. Xa induced NF-kappaB in HeLa cells efficiently but with delayed kinetics compared to thrombin. This delay caused no difference in gene expression patterns, as determined by high-density microarray analysis. Both proteases prominently induced the angiogenesis-promoting gene Cyr61 and connective tissue growth factor. Inhibition of PAR-1 cleavage abolished MAP kinase phosphorylation and gene induction by Xa, demonstrating that Xa signals through PAR-1 and not through a novel member of the PAR family. Activation of cell surface prothrombin with the snake venom enzyme Ecarin also produced PAR-1-dependent signaling. However, though the response to Ecarin was completely blocked by the thrombin inhibitor hirudin, the response to Xa was not. This suggests that the Xa response is not mediated by locally generated thrombin. The concentration dependence of Xa for PAR-1 activation is consistent with previously characterized Xa-mediated PAR-2 signaling, suggesting that local concentration of Xa on the cell surface, rather than sequence-specific recognition of the PAR scissile bond, determines receptor cleavage. This study demonstrates that PAR-1 cleavage by Xa can elicit the same cellular response as thrombin, but mechanistic differences in receptor recognition may be crucial for specific roles for Xa in signaling during spatial or temporal separation from thrombin generation.

[The mechanism of formation of Liesegang structures around Dictyostelium discoideum]

A theoretical study of the phenomenon of Liesegang structure formation induced by the Dictyostelium discoideum population in a medium containing folic acid was carried out. Using a "reaction-diffusion" model proposed in this work, it was shown that the formation of Liesegang structures around the Dictyostelium discoideum population depends on two competing processes: (a) inactivation of folic acid by vegetative amoebae and (b) the chemical reaction of folic acid with the products of amoeba metabolism, which results in the formation of insoluble sediment. The dependence of the model solutions on the geometric and functional parameters was studied. The results are in good agreement with experimental data.

[How does environment modify the spatial structure of Dictyostelium discoideum population]

The transformation of the spatial structure of a Dictyostelium discoideum population in response to environmental changes induced by this population was investigated. A comparative analysis of the spatial and temporal characteristics of the D. discoideum colony is given for two cases: (a) when the colony is cultivated on a bacterial lawn, i.e. under conditions close to natural, and (b) in the absence of the bacterial lawn when the colony grows on the nutrient substrate enriched with folic acid. It is shown that the environmental changes induced by cell metabolism modify the spatial structure of the D. discoideum population first, the rate of population propagation falls drastically, which correlates with a decrease in the substrate pH; second, the spatial redistribution of the D. discoideum cell density correlates with the redistribution of folic acid in the substrate. The mechanism of the environment impact on the D. discoideum colony transformation is discussed.

[Structural modification of environment by microorganisms: formation of Liesegang rings around Dictyostelium discoideum population]

The results of the experimental study of the environment modification--the emergence of Liesegang rings around a Dictyostelium discoideum population are presented. The formation of Liesegang rings induced by D. discoideum cells is observed on addition of glucose into the semi-solid nutrient medium (agar concentration 0.5-1.5%). We show that the emergence of Liesegang rings is attended with a redistribution of folic acid in the nutrient substrate. A pH decrease in the course of D. discoideum cultivation is shown to be a factor inducing the redistribution of folic acid. The mechanisms of structural modification of the D. discoideum environment are discussed.

Regulation of the MEF2 family of transcription factors by p38

Members of the MEF2 family of transcription factors bind as homo- and heterodimers to the MEF2 site found in the promoter regions of numerous muscle-specific, growth- or stress-induced genes. We showed previously that the transactivation activity of MEF2C is stimulated by p38 mitogen-activated protein (MAP) kinase. In this study, we examined the potential role of the p38 MAP kinase pathway in regulating the other MEF2 family members. We found that MEF2A, but not MEF2B or MEF2D, is a substrate for p38. Among the four p38 group members, p38 is the most potent kinase for MEF2A. Threonines 312 and 319 within the transcription activation domain of MEF2A are the regulatory sites phosphorylated by p38. Phosphorylation of MEF2A in a MEF2A-MEF2D heterodimer enhances MEF2-dependent gene expression. These results demonstrate that the MAP kinase signaling pathway can discriminate between different MEF2 isoforms and can regulate MEF2-dependent genes through posttranslational activation of preexisting MEF2 protein.

Regulation of an essential innate immune response by the p50 subunit of NF-kappaB

Recognition of bacterial endotoxin (LPS) elicits multiple host responses, including activation of cells of the innate immune system. LPS exposure occurs repeatedly during septicemia, making strict regulation of gene expression necessary. Such regulation might prevent, for example, the continuous production of proinflammatory cytokines such as tumor necrosis factor (TNF), which could lead to severe vascular collapse. Tolerance to LPS is characterized by a diminished production of TNF during prolonged exposure to LPS, and is therefore likely to represent an essential control mechanism during sepsis. In the present study, which uses mice with genetic deletions of the proteins of NF-kappaB complex, we provide data demonstrating that increased expression of the p50 subunit of NF-kappaB directly results in the downregulation of LPS-induced TNF production. This contention is supported by the following observations: (1) tolerance to LPS is not induced in macrophages from p50-/- mice; (2) long-term pretreatment with LPS does not block synthesis of TNF mRNA in p50-/- macrophages (in contrast to wild-type macrophages); (3) ectopic overexpression of p50 reduces transcriptional activation of the murine TNF promoter; and (4) analysis of the four kappaB sites from the murine TNF promoter demonstrates that binding of p50 homodimers to the positively acting kappaB3 element is associated with development of the LPS-tolerant phenotype. Thus, p50 expression plays a key role in the development of LPS tolerance.

Roles for LBP and soluble CD14 in cellular uptake of LPS

Roles for LBP and CD14 in the LPS dependent activation of a wide variety of cells have been established. In the work described here, we describe roles for these proteins in the binding and uptake of LPS by cells which express membrane CD14 and those which do not. Surprisingly, cell activation and LPS uptake appear to be independent phenomena with different protein requirements.

Cell activation mediated by glycosylphosphatidylinositol-anchored or transmembrane forms of CD14

CD14 is a glycosylphosphatidylinositol (GPI)-anchored membrane glycoprotein which functions as a receptor on myeloid cells for ligands derived from microbial pathogens such as lipopolysaccharide (LPS). We have studied the importance of the GPI tail of CD14 in signalling with the promonocytic cell line THP-1 expressing recombinant CD14 in a GPI-anchored form (THP1-wtCD14 cells) or in a transmembrane form (THP1-tmCD14). We found that, like other GPI-anchored molecules, GPI-anchored CD14 was recovered mainly from a Triton X-100-insoluble fraction, whereas transmembrane CD14 was fully soluble in Triton X-100. LPS induced cell activation of THP1-wtCD14 and of THP1-tmCD14 (protein tyrosine kinase phosphorylation, NF-kappaB activation, and cytokine production) in a very similar manner. However, anti-CD14 antibody-induced cross-linking caused a rapid calcium mobilization signal only in GPI-anchored CD14 cells. Studies with pharmacologic inhibitors of intracellular signalling events implicate phospholipase C and protein tyrosine kinases in the genesis of this antibody-induced calcium signal. Our results suggest that GPI anchoring and CD14 targeting to glycolipid-rich membrane microdomains are not required for LPS-mediated myeloid cell activation. GPI anchoring may however be important for other signalling functions, such as those events reflected by antibody cross-linking.

BMK1/ERK5 regulates serum-induced early gene expression through transcription factor MEF2C

Big MAP kinase 1 (BMK1), also known as ERK5, is a mitogen-activated protein (MAP) kinase member whose biological role is largely undefined. We have shown previously that the activity of BMK1 in rat smooth muscle cells is up-regulated by oxidants. Here, we describe a constitutively active form of the MAP kinase kinase, MEK5(D), which selectively activates BMK1 but not other MAP kinases in vivo. Through utilization of MEK5(D), we have determined that a member of the MEF2 transcription factor family, MEF2C, is a protein substrate of BMK1. BMK1 dramatically enhances the transactivation activity of MEF2C by phosphorylating a serine residue at amino acid position 387 in this transcription factor. Serum is also a potent stimulator of BMK1-induced MEF2C phosphorylation, since a dominant-negative form of BMK1 specifically inhibits serum-induced activation of MEF2C. One consequence of MEF2C activation is increased transcription of the c-jun gene. Taken together, these results strongly suggest that in some cell types the MEK5/BMK1 MAP kinase signaling pathway regulates serum-induced early gene expression through the transcription factor MEF2C.

Activation of the transcription factor MEF2C by the MAP kinase p38 in inflammation

For cells of the innate immune system to mount a host defence response to infection, they must recognize products of microbial pathogens such as lipopolysaccharide (LPS), the endotoxin secreted by Gram-negative bacteria. These cellular responses require intracellular signalling pathways, such as the four MAP kinase (MAPK) pathways. In mammalian cells the MAPK p38 is thought to play an important role in the regulation of cellular responses during infection through its effects on the expression of proinflammatory molecules. One means of understanding the role of p38 in these responses is to identify proteins with functions regulated by p38-catalysed phosphorylation. Here we demonstrate a link between the p38 pathway and a member of the myocyte-enhancer factor 2 (MEF2) group of transcription factors. We found that in monocytic cells, LPS increases the transactivation activity of MEF2C through p38-catalysed phosphorylation. One consequence of MEF2C activation is increased c-jun gene transcription. Our results show that p38 may influence host defence and inflammation by maintaining the balance of c-Jun protein consumed during infection.

[Regulation of translation of the distal lacZ gene in polycistronic mRNA by the ribosome stream from the proximal gene]

Four series of plasmids (pNSI, pNSII, pNLI, and pNLII) with artificial polycistrons containing the lacZ test gene were constructed. These plasmids coded for polycistronic mRNAs with two different types of cistron (orfZ and lacZ) coupling: in pNSI and pNLI, the orfZ termination codon and the lacZ initiation codon overlapped (type I); in pNSII and pNLII, the orfZ termination codon, was located upstream of the lacZ SD sequence. The length of the orfZ cistron was 60 bp in pNSI and pNSII or 300 bp in pNLI and pNLII. Plasmids with the same type of cistron coupling contained the same lacZ translation initiation region, whereas the structure of the orfZ translation initiation region varied, thereby providing varying efficiency of the orfZ gene translation. The effect of these variations on the efficiency of the lacZ gene translation was evaluated by direct measurement of the beta-galactosidase activity in Escherichia coli cells transformed with the corresponding plasmids. We found that the level of translation of the distal lacZ gene depended on the ribosome stream from the proximal gene and was maximal at the optimal ribosome stream level, which, in turn, depended on the type of cistron coupling.

Purification and molecular cloning of an inducible gram-negative bacteria-binding protein from the silkworm, Bombyx mori

A 50-kDa hemolymph protein, having strong affinity to the cell wall of Gram(-) bacteria, was purified from the hemolymph of the silkworm, Bombyx mori. The cDNA encoding this Gram(-) bacteria-binding protein (GNBP) was isolated from an immunized silkworm fat body cDNA library and sequenced. Comparison of the deduced amino acid sequence with known sequences revealed that GNBP contained a region displaying significant homology to the putative catalytic region of a group of bacterial beta-1,3 glucanases and beta-1,3-1,4 glucanases. Silkworm GNBP was also shown to have amino acid sequence similarity to the vertebrate lipopolysaccharide receptor CD14 and was recognized specifically by a polygonal anti-CD14 antibody. Northern blot analysis showed that GNBP was constitutively expressed in fat body, as well as in cuticular epithelial cells of naive silkworms. Intense transcription was, however, rapidly induced following a cuticular or hemoceolien bacterial challenge. An mRNA that hybridized with GNBP cDNA was also found in the l(2)mbn immunocompetent Drosophila cell line. These observations suggest that GNBP is an inducible acute phase protein implicated in the immune response of the silkworm and perhaps other insects.

Endotoxin tolerance is induced in Chinese hamster ovary cell lines expressing human CD14

Changes in patterns of gene induction by myeloid lineage cells following multiple exposures to endotoxin (lipopolysaccharide; LPS) is a feature of LPS tolerance. To further understand the mechanism of this phenomenon we describe studies using stably transfected Chinese hamster ovary cell lines that express human CD14 (CHO-hCD14). Using NF-kappa B activation as a measure of LPS-induced cell activation we show that a single treatment with LPS renders CHO-hCD14 cells tolerant to subsequent challenge with LPS, but not with other stimuli such as tumor necrosis factor. Tolerance may result from the induction of gene(s) that control LPS-induced signaling pathways and here we suggest that such genes may be found in the group of immediate, early response genes characterized by the protein phosphatase 3CH134. The CHO-hCD14 cell lines provide a novel model system to further explore the mechanism of endotoxin tolerance.

[Effect of the length of the loop segment of local mRNA secondary structure in the region of lacZ gene translation initiation on its expression]

A number of p50FNL plasmids with a polycistronic operon IX-VIII-IFN-LacZ have been constructed. These plasmids provide the synthesis of polycistronic mRNA translational terminator of gene IFN situated in the coding region of lacZ gene at 41 nucleotide downstreams from its initiation codon. The coding region of IFN gene has been altered by insertions, substitutions, and deletions which provided the formation in the region of local secondary structures differing only by the loop size. The effect of this characteristic of mRNA secondary structure on lacZ translation efficiency has been assessed by measuring the levels of beta-Gal synthesis in E. coli harboring the corresponding plasmids. The level of lacZ expression increased with increase of the loop size. These data confirm that the rate of formation of mRNA secondary structure in the region of translation initiation has a crucial effect on the translation efficacy.

Stimulation of NF-kappa B activation and gene expression by platelet-activating factor

PAF stimulation of NF-kappa B activation and transcription of immediate-early genes have been investigated in peripheral blood mononuclear cells and in transfected Chinese hamster ovary cells expressing the cloned PAF receptor. These studies identified a G protein-coupled pathway for PAF induction of gene expression and transcription factor activation, which differs from the mechanisms employed by other immediate-early gene inducers. Potential significance of PAF induced NF-kappa B activation is discussed.

Platelet-activating factor induces NF-kappa B activation through a G protein-coupled pathway

The capability of platelet-activating factor (PAF) to induce transcription factor activation was examined. In stably transfected Chinese hamster ovary cells expressing the PAF receptor (CHO-PAFR), PAF stimulation resulted in the nuclear expression of a DNA binding activity with specificity to the kappa B sequence. The p50 and p65 proteins, constituents of the prototypic nuclear factor kappa B (NF-kappa B), were identified as components of the DNA protein complexes by antipeptide antibodies in gel supershift as well as UV cross-linking experiments. PAF induced an initial decrease and subsequent increase of cytoplasmic I kappa B alpha levels, accompanied by up-regulation of the I kappa B alpha messenger RNA, a feature of NF-kappa B activation. PAF-induced kappa B binding activity was detected within 15 min after agonist stimulation, peaked at 30-40 min, and remained detectable by 2.5 h. SR 27417, a PAF receptor antagonist, blocked PAF-induced kappa B binding activity but not that induced by tumor necrosis factor-alpha (TNF alpha). Cholera toxin treatment markedly reduced PAF-induced kappa B binding activity, whereas pertussis toxin had no significant inhibitory effect. Neither of the two toxins affected the kappa B binding activity induced by TNF alpha in the same cells. In addition to the CHO-PAFR cells, PAF stimulated kappa B binding activity in the murine P388D1 macrophage and the human ASK.0 B cell lines that express endogenous PAF receptors. These results imply a potential role of PAF in the regulation of gene expression through a G protein-coupled transcription factor activation pathway.