1
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Morvay PL, Baes M, Van Veldhoven PP. Differential activities of peroxisomes along the mouse intestinal epithelium. Cell Biochem Funct 2017; 35:144-155. [PMID: 28370438 DOI: 10.1002/cbf.3255] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 01/10/2017] [Accepted: 01/26/2017] [Indexed: 02/01/2023]
Abstract
The presence of peroxisomes in mammalian intestine has been revealed formerly by catalase staining combined with electron microscopy. Despite the central role of intestine in lipid uptake and the established importance of peroxisomes in different lipid-related pathways, few data are available on the physiological role of peroxisomes in intestinal metabolism, more specifically, α-, β-oxidation, and etherlipid synthesis. Hence, the peroxisomal compartment was analyzed in more detail in mouse intestine. On the basis of immunohistochemistry, the organelles are mainly confined to the epithelial cells. The expression of the classical peroxisome marker catalase was highest in the proximal part of jejunum and decreased along the tract. PEX14 showed a similar profile, but was still substantial expressed in large intestinal epithelium. Immunoblotting of epithelial cells, isolated from the different segments, showed also such gradient for some enzymes, ie, catalase, ACOX1, and D-specific multifunctional protein 2, and for the ABCD1 transporter, being high in small and low or absent in large intestine. Other peroxisomal enzymes (PHYH, HACL1, and ACAA1), the ABCD2 and ABCD3 transporters, and peroxins PEX13 and PEX14, however, did not follow this pattern, displaying rather constant signals throughout the intestinal epithelium. The small intestine displayed the highest peroxisomal β-oxidation activity and is particularly active on dicarboxylic acids. Etherlipid synthesis was high in the large intestine, and colonic cells had the highest content of plasmalogens. Overall, these data suggest that peroxisomes exert different functions according to the intestinal segment.
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Affiliation(s)
- Petruta L Morvay
- Lipid Biochemistry and Protein Interactions (LIPIT), KU Leuven, Leuven, Belgium
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2
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Francisco T, Dias AF, Pedrosa AG, Grou CP, Rodrigues TA, Azevedo JE. Determining the Topology of Peroxisomal Proteins Using Protease Protection Assays. Methods Mol Biol 2017; 1595:27-35. [PMID: 28409448 DOI: 10.1007/978-1-4939-6937-1_3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Protease protection assays are powerful tools to determine the topology of organelle proteins. Their simplicity, together with the fact that they are particularly suited to characterize endogenous proteins, are their major advantages and the reason why these assays have been in use for so many years. Here, we provide a detailed protocol to use with mammalian peroxisomes. Suggestions on how these assays can be controlled, and how to identify some technical pitfalls, are also presented.
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Affiliation(s)
- Tânia Francisco
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Organelle Biogenesis and Function Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
| | - Ana F Dias
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Organelle Biogenesis and Function Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal
| | - Ana G Pedrosa
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Organelle Biogenesis and Function Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal
| | - Cláudia P Grou
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Organelle Biogenesis and Function Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
| | - Tony A Rodrigues
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Organelle Biogenesis and Function Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal
| | - Jorge E Azevedo
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.
- Organelle Biogenesis and Function Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal.
- Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal.
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3
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A cell-free organelle-based in vitro system for studying the peroxisomal protein import machinery. Nat Protoc 2016; 11:2454-2469. [PMID: 27831570 DOI: 10.1038/nprot.2016.147] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Here we describe a protocol to dissect the peroxisomal matrix protein import pathway using a cell-free in vitro system. The system relies on a postnuclear supernatant (PNS), which is prepared from rat/mouse liver, to act as a source of peroxisomes and cytosolic components. A typical in vitro assay comprises the following steps: (i) incubation of the PNS with an in vitro-synthesized 35S-labeled reporter protein; (ii) treatment of the organelle suspension with a protease that degrades reporter proteins that have not associated with peroxisomes; and (iii) SDS-PAGE/autoradiography analysis. To study transport of proteins into peroxisomes, it is possible to use organelle-resident proteins that contain a peroxisomal targeting signal (PTS) as reporters in the assay. In addition, a receptor (PEX5L/S or PEX5L.PEX7) can be used to report the dynamics of shuttling proteins that mediate the import process. Thus, different but complementary perspectives on the mechanism of this pathway can be obtained. We also describe strategies to fortify the system with recombinant proteins to increase import yields and block specific parts of the machinery at a number of steps. The system recapitulates all the steps of the pathway, including mono-ubiquitination of PEX5L/S at the peroxisome membrane and its ATP-dependent export back into the cytosol by PEX1/PEX6. An in vitro import(/export) experiment can be completed in 24 h.
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4
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The characterization and evolutionary relationships of a trypanosomal thiolase. Int J Parasitol 2011; 41:1273-83. [DOI: 10.1016/j.ijpara.2011.07.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 06/22/2011] [Accepted: 07/19/2011] [Indexed: 11/23/2022]
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Lopez D, Niesen M, Bedi M, McLean MP. Lauric acid dependent enhancement in hepatic SCPx protein requires an insulin deficient environment. Prostaglandins Leukot Essent Fatty Acids 2008; 78:131-5. [PMID: 18187312 DOI: 10.1016/j.plefa.2007.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2007] [Revised: 11/20/2007] [Accepted: 11/23/2007] [Indexed: 11/23/2022]
Abstract
Sterol carrier protein X (SCPx) is a peroxisomal protein with both lipid transfer and thiolase activity. Treating with the fatty acid, lauric acid, induced SCPx mRNA levels in rat liver and in rat hepatoma H4IIE cells but enhanced protein levels of SCPx and the thiolase produced as a post-translational modification of SCPx were only seen in H4IIE cells. Further investigation revealed that the presence of insulin can mask lauric acid effects on the SCPx gene especially at the protein level. These data are in agreement with the findings that diabetes, a medical condition characterized by high levels of fatty acids in an insulin deficient environment, enhances the hepatic expression of SCPx.
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Affiliation(s)
- Dayami Lopez
- Department of Molecular Medicine, School of Basic Biomedical Sciences, University of South Florida, College of Medicine, Tampa, FL 33612, USA.
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6
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Lopez D, Niesen M, Bedi M, Hale D, McLean MP. Activation of the SCPx promoter in mouse adrenocortical Y1 cells. Biochem Biophys Res Commun 2007; 357:549-53. [PMID: 17434450 DOI: 10.1016/j.bbrc.2007.03.194] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 03/31/2007] [Indexed: 10/23/2022]
Abstract
Sterol carrier protein X (SCPx) is a peroxisomal protein with both lipid transfer and thiolase activity. Treatment of mouse adrenal Y1 cells with cAMP for 24h caused a significant induction of SCPx mRNA levels. Reporter gene studies demonstrated that treatment with cAMP and SF-1 was able to activate the SCPx promoter. Sequence analysis revealed the presence of three putative steroidogenic factor-1 (SF-1) binding motifs (designated SFB1, SFB2, and SFB3) and one CRE. Only SFB1 and SFB3 were able to bind recombinant SF-1 protein in electrophoretic mobility shift assays. The CRE was able to form a DNA/protein complex in the presence of Y1 nuclear extracts. Mutational analysis studies demonstrated that SFB3 is required for full activation of the SCPx promoter by cAMP treatment. Regulation of the SCPx gene by SF-1 and cAMP is similar to the regulatory mechanisms observed for other steroidogenic genes.
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Affiliation(s)
- Dayami Lopez
- Department of Molecular Medicine, University of South Florida, College of Medicine, Tampa, FL 33612, USA
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7
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Atshaves BP, McIntosh AL, Landrock D, Payne HR, Mackie JT, Maeda N, Ball J, Schroeder F, Kier AB. Effect of SCP-x gene ablation on branched-chain fatty acid metabolism. Am J Physiol Gastrointest Liver Physiol 2007; 292:G939-51. [PMID: 17068117 DOI: 10.1152/ajpgi.00308.2006] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Despite the importance of peroxisomal oxidation in branched-chain lipid (phytol, cholesterol) detoxification, little is known regarding the factors regulating the peroxisomal uptake, targeting, and metabolism of these lipids. Although in vitro data suggest that sterol carrier protein (SCP)-x plays an important role in branched-chain lipid oxidation, the full physiological significance of this peroxisomal enzyme is not completely clear. To begin to resolve this issue, SCP-x-null mice were generated by gene ablation of SCP-x from the SCP-x/SCP-2 gene and fed a phytol-enriched diet to characterize the effects of lipid overload in a system with minimal 2/3-oxoacyl-CoA thiolytic activity. It was shown that SCP-x gene ablation 1) did not result in reduced expression of SCP-2 (previously thought to be derived in considerable part by posttranslational cleavage of SCP-x); 2) increased expression levels of key enzymes involved in alpha- and beta-oxidation; and 3) altered lipid distributions, leading to decreased hepatic fatty acid and triglyceride levels. In response to dietary phytol, lack of SCP-x resulted in 1) accumulation of phytol metabolites despite substantial upregulation of hepatic peroxisomal and mitochondrial enzymes; 2) reduced body weight gain and fat tissue mass; and 3) hepatic enlargement, increased mottling, and necrosis. In summary, the present work with SCP-x gene-ablated mice demonstrates, for the first time, a direct physiological relationship between lack of SCP-x and decreased ability to metabolize branched-chain lipids.
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Affiliation(s)
- Barbara P Atshaves
- Department of Physiology and Pharmacology, Texas A and M University, College Station, Texas 77843, USA
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8
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Kurochkin IV, Mizuno Y, Konagaya A, Sakaki Y, Schönbach C, Okazaki Y. Novel peroxisomal protease Tysnd1 processes PTS1- and PTS2-containing enzymes involved in beta-oxidation of fatty acids. EMBO J 2007; 26:835-45. [PMID: 17255948 PMCID: PMC1794383 DOI: 10.1038/sj.emboj.7601525] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Accepted: 12/05/2006] [Indexed: 12/21/2022] Open
Abstract
Peroxisomes play an important role in beta-oxidation of fatty acids. All peroxisomal matrix proteins are synthesized in the cytosol and post-translationally sorted to the organelle. Two distinct peroxisomal signal targeting sequences (PTSs), the C-terminal PTS1 and the N-terminal PTS2, have been defined. Import of precursor PTS2 proteins into the peroxisomes is accompanied by a proteolytic removal of the N-terminal targeting sequence. Although the PTS1 signal is preserved upon translocation, many PTS1 proteins undergo a highly selective and limited cleavage. Here, we demonstrate that Tysnd1, a previously uncharacterized protein, is responsible both for the removal of the leader peptide from PTS2 proteins and for the specific processing of PTS1 proteins. All of the identified Tysnd1 substrates catalyze peroxisomal beta-oxidation. Tysnd1 itself undergoes processing through the removal of the presumably inhibitory N-terminal fragment. Tysnd1 expression is induced by the proliferator-activated receptor alpha agonist bezafibrate, along with the increase in its substrates. A model is proposed where the Tysnd1-mediated processing of the peroxisomal enzymes promotes their assembly into a supramolecular complex to enhance the rate of beta-oxidation.
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Affiliation(s)
- Igor V Kurochkin
- Immunoinformatics Team, Advanced Genome Information Group, RIKEN Genomic Sciences Center, Yokohama, Japan
- Present address: Genome Annotation and Comparative Analysis Team, Computational and Experimental Systems Biology Group, RIKEN Genomic Sciences Center, Yokohama 230-0045, Japan
- IV Kurochkin, Genome Annotation and Comparative Analysis Team, Computational and Experimental Systems Biology Group, RIKEN Genomic Sciences Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan. Tel.: +81 45 503 9111 (ext 8106); Fax: +81 45 503 9176; E-mail:
| | - Yumi Mizuno
- Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Hidaka-shi, Saitama, Japan
| | | | - Yoshiyuki Sakaki
- Computational and Experimental Systems Biology Group, RIKEN Genomic Sciences Center, Yokohama, Japan
| | - Christian Schönbach
- Immunoinformatics Team, Advanced Genome Information Group, RIKEN Genomic Sciences Center, Yokohama, Japan
| | - Yasushi Okazaki
- Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Hidaka-shi, Saitama, Japan
- Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, 1397-1 Yamane, Hidaka-city, Saitama 350-1241, Japan. Tel.: +81 42 985 7319; Fax: +81 42 985 7329; E-mail:
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9
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Kriska T, Levchenko VV, Korytowski W, Atshaves BP, Schroeder F, Girotti AW. Intracellular Dissemination of Peroxidative Stress. J Biol Chem 2006; 281:23643-51. [PMID: 16772292 DOI: 10.1074/jbc.m600744200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sterol carrier protein-2 (SCP-2) plays a crucial role in the trafficking and metabolism of cholesterol and other lipids in mammalian cells. Lipid hydroperoxides generated under oxidative stress conditions are relatively long-lived intermediates that damage cell membranes and play an important role in redox signaling. We hypothesized that SCP-2-facilitated translocation of lipid hydroperoxides in oxidatively stressed cells might enhance cytolethality if highly sensitive sites are targeted and detoxification capacity is insufficient. We tested this using a clone (SC2A) of rat hepatoma cells that overexpress mature immunodetectable SCP-2. When challenged with liposomal cholesterol-7alpha-hydroperoxide (7alpha-OOH), SC2A cells were found to be much more sensitive to viability loss than vector control (VC) counterparts. Correspondingly, SC2A cells imported [14C]7alpha-OOH more rapidly. The clones were equally sensitive to tert-butyl hydroperoxide, suggesting that the 7alpha-OOH effect was SCP-2-specific. Fluorescence intensity of the probes 2',7'-dichlorofluorescein and C11-BODIPY increased more rapidly in SC2A than VC cells after 7alpha-OOH exposure, consistent with more rapid internalization and oxidative turnover in the former. [14C]7alpha-OOH radioactivity accumulated much faster in SC2A mitochondria than in VC, whereas other subcellular fractions showed little rate difference. In keeping with this, 7alpha-OOH-stressed SC2A cells exhibited a faster loss of mitochondrial membrane potential and development of apoptosis. This is the first reported evidence that peroxidative stress damage can be selectively targeted and exacerbated by an intracellular lipid transfer protein.
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Affiliation(s)
- Tamas Kriska
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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10
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Yang JW, Afjehi-Sadat L, Gelpi E, Kunze M, Höger H, Fleckner J, Berger J, Lubec G. Proteome Profiling in the Rat Harderian Gland. J Proteome Res 2006; 5:1751-62. [PMID: 16823983 DOI: 10.1021/pr060082b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Harderian gland is an orbital gland located behind the ocular bulb in most terrestrial vertebrates probably functioning for production of lipid secretion to protect the eye. We herein present a protein reference database of the rat Harderian gland that may serve as analytical tool for future proteomic work, report lipid and porphyrin handling cascades, address sequence conflicts and report structures that have not been so far described by proteomics methods.
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Affiliation(s)
- Jae-Won Yang
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
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11
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Gloerich J, van Vlies N, Jansen GA, Denis S, Ruiter JPN, van Werkhoven MA, Duran M, Vaz FM, Wanders RJA, Ferdinandusse S. A phytol-enriched diet induces changes in fatty acid metabolism in mice both via PPARalpha-dependent and -independent pathways. J Lipid Res 2005; 46:716-26. [PMID: 15654129 DOI: 10.1194/jlr.m400337-jlr200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Branched-chain fatty acids (such as phytanic and pristanic acid) are ligands for the nuclear hormone receptor peroxisome proliferator-activated receptor alpha (PPARalpha) in vitro. To investigate the effects of these physiological compounds in vivo, wild-type and PPARalpha-deficient (PPARalpha-/-) mice were fed a phytol-enriched diet. This resulted in increased plasma and liver levels of the phytol metabolites phytanic and pristanic acid. In wild-type mice, plasma fatty acid levels decreased after phytol feeding, whereas in PPARalpha-/- mice, the already elevated fatty acid levels increased. In addition, PPARalpha-/- mice were found to be carnitine deficient in both plasma and liver. Dietary phytol increased liver free carnitine in wild-type animals but not in PPARalpha-/- mice. Investigation of carnitine biosynthesis revealed that PPARalpha is likely involved in the regulation of carnitine homeostasis. Furthermore, phytol feeding resulted in a PPARalpha-dependent induction of various peroxisomal and mitochondrial beta-oxidation enzymes. In addition, a PPARalpha-independent induction of catalase, phytanoyl-CoA hydroxylase, carnitine octanoyltransferase, peroxisomal 3-ketoacyl-CoA thiolase, and straight-chain acyl-CoA oxidase was observed. In conclusion, branched-chain fatty acids are physiologically relevant ligands of PPARalpha in mice. These findings are especially relevant for disorders in which branched-chain fatty acids accumulate, such as Refsum disease and peroxisome biogenesis disorders.
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Affiliation(s)
- J Gloerich
- University of Amsterdam, Academic Medical Center, Departments of Clinical Chemistry and Pediatrics, Laboratory for Genetic Metabolic Diseases, 1100 DE Amsterdam, The Netherlands
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12
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Lan Q, Massey RJ. Subcellular localization of the mosquito sterol carrier protein-2 and sterol carrier protein-x. J Lipid Res 2004; 45:1468-74. [PMID: 15145982 DOI: 10.1194/jlr.m400003-jlr200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Subcellular distribution of Aedes aegypti sterol carrier protein-2 (AeSCP-2) and AeSCP-x was studied using electron microscopy. In both cultured A. aegypti cells and in the larval midgut, AeSCP-2 was detected mostly in the cytosol, with some labeling mitochondria and nucleus, but not in membranous vesicles. The widespread distribution of AeSCP-2 in the midgut epithelium is consistent with its potential lipid transfer function in all phases of cholesterol absorption. In contrast, AeSCP-x was found mostly in the peroxisome. Differences in the subcellular distribution of AeSCP-2 and AeSCP-x suggest that these two members of the SCP-2 gene family are functionally distinct. Overexpression of AeSCP-2 in A. aegypti cells showed increased localization of AeSCP-2 to cytosol, mitochondria, and nucleus. This is the first report on the nuclear distribution of an SCP. Overexpression of AeSCP-2 resulted in increased cholesterol incorporation in cells, suggesting that AeSCP-2 enhances cholesterol uptake.
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Affiliation(s)
- Que Lan
- Department of Entomology, University of Wisconsin-Madison, Madison, WI 53706, USA.
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13
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Dansen TB, Kops GJPL, Denis S, Jelluma N, Wanders RJA, Bos JL, Burgering BMT, Wirtz KWA. Regulation of sterol carrier protein gene expression by the forkhead transcription factor FOXO3a. J Lipid Res 2003; 45:81-8. [PMID: 14563822 DOI: 10.1194/jlr.m300111-jlr200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The SCP gene encodes two proteins, sterol carrier protein X (SCPx) and SCP2, that are independently regulated by separate promoters. SCPx has been shown to be the thiolase involved in the breakdown of branched-chain fatty acids and in the biosynthesis of bile acids. The in vivo function of SCP2 however remains to be established. The transcriptional regulation of SCPx and SCP2 is unclear, but their promoter regions contain several putative regulatory domains. We show here that both SCPx and SCP2 are upregulated by the daf-16-like Forkhead transcription factor FOXO3a (also known as FKHRL1) on the level of promoter activity. It was recently described that Forkheads regulate protection against (oxidative) stress in both Caenorhabditis elegans and mammalian cells. We looked into a role for SCP2 in the cellular defense against oxidative damage and found that a fluorescent fatty acid analog bound to SCP2 is protected against H2O2/Cu2+-induced oxidative damage. We propose a model for the way in which SCP2 could protect fatty acids from peroxidation.
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Affiliation(s)
- Tobias B Dansen
- Department of Biochemistry of Lipids, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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14
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Atshaves BP, Storey SM, Schroeder F. Sterol carrier protein-2/sterol carrier protein-x expression differentially alters fatty acid metabolism in L cell fibroblasts. J Lipid Res 2003; 44:1751-62. [PMID: 12810824 DOI: 10.1194/jlr.m300141-jlr200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sterol carrier protein-2 (SCP-2) and SCP-x are ubiquitous proteins found in all mammalian tissues. Although both proteins interact with fatty acids, their relative contributions to the uptake, oxidation, and esterification of straight-chain (palmitic) and branched-chain (phytanic) fatty acids in living cells has not been resolved. Therefore, the effects of each gene product on fatty acid metabolism was individually examined. Based on the following, SCP-2 and SCP-x did not enhance the uptake/translocation of fatty acids across the plasma membrane into the cell: i) a 2-fold increase in phytanic and palmitic acid uptake was observed at long incubation times in SCP-2- and SCP-x-expressing cells, but no differences were observed at initial time points; ii) uptake of 2-bromo-palmitate, a nonoxidizable, poorly metabolizable fatty acid analog, was unaffected by SCP-2 or SCP-x overexpression; and iii) SCP-2 and SCP-x expression did not increase targeting of radiolabeled phytanic and palmitic acid to the unesterified fatty acid pool. Moreover, SCP-2 and SCP-x expression enhanced fatty acid uptake by stimulating the intracellular metabolism via fatty acid oxidation and esterification. In summary, these data showed for the first time that SCP-2 and SCP-x stimulate oxidation and esterification of branched-chain as well as straight-chain fatty acids in intact cells.
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Affiliation(s)
- Barbara P Atshaves
- Department of Physiology and Pharmacology, Texas A&M University, TVMC College Station, TX 77843-4466, USA
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15
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Atshaves BP, Storey SM, Petrescu A, Greenberg CC, Lyuksyutova OI, Smith R, Schroeder F. Expression of fatty acid binding proteins inhibits lipid accumulation and alters toxicity in L cell fibroblasts. Am J Physiol Cell Physiol 2002; 283:C688-703. [PMID: 12176726 DOI: 10.1152/ajpcell.00586.2001] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
High levels of saturated, branched-chain fatty acids are deleterious to cells and animals, resulting in lipid accumulation and cytotoxicity. Although fatty acid binding proteins (FABPs) are thought to be protective, this hypothesis has not previously been examined. Phytanic acid (branched chain, 16-carbon backbone) induced lipid accumulation in L cell fibroblasts similar to that observed with palmitic acid (unbranched, C(16)): triacylglycerol >> free fatty acid > cholesterol > cholesteryl ester >> phospholipid. Although expression of sterol carrier protein (SCP)-2, SCP-x, or liver FABP (L-FABP) in transfected L cells reduced [(3)H]phytanic acid uptake (57-87%) and lipid accumulation (21-27%), nevertheless [(3)H]phytanic acid oxidation was inhibited (74-100%) and phytanic acid toxicity was enhanced in the order L-FABP >> SCP-x > SCP-2. These effects differed markedly from those of [(3)H]palmitic acid, whose uptake, oxidation, and induction of lipid accumulation were not reduced by L-FABP, SCP-2, or SCP-x expression. Furthermore, these proteins did not enhance the cytotoxicity of palmitic acid. In summary, intracellular FABPs reduce lipid accumulation induced by high levels of branched-chain but not straight-chain saturated fatty acids. These beneficial effects were offset by inhibition of branched-chain fatty acid oxidation that correlated with the enhanced toxicity of high levels of branched-chain fatty acid.
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Affiliation(s)
- Barbara P Atshaves
- Department of Physiology and Pharmacology, Texas A&M University, Texas Veterinary Medical Center, College Station 77843-4466, USA
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Ferdinandusse S, van Grunsven EG, Oostheim W, Denis S, Hogenhout EM, IJlst L, van Roermund CWT, Waterham HR, Goldfischer S, Wanders RJA. Reinvestigation of peroxisomal 3-ketoacyl-CoA thiolase deficiency: identification of the true defect at the level of d-bifunctional protein. Am J Hum Genet 2002; 70:1589-93. [PMID: 11992265 PMCID: PMC379147 DOI: 10.1086/340970] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2002] [Accepted: 03/26/2002] [Indexed: 11/04/2022] Open
Abstract
In this report, we reinvestigate the only patient ever reported with a deficiency of peroxisomal 3-ketoacyl-CoA thiolase (THIO). At the time when they were described, the abnormalities in this patient, which included accumulation of very-long-chain fatty acids and the bile-acid intermediate trihydroxycholestanoic acid, were believed to be the logical consequence of a deficiency of the peroxisomal beta-oxidation enzyme THIO. In light of the current knowledge of the peroxisomal beta-oxidation system, however, the reported biochemical aberrations can no longer be explained by a deficiency of this thiolase. In this study, we show that the true defect in this patient is at the level of d-bifunctional protein (DBP). Immunoblot analysis revealed the absence of DBP in postmortem brain of the patient, whereas THIO was normally present. In addition, we found that the patient had a homozygous deletion of part of exon 3 and intron 3 of the DBP gene, resulting in skipping of exon 3 at the cDNA level. Our findings imply that the group of single-peroxisomal beta-oxidation-enzyme deficiencies is limited to straight-chain acyl-CoA oxidase, DBP, and alpha-methylacyl-CoA racemase deficiency and that there is no longer evidence for the existence of THIO deficiency as a distinct clinical entity.
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Affiliation(s)
- S Ferdinandusse
- Department of Clinical Chemistry, Emma Children's Hospital, Academic Medical Center, University of Amsterdam, 1100 DE Amsterdam, The Netherlands
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17
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de Brouwer APM, Westerman J, Kleinnijenhuis A, Bevers LE, Roelofsen B, Wirtz KWA. Clofibrate-induced relocation of phosphatidylcholine transfer protein to mitochondria in endothelial cells. Exp Cell Res 2002; 274:100-11. [PMID: 11855861 DOI: 10.1006/excr.2001.5460] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The phosphatidylcholine transfer protein (PC-TP) is a specific transporter of phosphatidylcholine (PC) between membranes. To get more insight into its physiological function, we have studied the localization of PC-TP by microinjection of fluorescently labeled PC-TP in foetal bovine heart endothelial (FBHE) cells and by expression of an enhanced yellow fluorescent protein-PC-TP fusion protein in FBHE cells, human umbilical vein endothelial cells, and HepG2 cells. Analysis by confocal laser scanning microscopy showed that PC-TP was evenly distributed throughout the cytosol with an apparently elevated level in nuclei. By measuring the fluorescence recovery after bleaching it was established that PC-TP is highly mobile throughout the cell, with its transport into the nucleus being hindered by the nuclear envelope. Given the proposed function of PC-TP in lipid metabolism, we have tested a number of compounds (phorbol ester, bombesin, A23187, thrombin, dibutyryl cyclic AMP, oleate, clofibrate, platelet-derived growth factor, epidermal growth factor, and hydrogen peroxide) for their ability to affect intracellular PC-TP distribution. Only clofibrate (100 microM) was found to have an effect, with PC-TP moving to mitochondria within 5 min of stimulation. This relocation did not occur with PC-TP(S110A), lacking the putative protein kinase C (PKC)-dependent phosphorylation site, and was restricted to the primary endothelial cells. Relocation did not occur in HepG2 cells, possibly due to the fact that clofibrate does not induce PKC activation in these cells.
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Affiliation(s)
- A P M de Brouwer
- Department of Biochemistry of Lipids, Institute of Biomembranes, Padualaan 8, Utrecht, 3584 CH, The Netherlands.
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18
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Gallegos AM, Atshaves BP, Storey SM, Starodub O, Petrescu AD, Huang H, McIntosh AL, Martin GG, Chao H, Kier AB, Schroeder F. Gene structure, intracellular localization, and functional roles of sterol carrier protein-2. Prog Lipid Res 2001; 40:498-563. [PMID: 11591437 DOI: 10.1016/s0163-7827(01)00015-7] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Since its discovery three decades ago, sterol carrier protein-2 (SCP-2) has remained a fascinating protein whose physiological function in lipid metabolism remains an enigma. Its multiple proposed functions arise from its complex gene structure, post-translational processing, intracellular localization, and ligand specificity. The SCP-2 gene has two initiation sites coding for proteins that share a common 13 kDa SCP-2 C-terminus: (1) One site codes for 58 kDa SCP-x which is partially post-translationally cleaved to 13 kDa SCP-2 and a 45 kDa protein. (2) A second site codes for 15 kDa pro-SCP-2 which is completely post-translationally cleaved to 13 kDa SCP-2. Very little is yet known regarding how the relative proportions of the two transcripts are regulated. Although all three proteins contain a C-terminal SKL peroxisomal targeting sequence, it is unclear why all three proteins are not exclusively localized in peroxisomes. However, the recent demonstration that the SCP-2 N-terminal presequence in pro-SCP-2 dramatically modulated the intracellular targeting coded by the C-terminal peroxisomal targeting sequence may account for the observation that as much as half of total SCP-2 is localized outside the peroxisome. The tertiary and secondary structure of the 13 kDa SCP-2, but not that of 15 kDa pro-SCP-2 and 58 kDa SCP-x, are now resolved. Increasing evidence suggests that the 58 kDa SCP-x and 45 kDa proteins are peroxisomal 3-ketoacyl-CoA-thiolases involved in the oxidation of branched chain fatty acids. Since 15 kDa pro-SCP-2 is post-translationally completely cleaved to 13 kDa SCP-2, relatively little attention has been focused on this protein. Finally, although the 13 kDa SCP-2 is the most studied of these proteins, because it exhibits diversity of its ligand partners (fatty acids, fatty acyl CoAs, cholesterol, phospholipids), new potential physiological function(s) are still being proposed and questions regarding potential compensation by other proteins with overlapping specificity are only beginning to be resolved.
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Affiliation(s)
- A M Gallegos
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843-4467, USA
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19
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Starodub O, Jolly CA, Atshaves BP, Roths JB, Murphy EJ, Kier AB, Schroeder F. Sterol carrier protein-2 localization in endoplasmic reticulum and role in phospholipid formation. Am J Physiol Cell Physiol 2000; 279:C1259-69. [PMID: 11003606 DOI: 10.1152/ajpcell.2000.279.4.c1259] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Although sterol carrier protein-2 (SCP-2; also called nonspecific lipid transfer protein) binds fatty acids and fatty acyl-CoAs, its role in fatty acid metabolism is not fully understood. L-cell fibroblasts stably expressing SCP-2 were used to resolve the relationship between SCP-2 intracellular location and fatty acid transacylation in the endoplasmic reticulum. Indirect immunofluorescence double labeling and laser scanning confocal microscopy detected SCP-2 in peroxisomes > endoplasmic reticulum > mitochondria > lysosomes. SCP-2 enhanced incorporation of exogenous [(3)H]oleic acid into phospholipids and triacylglycerols of overexpressing cells 1.6- and 2.5-fold, respectively, stimulated microsomal incorporation of [1-(14)C]oleoyl-CoA into phosphatidic acid in vitro 13-fold, and exhibited higher specificity for unsaturated versus saturated fatty acyl-CoA. SCP-2 enhanced the rate-limiting step in microsomal phosphatidic acid biosynthesis mediated by glycerol-3-phosphate acyltransferase. SCP-2 also enhanced microsomal acyl-chain remodeling of phosphatidylethanolamine up to fivefold and phosphatidylserine twofold, depending on the specific fatty acyl-CoA, but had no effect on other phospholipid classes. In summary, these results were consistent with a role for SCP-2 in phospholipid synthesis in the endoplasmic reticulum.
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Affiliation(s)
- O Starodub
- Department of Pathobiology, Texas A&M University, College Station, Texas 77843-4466, USA
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20
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Schroeder F, Frolov A, Starodub O, Atshaves BB, Russell W, Petrescu A, Huang H, Gallegos AM, McIntosh A, Tahotna D, Russell DH, Billheimer JT, Baum CL, Kier AB. Pro-sterol carrier protein-2: role of the N-terminal presequence in structure, function, and peroxisomal targeting. J Biol Chem 2000; 275:25547-55. [PMID: 10833510 DOI: 10.1074/jbc.m000431200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although the 20-amino acid presequence present in 15-kDa pro-sterol carrier protein-2 (pro-SCP-2, the precursor of the mature 13-kDa SCP-2) alters the function of SCP-2 in lipid metabolism, the molecular basis for this effect is unresolved. The presequence dramatically altered SCP-2 structure as determined by circular dichroism, mass spectroscopy, and antibody accessibility such that pro-SCP-2 had 3-fold less alpha-helix, 7-fold more beta-structure, 6-fold more reactive C terminus to carboxypeptidase A, 2-fold less binding of anti-SCP-2, and did not enhance sterol transfer from plasma membranes. These differences were not due to protein stability since (i) the same concentration of guanidine hydrochloride was required for 50% unfolding, and (ii) the ligand binding sites displayed the same high affinity (nanomolar K(d) values) in the order: cholesterol straight chain fatty acid > kinked chain fatty acid. Laser scanning confocal microscopy and double immunofluorescence demonstrated that pro-SCP-2 was more efficiently targeted to peroxisomes. Transfection of l-cells or McAR7777 hepatoma cells with cDNA encoding pro-SCP-2 resulted in 45% and 59% of SCP-2, respectively, colocalizing with the peroxisomal marker PMP70. In contrast, l-cells transfected with cDNA encoding SCP-2 exhibited 3-fold lower colocalization of SCP-2 with PMP70. In summary, the data suggest for the first time that the 20-amino acid presequence of pro-SCP-2 alters SCP-2 structure to facilitate peroxisomal targeting mediated by the C-terminal SKL peroxisomal targeting sequence.
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MESH Headings
- ATP-Binding Cassette Transporters
- Animals
- Blotting, Western
- Carboxypeptidases/metabolism
- Carboxypeptidases A
- Carrier Proteins/chemistry
- Carrier Proteins/physiology
- Cell Line
- Cell Membrane/metabolism
- Cholesterol/metabolism
- Circular Dichroism
- DNA, Complementary/metabolism
- Dose-Response Relationship, Drug
- Electrophoresis, Polyacrylamide Gel
- Fatty Acids/metabolism
- Fluorescent Antibody Technique
- Fluorescent Antibody Technique, Indirect
- Guanidine/pharmacology
- Humans
- Immunoblotting
- Kinetics
- Ligands
- Membrane Proteins/metabolism
- Microscopy, Confocal
- Peroxisomes/metabolism
- Plant Proteins
- Protein Folding
- Protein Precursors/chemistry
- Protein Precursors/physiology
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Rats
- Recombinant Proteins/chemistry
- Recombinant Proteins/metabolism
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
- Structure-Activity Relationship
- Transfection
- Tumor Cells, Cultured
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Affiliation(s)
- F Schroeder
- Department of Physiology and Pharmacology, Texas A & M University, College Station 77843-4466, USA.
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21
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Antonenkov VD, Van Veldhoven PP, Mannaerts GP. Isolation and subunit composition of native sterol carrier protein 2/3-oxoacyl-coenzyme A thiolase from normal rat liver peroxisomes. Protein Expr Purif 2000; 18:249-56. [PMID: 10733876 DOI: 10.1006/prep.2000.1192] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the present report we describe a method for the complete purification of native sterol carrier protein 2/3-oxoacyl-CoA thiolase (SCP-2/thiolase) from normal rat liver peroxisomes. The isolation procedure is based on the alteration in chromatographic properties of the enzyme in the presence of low concentrations of CoA. The purified preparation of SCP-2/thiolase consisted of 58- and 46-kDa polypeptides. Peroxisomes prepared freshly from normal rat liver contained three SCP-2/thiolase isoforms, separable by conventional chromatography. Immunochemical, molecular sieving, and chemical cross-linking experiments indicated that these isoforms represent thiolytically active homo- and heterodimeric combinations of the 46- and 58-kDa subunits (2 x 58, 58-46, and 2 x 46-kDa proteins).
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Affiliation(s)
- V D Antonenkov
- Departement Moleculaire Celbiologie, Afdelingen Farmacologie, Katholieke Universiteit Leuven, Campus Gasthuisberg (O & N), Herestraat 49, Leuven, B-3000, Belgium.
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22
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Gallegos AM, Schoer JK, Starodub O, Kier AB, Billheimer JT, Schroeder F. A potential role for sterol carrier protein-2 in cholesterol transfer to mitochondria. Chem Phys Lipids 2000; 105:9-29. [PMID: 10727111 DOI: 10.1016/s0009-3084(99)00128-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Mitochondrial cholesterol oxidation rapidly depletes cholesterol from the relatively cholesterol-poor mitochondrial membranes. However, almost nothing is known regarding potential mechanism(s) whereby the mitochondrial cholesterol pool is restored. Since most exogenous cholesterol enters the cell via the lysosomal pathway, this could be a source of mitochondrial cholesterol. In the present study, an in vitro fluorescent sterol transfer assay was used to examine whether the lysosomal membrane could be a putative cholesterol donor to mitochondria. First, it was shown that spontaneous sterol transfer from lysosomal to mitochondrial membranes was very slow (initial rate, 0.316 +/- 0.032 pmol/min). This was due, in part, to the fact that 90% of the lysosomal membrane sterol was not exchangeable, while the remaining 10% also had a relatively long half-time of exchange t(1/2) = 202 +/- 19 min. Second, the intracellular sterol carrier protein-2 (SCP-2) and its precursor (pro-SCP-2) increased the initial rate of sterol transfer from the lysosomal to mitochondrial membrane by 5.2- and 2.0-fold, respectively, but not in the reverse direction. The enhanced sterol transfer was due to a 3.5-fold increase in exchangeable sterol pool size and to induction of a very rapidly (t(1/2) = 4.1 +/- 0.6 min) exchangeable sterol pool. Confocal fluorescence imaging and indirect immunocytochemistry colocalized significant amounts of SCP-2 with the mitochondrial marker enzyme cytochrome oxidase in transfected L-cells overexpressing SCP-2. In summary, SCP-2 and pro-SCP-2 both stimulated molecular sterol transfer from lysosomal to mitochondrial membranes, suggesting a potential mechanism for replenishing mitochondrial cholesterol pools depleted by cholesterol oxidation.
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Affiliation(s)
- A M Gallegos
- Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station 77843-4466, USA
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23
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Ferdinandusse S, Denis S, van Berkel E, Dacremont G, Wanders RJ. Peroxisomal fatty acid oxidation disorders and 58 kDa sterol carrier protein X (SCPx): activity measurements in liver and fibroblasts using a newly developed method. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)34472-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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24
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Maebuchi M, Togo SH, Yokota S, Ghenea S, Bun-Ya M, Kamiryo T, Kawahara A. Type-II 3-oxoacyl-CoA thiolase of the nematode Caenorhabditis elegans is located in peroxisomes, highly expressed during larval stages and induced by clofibrate. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 264:509-15. [PMID: 10491098 DOI: 10.1046/j.1432-1327.1999.00655.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We examined the expression and localization of type-II 3-oxoacyl-CoA thiolase in the nematode Caenorhabditis elegans. Type-II thiolase acts on 3-oxoacyl-CoA esters with a methyl group at the alpha carbon, whereas conventional thiolases do not. Mammalian type-II thiolase, which is also termed sterol carrier protein x (SCPx) or SCP2/3-oxoacyl-CoA thiolase, is located in the peroxisomes and involved in phytanic acid degradation and most probably in bile acid synthesis. The nematode enzyme lacks the SCP2 domain, which carries the peroxisomal-targeting signal, but produces bile acids in a cell-free system. Northern and Western blot analyses demonstrated that C. elegans expressed type-II thiolase throughout its life cycle, especially during the larval stages, and that the expression was significantly enhanced by the addition of clofibrate at 5 mM or more to the culture medium. Whole-mount in situ hybridization and immunostaining of L4 larvae revealed that the enzyme was mainly expressed in intestinal cells, which are multifunctional like many of the cell types in C. elegans. Subcellular fractionation and indirect immunoelectron microscopy of the nematode detected the enzyme in the matrix of peroxisomes. These results indicate the fundamental homology between mammalian SCPx and the nematode enzyme regardless of whether the SCP2 part is fused, suggesting their common physiological roles.
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Affiliation(s)
- M Maebuchi
- Faculty of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima, Japan
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25
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Atshaves BP, Petrescu AD, Starodub O, Roths JB, Kier AB, Schroeder F. Expression and intracellular processing of the 58 kDa sterol carrier protein-2/3-oxoacyl-CoA thiolase in transfected mouse L-cell fibroblasts. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)32140-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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26
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Antonenkov VD, Van Veldhoven PP, Waelkens E, Mannaerts GP. Substrate specificities of 3-oxoacyl-CoA thiolase A and sterol carrier protein 2/3-oxoacyl-CoA thiolase purified from normal rat liver peroxisomes. Sterol carrier protein 2/3-oxoacyl-CoA thiolase is involved in the metabolism of 2-methyl-branched fatty acids and bile acid intermediates. J Biol Chem 1997; 272:26023-31. [PMID: 9325339 DOI: 10.1074/jbc.272.41.26023] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The two main thiolase activities present in isolated peroxisomes from normal rat liver were purified to near homogeneity. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the first enzyme preparation displayed a single band of 41 kDa that was identified as 3-oxoacyl-CoA thiolase A (thiolase A) by N-terminal amino acid sequencing. The second enzyme preparation consisted of a 58- and a 46-kDa band. The 58-kDa polypeptide reacted with antibodies raised against either sterol carrier protein 2 or the thiolase domain of sterol carrier protein 2/3-oxoacyl-CoA thiolase (SCP-2/thiolase), formerly also called sterol carrier protein X, whereas the 46-kDa polypeptide reacted only with the antibodies raised against the thiolase domain. Internal peptide sequencing confirmed that the 58-kDa polypeptide is SCP-2/thiolase and that the 46-kDa polypeptide is the thiolase domain of SCP-2/thiolase. Thiolase A catalyzed the cleavage of short, medium, and long straight chain 3-oxoacyl-CoAs, medium chain 3-oxoacyl-CoAs being the best substrates. The enzyme was inactive with the 2-methyl-branched 3-oxo-2-methylpalmitoyl-CoA and with the bile acid intermediate 24-oxo-trihydroxycoprostanoyl-CoA. SCP-2/thiolase was active with medium and long straight chain 3-oxoacyl-CoAs but also with the 2-methyl-branched 3-oxoacyl-CoA and the bile acid intermediate. In peroxisomal extracts, more than 90% of the thiolase activity toward straight chain 3-oxoacyl-CoAs was associated with thiolase A. Kinetic parameters (Km and Vmax) were determined for each enzyme with the different substrates. Our results indicate the following: 1) the two (main) thiolases present in peroxisomes from normal rat liver are thiolase A and SCP-2/thiolase; 2) thiolase A is responsible for the thiolytic cleavage of straight chain 3-oxoacyl-CoAs; and 3) SCP-2/thiolase is responsible for the thiolytic cleavage of the 3-oxoacyl-CoA derivatives of 2-methyl-branched fatty acids and the side chain of cholesterol.
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Affiliation(s)
- V D Antonenkov
- Katholieke Universiteit Leuven, Departement Moleculaire Celbiologie, Afdeling, Campus Gasthuisberg (O & N), Herestraat 49, B-3000 Leuven, Belgium
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27
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Abstract
Phosphatidylinositol transfer protein (PI-TP) and the non-specific lipid transfer protein (nsL-TP) (identical with sterol carrier protein 2) belong to the large and diverse family of intracellular lipid-binding proteins. Although these two proteins may express a comparable phospholipid transfer activity in vitro, recent studies in yeast and mammalian cells have indicated that they serve completely different functions. PI-TP (identical with yeast SEC14p) plays an important role in vesicle flow both in the budding reaction from the trans-Golgi network and in the fusion reaction with the plasma membrane. In yeast, vesicle budding is linked to PI-TP regulating Golgi phosphatidylcholine (PC) biosynthesis with the apparent purpose of maintaining an optimal PI/PC ratio of the Golgi complex. In mammalian cells, vesicle flow appears to be dependent on PI-TP stimulating phosphatidylinositol 4,5-bisphosphate (PIP2) synthesis. This latter process may also be linked to the ability of PI-TP to reconstitute the receptor-controlled PIP2-specific phospholipase C activity. The nsL-TP is a peroxisomal protein which, by its ability to bind fatty acyl-CoAs, is most likely involved in the beta-oxidation of fatty acids in this organelle. This protein constitutes the N-terminus of the 58 kDa protein which is one of the peroxisomal 3-oxo-acyl-CoA thiolases. Further studies on these and other known phospholipid transfer proteins are bound to reveal new insights in their important role as mediators between lipid metabolism and cell functions.
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Affiliation(s)
- K W Wirtz
- Institute of Biomembranes, Centre for Biomembranes and Lipid Enzymology, Utrecht University, P.O. Box 80054, 3508 TB Utrecht, The Netherlands
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