bluuebunny/crossref_metadata_2025 huggingface dataset:
Hepatocyte nuclear factor 6: organization and chromosomal assignment of the rat gene and characterization of its promoter
Authors: RASTEGAR Mojgan , SZPIRER Claude , ROUSSEAU Guy G. , LEMAIGRE Frédéric P.
Published: August 2015

Hepatocyte nuclear factor 6 (HNF-6) is the prototype of a family of tissue-specific transcription factors characterized by a bipartite DNA-binding domain consisting of a single cut domain and a novel type of homeodomain. We have previously cloned rat cDNA species coding for two isoforms, HNF-6α (465 residues) and β (491 residues), which differ only by the length of the spacer between the two DNA-binding domains. We have now localized the rat Hnf6 gene to chromosome 8q24–q31 by Southern blotting of DNA from somatic cell hybrids and by fluorescence in situhybridization. Cloning and sequencing of the rat gene showed that the two HNF-6 isoforms are generated by alternative splicing of three exons that are more than 10 kb apart from each other. Exon 1 codes for the N-terminal part and the cut domain, exon 2 codes for the 26 HNF-6β-specific amino acids, and exon 3 codes for the homeodomain and the C-terminal amino acids. The transcription initiation site was mapped by ribonuclease protection and 5´ rapid amplification of cDNA ends. Transfection experiments showed that promoter activity was contained within 0.75 kb upstream of the transcription initiation site. This activity was detected by the transfection of liver-derived HepG2 cells, but not of Rat-1 fibroblasts, suggesting that the promoter is sufficient to confer liver-specific expression.
Leishmania major parasites express cyclophilin isoforms with an unusual interaction with calcineurin
Authors: RASCHER Christine , PAHL Andreas , PECHT Anja , BRUNE Kay , SOLBACH Werner , BANG Holger
Published: August 2015

The immunosuppressive effects of the fungal metabolite cyclosporin A (CsA) are mediated primarily by binding to cyclophilins (Cyps). The resulting CsA–Cyp complex inhibits the Ca2+-regulated protein phosphatase calcineurin and down-regulates signal transduction events. Previously we reported that CsA is a potent inhibitor of infections transmitted by the human pathogenic protozoan parasite Leishmania major in vitro and in vivo, but does not effect the extracellular growth of L. major itself. It is unknown how L. major exerts this resistance to CsA. Here we report that a major Cyp, besides additional isoforms with the same N-terminal amino acid sequence, was expressed in L. major. The cloned and sequenced gene encodes a putative 174-residue protein called L. major Cyp 19 (LmCyp19). The recombinant LmCyp19 exhibits peptidyl-prolyl cis/trans isomerase activity with a substrate specificity and an inhibition by CsA that are characteristic of other eukaryotic Cyps. To determine whether calcineurin is involved in the discrimination of the effects of CsA we also examined the presence of a parasitic calcineurin and tested the interaction with Cyps. Despite the expression of functionally active calcineurin by L. major, neither LmCyp19 nor other L. major Cyps bound to its own or mammalian calcineurin. The amino acid sequence of most Cyps includes an essential arginine residue around the calcineurin-docking side. In LmCyp19 this is replaced by an asparagine residue. This exchange and additional charged residues are apparently responsible for the lack of LmCyp19 interaction with calcineurin. These observations indicate that resistance of L. major to CsA in vitro is mediated by the lack of complex formation with calcineurin despite CsA binding by parasitic Cyp.
Human soluble guanylate cyclase: functional expression and revised isoenzyme family
Authors: ZABEL Ulrike , WEEGER Monika , LA Mylinh , SCHMIDT Harald H. H. W.
Published: August 2015

Soluble guanylate cyclase (sGC), a heterodimeric (α/β) haem protein that converts GTP to the second messenger cGMP, functions as the receptor for nitric oxide (NO) and nitrovasodilator drugs. Three distinct cDNA species of each subunit (α1–α3, β1–β3) have been reported from various species. From human sources, none of these have been expressed as functionally active enzyme. Here we describe the expression of human α/β heterodimeric sGC in Sf9 cells yielding active recombinant enzyme that was stimulated by the nitrovasodilator sodium nitroprusside or the NO-independent activator 3-(5´-hydroxymethyl-2´-furyl)-1-benzylindazole (YC-1). At the protein level, both α and β subunits were detected in human tissues, suggesting co-expression also in vivo. Moreover, resequencing of the human cDNA clones [originally termed α3 and β3; Giuili, Scholl, Bulle and Guellaen (1992) FEBS Lett. 304, 83–88] revealed several sequencing errors in human α3; correction of these eliminated major regions of divergence from rat and bovine α1. As human β3 also displays more than 98% similarity to rat and bovine β1 at the amino acid level, α3 and β3 represent the human homologues of rat and bovine α1 and β1, and the isoenzyme family is decreased to two isoforms for each subunit (α1, α2; β1, β2). Having access to the human key enzyme of NO signalling will now permit the study of novel sGC-modulating compounds with therapeutic potential.
Cloning and expression of mouse legumain, a lysosomal endopeptidase
Authors: CHEN Jinq-May , DANDO Pam M. , STEVENS Richard A. E. , FORTUNATO Mara , BARRETT Alan J.
Published: August 2015

Legumain, a recently discovered mammalian cysteine endopeptidase, was found in all mouse tissues examined, but was particularly abundant in kidney and placenta. The distribution in subcellular fractions of mouse and rat kidney showed a lysosomal localization, and activity was detectable only after the organelles were disrupted. Nevertheless, ratios of legumain activity to that of cathepsin B differed considerably between mouse tissues. cDNA encoding mouse legumain was cloned and sequenced, the deduced amino acid sequence proving to be 83% identical to that of the human protein [Chen, Dando, Rawlings, Brown, Young, Stevens, Hewitt, Watts and Barrett (1997) J. Biol. Chem. 272, 8090–8098]. Recombinant mouse legumain was expressed in human embryonic kidney 293 cells by use of a vector containing a cytomegalovirus promoter. The recombinant enzyme was partially purified and found to be an asparagine-specific endopeptidase closely similar to naturally occurring pig kidney legumain.
Phosphatidylinositol 3′-kinase associates with an insulin receptor substrate-1 serine kinase distinct from its intrinsic serine kinase
Authors: CENGEL Keith A. , KASON Rosanne E. , FREUND Gregory G.
Published: August 2015

Serine phosphorylation of insulin receptor substrate-1 (IRS-1) has been proposed as a counter-regulatory mechanism in insulin and cytokine signalling. Here we report that IRS-1 is phosphorylated by a wortmannin insensitive phosphatidylinositol 3´-kinase (PI 3-kinase)-associated serine kinase (PAS kinase) distinct from PI 3-kinase serine kinase. We found that PI 3-kinase immune complexes contain 5-fold more wortmannin-insensitive serine kinase activity than SH2-containing protein tyrosine phosphatase-2 (SHP2) and IRS-1 immune complexes. Affinity chromatography of cell lysates with a glutathione S-transferase fusion protein for the p85 subunit of PI 3-kinase showed that PAS kinase associated with the p85 subunit of PI 3-kinase. This interaction required unoccupied SH2 domain(s) but did not require the PI 3-kinase p110 subunit binding domain. In terms of function, PAS kinase phosphorylated IRS-1 and, after insulin stimulation, PAS kinase phosphorylated IRS-1 in PI 3-kinase–IRS-1 complexes. Phosphopeptide mapping showed that insulin-dependent in vivo sites of IRS-1 serine phosphorylation were comparable to those of PAS kinase phosphorylated IRS-1. More importantly, PAS kinase-dependent phosphorylation of IRS-1 reduced by 4-fold the ability of IRS-1 to act as an insulin receptor substrate. Taken together, these findings indicate that: (a) PAS kinase is distinct from the intrinsic serine kinase activity of PI 3-kinase, (b) PAS kinase associates with the p85 subunit of PI 3-kinase through SH2 domain interactions, and (c) PAS kinase is an IRS-1 serine kinase that can reduce the ability of IRS-1 to serve as an insulin receptor substrate.
Identification of Glu-277 as the catalytic nucleophile of Thermoanaerobacterium saccharolyticum β-xylosidase using electrospray MS
Authors: VOCADLO David J. , MACKENZIE Lloyd F. , HE Shouming , ZEIKUS Gregory J. , WITHERS Stephen G.
Published: August 2015

Thermoanaerobacterium saccharolyticum β-xylosidase is a member of family 39 of the glycosyl hydrolases. This grouping comprises both retaining β-d-xylosidases and α-l-iduronidases. T. saccharolyticum β-xylosidase catalyses the hydrolysis of short xylo-oligosaccharides into free xylose via a covalent xylosyl–enzyme intermediate. Incubation of T. saccharolyticum β-xylosidase with 2,4-dinitrophenyl 2-deoxy-2-fluoro-β-d-xyloside resulted in time-dependent inactivation of the enzyme (inactivation rate constant ki = 0.089 min-1, dissociation constant for the inactivator Ki = 65 µM) through the accumulation of a covalent 2-deoxy-2-fluoro-α-d-xylosyl–enzyme, as observed by electrospray MS. Removal of excess inactivator and regeneration of the free enzyme through transglycosylation with either xylobiose or thiobenzyl xyloside demonstrated that the covalent intermediate was kinetically competent. Peptic digestion of the 2-deoxy-2-fluoro-α-d-xylosyl–enzyme intermediate and subsequent analysis by electrospray ionization triple-quadrupole MS in the neutral-loss mode indicated the presence of a 2-deoxy-2-fluoro-α-d-xylosyl peptide. Sequence determination of the labelled peptide by tandem MS in the daughter-ion scan mode permitted the identification of Glu-277 (bold and underlined) as the catalytic nucleophile within the sequence IILNSHFPNLPFHITEY.
Stimulation of soluble guanylate cyclase by superoxide dismutase is mediated by NO
Authors: FRIEBE Andreas , SCHULTZ Günter , KOESLING Doris
Published: August 2015

Soluble guanylate cyclase (sGC), which is found in many cells and tissues, represents the receptor for the intra- and intercellular messenger molecule NO. Superoxide dismutase (SOD), an enzyme involved in the degradation of toxic superoxide radicals, has been proposed as a non-NO activator of sGC. Here we show that SOD stimulated sGC purified from bovine lung up to 10-fold. Activation by SOD was not influenced by the hydroxyl radical scavengers mannitol and DMSO. In contrast, the presence of the NO scavengers oxyhaemoglobin and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, as well as the O2--generating system xanthine oxidase/hypoxanthine, led to inhibition of SOD-stimulated cGMP production. NO-insensitive sGC mutants were not influenced either by SOD or by xanthine oxidase. We have previously shown that sGC was stimulated by NO present in the normal atmosphere. Here we show that the SOD effect depended on the NO concentration from the atmosphere, as the stimulation of sGC by defined NO gases (0, 120, 330 and 1000 parts per billion NO) was potentiated by SOD. NO stimulation of sGC and its potentiation by SOD were inhibited by oxyhaemoglobin to identical levels. We conclude that the SOD-mediated stimulation of sGC is due to the elimination of superoxide, thereby preventing its reaction with NO to form peroxynitrite.
Regulation of mammalian pyruvate dehydrogenase α subunit gene expression by glucose in HepG2 cells
Authors: TAN Jie , YANG Hsin-Sheng , PATEL Mulchand S.
Published: August 2015

We report the effect of glucose on the expression of the gene encoding the pyruvate dehydrogenase (E1) α subunit (E1α) in human hepatoma (HepG2) cells. Total pyruvate dehydrogenase complex activity as well as the levels of protein and mRNA of the E1α subunit were significantly increased in HepG2 cells cultured in medium containing 16.7 mM glucose compared with 1.0 mM glucose for a period of 4 weeks. The level of E1α mRNA was elevated approx. 2-fold in HepG2 cells cultured for 24 h in medium containing 16.7 mM glucose compared with 1 mM glucose. This effect was specific to glucose and independent of insulin. Nuclear run-on assays and promoter analysis indicate that the glucose-induced increases in the levels of E1α mRNA in HepG2 cells are due to increased transcription of the human E1α (PDHA1) gene. Mutational analysis of the E1α promoter region has identified two regions, from -78 to -73 bp (CCCCTG) and from -8 to -3 bp (GCGGTG), that are responsible for the effect of glucose on promoter activity; the former exhibits a larger effect. These two sequences represent new variations of the carbohydrate-response element that has been identified in other genes. The stimulation of E1α promoter activity by glucose was abolished by okadaic acid at 100 nM but not at 5 nM, suggesting that glucose-mediated regulation of pyruvate dehydrogenase complex E1α gene transcription involves a phosphorylation/dephosphorylation mechanism, possibly involving protein phosphatase-1.
A trypsin-like platelet protease propagates protease-activated receptor-1 cleavage and platelet activation
Authors: OFOSU Frederick A. , FREEDMAN John , DEWAR Lori , SONG Yinqi , FENTON John W.
Published: August 2015

Protease-activated receptor-1 (PAR-1) is a G-protein-linked receptor on platelets and perivascular cells activated by α-thrombin and the PAR-1-activating peptide, SFLLRN. α-Thrombin activates PAR-1 by cleaving it at R41–S42 to release the 41-residue peptide TR(1–41). Unexpectedly, platelet activation with SFLLRN was also associated with PAR-1 cleavage and the release of TR(1–41). Both PAR-1 cleavage and platelet activation resulting from SFLLRN addition to platelets were markedly inhibited by the serine protease inhibitor 4,2-(aminoethyl)-benzene sulphonylfluoride·HCl (pefabloc SC) and soybean trypsin inhibitor, but not by inhibitors of calpain, cysteine proteases or metalloproteases. Thus, a trypsin-like platelet protease propagates SFLLRN-dependent PAR-1 cleavage and platelet activation.
Human carbon catabolite repressor protein (CCR4)-associative factor 1: cloning, expression and characterization of its interaction with the B-cell translocation protein BTG1
Authors: BOGDAN John A. , ADAMS-BURTON Catherine , PEDICORD Donna L. , SUKOVICH Drew A. , BENFIELD Pamela A. , CORJAY Martha H. , STOLTENBORG Janet K. , DICKER Ira B.
Published: August 2015

The human BTG1 protein is thought to be a potential tumour suppressor because its overexpression inhibits NIH 3T3 cell proliferation. However, little is known about how BTG1 exerts its anti-proliferative activity. In this study, we used the yeast ‘two-hybrid ’ system to screen for interacting protein partners and identified human carbon catabolite repressor protein (CCR4)-associative factor 1 (hCAF-1), a homologue of mouse CAF-1 (mCAF-1) and Saccharomyces cerevisiae yCAF-1/POP2. In vitro the hCAF-1/BTG1 complex formation was dependent on the phosphorylation of a putative p34cdc2 kinase site on BTG1 (Ser-159). In yeast, the Ala-159 mutant did not interact with hCAF-1. In addition, phosphorylation of Ser-159 in vitro showed specificity for the cell cycle kinases p34CDK2/cyclin E and p34CDK2/cyclin A, but not for p34CDK4/cyclin D1 or p34cdc2/cyclin B. Cell synchrony experiments with primary cultures of rat aortic smooth-muscle cells (RSMCs) demonstrated that message and protein levels of rat CAF-1 (rCAF-1) were up-regulated under conditions of cell contact, as previously reported for BTG1 [Wilcox, Scott, Subramanian, Ross, Adams-Burton, Stoltenborg and Corjay (1995) Circulation 92, I34–I35]. Western blot and immunohistochemical analysis showed that rCAF-1 localizes to the nucleus of contact-inhibited RSMCs, where it was physically associated with BTG1, as determined by co-immunoprecipitation with anti-hCAF-1 antisera. Overexpression of hCAF-1 in NIH 3T3 and osteosarcoma (U-2-OS) cells was itself anti-proliferative with colony formation reduced by 67% and 90% respectively. Taken together, these results indicate that formation of the hCAF-1/BTG1 complex is driven by phosphorylation at BTG1 (Ser-159) and implicates this complex in the signalling events of cell division that lead to changes in cellular proliferation associated with cell–cell contact.
Tocopherol synthesis from homogentisate in Capsicum anuum L. (yellow pepper) chromoplast membranes: evidence for tocopherol cyclase
Authors: ARANGO Yolanda , HEISE Klaus-Peter
Published: August 2015

The present study shows for the first time appreciable tocopherol cyclase activities in plastidial membrane preparations of Capsicum annuum L. (yellow pepper) fruits. When chromoplast membranes from yellow peppers were incubated with [3H]homogentisate and phytyl pyrophosphate under strictly reducing conditions, all biosynthesis precursors were labelled. The main labelling was found in γ-tocopherol. These observations contradict the hypothesis that assigns a rate-limiting function to tocopherol cyclase in plastidial α-tocopherol biosynthesis. The stoichiometry of α-tocopherol, 2,3-dimethylphytylquinol and γ-tocopherol formation and the inhibition of α-tocopherol synthesis by increasing γ-tocopherol concentrations suggests the regulation of this pathway by its precursors.
Nutrient and hormonal regulation of pyruvate kinase gene expression
Authors: YAMADA Kazuya , NOGUCHI Tamio
Published: August 2015

Mammalian pyruvate kinase (PK), a key glycolytic enzyme, has two genes named PKL and PKM, which produce the L- and R-type isoenzymes by means of alternative promoters, and the M1-and M2-types by mutually exclusive alternative splicing respectively. The expression of these genes is tissue-specific and under developmental, dietary and hormonal control. The L-type isoenzyme (L-PK) gene contains multiple regulatory elements necessary for regulation in the 5´ flanking region, up to position -170. Both L-II and L-III elements are required for stimulation of L-PK gene transcription by carbohydrates such as glucose and fructose, although the L-III element is itself responsive to carbohydrates. The L-II element is also responsible for the gene regulation by polyunsaturated fatty acids. Nuclear factor-1 proteins and hepatocyte nuclear factor 4, which bind to the L-II element, may also be involved in carbohydrate and polyunsaturated fatty acid regulation of the L-PK gene respectively. However, the L-III-element-binding protein that is involved in carbohydrate regulation remains to be clarified, although involvement by an upstream stimulating factor has been proposed. Available evidence suggests that the carbohydrate signalling pathway to the L-PK gene includes a glucose metabolite, possibly glucose 6-phosphate or xylulose 5-phosphate, as well as phosphorylation and dephosphorylation mechanisms. In addition, at least five regulatory elements have been identified in the 5´ flanking region of the PKM gene up to position -279. Sp1-family proteins bind to two proximal elements, but the binding of proteins to other elements have not yet been clarified. Glucose may stimulate the transcription of the PKM gene via hexosamine derivatives. Sp1 may be involved in this regulation via its dephosphorylation, although the carbohydrate response element has not been determined precisely in the PKM gene. Thus glucose stimulates transcription of the PKM gene by the mechanism which is probably different from the L-PK gene.
Diminished expression of phosphatidylethanolamine N-methyltransferase 2 during hepatocarcinogenesis
Authors: TESSITORE Luciana , DIANZANI Irma , CUI Zheng , VANCE Dennis E.
Published: August 2015

Phosphatidylethanolamine N-methyltransferase (PEMT) is a liver-specific enzyme that converts phosphatidylethanolamine into phosphatidylcholine. At least two forms of PEMT are present in hepatocytes. However, PEMT activity is negligible in two hepatoma cell lines. Previous studies have indicated an inverse relationship between the expression of one form, PEMT2, and the rate of liver growth, suggesting that this enzyme might be involved in inhibition of hepatocyte proliferation. We have now investigated the expression of PEMT2 at various stages of hepatocarcinogenesis induced by chemical carcinogens. Expression of PEMT2 protein was decreased in liver samples that contained the first detectable proliferative lesions. At later stages of carcinogenesis, PEMT2 expression was obliterated. PEMT activity decreased, the levels of PEMT2 mRNA decreased and there was an increase in the activity of CTP:phosphocholine cytidylyltransferase, a key regulatory enzyme in the CDP-choline pathway of phosphatidylcholine biosynthesis. Southern blot analyses of restriction fragments of DNA showed no changes in the PEMT gene in hepatocarcinoma compared with normal liver. A role for PEMT2 in the control of hepatocyte proliferation remains an intriguing possibility.
Changes in polyamine catabolism in HL-60 human promyelogenous leukaemic cells in response to etoposide-induced apoptosis
Authors: LINDSAY Gayle S. , WALLACE Heather M.
Published: August 2015

The topoisomerase II inhibitor etoposide induced apoptosis in HL-60 cells within 4 h of exposure to the drug, as measured by changes in morphology, DNA fragmentation and cytotoxicity assays. Etoposide-induced apoptosis was accompanied by an increase in polyamine efflux from the cells and a decrease in total polyamine content during the first 24 h of exposure to the drug. Although both enzyme activities increased slightly, there were no significant changes in spermidine/spermine N1-acetyltransferase activity or polyamine oxidase activity. After longer exposures (48–72 h), significant induction of spermidine/spermine N1-acetyltransferase activity and loss of polyamine content occurred. These results suggest that polyamine oxidation and the resultant hydrogen peroxide produced may be associated with the initiation of apoptosis, while induction of the acetyltransferase and overall loss of intracellular polyamines may be involved in the final, possibly necrotic, stages of cell death.
Secretion and apparent activation of human hepatic lipase requires proper oligosaccharide processing in the endoplasmic reticulum
Authors: VERHOEVEN Adrie J. M. , NEVE Bernadette P. , JANSEN Hans
Published: August 2015

Human hepatic lipase (HL) is a glycoprotein with four N-linked oligosaccharide side chains. The importance of glycosylation for the secretion of catalytically active HL was studied in HepG2 cells by using inhibitors of intracellular trafficking, N-glycosylation and oligosaccharide processing. Secretion of HL was inhibited by carbonyl cyanide m-chlorophenylhydrazone (CCCP), monensin, brefeldin A (BFA), tunicamycin, castanospermine and N-methyldeoxynojirimycin, but not by 1-deoxymannojirimycin. Secretion of α1-antitrypsin, an unrelated N-glycoprotein, was also inhibited by monensin, BFA and tunicamycin, but not by CCCP, castanospermine or N-methyldeoxynojirimycin. Intracellular HL activity decreased with CCCP, tunicamycin, castanospermine and N-methyldeoxynojirimycin, but increased with monensin and BFA. In the absence of protein synthesis de novo, HL activity secreted into the medium was 7.8±2.1-fold higher (mean±S.D., n = 7) than the simultaneous fall in intracellular HL activity. In cells pretreated with monensin or BFA, this factor decreased to 1.3±0.5, indicating that the apparent increase in HL activity had already occurred within these cells. After chromatography on Sepharose–heparin, the specific triacylglycerol hydrolase activity of secreted HL was only 1.7±0.3-fold higher than that of intracellular HL, indicating that the secretion-coupled increase in HL activity is only partly explained by true activation. We conclude that oligosaccharide processing by glucosidases in the endoplasmic reticulum is necessary for the transport of newly synthesized human HL, but not α1-antitrypsin, to the Golgi, where the catalytic activity of HL is unmasked.
Gene structure, expression and chromosomal localization of murine Theta class glutathione transferase mGSTT1-1
Authors: WHITTINGTON Angela T. , VICHAI Vanicha , WEBB Graham C. , BAKER Rohan T. , PEARSON William R. , BOARD Philip G.
Published: August 2015

We have isolated and characterized a cDNA and partial gene encoding a murine subfamily 1 Theta class glutathione transferase (GST). The cDNA derived from mouse GSTT1 has an open reading frame of 720 bp encoding a peptide of 240 amino acids with a calculated molecular mass of 27356 Da. The encoded protein shares only 51% deduced amino acid sequence identity with mouse GSTT2, but greater than 80% deduced amino acid sequence identity with rat GSTT1 and human GSTT1. Mouse GSTT1-1 was expressed in Escherichia colias an N-terminal 6× histidine-tagged protein and purified using immobilized-metal affinity chromatography on nickel-agarose. The yield of the purified recombinant protein from E. coli cultures was approx. 14 mg/l. Recombinant mouse GSTT1-1 was catalytically active towards 1,2-epoxy-3-(p-nitrophenoxy)propane, 4-nitrobenzyl chloride and dichloromethane. Low activity towards 1-menaphthyl sulphate and 1-chloro-2,4-dinitrobenzene was detected, whereas mouse GSTT1-1 was inactive towards ethacrynic acid. Recombinant mouse GSTT1-1 exhibited glutathione peroxidase activity towards cumene hydroperoxide and t-butyl hydroperoxide, but was inactive towards a range of secondary lipid-peroxidation products, such as the trans-alk-2-enals and trans,trans-alka-2,4-dienals. Mouse GSTT1 mRNA is most abundant in mouse liver and kidney, with some expression in intestinal mucosa. Mouse GSTT1 mRNA is induced in liver by phenobarbital, but not by butylated hydroxyanisole, β-napthoflavone or isosafrole. The structure of mouse GSTT1 is conserved with that of the subfamily 2 Theta class GST genes mouse GSTT2 and rat GSTT2, comprising five exons interrupted by four introns. The mouse GSTT1 gene was found, by in situ hybridization, to be clustered with mouse GSTT2 on chromosome 10 at bands B5–C1. This region is syntenic with the location of the human Theta class GSTs clustered on chromosome 22q11.2. Similarity searches of a mouse-expressed sequence tag database suggest that there may be two additional members of the Theta class that share 70% and 88% protein sequence identity with mouse GSTT1, but less than 55% sequence identity with mouse GSTT2.
Association of protein-tyrosine phosphatase PTP-BAS with the transcription-factor-inhibitory protein IκBα through interaction between the PDZ1 domain and ankyrin repeats
Authors: MAEKAWA Kazuhiko , IMAGAWA Noriko , NAITO Akira , HARADA Shigenori , YOSHIE Osamu , TAKAGI Shin
Published: August 2015

PTP-BAS is a membrane-associated protein tyrosine phosphatase containing a band-4.1 homology region and five PDZ (PSD-95 Dlg ZO-1) [discs-large homology region (‘DHR’)/Gly-Leu-Gly-Phe (‘GLGF’)] domains. The second and fourth PDZ domains were reported to associate with Fas/CD95. By using the first PDZ domain as a bait in yeast two-hybrid screening, we have identified IκBα as a binding protein. IκBα associated with PDZ1 through the stretch of the N-terminal three ankyrin repeats. The association was also confirmed in HeLa cells by co-immunoprecipitation experiments. Inhibition of PTP-BAS by expression of dominant-negative PTP-BAS mutant resulted in tyrosine-phosphorylation of IκBα. Tyrosine-phosphorylation of IκBα is a key event in activation of nuclear factor (NF)-κB during reoxygenation. PTP-BAS may thus play a regulatory role in activation of NF-κB under high oxidative stress.
Monosodium urate-crystal-stimulated phospholipase D in human neutrophils
Authors: MARCIL Josée , HARBOUR Danielle , HOULE Martin G. , NACCACHE Paul H. , BOURGOIN Sylvain
Published: August 2015

Protein kinase Cα (PKCα) and small GTPases of the Rho and ADP-ribosylation factor (Arf) family are implicated in the regulation of phospholipase D1 (PLD1) activity. Although they are involved in fMet-Leu-Phe (fMLP)-mediated PLD activation, their role in monosodium urate (MSU)-stimulated PLD1 activity in human neutrophils is not clear. The translocation of PKCα, RhoA and Arf from the cytosol to the membranes was monitored. fMLP induced a cytochalasin B (CB)-dependent recruitment of Arf, RhoA and PKCα to neutrophil membranes. CB also increased the activation of PLD 10-fold. In contrast with fMLP, MSU stimulated a sustained and time-dependent relocalization of Arf and PKCα, but not of RhoA, to the membrane fraction. MSU-stimulated PLD was activated with a time course preceding membrane recruitment of Arf and PKCα in the absence of CB. Furthermore, MSU-induced PLD activation and the membrane recruitment of PKCα, but not that of Arf, were inhibited by CB. An anti-FcγRIIIB antibody, VIFcRIII, prevented the membrane relocalization of Arf and PKCα and the stimulation of the levels of tyrosine phosphorylation and of PLD activity induced by MSU. Erbstatin and ST-638, two inhibitors of tyrosine kinases, inhibited the MSU-induced translocation of Arf and PKCα but not MSU-induced tyrosine phosphorylation and PLD activation. Furthermore MSU crystals did not cause the tyrosine phosphorylation of PLD1. The present study indicates that soluble and particulate agonists show selectivity in inducing the translocation of RhoA in neutrophils and that the ability of MSU to increase PLD activation was independent of the membrane relocalization of Arf and PKCα.
Concerted action of cytosolic Ca2+ and protein kinase C in receptor-mediated phospholipase D activation in Chinese hamster ovary cells expressing the cholecystokinin-A receptor
Authors: BOSCH Remko R. , SMEETS Rolf L. L. , SLEUTELS Frank , PATEL Anjana M. P. , EMST-De VRIES Sjenet E. Van , DE PONT Jan Joep H. H. M. , WILLEMS Peter H. G. M.
Published: August 2015

Receptor-mediated activation of phosphatidylcholine phosphatidohydrolase or phospholipase D (PLD) was studied in Chinese hamster ovary (CHO) cells expressing the cholecystokinin-A (CCK-A) receptor. Cells were labelled with [3H]myristic acid for 24 h and PLD-catalysed [3H]phosphatidylethanol formation was measured in the presence of 1% (v/v) ethanol. Cholecystokinin-(26–33)-peptide amide (CCK8) increased PLD activity both time- and dose-dependently. Maximal activation of protein kinase C (PKC) with 1 µM PMA or sustained elevation of the cytosolic free Ca2+ concentration ([Ca2+]i) with 1 µM thapsigargin increased PLD activity to 50% and 70% of the maximal value obtained with CCK8 respectively. The stimulatory effects of CCK8, PMA and thapsigargin were abolished in cells in which PKC was downregulated or inhibited by chelerythrine. PMA/Ca2+-stimulated PLD activity was absent in a homogenate of PKC-downregulated cells but could be restored upon addition of purified rat brain PKC. CCK8-induced PLD activation was inhibited by 90% in the absence of external Ca2+, demonstrating that receptor-mediated activation of PKC in itself does not significantly add to PLD activation but requires a sustained increase in [Ca2+]i. Taken together, the results presented demonstrate that, in CHO-CCK-A cells, receptor-mediated PLD activation is completely dependent on PKC, but that the extent to which PLD becomes activated depends largely, if not entirely, on the magnitude and duration of the agonist-induced increase in [Ca2+]i.
Signalling pathway leading to an activation of mitogen-activated protein kinase by stimulating M3 muscarinic receptor
Authors: KIM Jee-Young , YANG Myung-Soon , OH Chun-Do , KIM Kyong-Tai , HA Mahn Joon , KANG Shin-Sung , CHUN Jang-Soo
Published: August 2015

The signalling pathway leading to an activation of mitogen-activated protein (MAP) kinase subtypes Erk-1 and -2 upon stimulation of muscarinic receptor with carbachol in human neuroblastoma SK-N-BE2(C) cells was investigated. Carbachol activated Erk-1/-2 by stimulating M3 muscarinic receptor, as determined by specific antagonists for individual muscarinic receptors. The activation of Erk-1/-2 by carbachol was blocked by the inhibition or down-regulation of protein kinase C (PKC). Among the multiple PKC isoforms expressed in SK-N-BE2(C) cells, only PKCε was activated by the treatment of carbachol, and selective down-regulation of PKCε was sufficient to block Erk-1/-2 activation. Carbachol treatment induced activation of the serine/threonine protein kinase Raf, and an inhibition of Raf blocked Erk-1/-2 activation. Ectopic expression of inhibitory small GTPase Ras, RasN17, blocked the carbachol-induced Raf activation without affecting the activation of PKCε, while the inhibition of PKC blocked the Raf activation. Thus, these results suggest that carbachol-induced activation of PKCε mediates Erk-1/-2 activation by a sequential activation of Ras, Raf and MAP kinase kinase.
Structural characterization of human aryl sulphotransferases
Authors: BRIX Lulu A. , DUGGLEBY Ronald G. , GAEDIGK Andrea , McMANUS Michael E.
Published: August 2015

Human aryl sulphotransferase (HAST) 1, HAST3, HAST4 and HAST4v share greater than 90% sequence identity, but vary markedly in their ability to catalyse the sulphonation of dopamine and p-nitrophenol. In order to investigate the amino acid(s) involved in determining differing substrate specificities of HASTs, a range of chimaeric HAST proteins were constructed. Analysis of chimaeric substrate specificities showed that enzyme affinities are mainly determined within the N-terminal end of each HAST protein, which includes two regions of high sequence divergence, termed Regions A (amino acids 44–107) and B (amino acids 132–164). To investigate the substrate-binding sites of HASTs further, site-directed mutagenesis was performed on HAST1 to change 13 individual residues within these two regions to the HAST3 equivalent. A single amino acid change in HAST1 (A146E) was able to change the specificity for p-nitrophenol to that of HAST3. The substrate specificity of HAST1 towards dopamine could not be converted into that of HAST3 with a single amino acid change. However, compared with wild-type HAST1, a number of the mutations resulted in interference with substrate binding, as shown by elevated Ki values towards the co-substrate 3´-phosphoadenosine 5´-phosphosulphate, and in some cases loss of activity towards dopamine. These findings suggest that a co-ordinated change of multiple amino acids in HAST proteins is needed to alter the substrate specificities of these enzymes towards dopamine, whereas a single amino acid at position 146 determines p-nitrophenol affinity. A HAST1 mutant was constructed to express a protein with four amino acids deleted (P87–P90). These amino acids were hypothesized to correspond to a loop region in close proximity to the substrate-binding pocket. Interestingly, the protein showed substrate specificities more similar to wild-type HAST3 than HAST1 and indicates an important role of these amino acids in substrate binding.
Lipoarabinomannans: characterization of the multiacylated forms of the phosphatidyl-myo-inositol anchor by NMR spectroscopy
Authors: NIGOU Jérôme , GILLERON Martine , PUZO Germain
Published: August 2015

Lipoarabinomannans, which exhibit a large spectrum of immunological activities, emerge as the major antigens of mycobacterial envelopes. The lipoarabinomannan structure is based on a phosphatidyl-myo-inositol anchor whose integrity has been shown to be crucial for lipoarabinomannan biological activity and particularly for presentation to CD4/CD8 double-negative αβT cells by CD1 molecules. In this report, an analytical approach was developed for high-resolution 31P-NMR analysis of native, i.e. multiacylated, lipoarabinomannans. The one-dimensional 31P spectrum of cellular lipoarabinomannans, from Mycobacterium bovis Bacillus Calmette–Guérin, exhibited four 31P resonances typifying four types of lipoarabinomannans. Two-dimensional 1H-31P heteronuclear multiple-quantum-correlation/homonuclear Hartmann–Hahn analysis of the native molecules showed that these four types of lipoarabinomannan differed in the number and localization of fatty acids (from 1 to 4) esterifying the anchor. Besides the three acylation sites previously described, i.e. positions 1 and 2 of glycerol and 6 of the mannosyl unit linked to the C-2 of myo-inositol, we demonstrate the existence of a fourth acylation position at the C-3 of myo-inositol. We report here the first structural study of native multiacylated lipoarabinomannans, establishing the structure of the intact phosphatidyl-myo-inositol anchor. Our findings would help gain more understanding of the molecular basis of lipoarabinomannan discrimination in the binding process to CD1 molecules.
Transcription factor Sp1 activates involucrin promoter activity in non-epithelial cell types
Authors: BANKS Eric B. , CRISH James F. , ECKERT Richard L.
Published: August 2015

The gene for human involucrin (hINV) is selectively expressed in stratifying epithelial cells lining external body surfaces. Previously, we characterized the hINV promoter 5´ distal regulatory region (DRR) located between nt -2473 and -2088 upstream of the transcription start site. This region is required for optimal hINV gene expression. The DRR contains weak and strong activator elements. The strong activator comprises AP1- and Sp1-binding sites that combine to drive high-level promoter expression in human keratinocytes. Here we show that the hINV promoter is expressed in a cell-specific manner in vitro and that the DRR contains elements that are partly responsible for cell-type-specific expression of hINV. hINV promoter activity is barely detectable in 3T3 fibroblasts or HEK-293 human embryonic kidney cells. Reporter plasmids containing the full-length promoter or the isolated DRR can, however, be activated in 3T3 and HEK-293 cells by co-transfection with a plasmid encoding the transcription factor Sp1. Consistently with the lower hINV promoter activity, immunoblotting studies indicate that Sp1 protein levels are lower in 3T3 and HEK-293 cells than in human epidermal keratinocytes. Increased Sp1 protein in transfected 3T3 cells and HEK-293 cells correlates with increased promoter activity. In addition, Sp1 transfection activates the expression of the endogenous gene for hINV in HEK-293 cells. These studies suggest that Sp1 might have a role in cell-specific expression of hINV.
Characterization of membrane polypeptides from pea leaf peroxisomes involved in superoxide radical generation
Authors: LÓPEZ-HUERTAS Eduardo , CORPAS Francisco J. , SANDALIO Luisa M. , DEL RÍO Luis A.
Published: August 2015

The production of superoxide radicals (O2-•) and the activities of ferricyanide reductase and cytochrome c reductase were investigated in peroxisomal membranes from pea (Pisum sativum L.) leaves using NADH and NADPH as electron donors. The generation of O2-• by peroxisomal membranes was also assayed in native polyacrylamide gels using an in situ staining method with NitroBlue Tetrazolium (NBT). When peroxisomal membranes were assayed under native conditions using NADH or NADPH as inducer, two different O2-•-dependent Formazan Blue bands were detected. Analysis by SDS/PAGE of these bands demonstrated that the NADH-induced NBT reduction band contained several polypeptides (PMP32, PMP61, PMP56 and PMP18, where PMP is peroxisomal membrane polypeptide and the number indicates molecular mass in kDa), while the NADPH-induced band was due exclusively to PMP29. PMP32 and PMP29 were purified by preparative SDS/PAGE and electroelution. Reconstituted PMP29 showed cytochrome c reductase activity and O2-• production, and used NADPH specifically as electron donor. PMP32, however, had ferricyanide reductase and cytochrome c reductase activities, and was also able to generate O2-• with NADH as electron donor, whereas NADPH was not effective as an inducer. The reductase activities of, and O2-• production by, PMP32 were inhibited by quinacrine. Polyclonal antibodies against cucumber monodehydroascorbate reductase (MDHAR) recognized PMP32, and this polypeptide is likely to correspond to the MDHAR reported previously in pea leaf peroxisomal membranes.
Dermatopontin interacts with transforming growth factor β and enhances its biological activity
Authors: OKAMOTO Osamu , FUJIWARA Sakuhei , ABE Mayumi , SATO Yasufumi
Published: August 2015

Dermatopontin, a recently found low-molecular-mass component of the extracellular matrix, was studied for its interaction with decorin and transforming growth factor β (TGF-β) and its influence on TGF-β bioactivity. Dermatopontin reacted with decorin with an apparent Kd of 100 nM in a solid-phase assay. Dermatopontin inhibited the formation of the decorin–TGF-β1 complex. Decorin also competed with dermatopontin for the binding of this cytokine. The dermatopontin–decorin complex bound 3-fold more TGF-β1 than did each component individually, and binding was inhibited more strongly by decorin preincubated with dermatopontin than by dermatopontin or decorin alone. Dermatopontin augmented the biological activity of TGF-β1, as analysed by the expression of luciferase in mink lung epithelial cells transfected with a plasminogen activator inhibitor–promoter–luciferase construct, although dermatopontin itself did not show apparent induction of luciferase. Dermatopontin showed weak inhibitory activity on the proliferation of mink lung epithelial cells, and it enhanced the growth-inhibitory activity of TGF-β on these cells. Thus dermatopontin increases the cellular response to TGF-β. These findings strongly suggest that dermatopontin modifies the behaviour of TGF-β through interaction with decorin in the microenvironment of the extracellular matrix in vivo.
Recognition of DNA alterations by the mismatch repair system
Authors: MARRA Giancarlo , SCHÄR Primo
Published: August 2015

Misincorporation of non-complementary bases by DNA polymerases is a major source of the occurrence of promutagenic base-pairing errors during DNA replication or repair. Base–base mismatches or loops of extra bases can arise which, if left unrepaired, will generate point or frameshift mutations respectively. To counteract this mutagenic potential, organisms have developed a number of elaborate surveillance and repair strategies which co-operate to maintain the integrity of their genomes. An important replication-associated correction function is provided by the post-replicative mismatch repair system. This system is highly conserved among species and appears to be the major pathway for strand-specific elimination of base–base mispairs and short insertion/deletion loops (IDLs), not only during DNA replication, but also in intermediates of homologous recombination. The efficiency of repair of different base-pairing errors in the DNA varies, and appears to depend on multiple factors, such as the physical structure of the mismatch and sequence context effects. These structural aspects of mismatch repair are poorly understood. In contrast, remarkable progress in understanding the biochemical role of error-recognition proteins has been made in the recent past. In eukaryotes, two heterodimers consisting of MutS-homologous proteins have been shown to share the function of mismatch recognition in vivo and in vitro. A first MutS homologue, MSH2, is present in both heterodimers, and the specificity for mismatch recognition is dictated by its association with either of two other MutS homologues: MSH6 for recognition of base–base mismatches and small IDLs, or MSH3 for recognition of IDLs only. Mismatch repair deficiency in cells can arise through mutation, transcriptional silencing or as a result of imbalanced expression of these genes.
Activity of human 11-cis-retinol dehydrogenase (Rdh5) with steroids and retinoids and expression of its mRNA in extra-ocular human tissue
Authors: WANG Jin , CHAI Xiyun , ERIKSSON Ulf , NAPOLI Joseph L.
Published: August 2015

This report describes the activity of recombinant human Rdh5 (11-cis-retinol dehydrogenase) with steroids and retinoids and expression of the Rdh5 mRNA in extra-ocular human tissue. The data show that Rdh5 catalyses 9-cis-retinol metabolism equally efficiently as 11-cis-retinol metabolism and recognizes 5α-androstan-3α,17β-diol and androsterone as substrates (3α-hydroxysteroid dehydrogenase activity), but not testosterone, dihydrotestosterone, oestradiol and corticosterone (lack of 17β-hydroxysteroid and 11β-hydroxysteroid dehydrogenase activities). Rdh5 mRNA expression was widespread in extra-ocular tissues with human liver (100% relative expression in extra-ocular tissues only) and mammary gland (97% relative to liver) showing the most intense signals. Other noteworthy relatively intense expression sites included colon (45%), thymus (43%), small intestine (39%), kidney (37%), bladder (29%), pancreas and spleen (28% each), heart (26%), uterus and ovary (25% each), testis (22%) and spinal cord (24%). Human fetal tissues also expressed Rdh5 with fetal liver showing the most intense expression among the fetal tissues (20%). Considered along with the identical nucleotide sequences in the untranslated regions of human Rdh5 and human 9-cis-retinol dehydrogenase cDNAs and the nearly identical nucleotide sequences overall (99% identity), the current results suggest that the two cDNAs represent a single gene product.
Cell-cycle-regulated phosphorylation of cAMP response element-binding protein: identification of novel phosphorylation sites
Authors: SAEKI Kumiko , YUO Akira , TAKAKU Fumimaro
Published: August 2015

We report that the cAMP response element binding protein (CREB) undergoes cell-cycle-regulated phosphorylation. In human amnion FL cells, CREB was expressed as two forms with different molecular masses, 45 and 45.5 kDa. Although asynchronous cells contained predominantly the 45 kDa forms, this form shifted to 45.5 kDa when the cells were synchronized with the early S-phase. Furthermore the expression of the 45.5 kDa band was increased when cells were treated with okadaic acid, confirming that the 45.5 kDa band was a phosphorylated form of the 45 kDa band. Mutation analysis indicated that neither Ser133, the target of cAMP-dependent protein kinase and calcium calmodulin kinase, nor Ser129, the target of glycogen synthetase kinase 3, was responsible for the expression of the 45.5 kDa band, but that Ser108, Ser111 and Ser114, located in a region matching the consensus sequence for the casein kinase II target, were required. A mutant in which Ser111 and Ser114 were each replaced by a glutamic residue, mimicking a phosphorylated state, had a higher activation potential in cAMP response element-mediated transcription. These results strongly suggest that the casein kinase II target region is involved in cell cycle-regulated phosphorylation of the CREB protein and also in transcriptional enhancement.
Regulation of the gene for human dipeptidyl peptidase IV by hepatocyte nuclear factor 1α
Authors: ERICKSON Roger H. , GUM James R. , LOTTERMAN Craig D. , HICKS James W. , LAI Roy S. , KIM Young S.
Published: August 2015

Hepatocyte nuclear factor 1 was identified as the transcription factor binding to a 20 bp (-150 to -131) region of the gene for human dipeptidyl peptidase IV, which has been shown to be important for the expression of dipeptidyl peptidase IV in the human intestinal and hepatic epithelial cell lines Caco-2 and HepG2. Functional analysis of the hepatocyte nuclear factor 1 site was performed with two minimal dipeptidyl peptidase IV promoter constructs (-250 to -41, and -150 to -41) with and without a 3 bp mutation in the hepatocyte nuclear factor 1 sequence, and used in transient transfection experiments with Caco-2 cells. The results show that the mutated constructs were able to drive transcription at only 5–10% of the activity of the non-mutated controls. Co-transfection of 3T3 cells with hepatocyte nuclear factor 1 (α or β) and dipeptidyl peptidase IV promoter constructs (-250 to -41 or -150 to -41) resulted in a 2.5–6-fold increase in transcription over controls with hepatocyte nuclear factor 1α but not with hepatocyte nuclear factor 1β. The results of this study show that hepatocyte nuclear factor 1 binds to the -150 to -131 region of the human dipeptidyl peptidase IV promoter and is necessary for transcriptional activation of the gene for dipeptidyl peptidase IV.