Molecular cloning and expression regulation of PRG-3, a new member of the plasticity-related gene family

Phospholipid-mediated signalling on neurons provokes diverse responses such as neurogenesis, pattern formation and neurite remodelling. We have recently uncovered a novel set of molecules in the mammalian brain, named plasticity-related genes (PRGs), which mediate lipid phosphate phosphatase activity and provide evidence for their involvement in mechanisms of neuronal plasticity. Here, we report on a new member of the vertebrate-specific PRG family, which we have named plasticity-related gene-3 (PRG-3). PRG-3 is heavily expressed in the brain and shows a specific expression pattern during brain development where PRG-3 expression is found predominantly in neuronal cell layers and is already expressed at embryonic day 16. In the mature brain, strongest PRG-3 expression occurs in the hippocampus and cerebellum. Overexcitation of neurons induced by kainic acid leads to a transient down-regulation of PRG-3. Furthermore, PRG-3 is expressed on neurite extensions and promotes neurite growth and a spreading-like cell body in neuronal cells and COS-7 cells. In contrast to previously described members of the PRG family, PRG-3 does not perform its function through enzymatic phospholipid degradation. In summary, our findings feature a new member of the PRG family which shows dynamic expression regulation during brain development and neuronal excitation.

PHOSPHO1-A novel phosphatase specifically expressed at sites of mineralisation in bone and cartilage

Mineralisation of bone and cartilage is essential for skeletal development and function. We have previously reported a novel gene (PHOSPHO1); a member of the large haloacid dehalogenase superfamily of hydrolases which has an active site indicative of a phosphatase. Its high expression in skeletal tissues has led us to speculate that PHOSPHO1 may be involved in the mineralisation process. Therefore, in this study, we have determined that PHOSPHO1 is localized to sites of mineralisation in both cartilage and bone. Recombinant derived PHOSPHO1 protein was produced and affinity purified PHOSPHO1 antiserum was generated and used to immunostain a range of skeletal and soft avian tissues. In addition, PHOSPHO1 gene expression was determined in SaOS-2 and MG-63 osteoblast-like cells by RT-PCR. In diaphyseal cortical bone, immunohistochemistry localized PHOSPHO1 protein to the osteoid layer of the periosteum, forming surfaces of growing osteons, and newly formed osteocytes, whereas the endosteum and closed osteons were negative. In growth plate cartilage, immunoreactivity was limited to the early hypertrophic chondrocytes and the ossification groove of Ranvier. Cartilage remnants and trabecular bone within the primary spongiosa exhibited strong immunoreactivity on their mineralising surfaces. In 17-day-old embryonic calvaria, the osteoid present on the intramembranous and periosteal bone surfaces stained positively for PHOSPHO1. All soft tissues examined were negative. PHOSPHO1 gene expression was detected in mineralising SaOS-2 but not in the non-mineralising MG-63 osteoblast-like cells and gene expression levels were unchanged by dexamethasone, estradiol, 1,25-dihydroxyvitamin D3 or PTHrP treatment. Western analysis of chick growth plate cell lysate yielded bands (30.4 and 28.6 kD) corresponding to transcripts initiated at each of two possible initiation codons indicating the presence of alternative transcripts for PHOSPHO1 in growth cartilage. These results confirm that the PHOSPHO1 protein and gene expression profile is consistent with a role for PHOSPHO1 in bone and cartilage matrix mineralisation.

Molecular and physiological characterisation of a 3-phytase from soil bacterium Klebsiella sp. ASR1

Klebsiella sp. strain ASR1 isolated from an Indonesian rice field is able to hydrolyse myo-inositol hexakis phosphate (phytate). The phytase protein was purified and characterised as a 42 kDa protein accepting phytate, NADP and sugar phosphates as substrates. The corresponding gene (phyK) was cloned from chromosomal DNA using a combined approach of protein and genome analysis, and expressed in Escherichia coli. The recombinant enzyme was identified as a 3-phytase yielding myo-inositol monophosphate, Ins(2)P, as the final product of enzymatic phytate hydrolysis. Based on its amino acid sequence, PhyK appears to be a member of a hitherto unknown subfamily of histidine acid phytate-degrading enzymes with the active site RHGXRXP and HD sequence motifs, and is different from other general phosphatases and phytases. Due to its ability to degrade sodium phytate to the mono phosphate ester, the phyK gene product is an interesting candidate for industrial and agricultural applications to make phytate phosphorous available for plant and animal nutrition.

Detection of endometrial intraepithelial neoplasia (EIN) in postmenopausal endometrium

OBJECTIVES

To detect the presence of endometrial intraepithelial neoplasia (EIN) in the endometrium of postmenopausal patients.

PATIENTS AND METHODS

Sixty-three postmenopausal patients with endometrial polyps (n=48), hyperplasia (n=12) and endometrioid carcinoma (n=3) were enrolled for this study. The diagnosis of EIN was made by using morphological criteria and immunohistochemical methods for detection of PTEN and bcl-2.

RESULTS

EIN lesions were found in cases of endometrial polyp (n=1), atrophic endometrium (n=1) and in hyperplasia (n=1). The glands were packed, showed cytological atypia and were negative for both PTEN and bcl-2. Three patients with endometrial hyperplasia had isolated PTEN-negative glands but they were still bcl-2 positive.

CONCLUSIONS

The use of immunohistochemical methods helps detect the presence of EIN in the postmenopausal endometrium but does not substitute the morphological criteria for this diagnosis.

Role of 2-phosphoglycolate phosphatase of Escherichia coli in metabolism of the 2-phosphoglycolate formed in DNA repair

The enzyme 2-phosphoglycolate phosphatase from Escherichia coli, encoded by the gph gene, was purified and characterized. The enzyme was highly specific for 2-phosphoglycolate and showed good catalytic efficiency (k(cat)/K(m)), which enabled the conversion of this substrate even at low intracellular concentrations. A comparison of the structural and functional features of this enzyme with those of 2-phosphoglycolate phosphatases of different origins showed a high similarity of the sequences, implying the use of the same catalytic mechanism. Western blot analysis revealed constitutive expression of the gph gene, regardless of the carbon source used, growth stage, or oxidative stress conditions. We showed that this housekeeping enzyme is involved in the dissimilation of the intracellular 2-phosphoglycolate formed in the DNA repair of 3'-phosphoglycolate ends. DNA strand breaks of this kind are caused by agents such as the radiomimetic compound bleomycin. The differential response between a 2-phosphoglycolate phosphatase-deficient mutant and its parental strain after treatment with bleomycin allowed us to connect the intracellular formation of 2-phosphoglycolate with the production of glycolate, which is subsequently incorporated into general metabolism. We thus provide evidence for a salvage function of 2-phosphoglycolate phosphatase in the metabolism of a two-carbon compound generated by the cellular DNA repair machinery.

[Study on the properties of methyl parathion hydrolase from Pseudomonas sp. WBC-3]

A methyl parathion degradation enzyme, or methyl parathion hydrolase (MPH, EC 3.1.8.1), locating in the soluble intracellular fraction of Pseudomonas sp. WBC-3, was purified 49.1-fold to homogeneity by one-step ion exchange chromatography. The physical and chemical properties of the purified MPH were studied. The purified MPH displayed relatively broad optimal temperature around 40 degrees. The activity of MPH was affected by pH and the optimal pH was 11.0. Cd2+ and Fe2+ could enhance the catalytic efficiency of MPH while Hg2+, Zn2+, Al3+ and Bi3+ showed inhibition effect. With methyl parathion as the optimal substrate, the Km was 0.0807mmol/L and the kcat was 2.1 x 10(6) min(-1). In addition, the comparison of native and subunit molecular weights of MPH suggested that this enzyme was a monomer of approximate 34kD.

The pH-induced glycosylation of secreted phosphatases is mediated in Aspergillus nidulans by the regulatory gene pacC-dependent pathway

In this communication, we show that the pacC(c)14 mutation drastically reduced the mannose and N-acetylglycosamine content of the pacA-encoded acid phosphatase secreted by the fungus Aspergillus nidulans when grown at 22 degrees C, pH 5.0, compared to a control strain. The staining after PAGE was not observed for the pacA-encoded acid phosphatase, while the palD-encoded Pi-repressible alkaline phosphatase had an altered electrophoretic mobility. In addition, the secreted acid phosphatase also had a reduced number of isoforms visualized by staining after IEF and glycosylation had a protective effect against its heat inactivation. We also show that a full-length version of gene pacC-1 cloned from Neurospora crassa complemented the pacC(c)14 mutation of A. nidulans, including the remediation of both the acid and alkaline Pi-repressible phosphatases secreted at pH 5.0, which indicates that glycosylation of secreted phosphatases is mediated in A. nidulans by the conserved PacC pathway that governs pH-responsive gene expression.

Purification, kinetic characterization, and molecular cloning of a novel enzyme ecdysteroid-phosphate phosphatase

From eggs of the silkworm Bombyx mori, we isolated a novel enzyme that is involved in the conversion of physiologically inactive conjugated ecdysteroids, such as ecdysone 22-phosphate and 20-hydroxyecdysone 22-phosphate, to active free ecdysteroids. This enzyme, called ecdysteroid-phosphate phosphatase (EPPase), was located in the cytosol fraction and differed from nonspecific lysosomal acid phosphatases in various enzymic properties. EPPase was purified about 3,000-fold to homogeneity by seven steps of column chromatography. The cDNA clone encoding EPPase was isolated by reverse transcription polymerase chain reaction using degenerate primers on the basis of the partial amino acid sequence obtained from purified EPPase and by subsequent 3'- and 5'-rapid amplification of cDNA ends. The full-length cDNA of EPPase was found to be composed of 1620 bp with an open reading frame encoding a protein of 331 amino acid residues. A data base search showed that there was no functional protein with the amino acid sequence identical to that of EPPase. Northern blot analysis revealed that EPPase mRNA was expressed predominantly during gastrulation and organogenesis in nondiapause eggs but was not detected in diapause eggs whose development was arrested at the late gastrula stage. In nondiapause eggs, the developmental changes in the expression pattern of EPPase mRNA corresponded closely to changes in the enzyme activity and in the amounts of free ecdysteroids in eggs.

A new phospholipid phosphatase, PRG-1, is involved in axon growth and regenerative sprouting

Outgrowth of axons in the central nervous system is governed by specific molecular cues. Molecules detected so far act as ligands that bind to specific receptors. Here, we report a new membrane-associated lipid phosphate phosphatase that we have named plasticity-related gene 1 (PRG-1), which facilitates axonal outgrowth during development and regenerative sprouting. PRG-1 is specifically expressed in neurons and is located in the membranes of outgrowing axons. There, it acts as an ecto-enzyme and attenuates phospholipid-induced axon collapse in neurons and facilitates outgrowth in the hippocampus. Thus, we propose a novel mechanism by which axons are able to control phospholipid-mediated signaling and overcome the growth-inhibiting, phospholipid-rich environment of the extracellular space.

Time to progression is dependent on the expression of the tumour suppressor PTEN in ovarian cancer patients

BACKGROUND

Quantitative analyses of PTEN expression of ovarian cancer tissues were performed in this study. PTEN expression was investigated in terms of each patient's progression-free interval to indicate the role of PTEN in the generation of platinum refractory tumours.

MATERIALS AND METHODS

The study group comprised 20 ovarian cancer patients from whom fresh frozen tissues of both the primary tumour and specimens of progressive disease were available. The PTEN protein and phosphorylation of the downstream effector protein kinase B (PKB) were quantified by Western blot analyses and subsequent densitometry. Data were analyzed for individual PTEN variation with respect to the clinical course as defined by the progression-free interval.

RESULTS

Applying the usual clinical criteria for platinum-sensitivity after progression, seven patients were considered platinum-sensitive whereas 13 patients had suffered a progression within 12 months after the chemotherapy. In 5/7 (71%) cases with prolonged time to progression, an increase in PTEN was observed. Decline of PTEN expression occurred in 9/13 (69%) patients with poor outcome. PTEN expression corresponds inversely to PKB phosphorylation in 14/20 (70%) tissues investigated.

CONCLUSIONS

The data suggest that decreased PTEN expression accompanies the progression of ovarian cancer. Declining PTEN expression results in a shortened relapse-free interval, whereas an increase of PTEN prolongs the time to progression. However, as far as recurrence occurs, PTEN is not the only mechanism to suppress tumour progression in ovarian cancer.

Rabbit liver dCMP phosphohydrolase: a pyrimidine 5'-nucleotidase I-like enzyme in non-erythrocytic cells

A nucleotide phosphomonoesterase activity that preferably hydrolyzed dCMP was detected in rabbit liver and purified approximately 20-fold. The enzyme was similar in the catalytic and molecular properties to pyrimidine 5'-nucleotidase subclass I (P5N-I), which distributed specifically in vertebrate erythrocytes. In addition to liver, the activity was found in rabbit kidney, spleen, heart, intestine, but was not detected in any rat or chicken tissues tested. The rabbit enzyme protein reacted with antibodies against chicken P5N-I. Its pI was estimated to be approximately 5.3, and the enzyme was concluded to consist of single polypeptide of an approximately 38 kDa based on gel filtration and Western blot analysis. The partially purified enzyme preferentially hydrolyzes dCMP, UMP and CMP, K(m) values for these substrates are approximately 0.3 mM, the optimal pH is approximately 7, and the enzyme requires Mg(2+). This nucleotidase may contribute to the regulation of intracellular pyrimidine nucleotides in the rabbit.

Evaluation of different methods for the detection of Clostridium perfringens phosphatases

In order to detect phosphatase activity a total of 137 isolates from 12 Clostridium (C.) species were examined via fluorescence on SCA-agar with methylumbelliferyl phosphate (SCA-MUP), via APIZYM and RAPID ID 32 A as well as using a phosphatase reagent containing 1-naphthyl phosphate. Fluorescence on SCA-MUP showed the presence of acid or alkaline phosphatase in almost all isolates examined. Likewise, acid or alkaline phosphatase could be detected via APIZYM and RAPID ID 32 A in most strains and species. Opposed to this, the majority of the Clostridium bifermentans isolates showed a positive reaction exclusively on SCA-MUP. On the other hand, the phosphatase reagent for the detection of acid phosphatase lead to unambiguously positive results only when examining Clostridium perfringens isolates. Therefore, the SCA-MUP-agar, in contrast to the phosphatase reagent, was proven to be unsuitable for the identification of C. perfringens via detection of acid phosphatase. Using the phosphatase reagent the activity of this enzyme was detected in 95.1% of the C. perfringens isolates included in the study. In addition, the phosphatase reagent showed identical reactions after a 24 h incubation at 37 degrees C and when used on cultures incubated for 6 h at 44 degrees C in the case of 98.5% of the C. perfringens isolates.

Purification, cloning, expression, and properties of mycobacterial trehalose-phosphate phosphatase

The trehalose-phosphate phosphatase (TPP) was purified from the cytosol of Mycobacterium smegmatis to near homogeneity using a variety of conventional steps to achieve a purification of about 1600-fold with a yield of active enzyme of about 1%. Based on gel filtration, the active enzyme had a molecular weight of about 27,000, and the most purified fraction also gave a major band on SDS-PAGE corresponding to a molecular weight of about 27,000. A number of peptides from the 27-kDa protein were sequenced and these sequences showed considerable homology to the trehalose-P phosphatase (otsB) of Escherichia coli. Based on these peptides, the M. smegmatis gene for TPP was cloned and expressed in E. coli. The recombinant protein was synthesized with a (His)(6) tag at the amino terminus. Most of the TPP activity in the crude E. coli sonicate was initially found in the membrane fraction, but it became solubilized in the presence of 0.2% Sarkosyl. The solubilized protein was purified to apparent homogeneity on a metal ion column and this fraction had high phosphatase activity that was completely specific for trehalose-P. The purified enzyme, either isolated from M. smegmatis, or expressed in E. coli, rapidly dephosphorylated trehalose-6-P, but had essentially no activity on any other sugar phosphates, or on p-nitrophenyl phosphate. The K(m) for trehalose-6-P was about 1.6 mm, and the pH optimum was about 7.5. The native enzyme showed an almost absolute requirement for Mg(2+) and was not very active with Mn(2+), whereas both of these cations were equally effective with the recombinant TPP. The enzyme activity was inhibited by the antibiotics, diumycin and moenomycin, but not by a number of other antibiotics or trehalose analogs. TPP activity was strongly inhibited by the detergents, Sarkosyl and deoxycholate, even at 0.025%, but it was not inhibited by Nonidet P-40, Triton X-100, or octyl glucoside, even at concentrations up to 0.3%. The purified enzyme was stable to heating at 60 degrees C for up to 6 min, but was slowly inactivated at 70 degrees C. Circular dichroism studies on recombinant TPP indicate that the secondary structure of this protein has considerable beta-pleated sheet and is very compact. TPP may play a key role in the biosynthesis of trehalose compounds, such as trehalose mycolates, and therefore may represent an excellent target site for chemotherapy against tuberculosis and other mycobacterial diseases.

A technique for mycelial development of ectomycorrhizal fungi on agar media

A technique was established to study ectomycorrhizal fungi on agar media. Petri dishes, 60 mm in diameter, containing 10 mL of culture medium covered with a cellophane disk were used for easy collection of the mycelium after growth. For analysis of fungal biomass production, a sterilized cellophane sheet was placed on the medium's surface. Inoculation was achieved by placing a mycelial block onto the center of the cellophane sheet and then incubating at 25 degrees C in the dark. Colony radial growth was measured and biomass dry wt was determined. Fresh mycelia were homogenized with 10 mL of acetate buffer (pH 5.5) for enzyme analysis. A crude extract was obtained by adding all culture medium to 90 mL of distilled water and homogenizing in a Potter. Reducing sugars, enzyme concentration, and pH were determined. Three fungal strains, Suillus collinitus, Pisosithus arrhizus, and Hebeloma cylindrosporum, were grown in different culture media (potato dextrose agar or Pintro's medium). Parameters measured over time included glucose concentration, phosphatase activity, biomass, and pH.

Processing of N-glycans of two yellow lupin phosphohydrolases during seed maturation and dormancy

Acid phosphatase (AP) and diphosphonucleoside phosphatase/phosphodiesterase (PPD1) were purified from yellow lupin (Lupinus luteus L.) immature green seeds (40 days after blooming), dry seeds (40 days later) and dry seeds stored for 160 days. Both enzymes are known to differ in the type of N-glycosylation: the first has an N-glycosylation pattern typical for a vacuolar protein, while the second enzyme has a pattern typical for an extracellular or membrane-bound protein. N-Glycans were released from each of the enzyme preparations, fluorescence labeled, separated and identified by HPLC (GlycoSep N and GlycoSep H columns). Changes in the level of each N-glycan during seed maturation and dormancy were compared. The results show that N-glycan processing in the case of AP and PPD1-two proteins residing in the same plant organ, but possibly in different compartments-is not synchronized and performed not only in metabolically active maturing seeds, but also in metabolically inactive dormant seeds.

Inositol phosphatase activity of the Escherichia coli agp-encoded acid glucose-1-phosphatase

When screening an Escherichia coli gene library for myo-inositol hexakisphosphate (InsP6) phosphatases (phytases), we discovered that the agp-encoded acid glucose-1-phosphatase also possesses this activity. Purified Agp hydrolyzes glucose-1-phosphate, p-nitrophenyl phosphate, and InsP6 with pH optima, 6.5, 3.5, and 4.5, respectively, and was stable when incubated at pH values ranging from 3 to 10. Glucose-1-phosphate was hydrolyzed most efficiently at 55 degrees C. while InsP6 and p-nitrophenyl phosphate were hydrolyzed maximally at 60 degrees C. The Agp exhibited Km values of (0.39 mM, 13 mM, and 0.54 mM for the hydrolysis of glucose-1-phosphate, p-nitrophenyl phosphate, and InsP6, respectively. High-pressure liquid chromatography (HPLC) analysis of inositol phosphate hydrolysis products of Agp demonstrated that the enzyme catalyzes the hydrolysis of phosphate from each of InsP6, D-Ins(1,2,3,4,5)P5, Ins(1,3,4,5,6)P5, and Ins(1,2,3,4,6)P5, producing D/L-Ins(1,2,4,5,6)P5. D-Ins(1,2,4,5)P4, D/L-Ins(1,4,5,6)P4 and D/L-Ins(1,2,4,6)P4, respectively. These data support the contention that Agp is a 3-phosphatase.

[Study on Pseudomonas sp. WBC-3 capable of complete degradation of methylparathion]

A bacterial strain was isolated from the polluted soil around Shashi Pesticides Factory, which was capable of complete degradation of methylparathion. Through chemotaxonomic characterizations and phylogenetic inference based on 16S rDNA sequence analysis, the strain was identified as a member of the genus and was named as Pseudomonas sp. WBC-3. It can tolerate high-concentration methylparathion up to 800 mg/L in basic medium and up to 2000 mg/L in 0.1% glucose medium. Using 300 mg/L methylparathion as its sole carbon and nitrogen sources, the strain was able to degrade 15 mg of parathion per liter per hour and reached its stationary phase in about 22 hours. The strain possessed broad-spectrum degradative capability to kinds of organophosphorus pesticides and aromatic compounds. Its organophosphate hydrolase was purified from the periplasm of WBC-3 to homogeneity, through a whose process consisting of ammonium sulfate precipitation, Sephadex G-75 gel filtration, Q Sepharose FF ionexchange column chromatography. The purified enzyme showed a single band on SDS-PAGE gel with an approximate molecular weight of 33.5 kD.

A mammalian expression system for rapid production and purification of active MAP kinase phosphatases

Expression of enzymatically active mammalian proteins in Escherichia coli can proven to be a challenging task due to poor solubility, improper folding, and lack of adequate posttranslational modification. Expression of mammalian proteins using baculovirus or yeast systems is time-consuming and may also be subject to inadequate modification. In order to overcome these technical difficulties, we have developed a mammalian expression system for the convenient subcloning of cDNA fragments, high-level expression, and one-step purification of enzymatically active proteins. The mammalian expression vector pEBG that expresses glutathione S-transferase fusion proteins was modified to create an SrfI restriction site in the multiple cloning site. The protein coding sequences of MAP kinase phosphatase-1 (MKP-1), MAP kinase phosphatase-2 (MKP-2), and the tumor suppressor PTEN were PCR-amplified using Pfu DNA polymerase and cloned into the SrfI site through SrfI digestion-coupled ligation. The resulting plasmids were transiently transfected into 293T cells using FuGENE 6 transfection reagent. Forty eight hours after transfection, cells were harvested and bioactive recombinant proteins were purified by glutathione-Sepharose beads. Protein yield, which ranged from 200 to 700 microg, was more than adequate for biochemical studies. The usefulness of this versatile system for studying protein function and its potential application for proteomics research are discussed.

Isolation of lysophosphatidic acid phosphatase from developing peanut cotyledons

The soluble fraction of immature peanut (Arachis hypogaea) was capable of dephosphorylating [(3)H]lysophosphatidic acid (LPA) to generate monoacylglycerol (MAG). The enzyme responsible for the generation of MAG, LPA phosphatase, has been identified in plants and purified by successive chromatography separations on octyl-Sepharose, Blue Sepharose, Superdex-75, and heparin-agarose to apparent homogeneity from developing peanuts. This enzyme was purified 5,048-fold to a final specific activity of 858 nmol min(-1) mg(-1). The enzyme has a native molecular mass of approximately 39 kD determined by gel filtration and migrates as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a subunit molecular mass of 39 +/- 1.5 kD. The K(m) values for oleoyl-, stearoyl-, and palmitoyl-sn-glycerol-3-phosphate were determined to be 28.6, 39.3, and 47.9 microM, respectively. The LPA phosphatase was specific to LPA and did not utilize any other substrate such as glycerol-3-phosphate, phosphatidic acid, or p-nitrophenylphosphate. The enzyme activity was stimulated by the low concentrations of detergents such as Triton X-100 and octylglucoside. Cations had no effect on the enzyme activity. Fatty acids, sphingosine, and sphingomyelin at low concentrations stimulated the enzyme activity. The identification of LPA phosphatase in plants demonstrates the existence of MAG biosynthetic machinery in plants.

Purification, crystallization and preliminary X-ray diffraction analysis of human phosphoserine phosphatase

Phosphoserine phosphatase (PSP), a human enzyme involved in the L-serine biosynthesis pathway, has been crystallized using the hanging-drop vapour-diffusion method at 277 K. The crystals are orthorhombic, belonging to space group C222(1), with unit-cell parameters a = 49.03 A, b = 130.25 A, c = 157.29 A. Calculation of the Matthews coefficient indicates that there are two molecules in the asymmetric unit. A complete native data set to a resolution of 1.53 A has been collected at 100 K using synchrotron radiation.