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J Ericsson

Publications and source records attributed to J Ericsson.

At least 19 recordsLinked to original sources
PubMed1997

Identification of glycerol-3-phosphate acyltransferase as an adipocyte determination and differentiation factor 1- and sterol regulatory element-binding protein-responsive gene.

We demonstrate that the mRNA levels of glycerol-3-phosphate acyltransferase (GPAT), a mitochondrial enzyme catalyzing the initial step in glycerolipid synthesis, are induced during the differentiation of 3T3-L1 preadipocytes to adipocytes and following ectopic expression of rat adipocyte determination and differentiation factor 1 (ADD1), a protein with high homology to the human sterol regulatory element-binding protein-1 (SREBP-1). The increase in GPAT mRNA levels that occurs during differentiation is partially prevented by ectopic expression of a dominant negative form of ADD1. Nucleotide sequences corresponding to the proximal promoter of the murine mitochondrial GPAT gene (Jerkins, A. A., Liu, W. R., Lee, S., and Sul, H. S. (1995) J. Biol. Chem. 270, 1416-1421) bound SREBP-1a and NF-Y in electromobility shift assays. In addition, GPAT promoter-luciferase reporter genes were stimulated by co-expression of SREBP-1a. This increase was attenuated when either a dominant negative form of NF-Y was co-transfected into the cells or when the GPAT promoter contained mutations in the putative binding sites for SREBP-1a or NF-Y. These studies demonstrate that the regulated expression of the mitochondrial GPAT gene requires both NF-Y and ADD1/SREBPs. Thus, SREBPs/ADD1 regulate not only genes involved in cholesterol homeostasis and fatty acid synthesis but also a key enzyme in glycerolipid synthesis.

Adipocytes↗
PubMed1997

Administration of G-CSF to healthy subjects: the effects on eosinophil counts and mobilization of eosinophil granule proteins.

Any influence of G-CSF on eosinophils is mostly negative, although reports which have studied this relationship are few with varied results. The aim of this study was to investigate the influence of G-CSF administration to healthy subjects on eosinophils in peripheral blood. Blood eosinophil counts, serum levels of eosinophil cationic protein (ECP), eosinophil peroxidase (EPO) and eosinophil protein X (EPX), as well as cell morphology were studied. 14 healthy volunteers received 7.5 microg (n = 8) or 10 microg/kg body weight (n = 6) G-CSF daily for six consecutive days. ECP and EPX were assessed by specific RIAs and EPO by a specific FEIA. Cell morphology was examined by electron microscopy. During G-CSF administration, eosinophil counts increased from 0.22 +/- 0.04 x 10(9)/l to 0.61 +/- 0.098 x 10(9)/l (P = 0.001), serum ECP from 12.39 +/- 2.45 microg/l to 61.82 +/- 7.38 microg/l (P = 0.0014), serum EPX from 28.05 +/- 4.54 microg/l to 87.86 +/- 9.84 microg/l (P = 0.002) and serum EPO from 8.89 +/- 2.2 microg/l to 19.98 +/- 5.1 microg/l (P = 0.003). All variables returned gradually to initial values after discontinuation of G-CSF. Distinct changes in the morphology of secondary granules were observed 24 h after G-CSF administration. The granules became irregular and their matrix less electron dense. We conclude that administration of G-CSF to healthy humans increases the number of circulating eosinophils and affects the mobilization of eosinophil granule proteins.

Adult↗
PubMed1996

Synergistic binding of sterol regulatory element-binding protein and NF-Y to the farnesyl diphosphate synthase promoter is critical for sterol-regulated expression of the gene.

Sterol-regulated transcription of the farnesyl diphosphate (FPP) synthase gene is dependent on two cis elements in the proximal promoter. These elements, an inverted CCAAT box and sterol regulatory element 3 (SRE-3), bind NF-Y and sterol regulatory element-binding protein 1 (SREBP-1), respectively. We now demonstrate that the binding of recombinant SREBP-1 to its cognate site (SRE-3) within the FPP synthase promoter in vitro is enhanced by binding of NF-Y to the upstream inverted CCAAT box. Using an FPP synthase promoter fragment containing the binding sites for both NF-Y and SREBP-1 in gel mobility shift assays, we demonstrate that the addition of NF-Y increases the binding of SREBP-1 to SRE-3 over 20-fold. In contrast, NF-Y does not stimulate the binding of SREBP-1 to SRE-3 when the inverted CCAAT box is either mutated or 4 base pairs (bp) are inserted between the inverted CCAAT box and SRE-3. Promoter-reporter genes, containing either the wild-type FPP synthase promoter sequence or containing the 4-bp insertion between the inverted CCAAT box and SRE-3, were transiently transfected into cells. The activity of the wild-type promoter-reporter gene increased when the cells were either incubated in sterol-depleted medium or were co-transfected with an expression vector encoding transcriptionally active SREBP-1. This increase in activity was attenuated when the promoter contained the 4-bp insert, consistent with defective binding of SREBP to the promoter in vivo. These studies suggest that the binding of SREBP-1 to SRE-3 in the FPP synthase promoter, and subsequent stimulation of transcription, is dependent on synergistic binding and a functional interaction between SREBP-1 and NF-Y.

Alkyl and Aryl Transferases↗
PubMed1996

Sterol regulatory element binding protein binds to a cis element in the promoter of the farnesyl diphosphate synthase gene.

Sterol-regulated transcription of the gene for rat farnesyl diphosphate (FPP) synthase (geranyl-diphosphate:isopentenyl-diphosphate geranyltranstransferase, EC 2.5.1.10) is dependent in part on the binding of the ubiquitous transcription factor NF-Y to a 6-bp element within the proximal promoter. Current studies identify a second element in this promoter that is also required for sterol-regulated transcription in vivo. Mutation of three nucleotides (CAC) within this element blocks the 8-fold induction of FPP synthase promoter-reporter genes that normally occurs when the transfected cells are incubated in medium deprived of sterols. Gel mobility-shift assays demonstrate that the transcriptionally active 68-kDa fragment of the sterol regulatory element (SRE-1)-binding protein assays (SREBP-1) binds to an oligonucleotide containing the wild-type sequence but not to an oligonucleotide in which the CAC has been mutated. DNase 1 protection pattern (footprint) analysis indicates that SREBP-1 binds to nucleotides that include the CAC. Both the in vivo and in vitro assays are affected by mutagenesis of nucleotides adjacent to the CAC. Coexpression of SREBP with a wild-type FPP synthase promoter-reporter gene in CV-1 cells results in very high levels of reporter activity that is sterol-independent. In contrast, the reporter activity remained low when the promoter contained a mutation in the CAC trinucleotide. We conclude that sterol-regulated transcription of FPP synthase is controlled in part by the interaction of SREBP with a binding site that we have termed SRE-3. Identification of this element may prove useful in the identification of other genes that are both regulated by SREBP and involved in lipid biosynthesis.

Alkyl and Aryl Transferases↗
PubMed1996

Role for sterol regulatory element binding protein in the regulation of farnesyl diphosphate synthase and in the control of cellular levels of cholesterol and triglyceride: evidence from sterol regulation-defective cells.

In order to define the factors involved in the regulation of farnesyl diphosphate (FPP) synthase, we used sterol regulation-defective (SRD) cell lines that constitutively express either high (SRD-2) or low (SRD-6) levels of transcriptionally active sterol regulatory element binding protein (SREBP). FPP synthase mRNA levels were high in SRD-2 cells and low in SRD-6 cells and were unaffected by the addition or removal of sterols from the media. In contrast, the mRNA levels in parental CHO-7 cells were regulated by sterols. SRD-2, SRD-6, and CHO-7 cells were also transiently transfected with plasmids containing FPP synthase promoter-reporter genes. Reporter gene activity was significantly higher in SRD-2 cells than in either SRD-6 or CHO-7 cells, consistent with a higher rate of transcription of the reporter gene in SRD-2 cells. The high expression of the reporter gene in SRD-2 cells was not observed when the FPP synthase promoter contained a three base pair mutation within an SREBP binding site, termed sterol regulatory element-3 (SRE-3). These observations are consistent with the hypothesis that high levels of transcription of the FPP synthase gene are dependent on the availability of transcriptionally active SREBP. We also demonstrate that the incorporation of radioactive acetate into both cholesterol and fatty acids was enhanced in SRD-2 cells as compared to CHO-7 or SRD-6 cells. Finally, we demonstrate that the concentrations of cholesterol, cholesteryl ester, and triglyceride were all significantly elevated in SRD-2 cells. We conclude that SREBP is involved not only in the regulation of FPP synthase and cholesterogenesis but also in fatty acid and triglyceride synthesis.

Acetates↗
PubMed1995

NF-Y has a novel role in sterol-dependent transcription of two cholesterogenic genes.

The transcription of farnesyl diphosphate (FPP) synthase is regulated up to 30-fold by the sterol status of the cell. Point mutations in a 6-base pair ATTGGC sequence in the promoter disrupt both sterol-dependent transcription in vivo as well as binding of the transcription factor NF-Y in vitro. Co-transfection of cells with NF-YA29, a dominant negative form of NF-Y, and various promoter-reporter genes specifically inhibits the sterol-dependent regulation of FPP synthase and 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) synthase. In contrast, NF-YA29 does not affect the regulation of reporter genes under the control of promoters derived from either the HMG-CoA reductase or the low density lipoprotein receptor gene. Transient expression of the 68-kDa transcriptionally active fragment of sterol regulatory element-binding protein in cells stimulates an HMG-CoA synthase-reporter gene over 90-fold. This induction is blocked in cells co-expressing NF-YA29. We hypothesize that NF-Y plays a novel role in sterol-dependent regulation of two key genes in the cholesterol biosynthetic pathway and that this role requires a specific interaction with the sterol regulatory element-binding protein or related transcription factors.

Alkyl and Aryl Transferases↗
PubMed1995

Digestive organs.

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Adolescent↗
PubMed1995

Urinary tract.

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Adolescent↗
PubMed1994

Effect of squalestatin 1 on the biosynthesis of the mevalonate pathway lipids.

The effects of squalestatin 1 on rat brain and liver homogenates and on Chinese hamster ovary tissue culture cells have been investigated. This compound effectively inhibits squalene biosynthesis in a highly selective manner. Cytoplasmic farnesyl pyrophosphate and geranylgeranyl pyrophosphate synthases are not affected, which is also the case for microsomal cis-prenyltransferase. In tissue culture cells, squalestatin 1 inhibits cholesterol biosynthesis completely, but does not alter dolichol synthesis or protein isoprenylation to a great extent. Incorporation of [3H]mevalonate into ubiquinone-9 and -10 increases 3-4-fold, probably as a result of increased synthesis of this lipid. Squalestatin 1 appears not only to be an effective inhibitor of cholesterol biosynthesis, but also to be more specific than other inhibitors used earlier in various in vitro and in vivo systems.

Animals↗
PubMed1994

Age-dependent changes in rat liver prenyltransferases.

Mevalonate pathway lipids including cholesterol, ubiquinone and dolichol, are of great importance for cellular function. Many of the enzymes of this pathway are thus strictly regulated. During development of the rat, the cellular levels of certain of these lipids vary. Prenyltransferases have been investigated and it is reported here that farnesyl pyrophosphate synthase activity in rat liver cytosol decreases after birth to a lower, steady level. This decrease is not paralleled by the level of synthase protein, which shows two maxima, one immediately after birth and the other 30 days later. cis-Prenyltransferase activity is low after birth, increases continuously up to day-54 and then decreases to a low level which was maintained throughout the remainder of the study (365 days). Squalene synthase exhibits high activity after birth, but decreases during the first 100 days thereafter, and subsequently remains at the low level thus reached. In contrast to these changes in the activities of the prenyltransferases, the level of cholesterol is constant and the dolichol concentration increases continuously throughout the entire period studied.

Aging↗
PubMed1994

Identification of a 6-base pair element involved in the sterol-mediated transcriptional regulation of farnesyl diphosphate synthase.

Previous studies identified a 115-base pair (bp) region of the farnesyl diphosphate (FPP) synthase promoter which is involved in the transcriptional regulation of this gene by sterols (Spear, D. H., Kutsunai, S. Y., Correll, C. C., and Edwards, P. A. (1992) J. Biol. Chem. 267, 14462-14469). In the current study we fused a 117-bp fragment, containing this region of interest, upstream of the heterologous minimal promoter of the herpes simplex virus thymidine kinase gene linked to the chloramphenicol acetyltransferase (CAT) reporter gene. Chinese hamster ovary (CHO) cells were stably transfected with this fusion gene and incubated in the absence or presence of sterols. Analysis of CAT mRNA by primer extension indicated that transcription of the fusion gene was under sterol-mediated control. Thus, when cellular sterols were present, the CAT mRNA levels were reduced 2-4-fold. To further localize the FPP synthase sterol-responsive element(s), additional promoter-reporter gene constructs containing either deletions or mutations were constructed and transfected into CHO or CV-1 cells. These studies localized a 6-bp region (ATTGGC) that is required for both transcriptional induction in the absence of sterols and transcriptional repression in the presence of sterols. Gel shift and footprinting analyses demonstrated that nuclear proteins isolated from CHO cells bound to six distinct regions of the promoter between nucleotides -293 to -47. Taken together, these results further define both the cis-acting elements controlling normal transcription of the FPP synthase gene and identify a novel sequence involved in sterol regulation.

Alkyl and Aryl Transferases↗
PubMed1994

Modulations in hepatic branch-point enzymes involved in isoprenoid biosynthesis upon dietary and drug treatments of rats.

Three branch-point enzymes of the mevalonate pathway, farnesyl pyrophosphate synthase, cis-prenyltransferase and squalene synthase were characterized in rat hepatic cytosol, microsomes and peroxisomes isolated from rats after treatment with peroxisome proliferators, inducers of the endoplasmic reticulum or modulators of lipid metabolism. Cholestyramine and phenobarbital induced primarily the cytosolic farnesyl pyrophosphate synthase, whereas clofibrate and phthalates elevated the corresponding peroxisomal activity. cis-Prenyltransferase activities in microsomes were induced 4-5-fold after clofibrate, phthalate and phenobarbital administration, but these same treatments affected the peroxisomal activity to only a limited extent. Squalene synthase activity in microsomes was completely abolished, but the peroxisomal activity was unaffected after administration of cholesterol. On the other hand, clofibrate and phthalate induced only the microsomal activities. Mevinolin treatment greatly increased peroxisomal and cytosolic farnesyl pyrophosphate synthase activities, but not the mitochondrial activity, and the cis-prenyltransferase activities were elevated in peroxisomes, but not in microsomes. These results demonstrate that the branch-point enzymes in cholesterol and dolichol biosynthesis at various cellular locations are regulated differentially and that the capacities of peroxisomes and the endoplasmic reticulum to participate in the synthesis of polyisoprenoid lipids is affected profoundly by treatment with different xenobiotics.

Animals↗
PubMed1994

Farnesyl-diphosphate synthase is localized in peroxisomes.

In this study, we have investigated the subcellular localization of farnesyl-diphosphate synthase (FPP synthase). FPP synthase produces FPP, which is utilized in the synthesis of squalene, cholesterol, farnesylated and geranylgeranylated proteins, dolichols, coenzyme Q, and the isoprenoid moiety of heme a. This enzyme is found in the 100,000 x g supernatant fraction of cells or tissues and has been considered to be a cytoplasmic protein. In this study, analysis of FPP synthase activity and protein in fractionated rat liver together with immunofluorescent and immunoelectron microscopy studies demonstrated unequivocally that FPP synthase is largely localized in peroxisomes. These data, in combination with the previous observation that mevalonate kinase is predominantly localized in peroxisomes, suggest that peroxisomes are the major site of synthesis of FPP from mevalonate. We also demonstrate that in liver tissue obtained from patients with peroxisomal deficiency diseases (Zellweger syndrome and neonatal adrenoleukodystrophy), the activities of five enzymes involved in isoprenoid synthesis, namely mevalonate kinase, phosphomevalonate kinase, mevalonate-diphosphate decarboxylase, isopentenyl-diphosphate isomerase, and FPP synthase, are significantly reduced, consistent with a peroxisomal localization of these enzymes.

Adrenoleukodystrophy↗