The subcellular distribution of the nonspecific lipid transfer protein (sterol carrier protein 2) in rat liver and adrenal gland

Amerongen, A. van; Noort, Marjolein van; Beckhoven, J.R.C.M. van; Rommerts, F. F. G.; Orly, Joseph; Wirtz, K.W.A.

doi:10.1016/0005-2760(89)90106-9

Cited by 65 publications

(34 citation statements)

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“…Since SCP-2 proteins are located in peroxisomes as well as in endoplasmic reticulum and cytosol (22,(27)(28)(29), we speculate here that the SCP-2 gene could have important regulatory functions on VLDL production. Specifically, we postulate that hepatic SCP-2 gene products inhibit VLDL production by preferentially channeling phospholipids and sterols to the canalicular pole rather than to the sinusoidal domain of the hepatocyte.…”

mentioning

confidence: 90%

Hepatic overexpression of sterol carrier protein-2 inhibits VLDL production and reciprocally enhances biliary lipid secretion

Amigo

Zanlungo

Miquel

et al. 2003

Journal of Lipid Research

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We examined in vivo a role for sterol carrier protein-2 (SCP-2) in the regulation of lipid secretion across the hepatic sinusoidal and canalicular membranes. Recombinant adenovirus Ad.rSCP2 was used to overexpress SCP-2 in livers of mice. We determined plasma, hepatic, and biliary lipid concentrations; hepatic fatty acid (FA) and cholesterol synthesis; hepatic and biliary phosphatidylcholine (PC) molecular species; and VLDL triglyceride production. In Ad.rSCP2 mice, there was marked inhibition of hepatic fatty acids and cholesterol synthesis to Ͻ 62% of control mice. Hepatic triglyceride contents were decreased, while cholesterol and phospholipids concentrations were elevated in Ad.rSCP2 mice. Hepatic VLDL triglyceride production fell in Ad.rSCP2 mice to 39% of control values. As expected, biliary cholesterol, phospholipids, bile acids outputs, and biliary PC hydrophobic index were significantly increased in Ad.rSCP2 mice. These studies indicate that SCP-2 overexpression in the liver markedly inhibits lipid synthesis as well as VLDL production, and alters hepatic lipid contents. In contrast, SCP-2 increased biliary lipid secretion and the proportion of hydrophobic PC molecular species in bile. These effects suggest a key regulatory role for SCP-2 in hepatic lipid metabolism and the existence of a reciprocal relationship between the fluxes of lipids across the sinusoidal and canalicular membranes. Hepatic fatty acid (FA), triglyceride, and cholesterol metabolism are highly regulated processes determined by the concerted feedback regulation of genes governing their synthesis, lipoprotein uptake and production, and biliary lipid secretion (1-7). Regulation of FA and cholesterol synthesis are highly interrelated processes and share common transcription regulatory factors (8, 9). Even though the physiological role(s) for sterol carrier protein-2 (SCP-2) gene products remain elusive, several studies suggest a number of important transport and catalytic functions of these proteins in the regulation of lipid metabolism (10-14).SCP-2 gene products not only bind cholesterol, FA, FAacyl-CoA, and phospholipids, but also enhance trafficking of these lipids within cells (15)(16)(17)(18). Experiments in cultured cell systems transfected with cDNAs encoding for the SCP-2/sterol carrier protein X (SCP-X) products demonstrated the role of these proteins in microsomal membrane utilization of FA for phospholipids, triglyceride, and cholesterol ester synthesis (19)(20)(21)(22). Overexpression of SCP-2 in rat hepatoma cells enhanced intracellular cholesterol cycling, increased plasma membrane cholesterol content, and inhibited cholesterol esterification and HDL production (23). In addition, studies in mice with disruption of the SCP-2/SCP-X gene have shown a failure in the oxidation of 2-methyl-branched FA and the side chain of cholesterol. Furthermore, liver triglyceride and cholesterol ester concentrations significantly decreased in these SCP-2-knockout mice, suggesting that these animals have altered phospholipid, fatty ac...

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mentioning

confidence: 90%

Hepatic overexpression of sterol carrier protein-2 inhibits VLDL production and reciprocally enhances biliary lipid secretion

Amigo

Zanlungo

Miquel

et al. 2003

Journal of Lipid Research

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“…Purification of pre-nsL-TP was followed by SDS-PAGE, hnmunoblotting was carried out on gradient gels (7,5-25% acrylamid¢) [20]. Protein concentration was determined by a microtiter-plate version of the Lowry method [33],…”

Section: 4 Purification Of Prensl-tpmentioning

confidence: 99%

The precursor form of the rat liver non‐specific lipid‐transfer protein, expressed in Escherichia coli, has lipid transfer activity

1992

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The cDNA encoding the precursor form of non-specific lipid-transfer protein (pre-nsL-TP) from rat liver was cloned into the expression vector pET3d. The resulting plasmid was transformed to the Esrherichia colt strain BL21(DE3). After induction of the bacteria with isopropyl./5'-Dthiogalactopyranoside (IPTG) pre-nsL-TP was purified from the bacterial lysat¢ by anion exchange chromatosraphy followed by 8elliltration. From 1 I of culture, 6-7 nag of pre-nsL-TP was obtained, equal to approximately 7% of the cytoplasmic protein. By use of a fluorescence lipid transfer assay, prc.nsL-TP was found to have lipid transfer activity identical to mature nsL-TP.Non-specific lipid-transfer protein; Sterol carrier prolein-2l Lipid transfer; Bacterial expression; Rat liver

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“…However, PXP-18 is probably mainly to be found in the peroxisomal matrix, because it was almost all in the peroxisomal fraction; its nonspecific lipid-transfer activity was undetectable without disruption of the organelle; and it was not an integral membrane protein, according to the criterion of Fujiki et al [35]. Rat liver nsLTP was immunocytologically located mainly in the matrix of peroxisomes [13, 141, although the location of this protein in rat hepatocytes is still controversial [36] and the nature of a cross-reactive 58-kDa protein 1371 is not known. In addition, the largest concentration of castor bean nsLTP was found to be in the matrix of germinated seed glyoxysomes (M. Yamada, personal communication).…”

Section: Possible Role Of Pxp-18mentioning

confidence: 99%

A novel peroxisomal nonspecific lipid‐transfer protein from Candida tropicalis

Tan

Okazaki

Kubota

et al. 1990

European Journal of Biochemistry

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We have sequenced the nucleotides of the gene POX18 that encodes PXP-18, a major peroxisomal polypeptide inducible by oleic acid in the yeast Candida tropicalis. POX18 had a single open reading frame of 127 amino acids. Some 33% of the amino acid sequence of the predicted basic polypeptide (13805 Da), was identical to that of the nonspecific lipid-transfer protein (sterol carrier protein 2) from rat liver. PXP-18, purified to near homogeneity from isolated peroxisomes, had an amino-terminal sequence identical to that of the predicted polypeptide except for the initiator methionine, and had nonspecific lipid-transfer activity comparable to that of its mammalian equivalents. Unexpectedly, PXP-18 lacked the cysteine residue thought to be essential for the activity of this protein in mammals. RNA blot analysis showed that the POX18 gene was expressed exclusively in cells grown on oleic acid, suggesting that PXP-18 has a role in the /I-oxidation of long-chain fatty acids. PXP-18 modulated acylcoenzyme A oxidase activity at low pH.Peroxisomal proteins are synthesized on free polysomes and imported post-translationally into the organelle, but most of them have no cleavable targeting (topogenic) sequence at the amino-terminus (for review, see [l]). The targeting sequences of five peroxisomal proteins from higher eucaryotes have been found at the carboxy-terminus and shown to contain a tripeptide, Ser-Lys/His-Leu, at or near the end of the sequence [2 -41. We have cloned genes encoding peroxisomal proteins of the yeast Candida tropicalis [5] and sequenced three genes for the subunits (PXP-2, PXP-4 and PXP-5) of acylCoA oxidase isozymes [6, 71 and the gene for catalase (PXP-9) [8]. None of the polypeptides encoded by these genes has the Ser-Lys/His-Leu sequence in their carboxy-terminal regions. The targeting information of PXP-4, which has a molecular mass of 78554 Da, was found in various locations by both in vitro [9] and in vivo [lo] experiments. Thus, the entire protein molecule must be systematically analysed if the yeast peroxisomal targeting sequence is to be identified. Since a small protein is more convenient for this purpose, we chose a 16-kDa protein, PXP-18, which is encoded by the gene POX18 and induced markedly by oleic acid [5]. Its function is not known.

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The subcellular distribution of the nonspecific lipid transfer protein (sterol carrier protein 2) in rat liver and adrenal gland

Cited by 65 publications

References 34 publications

Hepatic overexpression of sterol carrier protein-2 inhibits VLDL production and reciprocally enhances biliary lipid secretion

Hepatic overexpression of sterol carrier protein-2 inhibits VLDL production and reciprocally enhances biliary lipid secretion

The precursor form of the rat liver non‐specific lipid‐transfer protein, expressed in Escherichia coli, has lipid transfer activity

A novel peroxisomal nonspecific lipid‐transfer protein from Candida tropicalis

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