Effect of lipid composition on rat liver nuclear membrane fluidity

Albi, Elisabetta; Tomassoni, Maria Letizia; Viola-Magni, Mariapia

doi:10.1002/(sici)1099-0844(199709)15:3<181::aid-cbf737>3.0.co;2-6

Cited by 22 publications

(18 citation statements)

References 70 publications

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“…This in turn modulates the ratio of saturated to unsaturated fatty acids in the cell membrane. This ratio is a key regulator of cell membrane fluidity and structural integrity (3,42). Alteration in the unsaturated fatty acid content in the membrane caused by changes in the SCD enzyme activity has been shown to control membrane fluidity (43).…”

Section: Discussionmentioning

confidence: 99%

Transforming Growth Factor-β Regulates Stearoyl Coenzyme A Desaturase Expression through a Smad Signaling Pathway

Samuel¹,

Nagineni²,

Kutty³

et al. 2002

Journal of Biological Chemistry

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The regulation of stearoyl-CoA desaturase (SCD), a rate-limiting enzyme in the synthesis of unsaturated fatty acids, is physiologically important because the ratio of saturated to unsaturated fatty acids is thought to control cellular functions by modulating the structural integrity and fluidity of cell membranes. Transforming growth factor-␤ (TGF-␤), a multifunctional cytokine, increased SCD mRNA expression in cultured human retinal pigment epithelial cells. This response was elicited by all three TGF-␤ isoforms, ␤1, ␤2, and ␤3. However, SCD mRNA expression was not increased either by other members of the TGF-␤ family or by other growth factors or cytokines. TGF-␤ also increased SCD mRNA expression in several other cell lines tested. The increase in SCD mRNA expression was preceded by a marked increase in Smad2 phosphorylation in TGF-␤-treated human retinal pigment epithelial cells. TGF-␤ did not induce SCD mRNA expression in a Smad4-deficient cell line. However, Smad4 overexpression restored the TGF-␤ effect in this cell line. Moreover, TGF-␤-induced SCD mRNA expression was effectively blocked by the overexpression of Smad7, an inhibitory Smad. Thus, a TGF-␤ signal transduction pathway involving Smad proteins appears to regulate the cellular expression of the SCD gene, and this regulation may play an important role in lipid metabolism.

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Section: Discussionmentioning

confidence: 99%

Transforming Growth Factor-β Regulates Stearoyl Coenzyme A Desaturase Expression through a Smad Signaling Pathway

Samuel¹,

Nagineni²,

Kutty³

et al. 2002

Journal of Biological Chemistry

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“…Final phospholipid concentration was determined by the Stewart method (23). Anionic liposomes were formed by egg phosphatidylcholine, egg phosphatidylglycerol, and cholesterol (8:1:1 molar ratio) to reproduce the charged lipid and cholesterol content of the nuclear membrane (24). Neutral liposomes were formed by phosphatidylcholine and cholesterol (9:1 molar ratio).…”

Section: Methodsmentioning

confidence: 99%

Electrostatic Association of Glutathione Transferase to the Nuclear Membrane

Stella¹,

Pallottini

Moreno

et al. 2007

Journal of Biological Chemistry

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The possible nuclear compartmentalization of glutathione S-transferase (GST) isoenzymes has been the subject of contradictory reports. The discovery that the dinitrosyl-diglutathionyl-iron complex binds tightly to Alpha class GSTs in rat hepatocytes and that a significant part of the bound complex is also associated with the nuclear fraction (Pedersen, J. Z., De Maria, F., Turella, P., Federici, G., Mattei, M., Fabrini, R., Dawood, K. F., Massimi, M., Caccuri, A. M., and Ricci, G. (2007) J. Biol. Chem. 282, 6364 -6371) prompted us to reconsider the nuclear localization of GSTs in these cells. Surprisingly, we found that a considerable amount of GSTs corresponding to 10% of the cytosolic pool is electrostatically associated with the outer nuclear membrane, and a similar quantity is compartmentalized inside the nucleus. Mainly Alpha class GSTs, in particular GSTA1-1, GSTA2-2, and GSTA3-3, are involved in this double modality of interaction. Confocal microscopy, immunofluorescence experiments, and molecular modeling have been used to detail the electrostatic association in hepatocytes and liposomes. A quantitative analysis of the membrane-bound Alpha GSTs suggests the existence of a multilayer assembly of these enzymes at the outer nuclear envelope that could represent an amazing novelty in cell physiology. The interception of potentially noxious compounds to prevent DNA damage could be the possible physiological role of the perinuclear and intranuclear localization of Alpha GSTs. Glutathione S-transferases (GSTs)2 are a superfamily of enzymes that protect the cell from toxic endogenous or xenobiotic compounds. Eight different gene-independent, isoenzymatic classes have been found in mammals, and two of these, Alpha and Mu classes, are abundantly expressed in rat liver, where they represent 43 and 56%, respectively, of the entire pool of cytosolic GSTs (1). Beside their catalytic competence to conjugate GSH to many toxic substances having an electrophilic center, these enzymes also display peroxidase activity and ligandin properties (2, 3). In hepatocytes, Alpha GSTs efficiently trap a natural nitric oxide carrier, the dinitrosyl-diglutathionyl-iron complex (DNDGIC), thus preventing the irreversible inhibition of glutathione reductase caused by this compound (4). Preliminary evidence was also reported that GSTs could be associated with the nuclear membrane or compartmentalized in nuclei. The presence of GSTs on intracellular membranes is not a new finding. MGST1 is a peculiar trimeric microsomal integral membrane isoenzyme discovered and characterized many years ago (5). GSTA4-4, a specific isoenzyme able to detoxify hydroxyalkenals, displays a widespread mitochondrial, peroxisomal, and cytosolic localization, but the plasma membrane also binds detectable amounts of this enzyme (6). Furthermore, the tight association of Alpha and Mu class GSTs with the microsomal membrane fraction of rat liver was demonstrated by Morgenstern et al. (7), and about 2% of the cytosolic GSTA1-1 has been found in the microsomal membrane...

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“…The possibility that PC can be transported by speci¢c protein inside the nucleus cannot be excluded, as well as that other minor pathways may be used for its synthesis. The complex of base exchanges has been detected in nucleus [11]. It has been shown that the content of PC may change inside the nucleus in many physiological situations, suggesting some rapid mechanisms with respect to the transport from the cytoplasm.…”

Section: Discussionmentioning

confidence: 99%

“…The nuclear pellet still contains some rRNA which completely disappears after two washings in Barnes et al solution [20]. The nuclei were checked for possible cytoplasmic contamination also by evaluating the activity of a microsomal marker (NADH-cytochrome c-reductase) [11]. The swelling of nuclei and chromatin extraction were performed according to the method of Shaw and Huang [22], modi¢ed by Viola Magni et al [19].…”

Section: Methodsmentioning

confidence: 99%

“…In fact, in several cell types (HepG2, NIH-3T3, and L-cells) the CTP:phosphocholine cytidyltransferase is associated with the nuclear envelope [9]; in CHO cells and hepatocytes the activity of this enzyme was recovered in the nuclear fraction, for 76% and 32%, respectively, [10]. In rat hepatocyte nuclei and isolated nuclear membranes, the choline base exchange activity was also demonstrated [11]. Until now no evidence is available on PC synthesis at the level of chromatin.…”

Section: Introductionmentioning

confidence: 99%

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Reverse sphingomyelin‐synthase in rat liver chromatin

Albi¹,

Lazzarini²,

Magni³

2003

FEBS Letters

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The chromatin phospholipid fraction is enriched in sphingomyelin content which changes during cell maturation and proliferation. Recently, we have demonstrated that the sphingomyelin variations can be due to chromatin neutral sphingomyelinase and sphingomyelin-synthase activities which di¡er in pH and K m optima from those present in nuclear membranes. The sphingomyelin can be used also as a source of phosphorylcholine for phosphatidylcholine synthesis by reverse sphingomyelin-synthase. In the present work we have studied the possible existence of reverse sphingomyelin-synthase activity in nuclear membrane and chromatin. A very low activity was detected in the homogenate, cytosol and nuclear membrane (0.93 þ 0.14, 2.61 þ 0.33 and 0.87 þ 0.13 pmol/mg protein/min, respectively), whereas the activity present in chromatin was 37.09 þ 2.05 pmol/mg protein/min. The reverse sphingomyelinsynthase decreases the intranuclear diacylglycerol pool and increases the intranuclear ceramide pool, whereas sphingomyelinsynthase has an opposite e¡ect. The possible correlation between these enzymes is discussed. ß

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Effect of lipid composition on rat liver nuclear membrane fluidity

Cited by 22 publications

References 70 publications

Transforming Growth Factor-β Regulates Stearoyl Coenzyme A Desaturase Expression through a Smad Signaling Pathway

Transforming Growth Factor-β Regulates Stearoyl Coenzyme A Desaturase Expression through a Smad Signaling Pathway

Electrostatic Association of Glutathione Transferase to the Nuclear Membrane

Reverse sphingomyelin‐synthase in rat liver chromatin

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