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R B Pilz

Publications and source records attributed to R B Pilz.

34 records · Page 2Linked to original sources
PubMed1995

Nitric oxide and cGMP analogs activate transcription from AP-1-responsive promoters in mammalian cells.

Nitric oxide (NO) increases cytosolic guanylate cyclase activity and thereby activates the cGMP signal transduction pathway. The cAMP and Ca2+/phospholipid signal transduction pathways activate transcription factors that bind to the cAMP response element (CRE) and phorbol ester response element (TRE), respectively. Little is known about transcriptional regulation of gene expression by NO/cGMP. In transient and stable transfection experiments and in microinjection studies we found that three different NO-releasing agents and two membrane-permeable cGMP analogs activated TRE-regulated but not CRE-regulated reporter genes in rodent fibroblast and epithelial cell lines. Activation of TRE-regulated genes by NO-releasing agents and cGMP analogs appeared to be mediated by the AP-1 (Jun/Fos) transcription factor complex because we observed increased DNA binding of AP-1 and increased junB and c-fos mRNA in cells treated with these agents. The mechanism of gene activation by NO/cGMP was distinct from that used by phorbol esters and cAMP because it was not associated with c-jun mRNA induction and was not observed with CRE-containing promoters.

Animals↗
PubMed1995

Nitric oxide-releasing agents and cGMP analogues inhibit murine erythroleukemia cell differentiation and suppress erythroid-specific gene expression: correlation with decreased DNA binding of NF-E2 and altered c-myb mRNA expression.

Differentiation of murine erythroleukemia (MEL) cells induced by hexamethylene bisacetamide (HMBA) and DMSO was inhibited by several structurally unrelated nitric oxide (NO)-releasing agents and two membrane-permeable cGMP analogues. Since the effect of the NO-releasing agents was augmented by a cGMP phosphodiesterase inhibitor, at least some of their effect appeared to be mediated by activation of cytosolic guanylate cyclase. The drugs did not globally block differentiation since hemin-induced differentiation was undisturbed. In HMBA-treated cells, the NO-releasing agents and cGMP analogues reduced beta-globin and delta-aminolevulinate synthetase mRNA expression and inhibited the late down-regulation of c-myb mRNA that is required for HMBA-induced differentiation of MEL cells; the regulation of c-myc mRNA was not changed by the drugs. Nuclear run-off analyses showed that the drugs inhibited the HMBA-induced changes in beta-globin and c-myb transcription rates, and transient transfection of a reporter gene construct demonstrated that the drugs inhibited HMBA-inducible enhancer function of the alpha-globin control region, which contains binding sites for the erythroid transcription factors NF-E2 and GATA-1. The NO-releasing agents and cGMP analogues largely prevented HMBA-induced increases in DNA binding of NF-E2, whereas DNA binding of GATA-1 and SP-1 was not affected. The inhibition of erythroid gene expression by NO and cGMP analogues may be physiologically important under conditions of high NO production by endothelial cells and macrophages, i.e. during acute or chronic inflammation.

5-Aminolevulinate Synthetase↗
PubMed1994

Isolation and characterization of HL-60 cells resistant to nitroprusside-induced differentiation.

Sodium nitroprusside and sodium nitrite, which generate nitric oxide and increase the intracellular cGMP concentration, and 8-bromo-cGMP, a membrane-permeable cGMP analog, induce myelomonocytic differentiation of HL-60 cells (Boss, G. R. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 7174-7178). We have selected HL-60 cells resistant to nitroprusside-induced differentiation as assessed by acquisition of the OKM-1 antigen, reduction of nitro blue tetrazolium, and morphologic maturation. The variant cells were also resistant to differentiation induced by sodium nitrite and two cGMP analogs but still differentiated in response to other inducing agents such as dimethyl sulfoxide and cAMP analogs and showed the same changes in c-myc and c-fos expression in response to the latter drugs as occurred in parental cells. We studied the early steps of the NO/cGMP signal transduction pathway in the variant cells and found that basal and nitroprusside-stimulated guanylate cyclase activity was similar in parental and variant cell extracts and that nitroprusside increased the intracellular cGMP concentration to the same extent in parental and variant cells. As part of these studies we found that HL-60 cells expressed only alpha 2 and beta 2 guanylate cyclase mRNA; the abundance of these two mRNA species was similar in parental and variant cells. Neither nitroprusside nor 8-bromo-cGMP changed the intracellular calcium concentration in parental or variant cells. The data suggest that the defect in the variant cells is after guanylate cyclase activation in the NO/cGMP transduction pathway and that the cGMP and cAMP transduction pathways operate independently in inducing differentiation of HL-60 cells.

Cell Differentiation↗
PubMed1994

Identification of a ras-related protein in murine erythroleukemia cells that is a cAMP-dependent protein kinase substrate and is phosphorylated during chemically induced differentiation.

Murine erythroleukemia (MEL) cells deficient in cAMP-dependent protein kinase (A-kinase) activity are impaired in chemically induced differentiation (Pilz, R. B., Eigenthaler, M., and Boss, G. R. (1992) J. Biol. Chem. 267, 16161-16167). We identified by two-dimensional polyacrylamide gel electrophoresis two low molecular weight proteins (referred to as pp 21-1 and 21-2) that were phosphorylated when parental MEL cells, but not A-kinase-deficient MEL cells, were treated with the membrane-permeable cAMP analog 8-bromo-cAMP. We showed that pp 21-1 and 21-2: (a) were direct A-kinase substrates; (b) bound GTP; and (c) belonged to the ras superfamily of proteins. The only ras-related proteins that are clearly A-kinase substrates both in vitro and in vivo are Rap 1A and 1B while H- and K-Ras can be A-kinase substrates in vitro; we showed by immunological methods, phosphopeptide mapping, and migration on two-dimensional gels that pp 21-1 and 21-2 were not identical to one of these four proteins. We found a 3-fold increase of 32PO4 incorporation into pp 21-2 in hexamethylene bisacetamide-treated parental MEL cells which was not secondary to an increase in pp 21-2 protein but appeared secondary to increased phosphorylation of pp 21-2 by A-kinase. Thus, pp 21-1 and 21-2 are either new ras-related proteins or are previously identified ras-related proteins not known to be A-kinase substrates, and increased phosphorylation of pp 21-2 occurs during differentiation of MEL cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Impaired erythroid-specific gene expression in cAMP-dependent protein kinase-deficient murine erythroleukemia cells.

Murine erythroleukemia cells rendered deficient in cAMP-dependent protein kinase (A-kinase) activity by gene transfection are severely impaired in hexamethylene bisacetamide (HMBA)-induced differentiation (Pilz, R. B., Eigenthaler, M., and Boss, G. R. (1992) J. Biol. Chem. 267, 16161-16167). We now demonstrate that the A-kinase-deficient cells produce hemoglobin normally in response to exogenous hemin and that the heme precursor delta-aminolevulinate (delta-ALA) significantly increases HMBA-induced synthesis of heme and globin chains in these cells; these data suggest that impaired heme synthesis is at least partially responsible for the cells' deficient hemoglobin synthesis. HMBA-induced expression of the erythroid-specific delta-ALA synthetase, porphobilinogen deaminase, and beta-globin mRNAs was less in A-kinase-deficient cells than in parental cells and was reduced in proportion to the cells' residual A-kinase activity; relative transcription rates of these genes were reduced concordantly. Impaired expression of these three erythroid-specific genes was a feature of many independently-derived A-kinase-deficient clones, and normal expression was found in transfectants with normal A-kinase activity. The A-kinase-deficient cells did not exhibit a generalized defect in gene regulation since mRNA expression and transcription rates of H- and L-ferritin, c-myc, c-myb, and several housekeeping enzymes were similar in HMBA-treated parental and A-kinase-deficient cells. Our data suggest that A-kinase may be involved in regulating genes with erythroid-specific promoters and provide further evidence for heme as a regulator of globin chain synthesis.

5-Aminolevulinate Synthetase↗
PubMed1992

Chemically induced murine erythroleukemia cell differentiation is severely impaired when cAMP-dependent protein kinase activity is repressed by transfected genes.

During chemically induced differentiation of murine erythroleukemia (MEL) cells, cAMP-dependent protein kinase activity increases, and the enzyme's isozyme pattern changes. To examine the enzyme's role during MEL cell differentiation, we stably transfected MEL cells with recombinant plasmids in which the mouse metallothionein I promoter controlled expression of either a mutant form of the type I regulatory subunit of cAMP-dependent protein kinase (RI) or the enzyme's specific peptide inhibitor (PKI); expressing either sequence rendered cells cAMP-dependent protein kinase-deficient. Chemically induced differentiation of MEL cells as assessed by beta-globin mRNA and hemoglobin accumulation was inhibited in RI mutant and PKI transfectants; adding zinc further inhibited differentiation in the transfectants but had no effect on parental MEL cells. The inhibition of differentiation correlated with the amount of RI mutant mRNA and protein in the RI mutant transfectants and with the cells' degree of cAMP-dependent protein kinase deficiency in both the RI mutant and PKI transfectants. Overexpression of wild type RI did not interfere with differentiation or enzyme activity. We conclude that cAMP-dependent protein kinase activity is important for chemically induced differentiation of MEL cells and that the down-regulation of RI protein which occurs during MEL cell differentiation is not essential for differentiation to proceed.

Acetamides↗
PubMed1992

Studies on cytosolic guanylate cyclase from human placenta.

We have purified the soluble form of guanylate cyclase from human placenta greater than 2400-fold. The enzyme shared several characteristics with the enzyme purified from other sources including molecular mass and subunit composition, activation by divalent cations, inhibition by ATP and Michaelis constants. The enzyme, however, had a lower absorption maximum in the Soret region (417 +/- 1 nm) than the enzyme from other sources and was activated only one-fifth as much by nitric oxide as the bovine lung enzyme. It appears that the heme prosthetic group in the human placental enzyme may be hexa-coordinate and in the bovine lung enzyme the heme group may be penta-coordinate.

Cations, Divalent↗
PubMed1990

Molecular and genetic characterization of an ornithine decarboxylase-deficient Chinese hamster cell line.

The ornithine decarboxylase (ODC)-deficient Chinese hamster ovary (CHO) cell line C55.7 has normal amounts of ODC mRNA with very low amounts of immunologically detectable ODC protein, suggesting a structural mutation; however, 5-azacytidine treatment leads to phenotypical reversion (Steglich, C., and Scheffler, I. E. (1985) Somat. Cell Mol. Genet. 11, 11-23). We have demonstrated by chemical cleavage a single base mismatch in DNA heteroduplexes composed of wild-type and mutant cDNA strands. DNA sequencing showed that the mutant phenotype results from an aspartate-glycine substitution at amino acid 381 of the protein. When 5-azacytidine-revertant cell lines were selected for resistance to alpha-difluoromethylornithine, the resulting amplified ODC gene was structurally indistinguishable from the wild type gene. These results suggested the existence of a single active ODC locus in CHO cells. Using the methylation-sensitive restriction endonucleases AvaI and HpaII, we found evidence for two differentially methylated alleles in wild type, ODC-deficient and alpha-difluoromethylornithine-resistant cells. One of the alleles appeared completely inactivated by hypermethylation but could be reactivated by demethylation in spontaneous or 5-azacytidine-induced revertants.

Animals↗
PubMed1987

Induction of HL-60 differentiation by starvation for a single essential amino acid but not by protein synthesis inhibitors.

Starvation for a single essential amino acid induced differentiation of the human promyelocytic leukemia line HL-60 into morphologically and functionally mature granulocytes. Differentiation occurred when protein synthesis was inhibited up to 90% but was not simply secondary to growth arrest or protein synthesis inhibition, because neither glucose starvation nor treatment with protein synthesis inhibitors induced differentiation. Induction of differentiation by an aminoacyl tRNA synthetase inhibitor and the effect of cycloheximide and puromycin on amino acid-starved cells suggested an important regulatory role of tRNA molecules during differentiation.

Amino Acids, Essential↗
PubMed1987

Adenosine dialdehyde and nitrous oxide induce HL-60 differentiation.

Adenosine dialdehyde and nitrous oxide, specific S-adeno-sylhomocysteine hydrolase and methionine synthetase inhibitors, respectively, induced differentiation of the human promyelocytic cell line HL-60. Their effect did not appear to be mediated through changes in transmethylation or decreased S-adenosylmethionine synthesis because (1) there was little correlation between the concentrations of adenosine dialdehyde that induced differentiation and those that changed the ratio of the intracellular concentrations of S-adenosylmethionine to S-adenosylhomocysteine, and (2) inhibition of methionine adenosyltransferase by cycloleucine did not induce differentiation. The differentiation induced by adenosine dialdehyde was prevented by homocysteine and that by nitrous oxide was inversely related to the medium methionine concentration. This suggested that differentiation was secondary to decreased methionine synthesis.

Adenosine↗
PubMed1985

Phosphoribosylpyrophosphate synthesis from glucose decreases during amino acid starvation of human lymphoblasts.

When cultured human lymphoblasts are starved 3 h for an essential amino acid, rates of purine nucleotide synthesis decrease markedly because of a decrease in the intracellular phosphoribosylpyrophosphate concentration (Boss, G.R., and Erbe, R.W. (1982) J. Biol. Chem. 257, 4242-4247; Boss, G. R. (1984) J. Biol. Chem. 259, 2936-2941). In amino acid-starved cells, glucose transport was not changed, whereas total glucose consumption and lactate production decreased by approximately 25 and 10%, respectively. Carbon flow through the oxidative pentose phosphate pathway, measured by 14CO2 release from [1-14C]glucose, decreased by 18% during amino acid starvation. However, kinetic studies of ribulose-5-phosphate 3-epimerase and phosphoriboisomerase suggested that the ribulose 5-phosphate produced by this pathway is converted mostly to xylulose 5-phosphate instead of to ribose 5-phosphate so that this pathway produces little phosphoribosylpyrophosphate. The activity of the nonoxidative pentose phosphate pathway, measured by high performance liquid chromatography following the incorporation of [1-14C]glucose into phosphoribosylpyrophosphate, ATP, and GTP, decreased by approximately 55% during amino acid starvation. None of the enzymes of either pathway changed in specific activity during amino acid starvation. We conclude that the nonoxidative pentose phosphate pathway is the major source of phosphoribosylpyrophosphate for purine nucleotide synthesis and that this pathway is regulated by a metabolite which changes in concentration during amino acid starvation.

Aldose-Ketose Isomerases↗
PubMed1984

The influence of ribose 5-phosphate availability on purine synthesis of cultured human lymphoblasts and mitogen-stimulated lymphocytes.

The intracellular ribose 5-phosphate concentration was found to be an important determinant of rates of de novo purine synthesis. When ribose 5-phosphate production was reduced in cultured human lymphoblasts by glucose starvation, the intracellular phosphoribosylpyrophosphate concentration and rates of de novo purine synthesis decreased. Inosinate-guanylate:pyrophosphate phosphoribosyltransferase (HPR transferase)-deficient cells were relatively more resistant to glucose starvation. To minimize the effect of purine nucleotide feedback inhibition on the de novo pathway, cells were treated with inhibitors of IMP dehydrogenase and adenylosuccinate synthetase. In normal lymphoblasts, purine synthesis was stimulated only at glucose concentrations greater than 100 microM while in HPR transferase-deficient lymphoblasts, stimulation occurred even in the absence of glucose. The differences between the normal and HPR transferase-deficient cells were lost when ribose reutilization from endogenous nucleotide breakdown was impaired in the HPR transferase-deficient cells by incubation with 2'-deoxyinosine. Endogenous ribose reutilization for purine synthesis is, therefore, important when either glucose availability is limited or synthesis is stimulated. In the absence of glucose, exogenous purine nucleotides restored the intracellular concentrations of ribose 5-phosphate, phosphoribosylpyrophosphate, and purine nucleotides to almost 100% and rates of purine synthesis to 50-75% of those at 10 mM glucose. When ribose 5-phosphate production was increased in peripheral blood lymphocytes by phytohemagglutinin activation, the intracellular phosphoribosylpyrophosphate concentration and rates of de novo purine synthesis increased.

Cell Line↗
PubMed1984

Decreased methionine synthesis in purine nucleoside-treated T and B lymphoblasts and reversal by homocysteine.

Purine nucleosides, which accumulate in adenosine deaminase and purine nucleoside phosphorylase deficiency, are toxic to lymphoid cells. Since adenine nucleosides inhibit S-adenosylhomocysteine hydrolase, they could potentially decrease intracellular methionine synthesis. To test this hypothesis, we measured methionine synthesis by the use of [14C]formate as a radioactive precursor in cultured human T and B lymphoblasts treated with varying concentrations of purine nucleosides; 2'-deoxycoformycin and 8-aminoguanosine were added to inhibit adenosine deaminase and purine nucleoside phosphorylase, respectively. In the T lymphoblasts methionine synthesis was inhibited approximately 50% by 10 microM of 2'-deoxyadenosine, adenine arabinoside, or 2'-deoxyguanosine. By contrast, in the B lymphoblasts methionine synthesis was considerably less affected by these nucleosides, with 50% inhibition occurring at 100 microM of 2'-deoxyadenosine and adenine arabinoside; 100 microM of 2'-deoxyguanosine yielded less than 10% inhibition. Adenosine and guanosine were considerably less potent inhibitors of methionine synthesis in both the T and B lymphoblasts. An adenosine deaminase-deficient and a purine nucleoside phosphorylase-deficient cell line, both of B cell origin, exhibited sensitivities to the nucleosides similar to those of the normal B cell lines. In both the T and B cell lines homocysteine reversed the methionine synthesis inhibition induced by the adenine nucleosides and guanosine and largely reversed that induced by 2'-deoxyguanosine. Methionine synthesis from homocysteine generates free tetrahydrofolate from 5-methyltetrahydrofolate, the main intracellular storage form of folate. We conclude that purine nucleoside toxicity may be partly mediated through (a) decreased intracellular methionine synthesis, and (b) altered folate metabolism.

Adenosine↗