Chronic Psychological Stress Disrupted the Composition of the Murine Colonic Microbiota and Accelerated a Murine Model of Inflammatory Bowel Disease

The effect of psychological stress on the gastrointestinal microbiota is widely recognized. Chronic psychological stress may be associated with increased disease activity in inflammatory bowel disease, but the relationships among psychological stress, the gastrointestinal microbiota, and the severity of colitis is not yet fully understood. Here, we examined the impact of 12-week repeated water-avoidance stress on the microbiota of two inbred strains of T cell receptor alpha chain gene knockout mouse (background, BALB/c and C57BL/6) by means of next-generation sequencing of bacterial 16S rRNA genes. In both mouse strains, knockout of the T cell receptor alpha chain gene caused a loss of gastrointestinal microbial diversity and stability. Chronic exposure to repeated water-avoidance stress markedly altered the composition of the colonic microbiota of C57BL/6 mice, but not of BALB/c mice. In C57BL/6 mice, the relative abundance of genus Clostridium, some members of which produce the toxin phospholipase C, was increased, which was weakly positively associated with colitis severity, suggesting that expansion of specific populations of indigenous pathogens may be involved in the exacerbation of colitis. However, we also found that colitis was not exacerbated in mice with a relatively diverse microbiota even if their colonic microbiota contained an expanded phospholipase C-producing Clostridium population. Exposure to chronic stress also altered the concentration of free immunoglobulin A in colonic contents, which may be related to both the loss of bacterial diversity in the colonic microbiota and the severity of the colitis exacerbation. Together, these results suggest that long-term exposure to psychological stress induces dysbiosis in the immunodeficient mouse in a strain-specific manner and also that alteration of microbial diversity, which may be related to an altered pattern of immunoglobulin secretion in the gastrointestinal tract, might play a crucial role in the development of chronic stress-induced colitis.

Genome-Wide Analysis and Expression Profiling of the Phospholipase C Gene Family in Soybean (Glycine max)

Phosphatidylinositol-specific phospholipase C (PI-PLC) hydrolyses phosphatidylinositol-4,5-bisphosphate to produce diacylglycerol and inositol 1,4,5-trisphosphate. It plays an important role in plant development and abiotic stress responses. However, systematic analysis and expression profiling of the phospholipase C (PLC) gene family in soybean have not been reported. In this study, 12 putative PLC genes were identified in the soybean genome. Soybean PLCs were found on chromosomes 2, 11, 14 and 18 and encoded 58.8-70.06 kD proteins. Expression pattern analysis by RT-PCR demonstrated that expression of the GmPLCs was induced by PEG, NaCl and saline-alkali treatments in roots and leaves. GmPLC transcripts accumulated specifically in roots after ABA treatment. Furthermore, GmPLC transcripts were analyzed in various tissues. The results showed that GmPLC7 was highly expressed in most tissues, whereas GmPLC12 was expressed in early pods specifically. In addition, subcellular localization analysis was carried out and confirmed that GmPLC10 was localized in the plasma membrane in Nicotiana benthamiana. Our genomic analysis of the soybean PLC family provides an insight into the regulation of abiotic stress responses and development. It also provides a solid foundation for the functional characterization of the soybean PLC gene family.

Isolation and gene expression analysis of Phospholipase C in response to abiotic stresses from Vigna radiata (L.) Wilczek

Phosphatidylinositol (PtdIns) is a major phospholipid in eukaryotic cells. Many studies have revealed that the phosphoinositide (PI) signaling pathway plays an important role in plant growth and development. Phospholipase C (PLC) is reported to have a crucial role in the PI pathway. This work focuses on the isolation and investigation of PLC in response to abiotic stress factors in green gram. The PLC cDNA, designated VrPLC, encoding a protein of 591 amino acids was cloned and expressed in E. coli. The predicted isoelectric point (pI) and molecular weight were 5.96 and 67.3 kDa, respectively. The tertiary structure of the PLC was also predicted and found to be mainly composed of random coils. In addition, VrPLC expression analysis was performed under environmental stress and the results showed that the expression of VrPLC was rapidly induced in an abscisic acid independent manner in response to drought and salt stress. PLC expression was found to be up-regulated by SA and down-regulated by wound in leaf tissues; however, there was no significant difference in the expression of PLC in plants subjected to high temperature and H2O2. Our results suggest that a close link/relationship between PLC expression and stress responses in green gram.

Cellular choline and glycine betaine pools impact osmoprotection and phospholipase C production in Pseudomonas aeruginosa

Choline is abundantly produced by eukaryotes and plays an important role as a precursor of the osmoprotectant glycine betaine. In Pseudomonas aeruginosa, glycine betaine has additional roles as a nutrient source and an inducer of the hemolytic phospholipase C, PlcH. The multiple functions for glycine betaine suggested that the cytoplasmic pool of glycine betaine is regulated in P. aeruginosa. We used (13)C nuclear magnetic resonance ((13)C-NMR) to demonstrate that P. aeruginosa maintains both choline and glycine betaine pools under a variety of conditions, in contrast to the transient glycine betaine pool reported for most bacteria. We were able to experimentally manipulate the choline and glycine betaine pools by overexpression of the cognate catabolic genes. Depletion of either the choline or glycine betaine pool reduced phospholipase production, a result unexpected for choline depletion. Depletion of the glycine betaine pool, but not the choline pool, inhibited growth under conditions of high salt with glucose as the primary carbon source. Depletion of the choline pool inhibited growth under high-salt conditions with choline as the sole carbon source, suggesting a role for the choline pool under these conditions. Here we have described the presence of a choline pool in P. aeruginosa and other pseudomonads that, with the glycine betaine pool, regulates osmoprotection and phospholipase production and impacts growth under high-salt conditions. These findings suggest that the levels of both pools are actively maintained and that perturbation of either pool impacts P. aeruginosa physiology.

Molecular mechanisms of ethanol-induced pathogenesis revealed by RNA-sequencing

Acinetobacter baumannii is a common pathogen whose recent resistance to drugs has emerged as a major health problem. Ethanol has been found to increase the virulence of A. baumannii in Dictyostelium discoideum and Caenorhabditis elegans models of infection. To better understand the causes of this effect, we examined the transcriptional profile of A. baumannii grown in the presence or absence of ethanol using RNA-Seq. Using the Illumina/Solexa platform, a total of 43,453,960 reads (35 nt) were obtained, of which 3,596,474 mapped uniquely to the genome. Our analysis revealed that ethanol induces the expression of 49 genes that belong to different functional categories. A strong induction was observed for genes encoding metabolic enzymes, indicating that ethanol is efficiently assimilated. In addition, we detected the induction of genes encoding stress proteins, including upsA, hsp90, groEL and lon as well as permeases, efflux pumps and a secreted phospholipase C. In stationary phase, ethanol strongly induced several genes involved with iron assimilation and a high-affinity phosphate transport system, indicating that A. baumannii makes a better use of the iron and phosphate resources in the medium when ethanol is used as a carbon source. To evaluate the role of phospholipase C (Plc1) in virulence, we generated and analyzed a deletion mutant for plc1. This strain exhibits a modest, but reproducible, reduction in the cytotoxic effect caused by A. baumannii on epithelial cells, suggesting that phospholipase C is important for virulence. Overall, our results indicate the power of applying RNA-Seq to identify key modulators of bacterial pathogenesis. We suggest that the effect of ethanol on the virulence of A. baumannii is multifactorial and includes a general stress response and other specific components such as phospholipase C.

Acinetobacter baumannii has recently emerged as a frequent opportunistic pathogen. In the presence of ethanol A. baumannii increases its pathogenicity towards Dictyostelium discoideum and Caenorhabditis elegans, and community-acquired infections of A. baumannii are associated with alcoholism. Ethanol negatively affects both epithelial cells and alters the bacterial physiology. To explore the underlying basis for the increased virulence of A. baumannii in the presence of ethanol we examined the transcriptional profile of this bacterium using the novel methodology known as RNA-Seq. We show that ethanol induces the expression of a phospholipase C, which contributes to A. baumannii cytotoxicity. We also show that many proteins related to stress were induced and that ethanol is efficiently assimilated as a carbon source leading to induction in stationary phase of two different Fe uptake systems and a phosphate transport system. Interestingly, a previous study showed that a mutant in the high-affinity phosphate uptake system was avirulent. Our work contributes to the understanding of A. baumannii pathogenesis and provides a powerful approach that can be extended to other pathogenic bacteria.

[Construction and immunogenicity of a genetic engineered strain expressing nontoxic ST1-LT(B)-alpha-beta fusion protein against diarrhea of piglet]

We constructed a recombinant strain BL21 (DE3) (pETST3LTBalphabeta) including ST1-LT(B)-alpha-beta fusion gene via molecular technology. The SDS-PAGE and Western blotting indicated that the ST1-LT(B)-alpha-beta fusion protein was highly expressed in Escherichia coli and the molecular weight of the fusion protein was about 110 kD. The recombinant strain was induced in different concentrations of lactose and different aeration rate. The optimal culture conditions in 20 L fermentor were 1% inoculation (V/V), initial aeration 5 L/min, 0.03 mol/L lactose addition 3 hours after inoculation, and increased the aeration to 12.5 L/min for the following 6 hours. The fusion protein was about 38.53% of total cellular protein. It was nontoxic, immunogenic and protective against enterotoxigenic E. coli and Clostridium perfringens infection. The constructed recombinant strain BL21 (DE3) (pETST3LTBalphabeta) could serve as a candidate vaccine strain against diarrhea of piglet.

Alternative splice variants of phospholipase C-beta2 are expressed in platelets: effect on Galphaq-dependent activation and localization

Phospholipase C (PLC) beta2 plays a pivotal role in G-protein dependent signal transduction in platelets. We have previously demonstrated in platelets, leukocytes and human erythroleukemia cells the presence of transcripts of two forms of PLC-beta2 generated by alternative splicing. They differ by 45 nucleotides in the carboxyl-terminal region and are designated as PLC-beta2a and PLC-beta2b, with and without by 15 amino acid residues (corresponding to 864-878). The presence of the two variants has not been shown at the protein level in cells. Moreover, the carboxy-terminal region of PLC-beta has been implicated in Galphaq activation, particulate association, and nuclear localization, suggesting that the PLC-beta2 splice variants may be regulated differentially. We demonstrate for the first time that both PLC-beta2 isoforms are expressed in platelets at the protein level. Studies in CV-1 cells transfected with PLC-beta2a or beta2b cDNAs, along with constitutively activated Galphaq (Q209L), showed that inositolphosphate formation was comparable between the two variants. However, the nuclear localization of the two isoforms was different with a higher cytoplasmic to nuclear ratio for PLC-beta2b compared to PLC-beta2a, suggesting that a great proportion of the total PLC-beta2a was in the nucleus relative to PLC-beta2b. There was no difference in the relative distribution of the two variants between the cytosol and particulate fractions. Both PLC-beta2 alternative splice variants are expressed at the protein level in platelets. In transfected CV-1 cells, PLC-beta2a is relatively more enriched in the nuclei than PLC-beta2b suggesting that the two variants may have different effects in cell proliferation and differentiation.

Immunization of broiler chickens against Clostridium perfringens-induced necrotic enteritis

Necrotic enteritis (NE) in broiler chickens is caused by Clostridium perfringens. Currently, no vaccine against NE is available and immunity to NE is not well characterized. Our previous studies showed that immunity to NE followed oral infection by virulent rather than avirulent C. perfringens strains and identified immunogenic secreted proteins apparently uniquely produced by virulent C. perfringens isolates. These proteins were alpha-toxin, glyceraldehyde-3-phosphate dehydrogenase, pyruvate:ferredoxin oxidoreductase (PFOR), fructose 1,6-biphosphate aldolase, and a hypothetical protein (HP). The current study investigated the role of each of these proteins in conferring protection to broiler chickens against oral infection challenges of different severities with virulent C. perfringens. The genes encoding these proteins were cloned and purified as histidine-tagged recombinant proteins from Escherichia coli and were used to immunize broiler chickens intramuscularly. Serum and intestinal antibody responses were assessed by enzyme-linked immunosorbent assay. All proteins significantly protected broiler chickens against a relatively mild challenge. In addition, immunization with alpha-toxin, HP, and PFOR also offered significant protection against a more severe challenge. When the birds were primed with alpha-toxoid and boosted with active toxin, birds immunized with alpha-toxin were provided with the greatest protection against a severe challenge. The serum and intestinal washings from protected birds had high antigen-specific antibody titers. Thus, we conclude that there are certain secreted proteins, in addition to alpha-toxin, that are involved in immunity to NE in broiler chickens.

Gene identification and evidence for expression of G protein alpha subunits, phospholipase C, and an inositol 1,4,5-trisphosphate receptor in Aplysia californica rhinophore

In the marine mollusk Aplysia californica, waterborne protein pheromones that are released during egg laying act in concert to stimulate mate attraction. However, molecular information concerning the cellular receptors and signaling mechanisms that may be involved in waterborne peptide and protein pheromonal communication is lacking. As a first step toward examining whether members of the G protein family and phosphoinositide signaling pathway are present in the primary peripheral chemosensory organs (i.e., rhinophores), we isolated five full-length cDNA clones from an A. californica central nervous system cDNA library. These clones encoded (1) the G protein alpha subunits of the Gq, Gi, and Go families, (2) a protein with homology to phospholipase C (PLC) isoforms, and (3) an inositol 1,4,5-trisphosphate receptor (IP3R). The expression of these genes was examined using laser capture microdissection/reverse transcription-polymerase chain reaction and in situ hybridization. All of them are expressed in the rhinophore sensory epithelium, suggesting that Galphaq, Galphai, Galphao, PLC-like protein, and IP3R may be involved in waterborne protein pheromone detection in Aplysia-possibly via a phosphoinositide signaling mechanism.

Phospholipase C-β2 promotes mitosis and migration of human breast cancer-derived cells

Like most human neoplasm, breast cancer has aberrations in signal transduction elements that can lead to increased proliferative potential, apoptosis inhibition, tissue invasion and metastasis. Due to the high heterogeneity of this tumor, currently, no markers are clearly associated with the insurgence of breast cancer, as well as with its progression from in situ lesion to invasive carcinoma. We have recently demonstrated an altered expression of the beta2 isoform of the phosphoinositide-dependent phospholipase C (PLC) in invasive breast tumors with different histopathological features. In primary breast tumor cells, elevated amounts of this protein are closely correlated with a poor prognosis of patients with mammary carcinoma, suggesting that PLC-beta2 may be involved in the development and worsening of the malignant phenotype. Here we demonstrate that PLC-beta2 may improve some malignant characteristics of tumor cells, like motility and invasion capability, but it fails to induce tumorigenesis in non-transformed breast-derived cells. We also report that, compared with the G(0)/G(1) phases of the cell cycle, the cells in S/G(2)/M phases show high PLC-beta2 expressions that reach the greatest levels during the late mitotic stages. In addition, even if unable to modify the proliferation rate and the expression of cell cycle-related enzymes of malignant cells, PLC-beta2 may promote the G(2)/M progression, a critical event in cancer evolution. Since phosphoinositides, substrates of PLC, are involved in regulating cytoskeleton architecture, PLC-beta2 in breast tumor cells may mediate the modification of cell shape that characterizes cell division, motility and invasion. On the basis of these data, PLC-beta2 may constitute a molecular marker of breast tumor cells able to monitor the progression to invasive cancers and a target for novel therapeutic breast cancer strategies.

Immunolocalization of SNARE proteins in both type II and type III cells of rat taste buds

Double immunohistochemistry of soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) proteins [synaptosomal-associated protein of 25 kDa (SNAP-25), syntaxin and vesicle-associated protein-2 (VAMP-2)], and specific cell markers of taste buds cells [alpha-gustducin and phospholipase Cbeta2 (PLCbeta2) for type II cells; neural cell adhesion molecule (NCAM) for type III cells] was applied to gustatory epithelia of the rat circumvallate papillae. All three SNARE proteins were present in some elongated taste buds cells as well as intra-, peri- and subgemmal nerve fibers. Double immunohisotochemistry revealed that nearly all alpha-gustducin and PLCbeta2 immunoreactive cells expressed SNAP-25, syntaxin, and VAMP-2. A majority of NCAM immunoreactive cells showed immunoreactivity for these SNARE proteins. These results indicate that these synapse-associated proteins (SNAP-25, syntaxin and VAMP-2) are present in both type II cells and type III cells. Moreover, more than 50% of intragemmal cells containing SNARE proteins showed immunoreactivities for alpha-gustducin, PLCbeta2, and NCAM, suggesting the possible presence of transitional cells having histochemical properties of both type II and type III cells.

Expression and role of phosphatidylcholine-specific phospholipase C in human NK and T lymphocyte subsets

We recently reported evidence of phosphatidylcholine-specific phospholipase C (PC-PLC) involvement in NK cell-mediated cytotoxicity and in lytic granule exocytosis. In the present study, different subpopulations of human PBL were investigated in relation to PC-PLC enzyme expression. While a substantial intracellular amount of PC-PLC was detected in all lymphoid subsets, expression of this enzyme on the outer membrane surface reached high levels only in NK cells, was present at low levels in B lymphocytes and in some TCR gamma/delta T cells and was practically absent in CD4(+) and CD8(+ )T lymphocytes. Moreover, in NK cells two different subpopulations were identified, CD56(dim) PC-PLC(bright) and CD56(bright) PC-PLC(low/-) cells, corresponding to distinct subsets with cytolytic and immunoregulatory functions, respectively. Interestingly, the PC-PLC expression level on the NK membrane surface correlated closely with that of the CD16 receptor, suggesting a possible relationship between enzyme externalization and NK cell maturation. In summary, our results suggest that a high PC-PLC expression on the cell membrane surface of PBL is a peculiarity of NK cytolytic cells, in which the enzyme is apparently involved in the ability of this subset to lyse sensitive target cells.

High level expression of a recombinant phospholipase C from Bacillus cereus in Bacillus subtilis

Twenty-two Bacillus cereus strains were screened for phospholipase C (PLC, EC 3.1.4.3) activity using p-nitrophenyl phosphorylcholine as a substrate. Two strains (B. cereus SBUG 318 and SBUG 516) showed high activity at elevated temperatures (>70 degrees C) at acidic pH (pH 3.5-6) and were selected for cloning and functional expression using Bacillus subtilis. The genes were amplified from B. cereus DNA using primers based on a known PLC sequence and cloned into the expression vector pMSE3 followed by transformation into B. subtilis WB800. On the amino acid level, one protein (PLC318) was identical to a PLC described from B. cereus, whereas PLC516 contained an amino acid substitution (E173D). PLC production using the recombinant strains was performed by an acetoin-controlled expression system. For PLC516, 13.7 U g(-1) wet cell weight was determined in the culture supernatant after 30 h cultivation time. Three purification steps resulted in pure PLC516 with a specific activity of 13,190 U mg(-1) protein.

Stable Association between Gαq and Phospholipase Cβ1 in Living Cells

Signal transduction through G alpha(q) involves stimulation of phospholipase C beta (PLC beta) that results in increased intracellular Ca2+ and activation of protein kinase C. We have measured complex formation between G alpha(q) and PLC beta1 in vitro and in living PC12 and HEK293 cells by fluorescence resonance energy transfer. In vitro measurements show that PLC beta1 will bind to G alpha(q)(guanosine 5'-3-O-(thio)triphosphate) and also to G alpha(q)(GDP), and the latter association has a different protein-protein orientation. In cells, image analysis of fluorescent-tagged proteins shows that G alpha(q) is localized almost entirely to the plasma membrane, whereas PLC beta1 has a significant cytosolic population. By using fluorescence resonance energy transfer, we found that these proteins are pre-associated in the unstimulated state in PC12 and HEK293 cells. By determining the cellular levels of the two proteins in transfected versus nontransfected cells, we found that under our conditions overexpression should not significantly promote complex formation. G alpha(q)-PLC beta1 complexes are observed in both single cell measurements and measurements of a large (i.e. 10(6)) cell suspension. The high level (approximately 40% maximum) of FRET is surprising considering that G alpha(q) is more highly expressed than PLC beta1 and that not all PLC beta1 is plasma membrane-localized. Our measurements suggest a model in which G proteins and effectors can exist in stable complexes prior to activation and that activation is achieved through changes in intermolecular interactions rather than diffusion and association. These pre-formed complexes in turn give rise to rapid, localized signals.

Phospholipase C-delta1 is a critical target for tumor necrosis factor receptor-mediated protection against adriamycin-induced cardiac injury

The clinical application of adriamycin, an exceptionally good chemotherapeutic agent, is limited by its dose-related cardiomyopathy. Our recent study showed that tumor necrosis factor-alpha (TNF-alpha) receptors mediated cytoprotective signaling against adriamycin-induced mitochondrial injury and cardiomyocyte apoptosis. In the present study, we investigated the potential targets of TNF receptor-mediated cytoprotective signaling by global genome microarray analysis using wild-type and TNF receptor-deficient mice. Microarray analysis revealed that adriamycin treatment induced the down-regulation of several mitochondrial functions and energy production-related genes in double TNF receptor-deficient mice, notably, phospholipase C-delta1, a protein involved in fatty acid metabolism and calcium regulation. The role of phospholipase C-delta1 in TNF receptor-mediated cardioprotection against adriamycin-induced injury was evaluated by measuring changes in cardiac function using high-frequency ultrasound biomicroscopy. Selective inhibition of phospholipase C activity in wild-type mice by its inhibitor, U73122, exacerbated adriamycin-induced cardiac dysfunction. Inhibition of phospholipase C-delta1 resulted in the significant decrease of left ventricular ejection fraction and fractional shortening, and the decreased levels were similar to those observed in adriamycin-treated double TNF receptor-deficient mice. The data derived from the global genome analysis identified phospholipase C-delta1 as an important target for TNF receptors and revealed the critical role of TNF receptor signaling in the protection against adriamycin-induced cardiotoxicity.

In vitro inhibitory effect of hen egg white lysozyme on Clostridium perfringens type A associated with broiler necrotic enteritis and its alpha-toxin production

AIMS

Clostridium perfringens type A causes both clinical and subclinical forms of necrotic enteritis in domestic avian species. In this study the inhibitory effect of hen egg white lysozyme on the vegetative form of Cl. perfringens type A and the production of alpha-toxin in vitro was investigated.

METHODS AND RESULTS

A micro-broth dilution assay was used to evaluate the minimal inhibitory concentrations (MIC) of lysozyme against three clinical isolates of Cl. perfringens type A in 96-well microtitre plates. The MIC of lysozyme against Cl. perfringens isolates was found to be 156 microg ml(-1). Scanning electron micrographs of the cells treated with 100 microg ml(-1) of lysozyme revealed extensive cell wall damage. A quantitative sandwich ELISA for alpha-toxin produced by Cl. perfringens was developed based on a commercial ELISA kit allowing only qualitative detection. Addition of 50 microg ml(-1) of lysozyme did not inhibit the growth of Cl. perfringens but significantly inhibited the toxin production.

CONCLUSIONS

Lysozyme inhibited the growth of Cl. perfringens type A at 156 microg ml(-1). At sublethal levels, lysozyme was able to inhibit the alpha-toxin production.

SIGNIFICANCE AND IMPACT OF STUDY

Inhibition of Cl. perfringens type A and its alpha-toxin production by hen egg white lysozyme had never previously been reported. By inhibiting this avian pathogen and its toxin production, lysozyme showed potential for use in the treatment and prevention of necrotic enteritis and other Cl. perfringens type A related animal diseases.

Regulation of phospholipase C isozymes by ras superfamily GTPases

The physiological effects of many extracellular stimuli are mediated by receptor-promoted activation of phospholipase C (PLC) and consequential activation of inositol lipid-signaling pathways. These signaling responses include the classically described conversion of PtdIns(4,5)P(2) to the Ca(2+)-mobilizing second messenger Ins(1,4,5)P(3) and the protein kinase C-activating second messenger diacylglycerol as well as alterations in membrane association or activity of many proteins that harbor phosphoinositide binding domains. Here we discuss how the family of PLCs elaborates a minimal catalytic core typified by PLC-delta to confer multiple modes of regulation on their phospholipase activities. Although PLC-dependent signaling is prominently regulated by direct interactions with heterotrimeric G proteins or tyrosine kinases, the existence of at least 13 divergent PLC isozymes promises a diverse repertoire of regulatory mechanisms for this class of important signaling proteins. We focus here on the recently realized and extensive regulation of inositol lipid signaling by Ras superfamily GTPases directly acting on PLC isozymes and conclude by considering the biological and pharmacological ramifications of this regulation.

PLC-beta2 is highly expressed in breast cancer and is associated with a poor outcome: a study on tissue microarrays

Despite the identification of many putative biomarkers in breast cancer, a specific pattern of proteins to be used as a prognosticator is not well defined. A growing body of evidence supports the role of phospholipase C (PLC) in the invasion and metastasis of different tumors, including breast cancer. To assess whether the expression of specific PLC isoforms correlates with malignancy-related features of human breast tumors and, hence, could have prognostic significance, an immunohistochemical analysis of PLC-beta2 was performed on tissue microarrays and the relationship between PLC-beta2 expression and biological and clinico-pathological factors was assessed. The analysis of 77 samples of breast tumors with different histotypes revealed that PLC-beta2 is highly expressed in a large majority of the analyzed cancer tissue, particularly ductal and lobular carcinomas, in comparison with normal breast. The expression of PLC-beta2 in primary tumors correlated with size, proliferation index and final grade, while no significant relationship was observed with nodal status or estrogen receptor levels, or with the expression of tumor suppressor p53. Remarkably, high PLC-beta2 levels in primary tumors predict an unfavourable prognosis, suggesting the contribution of this protein to the progression of human mammary carcinomas. Our data indicate that PLC-beta2 expression correlates highly with breast cancer malignancy and suggest that it can be included, as an independent marker, among the prognostic indicators in current use.

Characterization and long-term maintenance of rat taste cells in culture

Taste cells have a limited life span and are replaced from a basal cell population, although the specific factors involved in this process are not well known. Short- and long-term cultures of other sensory cells have facilitated efforts to understand the signals involved in proliferation, differentiation, and senescence, yet few studies have reported successful primary culture protocols for taste cells. Furthermore, no studies have demonstrated both proliferation and differentiation in vitro. In this study, we have developed an in vitro culture system to maintain and utilize rat primary taste cells for more than 2 months without losing key molecular and biochemical features. Gustducin, phospholipase C-beta2 (PLC-beta2), T1R3, and T2R5 mRNA were detected in the cultured cells by reverse transcriptase-polymerase chain reaction. Western blot analysis demonstrated gustducin and PLC-beta2 expression in the same samples, which was confirmed by immunocytochemistry. Labeling with bromo-2-deoxyuridine (BrdU) demonstrated proliferation, and a subset of BrdU-labeled cells were also immunoreactive for either gustducin or PLC-beta2, indicating differentiation of newly generated cells in vitro. Cultured cells also exhibited increases in intracellular calcium in response to several taste stimuli. These results indicate that taste cells from adult rats can be generated and maintained under the described conditions for at least 2 months. This system will enable further studies of the processes involved in proliferation, differentiation, and function of mammalian taste receptor cells in an in vitro preparation.

Alpha-toxin is produced by skin colonizing Staphylococcus aureus and induces a T helper type 1 response in atopic dermatitis

BACKGROUND

Staphylococcus aureus is a well known trigger factor of atopic dermatitis (AD). Besides the superantigens, further exotoxins are produced by S. aureus and may have an influence on the eczema.

OBJECTIVE

To explore the impact of staphylococcal alpha-toxin on human T cells, as those represent the majority of skin infiltrating cells in AD.

METHODS

Adult patients with AD were screened for cutaneous colonization with alpha-toxin producing S. aureus. As alpha-toxin may induce necrosis, CD4(+) T cells were incubated with sublytic alpha-toxin concentrations. Proliferation and up-regulation of IFN-gamma on the mRNA and the protein level were assessed. The induction of t-bet translocation in CD4(+) T cells was detected with the Electrophoretic Mobility Shift Assay.

RESULTS

Thirty-four percent of the patients were colonized with alpha-toxin producing S. aureus and alpha-toxin was detected in lesional skin of these patients by immunohistochemistry. Sublytic alpha-toxin concentrations induced a marked proliferation of isolated CD4(+) T cells. Microarray analysis indicated that alpha-toxin induced particularly high amounts of IFN-gamma transcripts. Up-regulation of IFN-gamma was confirmed both on the mRNA and the protein level. Stimulation of CD4(+) T cells with alpha-toxin resulted in DNA binding of t-bet, known as a key transcription factor involved into primary T helper type 1 (Th1) commitment.

CONCLUSION

alpha-toxin is produced by S. aureus isolated from patients with AD. We show here for the first time that sublytic alpha-toxin concentrations activate T cells in the absence of antigen-presenting cells. Our results indicate that alpha-toxin is relevant for the induction of a Th1 like cytokine response. In AD, this facilitates the development of Th1 cell dominated chronic eczema.

Faithful Expression of GFP from the PLCβ2 Promoter in a Functional Class of Taste Receptor Cells

Phospholipase C-type beta2 (PLCbeta2) is expressed in a subset of cells within mammalian taste buds. This enzyme is involved in the transduction of sweet, bitter, and umami stimuli and thus is believed to be a marker for gustatory sensory receptor cells. We have developed transgenic mice expressing green fluorescent protein (GFP) under the control of the PLCbeta2 promoter to enable one to identify these cells and record their physiological activity in living preparations. Expression of GFP (especially in lines with more than one copy integrated) is strong enough to be detected in intact tissue preparations using epifluorescence microscopy. By immunohistochemistry, we confirmed that the overwhelming majority of cells expressing GFP are those that endogenously express PLCbeta2. Expression of the GFP transgene in circumvallate papillae occurs at about the same time during development as endogenous PLCbeta2 expression. When loaded with a calcium-sensitive dye in situ, GFP-positive taste cells produce typical Ca2+ responses to a taste stimulus, the bitter compound cycloheximide. These PLCbeta2 promoter-GFP transgenic lines promise to be useful for studying taste transduction, sensory signal processing, and taste bud development.

Expression of galanin and the galanin receptor in rat taste buds

Galanin, a 29-amino-acid neuropeptide, was initially isolated from porcine intestine. It has a wide spread distribution in the central nervous system and is also present in the primary sensory neuron. Galanin has been suggested to be involved in numerous neuronal and endocrine functions as a neurotransmitter and neuromodulator. We examined the expression of galanin and galanin receptors by using a reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and in situ hybridization. RT-PCR analysis showed that mRNA of galanin and GalR2 were detected in the taste bud-containing epithelium of the circumvallate papilla of rats. Immunohistochemical analyses detected galanin was detected in a subset of taste bud cells of the circumvallate papillae. Double-label studies showed that galanin colocalized with alpha-gustducin, NCAM, and PLCbeta2. Our results of double staining with galanin and taste cell markers indicate that galanin-expressing taste cells are type II and type III cells. Taken together with previous studies, these findings show that galanin may function as a taste bud neurotransmitter. Furthermore, GalR2 mRNA was expressed in some taste bud cells. This suggests that, galanin release may not only excite the peripheral afferent nerve fiber but also may act on neighboring taste receptor cells via the activation of GalR2.

Live attenuated vaccine-based control of necrotic enteritis of broiler chickens

A vaccine for necrotic enteritis (NE) of chickens would reduce the current need to prevent or treat the disease in broiler chickens with antimicrobial drugs. The objective of this study was to understand aspects of immunity to the disease. The first experiment examined the virulence of six strains of Clostridium perfringens isolated from cases of NE in broiler chickens. Using a 5-day experimental oral infection of 2-week-old broiler chickens, four of the six strains were found to be virulent. Pulsed-field gel electrophoresis and PCR showed that virulence was not associated with a plasmid encoding the beta2 toxin gene, cpb2, since this was present in virulent and one of the two avirulent strains. In the second experiment, two virulent and one avirulent strains were tested for their ability to immunize ("infection-immunization") chickens through the oral route. The procedure used experimental infection for 5 days followed by bacitracin treatment for 9 days, and then re-challenge 2 days later with a virulent strain, CP4. Infection-immunization with the virulent isolates protected chickens from subsequent virulent challenge, whereas the infection-immunization with the avirulent isolate did not. In a third experiment, two of four alpha-toxin-negative mutants of CP4 protected birds from experimental NE after oral immunization. These two mutants were also attenuated for virulence. We conclude that it is possible to immunize chickens successfully against NE and that immunogen(s) other than alpha-toxin are important in protective immunity against oral infection.

Phospholipase C-gamma 2 is a critical signaling mediator for murine NK cell activating receptors

Phospholipase C-gamma (PLCgamma) is a key regulator of intracellular Ca(2+) mobilization. Two isoforms of PLCgamma have been identified, PLCgamma1 and PLCgamma2. Previously, in vitro studies indicated that activating NK cell receptors signal through both isoforms. However, PLCgamma2 deficiency alone was sufficient to induce a substantial impairment of NK cell-mediated cytotoxicity in vitro. Why PLCgamma2 is more important than PLCgamma1 for NK cell activation and whether PLCgamma2 is also critical for NK cell development, secretion of IFN-gamma, and clearance of viral infections in vivo is not known. In this study, we report that PLCgamma2 is the predominant isoform expressed in murine NK cells. PLCgamma2 deficiency did not affect NK cell numbers in bone marrow and spleen, but acquisition of Ly49 receptors by NK cells was partially impaired. PLCgamma2-deficient NK cells exhibited a dramatic impairment of cytolytic function and IFN-gamma production upon ligation of activating receptors, whereas they did secrete IFN-gamma in response to cytokines. Consequently, mice lacking PLCgamma2 controlled murine CMV infection substantially less effectively than did wild-type animals, and this defect was most evident in the spleen, where viral clearance mostly depends on NK cell lytic function. These results demonstrate that PLCgamma2 is crucial for development of the NK cell receptor repertoire and signaling of activating NK cell receptors, mediating optimal NK cell function in vivo.

Cyclosporin A specifically affects nuclear PLCbeta1 in immunodepressed heart transplant patients with gingival overgrowth

One of the most commonly observed adverse effects of cyclosporin A (CsA) is the development of gingival overgrowth (GO). Fibroblasts are involved in GO, but the question why only a percentage of patients undergoing CsA treatment shows this side-effect remains unanswered. In a previous study, CsA has been demonstrated to induce over-expression of phospholipase C (PLC) beta(1) in fibroblasts of patients with clinical GO, in cells from both enlarged and clinically healthy gingival sites. In this work, we assessed the expression of PLCbeta isoforms to investigate whether the exaggerated fibroblast response to CsA related to increased PLCbeta(1) expression could also be detected in CsA-treated patients without clinical signs of GO. Our results support the hypothesis of a multi-factorial origin of gingival overgrowth, including specific changes within the gingival tissues orchestrating fibroblastic hyper-responsiveness as a consequence of a long-term in vivo exposure to cyclosporin A.

Role of phospholipase C and diacylglyceride lipase pathway in arachidonic acid release and acetylcholine-induced vascular relaxation in rabbit aorta

ACh stimulates arachidonic acid (AA) release from membrane phospholipids of vascular endothelial cells (ECs). In rabbit aorta, AA is metabolized through the 15-lipoxygenase pathway to form vasodilatory eicosanoids 15-hydroxy-11,12-epoxyeicosatrienoic acid (HEETA) and 11,12,15-trihydroxyeicosatrienoic acid (THETA). AA is released from phosphatidylcholine (PC) and phosphatidylethanolamine (PE) by phospholipase A2 (PLA2), or from phosphatidylinositol (PI) by phospholipase C (PLC) pathway. The diacylglycerol (DAG) lipase can convert DAG into 2-arachidonoylglycerol from which free AA can be released by monoacylglycerol (MAG) lipase or fatty acid amidohydrolase (FAAH). We used specific inhibitors to determine the involvement of the PLC pathway in ACh-induced AA release. In rabbit aortic rings precontracted by phenylephrine, ACh induced relaxation in the presence of indomethacin and N(omega)-nitro-L-arginine (L-NNA). These relaxations were blocked by the PLC inhibitor U-73122, DAG lipase inhibitor RHC-80267, and MAG lipase/FAAH inhibitor URB-532. Cultured rabbit aortic ECs were labeled with [14C]AA and stimulated with methacholine (10(-5) M). Free [14C]AA was released by methacholine. Methacholine decreased the [14C]AA content of PI, DAG, and MAG fractions but not PC or PE fractions. Methacholine-induced release of [14C]AA was blocked by U-73122, RHC-80267, and URB-532 but not by U-73343, an inactive analog of U-73122. The data suggested that ACh activates PLC, DAG lipase, and MAG lipase pathway to release AA from membrane lipids. This pathway is important in regulating vasodilatory eicosanoid synthesis and vascular relaxation in rabbit aorta.

Expression pattern of intracellular leukocyte-associated proteins in primary mediastinal B cell lymphoma

Two microarray studies of mediastinal B cell lymphoma have shown that this disease has a distinct gene expression profile, and also that this is closest to the pattern seen in classical Hodgkin's disease. We reported previously an immunohistologic study in which the loss of intracellular B cell-associated signaling molecules in Reed-Sternberg cells was demonstrated, and in this study we have investigated the expression of the same components in more than 60 mediastinal B cell lymphomas. We report that these signaling molecules are frequently present, and in particular that Syk, BLNK and PLC-gamma2 (absent from Reed-Sternberg cells) are present in the majority of mediastinal B cell lymphomas. The overall pattern of B cell signaling molecules in this disease is therefore closer to that of diffuse large B cell lymphoma than to Hodgkin's disease, and is consistent with a common cell of origin as an explanation of the similar gene expression profiles.

G-protein-activated phospholipase C-β, new partners for cell polarity proteins Par3 and Par6

Cell polarity and asymmetric cell division are fundamental traits of all living cells and play an essential role in embryonic development, neuronal cell chirality formation, and maintenance of mammalian epithelial cell morphology. Heterotrimeric GTP-binding proteins (G proteins) are involved in directing cell polarity and asymmetric cell division in different organisms. However, the mechanism for G-protein-mediated cell polarity and asymmetric cell division is poorly understood. In this study, we have demonstrated that G-protein-activated phospholipase C-beta (PLC-beta) interacts with cell polarity proteins Par3 and Par6 (Par: partition-defective) to form protein complexes and to mediate downstream signal transduction. The interactions between PLC-beta and Par proteins are direct and require the extreme C-terminal-specific sequence motifs of PLC-beta and the PDZ (PSD95/Dlg/ZO-1) domains of Par proteins. Binding of Par proteins with PLC-beta stimulates PLC-beta enzymatic activity, leading to the hydrolysis of phosphatidylinositol-4,5-bisphosphate, and the production of diacylglycerol and inositol 1,4,5-triphosphate, important mediators in cell polarity and cell asymmetric division processes. Furthermore, we have shown that coexpression of PLC-beta with Par proteins induces transcriptional activation coupled to intracellular Ca2+ and the Wnt signaling pathway. Therefore, our data suggest that the interaction of PLC-beta with cell polarity Par proteins may serve as a nexus to transduce extracellular signals to transcriptional regulation through G-protein-mediated signaling pathway in cell polarity and cell asymmetric division.

Up-regulation of phospholipase Cgamma1 and phospholipase D during the differentiation of human monocytes to dendritic cells

Phospholipase C (PLC)gamma and phospholipase D (PLD) play pivotal roles in the signal transduction required for various cellular responses, including cell proliferation and differentiation. Dendritic cells (DCs), which are professional antigen-presenting cells, can be generated from human monocytes by stimulating the cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 4 (IL-4). We investigated whether PLCgamma and PLD expression levels can be changed during the differentiation of the human monocytes into DCs. The enzymatic activity and protein level of PLC gamma1 were significantly increased in the human monocyte-derived DCs by GM-CSF/IL-4, but the protein levels of PLC gamma2 were unaltered. Moreover, the enzymatic activity and protein level of PLD1b and PLD2 were up-regulated during the differentiation of human monocytes to DCs, but those of PLD1a were not changed. A higher phagocytic activity of DCs was found to be correlated with the up-regulations of PLCgamma1 and PLD, and the phagocytic activity of DCs was inhibited by a PLC-specific inhibitor (U73122) and by a phosphatidic acid acceptor (n-butanol), but to be increased by phosphatidic acid. Thus, suggesting that PLC and PLD participate in the process. This study suggests that the up-regulations of PLCgamma1 and PLD are accompanied by the differentiation of monocytes into DCs, which results in increased phagocytic activity.

Hypersensitivity to pentylenetetrazol-induced convulsion in mice lacking the PLC-related inactive protein-1

In the present study, we investigated the effects of pentylenetetrazol (PTZ), a chemical convulsant that interacts with the GABA(A) receptor, in mice lacking the phospholipase C (PLC)-related inactive protein-1 (PRIP-1). PRIP-1 knockout mice did not develop spontaneous behavioral seizure. PRIP-1 knockout mice had markedly shorter latencies until the first clonic convulsion (CL) and tonic extensor (TE) following PTZ administration and increased incidence of convulsion compared to those in wild-type mice. Furthermore, the mortality rate by PTZ in mice lacking the PRIP-1 was also significantly increased in comparison with that in wild-type mice. These findings suggested that mice lacking the PRIP-1 were hypersensitive to PTZ-induced convulsion, and PRIP-1 might play roles in suppressing excessive excitability via interactions with the GABA(A) receptor.

Metabotropic glutamate receptor/phospholipase C pathway: A vulnerable target to Creutzfeldt-Jakob disease in the cerebral cortex

Glutamate is the main excitatory neurotransmitter in the cerebral cortex. Altered glutamatergic transmission has been suggested as having a central role in many neurodegenerative diseases. Metabotropic glutamate receptors (mGluRs) are coupled to intracellular signal transduction via G proteins, and they mediate slower responses than ionotropic glutamate receptors. Group I mGluRs are positively coupled to phospholipase C beta1 (PLCbeta1). Creutzfeldt-Jakob disease (CJD) is a human transmissible spongiform encephalopathy associated with a dysfunction in the membrane glycoprotein PrP which is converted into an abnormal isoform, with a predominant beta-sheet structure, that is pathogenic and partially resistant to protease digestion. Proteins associated with the signal transduction of group I mGluRs were examined in the frontal cortex (area 8) of 12 cases with sCJD and four age-matched controls, by means of gel electrophoresis and Western blotting of total homogenates. Densitometric analysis of the bands demonstrated decreased expression levels of PLCbeta1 and PLCgamma, a non-related phospholipase which is a substrate of tyrosine kinase, in CJD cases when compared with controls. Novel protein kinase C delta (nPKCdelta) has also been found to be significantly decreased in CJD cases. However, no modifications in mGluR1 cPKCalpha expression levels are found in CJD when compared with controls. No modifications in PLCbeta1 solubility in PBS-, deoxycholate- and sodium dodecylsulphate-soluble fractions have been observed in CJD when compared with controls. Finally, no interactions between PLCbeta1 and PrP, as revealed by immunoprecipitation assays, have been found in CJD and controls. The present results show, for the first time, reduced expression levels of phospholipases, particularly PLCbeta1, which may interfere with group I mGluR signaling in the cerebral cortex in CJD. These abnormalities are not the result of abnormal PLC solubility or interactions with PrP. Selective involvement of group I mGluRs may have functional effects on glutamatergic transmission modulation and processing in CJD.

A novel phosphatidylcholine-hydrolyzing phospholipase C induced by phosphate starvation in Arabidopsis

During phosphate starvation, it is known that phospholipids are degraded, and conversely, a nonphosphorus galactolipid digalactosyldiacylglycerol accumulates in the root plasma membrane of plants. We report a novel phospholipase C that hydrolyzes phosphatidylcholine and is greatly induced in response to phosphate deprivation in Arabidopsis. Since phosphatidylcholine-hydrolyzing activity by phospholipase C was highly up-regulated in phosphate-deprived plants, gene expression of some phospholipase C was expected to be induced during phosphate starvation. Based on amino acid sequence similarity to a bacterial phosphatidylcholine-hydrolyzing phospholipase C, six putative phospholipase Cs were identified in the Arabidopsis genome, one of which, NPC4, showed significant transcriptional activation upon phosphate limitation. Molecular cloning and functional expression of NPC4 confirmed that the NPC4 gene encoded a functional phosphatidylcholine-hydrolyzing phospholipase C that did not require Ca(2+) for its activity. Subcellular localization analysis showed that NPC4 protein was highly enriched in the plasma membrane. Analyses of transferred DNA-tagged npc4 mutants revealed that disruption of NPC4 severely reduces the phosphatidylcholine-hydrolyzing phospholipase C activity in response to phosphate starvation. These results suggest that NPC4 plays an important role in the supply of both inorganic phosphate and diacylglycerol from membrane-localized phospholipids that would be used for phosphate supplementation and the replacement of polar lipids in the root plasma membrane during phosphate deprivation.

Crucial Role of Phospholipase Cε in Chemical Carcinogen-Induced Skin Tumor Development

Mutational activation of the ras proto-oncogenes is frequently found in skin cancers. However, the nature of downstream signaling pathways from Ras involved in skin carcinogenesis remains poorly understood. Recently, we and others identified phospholipase C (PLC) epsilon as an effector of Ras. Here we have examined the role of PLCepsilon in de novo skin chemical carcinogenesis by using mice whose PLCepsilon is genetically inactivated. PLCepsilon(-/-) mice exhibit delayed onset and markedly reduced incidence of skin squamous tumors induced by initiation with 7,12-dimethylbenz(a)anthracene followed by promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). Furthermore, the papillomas formed in PLCepsilon(-/-) mice fail to undergo malignant progression into carcinomas, in contrast to a malignant conversion rate of approximately 20% observed with papillomas in PLCepsilon(+/+) mice. In all of the tumors analyzed, the Ha-ras gene is mutationally activated irrespective of the PLCepsilon background. The skin of PLCepsilon(-/-) mice fails to exhibit basal layer cell proliferation and epidermal hyperplasia in response to TPA treatment. These results indicate a crucial role of PLCepsilon in ras oncogene-induced de novo carcinogenesis and downstream signaling from TPA, introducing PLCepsilon as a candidate molecular target for the development of anticancer drugs.

Influence of subinhibitory concentrations of plant essential oils on the production of enterotoxins A and B and alpha-toxin by Staphylococcus aureus

The data presented show the ability of subinhibitory concentrations of plant essential oils to influence the production of enterotoxins A and B and alpha-toxin by Staphylococcus aureus. Subinhibitory concentrations of the oils of bay, clove, cinnamon, nutmeg and thyme had no significant effect on the overall quantity of extracellular protein produced. Haemolysis due to alpha-toxin was significantly reduced after culture with all five plant essential oils. This reduction was greatest with the oils of bay, cinnamon and clove. These three oils also significantly decreased the production of enterotoxin A; the oils of clove and cinnamon also significantly decreased the production of enterotoxin B.

Low power microwave interaction with phospholipase C and D signal transduction pathways in myogenic cells

Ionic channel proteins are possible sites of microwave interaction at the cell membrane level. Patch-clamp data, using single channel and total current recording, indicated that low level microwave fields may modify some functional parameters of the nicotinic acetylcholine receptor in primary chick myotubes, suggesting a possible effect of microwaves on myogenic cells. Here, we investigated the biological relevance of such results, in relation to the possible involvement of intracellular signaling processes. We exposed L6-C5 myogenic cells to low power electromagnetic fields and observed the consequences on hormonal activation of phospholipases C and D. We found that increased inositol phospholipid turnover, induced by acetylcholine and arginine vasopressin activation of phospholipase C, was not modified in microwave irradiated myoblasts or myotubes. Moreover, vasopressin-dependent phospholipase D activation, assessed by measuring the [3H]-free choline release, was not modified by microwave irradiation. Our conclusions suggest that low level microwave fields do not modify signal transduction pathways activated by acetylcholine and vasopressin in L6-C5 myogenic cells.

High-level expression of recombinant phospholipase C from Bacillus cereus in Pichia pastoris and its characterization

The phospholipase c (plc) gene from Bacillus cereus was cloned into the pPICZC vector and integrated into the genome of Pichia pastoris. The phospholipase C (PLC) when expressed in P. pastoris was fused to the alpha-factor secretion signal peptide of Saccharomyces cerevisiae and secreted into a culture medium. Recombinant P. pastoris X-33 had a clear PLC band at 28.5 kDa and produced an extracellular PLC with an activity of 678 U mg(-1) protein which was more than a recombinant P. pastoris GS115 (552 U mg(-1) protein) or KM71H (539 U mg(-1) protein). The PLCs were purified using a HiTrap affinity column with a specific activity of 1335 U mg(-1) protein by P. pastoris GS115, 1176 U mg(-1) protein by P. pastoris KM71H and 1522 U mg(-1) protein by P. pastoris X-33. The three recombinant PLCs had high PLC activity in the low pH range of 4-5 and higher thermal stability (e.g. stable at 75 degrees C) than the wild-type PLC from B. cereus . Some organic solvents, surfactants and metal ions, e.g. methanol, acetone, Co(2+) and Mn(2+) etc., also influenced the activity of the recombinant PLCs.

The Tyrosine Phosphorylation and Cytoskeletal Translocation of Phospholipase C 1 in Bovine Adrenal Medullary Chromaffin Cells

The tyrosine phosphatase inhibitor BpV(phen) stimulated a concentration-dependent increase of phospholipase C (PLC) activity in bovine adrenal medullary chromaffin cells. This response was accompanied by an increase in PLCgamma1 tyrosine phosphorylation and its cytosketetal translocation. Insulin, at high concentrations, stimulated PLC activity to a similar extent as BpV(phen), a response that was also accompanied by an increase in PLCgamma1 translocation but not its tyrosine phosphorylation. BpV(phen) strongly enhanced the insulin-stimulated increase in PLC activity and caused a small rise in PLCgamma1 translocation above that seen with insulin alone. Despite the synergistic rise in activity PLCgamma1 tyrosine phosphorylation did not increase beyond that seen with BpV(phen) alone. These results indicate that PLCgamma1 activation in chromaffin cells may be more closely associated with its cytoskeletal translocation than its tyrosine phosphorylation although other factors may also be important for activation of enzyme activity.

Phospholipase-C beta1 is predominantely expressed in the granular layer of rat cerebellar cortex

The beta1 isoform of phospholipase-C is exclusively present in the nucleus of several hematopoietic and non-hematopoietic cell lines and primary cells of different species. When present, it represents the key enzyme for initiating the nuclear phospholipid breakdown that is involved in the cellular response to proliferating and differentiating stimuli. We have studied the expression of this enzyme isoform in the rat cerebellar cortex. We demonstrate that phospholipase-C beta1 (PLCbeta1) is predominantly expressed in the neurons of the granular layer, while it is virtually absent in the molecular and Purkinje cell layers of rat cerebellar cortex. This pattern of expression is partially different from that of the mouse cerebellar cortex, where not only granular cells, but also Purkinje cells express PLCbeta1. The high level of synaptic inputs that converge on granular cells may imply a constantly active nuclear phospholipid metabolism that may not be strictly required for the appropriate cellular responses of the other cell types of rat cerebellar cortex.

The CcpA protein is necessary for efficient sporulation and enterotoxin gene (cpe) regulation in Clostridium perfringens

Clostridium perfringens is the cause of several human diseases, including gas gangrene (clostridial myonecrosis), enteritis necroticans, antibiotic-associated diarrhea, and acute food poisoning. The symptoms of antibiotic-associated diarrhea and acute food poisoning are due to sporulation-dependent production of C. perfringens enterotoxin encoded by the cpe gene. Glucose is a catabolite repressor of sporulation by C. perfringens. In order to identify the mechanism of catabolite repression by glucose, a mutation was introduced into the ccpA gene of C. perfringens by conjugational transfer of a nonreplicating plasmid into C. perfringens, which led to inactivation of the ccpA gene by homologous recombination. CcpA is a transcriptional regulator known to mediate catabolite repression in a number of low-G+C-content gram-positive bacteria, of which C. perfringens is a member. The ccpA mutant strain sporulated at a 60-fold lower efficiency than the wild-type strain in the absence of glucose. In the presence of 5 mM glucose, sporulation was repressed about 2,000-fold in the wild-type strain and 800-fold in the ccpA mutant strain compared to sporulation levels for the same strains grown in the absence of glucose. Therefore, while CcpA is necessary for efficient sporulation in C. perfringens, glucose-mediated catabolite repression of sporulation is not due to the activity of CcpA. Transcription of the cpe gene was measured in the wild-type and ccpA mutant strains grown in sporulation medium by using a cpe-gusA fusion (gusA is an Escherichia coli gene encoding the enzyme beta-glucuronidase). In the exponential growth phase, cpe transcription was two times higher in the ccpA mutant strain than in the wild-type strain. Transcription of cpe was highly induced during the entry into stationary phase in wild-type cells but was not induced in the ccpA mutant strain. Glucose repressed cpe transcription in both the wild-type and ccpA mutant strain. Therefore, CcpA appears to act as a repressor of cpe transcription in exponential growth but is required for efficient sporulation and cpe transcription upon entry into stationary phase. CcpA was also required for maximum synthesis of collagenase (kappa toxin) and acted as a repressor of polysaccharide capsule synthesis in the presence of glucose, but it did not regulate synthesis of the phospholipase PLC (alpha toxin).

Ca2+ oscillation-inducing phospholipase C zeta expressed in mouse eggs is accumulated to the pronucleus during egg activation

Sperm-specific phospholipase C zeta (PLC zeta) is known to induce intracellular Ca(2+) oscillations and egg activation when expressed in mouse eggs by injection of RNA encoding PLC zeta. We investigated the expression level and spatial distribution of PLC zeta in the egg in real time and in relation to the initiation and termination of Ca(2+) oscillations by monitoring fluorescence of a yellow fluorescent protein 'Venus' fused with PLC zeta. Ca(2+) oscillations similar to those at fertilization were induced at 40-50 min after RNA injection, when expressed PLC zeta reached 10-40 x 10(-15) g in the egg. PLC zeta-Venus increased up to 3 h and attained a steady level at 4-5 h. Interestingly, PLC zeta-Venus is accumulated to the pronucleus (PN) formed at 5-6 h and continuously increased there. Ca(2+) oscillations stopped in most eggs before initiation of the accumulation. A variant of PLC zeta that lacks three EF hand domains was much less effective in induction of Ca(2+) oscillations and little accumulated in the pronucleus, indicating a critical role of those domains. The ability of the accumulation to the pronucleus qualifies PLC zeta for a strong candidate of the Ca(2+) oscillation-inducing sperm factor, which is introduced into the ooplasm upon sperm-egg fusion and concentrated to the pronucleus after inducing egg activation.

A simple and reliable method for rapid production and purification of Pseudomonas aeruginosa haemolytic phospholipase C

AIMS

To design a simple method to produce active recombinant Pseudomonas aeruginosa haemolytic phospholipase C (PLC).

METHOD AND RESULTS

Pseudomonas aeruginosa PLC is a virulence factor mainly involved in inflammatory and cytotoxic responses. While ammonium sulphate purification requires large amounts of bacterial suspensions and leads to low yields, production of recombinant protein in Escherichia coli is no more successful because of frequent inclusion bodies and accumulation of inactive PLC in the periplasmic space. Using an inducible system based on the glucose-repressed inv1 promoter in the yeast Schizosaccharomyces pombe, we were able to produce up to 10 IU ml(-1) of pure toxin within 24 h.

CONCLUSIONS

This work describes the first method to easily get recombinant haemolytic PLC.

SIGNIFICANCE AND IMPACT OF THE STUDY

This method provides a powerful tool to study the mechanisms leading to its cellular toxicity.

Increased Renal Fibrosis and Expression of Renal Phosphatidylinositol 4-Kinase-β and Phospholipase Cγ1 Proteins in Piglets Exposed to Ochratoxin-A

Endemic nephropathy has been linked to exposure of ochratoxin-A (OA) in grains and animal products. The underlying events surrounding this form of renal injury are not well known, partly due to the lack of a suitable animal model of the disease. Therefore, in this study, a pig model of OA-induced renal injury was established and used to examine whether elements of the phosphoinositide signalling pathway are altered in this disease. Weanling piglets were fed diets containing 0, 2, and 4 ppm OA for 6 weeks. Serum creatinine and urea and renal fibrosis were monitored biweekly using serial blood samples and renal biopsies. At termination, the protein levels of renal phosphatidylinositol 4-kinase-beta (PtdIns4Kbeta) and phospholipase C(gamma1) (PLC(gamma1)) were determined using immunoblotting and scanning densitometry. Serum creatinine was elevated by 2 weeks and renal fibrosis was elevated by 4 weeks at both levels of inclusion of OA. At the end of the experimental period, kidney size and water content were elevated, as were the protein levels of renal PtdIns4Kbeta and PLC(gamma1) in OA-exposed animals. Therefore, serial biopsies can be used to track changes in renal pathology in the OA-exposed piglet. We conclude that this is a useful model for OA-induced renal injury in which the underlying molecular events associated with this form of renal injury can be studied.

Regulation of nuclear phospholipase C activity

A body of evidence, linking inositide-specific phospholipase C (PI-PLC) to the nucleus, is quite extensive. The main isoform in the nucleus is PI-PLCbeta1, whose activity is up-regulated in response to insulin-like growth factor-1 (IGF-1) or insulin stimulation. Whilst at the plasma membrane this PI-PLC is activated and regulated by Galphaq/alpha(11) and Gbetagamma subunits, there is yet no evidence that qalpha/alpha(11) is present within the nuclear compartment, neither GTP-gamma-S nor AlF4 can stimulate PI-PLCbeta1 activity in isolated nuclei. Here we review the evidence that upon occupancy of type 1 IGF receptor there is translocation to the nucleus of phosphorylated mitogen-activated protein kinase (MAPK) which phosphorylates nuclear PI-PLCbeta1 and triggers its signalling, hinting at a separate pathway of regulation depending on the subcellular location of PI-PLCbeta1. The difference in the regulation of the activity of PI-PLCbeta1mirrors the evidence that nuclear and cytoplasmatic inositides can differ markedly in their signalling capability. Indeed, we do know that agonists which affect nuclear inositol lipid cycle at the nucleus do not stimulate the one at the plasma membrane.

Decreased adenylyl cyclase and cAMP-dependent protein kinase activities inhibit the cytotoxic function of human natural killer cells

Natural killer (NK) cells are lymphocytes that are capable of destroying tumor cells and virally infected cells without prior sensitization. Elevation of cyclic 3', 5' adenosine monophosphate (cAMP) levels in NK cells is known to cause dramatic inhibition of NK cytolytic function. However, the effect of lowering cellular levels of cAMP on the cytolytic function of natural killer (NK) cells has not been studied. The current study investigated the effects of inhibiting adenylyl cyclase (AC) or cAMP-dependent protein kinase (PKA) activities on the ability of NK cells to lyse K562 tumor cells, and on the activation of NK-cell phospholipase C (PLC) by tumor targets. Exposure of NK cells to the AC inhibitors MDL-12,330A (MDL) or 2',5',-Dideoxyadenosine (DDA) completely blocked their ability to destroy K562 tumor cells. Further, target-induced stimulation of NK-cell PLC was inhibited by as much as 90% when NK cells were treated with the AC inhibitors. Treatment of NK cells with the PKA inhibitor, H-89, caused essentially complete inhibition of cytotoxic function while decreasing target-induced stimulation of PLC by about 50%. Additionally, exposure to the organotin compound, tributyltin (TBT), which decreases cAMP levels in NK cells (as much as 80%) caused a decrease in cytotoxic function by as much as 90%. These data suggest that decreased levels of cAMP may cause very significant loss of NK cytotoxic function and that this may be mediated by decreased PKA activity. These data coupled with previous work revealing that increased cAMP levels inhibit NK cytotoxic function, suggest that tight regulation of cAMP levels is critical to NK cell function.

Epidermal growth factor receptor-stimulated activation of phospholipase Cgamma-1 promotes invasion of head and neck squamous cell carcinoma

Lymph node metastasis and local invasion of head and neck squamous cell carcinoma (HNSCC) is associated with a poor prognosis. However, little is known about the factors governing tumor cell invasion in HNSCC. Phospholipase Cgamma-1 (PLCgamma-1) contributes to tumor cell invasion in experimental systems when activated by the epidermal growth factor receptor (EGFR). We hypothesized that EGFR overexpression in HNSCC mediates invasion via PLCgamma-1. On EGFR ligand stimulation, phosphorylation of PLCgamma-1 increased in all of the HNSCC cell lines tested (4 of 4). In the presence of EGFR-specific tyrosine kinase inhibitor (PD153035) or an anti-EGFR antibody (C225), PLCgamma-1 activation was abrogated indicating that PLCgamma-1 was downstream of EGFR. Blocking cellular PLC with an inhibitor (U73122) reduced inositol phosphate turnover in all of the HNSCC cell lines examined, and treatment with the PLC inhibitor or antisense oligonucleotides targeting PLCgamma-1 significantly reduced in vitro invasiveness of HNSCC cell lines through Matrigel. To determine the clinical relevance of these findings, we compared levels of PLCgamma-1 in tumor and paired normal tissue from 33 patients with HNSCC. PLCgamma-1 levels were significantly higher (P < 0.0001) in the tumors compared with the normal mucosa of HNSCC patients. Levels of activated PLCgamma-1 were analyzed in 20 patients. Tumors expressed higher levels of phosphorylated PLCgamma-1 compared with normal adjacent mucosa (P = 0.05). Thus, PLCgamma-1 may mediate invasion and metastasis downstream of EGFR in HNSCC.

Prognostic relevance of MAPK expression in glioblastoma multiforme

The objective of this study was to determine the immunoexpression pattern of the mitogen-activated protein kinase (MAPK), and related signalling proteins [protein kinase C (PKC), phospholipase Cgamma (PLCgamma)], in glioblastoma multi-forme, and to investigate their prognostic value. Paraffin-embedded biopsy samples from 26 patients [13 patients with long-term survival (LTS; N=13; median 28 months, range 13-76 months), and, for comparison, 13 patients with short-term survival (STS; N=13; median 7 months, range 1-12 months)] were investigated for the immunoexpression of MAPK, the activated pMAPK, PKC, PLCgamma, EGFR, and PTEN. Additionally, the MIB-1 proliferation index was determined. The immunoexpression pattern were related to clinical data, including analysis of their prognostic value using the Cox-proportional hazard model. No significant differences were found between STS and LTS in terms of age, Karnofsky performance status, and treatment. Whereas EGFR expression did not differ between STS and LTS and does not influence survival, expression of MAPK and activated pMAPK was significantly correlated with survival time. The percentage of pMAPK expressing cells correlated strongly with the percentage of MIB-1 positive cells. Furthermore, survival in patients with tumors expressing PKC or PLCgamma was significantly shorter. No differences were found for PTEN expression. Our findings indicate that the MAPK pathway is correlated with proliferation in gliomas, and that patient subgroups exist, in which expression of MAPK-related signalling proteins (PKC, PLCgamma) is associated with poorer prognosis. These patient subgroups may benefit from additional chemotherapeutic agents which specifically inhibit these signalling proteins.

Dexamethasone decreases phospholipase C beta1 isozyme expression in human vascular smooth muscle cells

The molecular characterization of the human PLC beta1 gene was just reported by Peruzzi et al. [Biochim. Biophys. Acta 1582 (2002) 46]. This prompted us to investigate the effects of dexamethasone on PLC beta1 expression in two types of human vascular smooth muscle cells--coronary artery smooth muscle cells (hCASMC) and aortic smooth muscle cells (hAoSMC), since glucocorticoids are known to affect the signaling pathways of Gprotein coupled receptors. Semi-quantitative RT-PCR was used to analyze mRNA expression and Western-blot for protein expression. Dexamethasone treatment in the two types of cells studied decreased (mRNA and protein) PLC beta1 isozyme expression. A rapid (2 h) fall in mRNA occurred in hCASMC after treatment, and hCASMC were more sensitive to dexamethasone (1 nM versus 100 nM) than hAoSMC. The major reduction (80%) was observed after 48 h of exposure in both VSMC. Treatment with mifeprisone, an antagonist of glucocorticoid receptors, blunted the dexamethasone effect on PLC beta1 mRNA and showed that this effect was mediated by glucocorticoids receptors.