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Severance ZC, Nuñez JI, Le-McClain AT, Malinky CA, Bensen RC, Fogle RS, Manginelli GW, Sakers SH, Falcon EC, Bui RH, Snead KJ, Bourne CR, Burgett AWG. Structure-Activity Relationships of Ligand Binding to Oxysterol-Binding Protein (OSBP) and OSBP-Related Protein 4. J Med Chem 2023; 66:3866-3875. [PMID: 36916802 PMCID: PMC10786236 DOI: 10.1021/acs.jmedchem.2c01025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
Oxysterol-binding protein (OSBP) and OSBP-related protein 4 (ORP4) have emerged as potentially druggable targets in antiviral and precision cancer drug development. Multiple structurally diverse small molecules function through targeting the OSBP/ORP family of proteins, including the antiviral steroidal compounds OSW-1 and T-00127-HEV2. Here, the structure-activity relationships of oxysterols and related compound binding to human OSBP and ORP4 are characterized. Oxysterols with hydroxylation at various side chain positions (i.e., C-20, C-24, C-25, and C-27)─but not C-22─confer high affinity interactions with OSBP and ORP4. A library of 20(S)-hydroxycholesterol analogues with varying sterol side chains reveal that side chain length modifications are not well tolerated for OSBP and ORP4 interactions. This side chain requirement is contradicted by the high affinity binding of T-00127-HEV2, a steroidal compound lacking the side chain. The binding results, in combination with docking studies using homology models of OSBP and ORP4, suggest multiple modes of steroidal ligand binding to OSBP and ORP4.
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Affiliation(s)
- Zachary C Severance
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
- Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73117, United States
| | - Juan I Nuñez
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Anh T Le-McClain
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Cori A Malinky
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Ryan C Bensen
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Robert S Fogle
- Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73117, United States
| | - Gianni W Manginelli
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Sophia H Sakers
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Emily C Falcon
- Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73117, United States
| | - Richard Hoang Bui
- Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73117, United States
| | - Kevin J Snead
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Christina R Bourne
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Anthony W G Burgett
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
- Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73117, United States
- Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, United States
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2
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Arora A, Taskinen JH, Olkkonen VM. Coordination of inter-organelle communication and lipid fluxes by OSBP-related proteins. Prog Lipid Res 2022; 86:101146. [PMID: 34999137 DOI: 10.1016/j.plipres.2022.101146] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 12/10/2021] [Accepted: 01/03/2022] [Indexed: 12/31/2022]
Abstract
Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute one of the largest families of lipid-binding/transfer proteins (LTPs) in eukaryotes. The current view is that many of them mediate inter-organelle lipid transfer over membrane contact sites (MCS). The transfer occurs in several cases in a 'counter-current' fashion: A lipid such as cholesterol or phosphatidylserine (PS) is transferred against its concentration gradient driven by transport of a phosphoinositide in the opposite direction. In this way ORPs are envisioned to maintain the distinct organelle lipid compositions, with impacts on multiple organelle functions. However, the functions of ORPs extend beyond lipid homeostasis to regulation of processes such as cell survival, proliferation and migration. Important expanding areas of mammalian ORP research include their roles in viral and bacterial infections, cancers, and neuronal function. The yeast OSBP homologue (Osh) proteins execute multifaceted functions in sterol and glycerophospholipid homeostasis, post-Golgi vesicle transport, phosphatidylinositol-4-phosphate, sphingolipid and target of rapamycin (TOR) signalling, and cell cycle control. These observations identify ORPs as lipid transporters and coordinators of signals with an unforeseen variety of cellular processes. Understanding their activities not only enlightens the biology of the living cell but also allows their employment as targets of new therapeutic approaches for disease.
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Affiliation(s)
- Amita Arora
- Minerva Foundation Institute for Medical Research, and Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland
| | - Juuso H Taskinen
- Minerva Foundation Institute for Medical Research, and Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, and Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland.
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3
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Delfosse V, Bourguet W, Drin G. Structural and Functional Specialization of OSBP-Related Proteins. ACTA ACUST UNITED AC 2020. [DOI: 10.1177/2515256420946627] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Lipids are precisely distributed in the eukaryotic cell where they help to define organelle identity and function, in addition to their structural role. Once synthesized, many lipids must be delivered to other compartments by non-vesicular routes, a process that is undertaken by proteins called Lipid Transfer Proteins (LTPs). OSBP and the closely-related ORP and Osh proteins constitute a major, evolutionarily conserved family of LTPs in eukaryotes. Most of these target one or more subcellular regions, and membrane contact sites in particular, where two organelle membranes are in close proximity. It was initially thought that such proteins were strictly dedicated to sterol sensing or transport. However, over the last decade, numerous studies have revealed that these proteins have many more functions, and we have expanded our understanding of their mechanisms. In particular, many of them are lipid exchangers that exploit PI(4)P or possibly other phosphoinositide gradients to directionally transfer sterol or PS between two compartments. Importantly, these transfer activities are tightly coupled to processes such as lipid metabolism, cellular signalling and vesicular trafficking. This review describes the molecular architecture of OSBP/ORP/Osh proteins, showing how their specific structural features and internal configurations impart unique cellular functions.
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Affiliation(s)
- Vanessa Delfosse
- Centre de Biochimie Structurale, Inserm, CNRS, Univ Montpellier, Montpellier, France
| | - William Bourguet
- Centre de Biochimie Structurale, Inserm, CNRS, Univ Montpellier, Montpellier, France
| | - Guillaume Drin
- CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d’Azur, Valbonne, France
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4
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Lipp NF, Ikhlef S, Milanini J, Drin G. Lipid Exchangers: Cellular Functions and Mechanistic Links With Phosphoinositide Metabolism. Front Cell Dev Biol 2020; 8:663. [PMID: 32793602 PMCID: PMC7385082 DOI: 10.3389/fcell.2020.00663] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 07/01/2020] [Indexed: 12/28/2022] Open
Abstract
Lipids are amphiphilic molecules that self-assemble to form biological membranes. Thousands of lipid species coexist in the cell and, once combined, define organelle identity. Due to recent progress in lipidomic analysis, we now know how lipid composition is finely tuned in different subcellular regions. Along with lipid synthesis, remodeling and flip-flop, lipid transfer is one of the active processes that regulates this intracellular lipid distribution. It is mediated by Lipid Transfer Proteins (LTPs) that precisely move certain lipid species across the cytosol and between the organelles. A particular subset of LTPs from three families (Sec14, PITP, OSBP/ORP/Osh) act as lipid exchangers. A striking feature of these exchangers is that they use phosphatidylinositol or phosphoinositides (PIPs) as a lipid ligand and thereby have specific links with PIP metabolism and are thus able to both control the lipid composition of cellular membranes and their signaling capacity. As a result, they play pivotal roles in cellular processes such as vesicular trafficking and signal transduction at the plasma membrane. Recent data have shown that some PIPs are used as energy by lipid exchangers to generate lipid gradients between organelles. Here we describe the importance of lipid counter-exchange in the cell, its structural basis, and presumed links with pathologies.
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Affiliation(s)
- Nicolas-Frédéric Lipp
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, Université Côte d'Azur, Valbonne, France
| | - Souade Ikhlef
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, Université Côte d'Azur, Valbonne, France
| | - Julie Milanini
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, Université Côte d'Azur, Valbonne, France
| | - Guillaume Drin
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, Université Côte d'Azur, Valbonne, France
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5
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Zhang X, Liu L, Hu J, Chen F, Zeng B. Recombinant expression and purification of an Oxysterol Binding Protein fromAspergillus oryzae3.042. BIO WEB OF CONFERENCES 2017. [DOI: 10.1051/bioconf/20170803006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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6
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Mukherjee V, Vijayalaksmi D, Gulipalli J, Premalatha R, Sufi SA, Velan A, Srikumar K. A plant oxysterol, 28-homobrassinolide binds HMGCoA reductase catalytic cleft: stereoselective avidity affects enzyme function. Mol Biol Rep 2016; 43:1049-58. [PMID: 27585573 DOI: 10.1007/s11033-016-4052-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 08/01/2016] [Indexed: 10/21/2022]
Abstract
Understanding the influence of ubiquitously present plant steroids on mammalian cell biology is currently of interest. Feedback inhibition of HMGCoA reductase (HMGCR) catalytic activity in the transformation of HMG-CoA to mevalonate is a significant regulatory step in sterol biosynthetic pathway. To assess the role of dietary steroids in this biochemical transformation, the phytosteroid isoform 28-homobrassinolide (28-HB), 90 % pure, obtained from Godrej Agrovet (India) was used to determine its effect on mammalian HMG-CoA reductase. Photometric assay of pure human and select rat tissue HMGCR post 28-HB oral feed, PCR-HMGCR gene expression, and in silico docking of 28-HB and HMGCoA on HMGCR protein template were carried out. Using an oral feed regimen of pure 28-HB, we noted a decrease of 16 % in liver, 17.1 % in kidney and 9.3 % in testicular HMGCR enzyme activity, 25 % in HMGCR gene expression and 44 % in the activity of pure human HMGCR due to this plant oxysterol. In silico docking studies yielded binding metrics for 28-HB-HMGCR lower than for HMGCoA-HMGCR, indicating stronger binding of HMGCR by this ligand. 28-HB exerts differential effects on rat tissue HMGCR, down regulates liver HMGCR gene expression and significantly inhibits HMGCR activity.
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Affiliation(s)
- Victor Mukherjee
- Department of Biochemistry & Molecular Biology, School of Life Sciences, Pondicherry University, Puducherry, 605014, India.,Interdisciplinary Program in Life Sciences, Department of Biotechnology, Govt. of India, Pondicherry University, Puducherry, 605014, India
| | - D Vijayalaksmi
- Centre for Bioinformatics, School of Life Sciences, Pondicherry University, Puducherry, 605014, India
| | - Jagadeesh Gulipalli
- Department of Biochemistry & Molecular Biology, School of Life Sciences, Pondicherry University, Puducherry, 605014, India
| | - R Premalatha
- Department of Biochemistry & Molecular Biology, School of Life Sciences, Pondicherry University, Puducherry, 605014, India
| | - Shamim A Sufi
- Department of Biochemistry & Molecular Biology, School of Life Sciences, Pondicherry University, Puducherry, 605014, India.,Interdisciplinary Program in Life Sciences, Department of Biotechnology, Govt. of India, Pondicherry University, Puducherry, 605014, India
| | - Athithan Velan
- Department of Biochemistry & Molecular Biology, School of Life Sciences, Pondicherry University, Puducherry, 605014, India
| | - Kotteazeth Srikumar
- Department of Biochemistry & Molecular Biology, School of Life Sciences, Pondicherry University, Puducherry, 605014, India. .,Interdisciplinary Program in Life Sciences, Department of Biotechnology, Govt. of India, Pondicherry University, Puducherry, 605014, India.
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7
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Serviddio G, Blonda M, Bellanti F, Villani R, Iuliano L, Vendemiale G. Oxysterols and redox signaling in the pathogenesis of non-alcoholic fatty liver disease. Free Radic Res 2013; 47:881-93. [PMID: 24000796 DOI: 10.3109/10715762.2013.835048] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Oxysterols are oxidized species of cholesterol coming from exogenous (e.g. dietary) and endogenous (in vivo) sources. They play critical roles in normal physiologic functions such as regulation of cellular cholesterol homeostasis. Most of biological effects are mediated by interaction with nuclear receptor LXRα, highly expressed in the liver as well as in many other tissues. Such interaction participates in the regulation of whole-body cholesterol metabolism, by acting as "lipid sensors". Moreover, it seems that oxysterols are also suspected to play key roles in several pathologies, including cardiovascular and inflammatory disease, cancer, and neurodegeneration. Growing evidence suggests that oxysterols may contribute to liver injury in non-alcoholic fatty liver disease. The present review focuses on the current status of knowledge on oxysterols' biological role, with an emphasis on LXR signaling and oxysterols' physiopathological relevance in NAFLD, suggesting new pharmacological development that needs to be addressed in the near future.
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Affiliation(s)
- G Serviddio
- C.U.R.E. Centre for Liver Diseases Research and Treatment, Institute of Internal Medicine, Department of Medical and Surgical Sciences, University of Foggia , Italy
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8
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Ma Z, Liu Z, Huang X. OSBP- and FAN-mediated sterol requirement for spermatogenesis in Drosophila. Development 2010; 137:3775-84. [DOI: 10.1242/dev.049312] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Members of the oxysterol binding protein (OSBP) family are involved in diverse biological processes, including non-vesicular sterol transport and vesicle trafficking. The mechanisms by which OSBPs integrate functionally with developmental and physiological processes remain elusive. Here, we report the in vivo analysis of OSBP function in the model organism Drosophila. Osbp mutants are male-sterile and exhibit defects in individualization, the process by which each spermatid is packaged into its own membrane. Overexpression of OSBP leads to post-eclosion behaviour defects that can be suppressed by co-expression of endoplasmic reticulum-specific VAP family proteins. Most notably, FAN, a testis-specific VAP protein, acts together with OSBP genetically and physically to regulate the individualization process. OSBP-positive and sterol-enriched speckles are found at the leading edge of the individualization complex in wild type but not in Osbp or fan mutants, suggesting that sterol trafficking might play key roles during the membrane-remodelling phase of individualization. In addition, Osbp mutants that are fed additional sterols partially recover fertility, implying that male sterility is attributable to sterol shortage. Thus, we have identified an OSBP- and FAN-mediated sterol requirement in Drosophila spermatogenesis.
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Affiliation(s)
- Zhiguo Ma
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhonghua Liu
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Xun Huang
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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9
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Li DY, Inoue H, Takahashi M, Kojima T, Shiraiwa M, Takahara H. Molecular characterization of a novel salt-inducible gene for an OSBP (oxysterol-binding protein)-homologue from soybean. Gene 2008; 407:12-20. [PMID: 17466467 DOI: 10.1016/j.gene.2007.02.029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2006] [Revised: 01/19/2007] [Accepted: 02/27/2007] [Indexed: 11/28/2022]
Abstract
Oxysterol-binding protein (OSBP) and its homologues constitute a protein family in many eukaryotes from yeast to humans, which are involved in cellular lipid metabolism, vesicle transport and signal transduction. In this study, we characterized a novel salt-inducible gene for an OSBP-homologue from soybean (Glycine max [L.] Merr.). The soybean OSBP-homologous gene, denoted as G. max OSBP (GmOSBP), encoded a 789 aa putative protein with two characteristic domains; the pleckstrin homology (PH) domain and the ligand-binding (LB) domain, in the N- and C-terminus, respectively. The GmOSBP-PH domain showed localization into/around the nucleus in a transient subcellular localization assay. The phylogenetic relationship of the GmOSBP-LB domain to those in other OSBP-homologues suggested that GmOSBP might bind a lipid molecule(s) different from the ligand-candidates found for the human/yeast OSBP-homologues. The GmOSBP gene was constitutively transcribed in all of the soybean organs examined--root, stem and trifoliate leaf--at low levels and was highly induced in all these organs by high-salt stress (300 mM NaCl). Interestingly, gene expression of GmOSBP was also markedly induced in the senesced soybean cotyledon, which contains high levels of a variety of cellular lipids utilized for energy for germination and as membrane components. Therefore, we suggest that GmOSBP may be involved in some physiological reactions for stress-response and cotyledon senescence in the soybean.
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Affiliation(s)
- Dong Yan Li
- Laboratory of Biochemistry and Molecular Biology, Department of Applied Biological Resource Sciences, School of Agriculture, Ibaraki University, Chuo 3-21-1, Ami-machi, Inashiki-gun, Ibaraki, Japan
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10
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Yan D, Olkkonen VM. Characteristics of oxysterol binding proteins. INTERNATIONAL REVIEW OF CYTOLOGY 2008; 265:253-85. [PMID: 18275891 DOI: 10.1016/s0074-7696(07)65007-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Protein families characterized by a ligand binding domain related to that of oxysterol binding protein (OSBP) have been identified in eukaryotic species from yeast to humans. These proteins, designated OSBP-related (ORP) or OSBP-like (OSBPL) proteins, have been implicated in various cellular functions. However, the detailed mechanisms of their action have remained elusive. Data from our and other laboratories suggest that binding of sterol ligands may be a unifying theme. Work with Saccharomyces cerevisiae ORPs suggests a function of these proteins in the nonvesicular intracellular transport of sterols, in secretory vesicle transport from the Golgi complex, and in the establishment of cell polarity. Mammals have more ORP genes, and differential splicing substantially increases the complexity of the encoded protein family. Functional studies on mammalian ORPs point in different directions: integration of sterol and sphingomyelin metabolism, sterol transport, regulation of neutral lipid metabolism, control of the microtubule-dependent motility of endosomes/lysosomes, and regulation of signaling cascades. We envision that during evolution, the functions of ORPs have diverged from an ancestral one in sterol transport, to meet the increasing demand of the regulatory potential in multicellular organisms. Our working hypothesis is that mammalian ORPs mainly act as sterol sensors that relay information to a spectrum of different cellular processes.
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Affiliation(s)
- Daoguang Yan
- Department of Molecular Medicine, National Public Health Institute, Biomedicum, FI-00290 Helsinki, Finland
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11
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Levine T, Loewen C. Inter-organelle membrane contact sites: through a glass, darkly. Curr Opin Cell Biol 2006; 18:371-8. [PMID: 16806880 DOI: 10.1016/j.ceb.2006.06.011] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Accepted: 06/08/2006] [Indexed: 11/13/2022]
Abstract
Inter-organelle membrane contact sites are zones where heterologous membranes, usually the endoplasmic reticulum plus a partner organelle, come into close apposition. These sites are very poorly understood because so few of their components have been identified; however, it is clear that they are specialised for traffic of material and information between the two membranes. There have been recent advances in the study of lipid transfer proteins, such as ceramide transfer protein (CERT) and homologues of oxysterol binding protein (OSBP). Not only can these proteins carry lipids across the cytoplasm, but they have been found to target both the endoplasmic reticulum and a partnering organelle, and in some cases have been localised to membrane contact sites. Further work will be needed to test whether these lipid transfer proteins act when anchored at inter-organelle contact sites.
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Affiliation(s)
- Tim Levine
- Division of Cell Biology, UCL Institute of Ophthalmology, Bath St, London EC1V 9EL, UK.
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12
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Wiltschi B, Schober M, Kohlwein SD, Oesterhelt D, Sinner EK. Sterol Binding Assay Using Surface Plasmon Fluorescence Spectroscopy. Anal Chem 2005; 78:547-55. [PMID: 16408938 DOI: 10.1021/ac051388p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe the design of a novel in vitro assay to study the interaction of soluble proteins with small hydrophobic sterol ligands. The sterol molecules are incorporated in an artificial membrane system in order to mimic their arrangement found in a biomembrane. The artificial membrane setup is monitored in real time by surface plasmon spectroscopy. Binding of fluorescently labeled soluble protein is observed by optical detection with surface plasmon enhanced fluorescence spectroscopy. By application of the novel assay, we demonstrate that four different oxidized sterol molecules are specifically recognized by the yeast protein Osh5p, a presumed oxysterol binding protein. Osh5p from yeast is the first oxysterol binding protein homologue for which oxysterol binding is shown with this new technique. With the design of our novel in vitro oxysterol binding assay, we have solved the technically challenging difficulty of presenting hydrophobic ligands to hydrophilic proteins in aqueous media.
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Affiliation(s)
- Birgit Wiltschi
- Department of Membrane Biochemistry, Max Planck Institute of Biochemistry, D-82152 Martinsried, Germany.
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13
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Lehto M, Olkkonen VM. The OSBP-related proteins: a novel protein family involved in vesicle transport, cellular lipid metabolism, and cell signalling. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1631:1-11. [PMID: 12573443 DOI: 10.1016/s1388-1981(02)00364-5] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Proteins/genes showing high sequence homology to the mammalian oxysterol binding protein (OSBP) have been identified in a variety of eukaryotic organisms from yeast to man. The unifying feature of the gene products denoted as OSBP-related proteins (ORPs) is the presence of an OSBP-type ligand binding (LB) domain. The LB domains of OSBP and its closest homologue bind oxysterols, while data on certain other family members suggest interaction with phospholipids. Many ORPs also have a pleckstrin homology (PH) domain in the amino-terminal region. The PH domains of the family members studied in detail are known to interact with membrane phosphoinositides and play an important role in the intracellular targeting of the proteins. It is plausible that the ORPs constitute a regulatory apparatus that senses the status of specific lipid ligands in membranes, using the PH and/or LB domains, and mediates information to yet poorly known downstream machineries. Functional studies carried out on the ORP proteins in different organisms indicate roles of the gene family in diverse cellular processes including control of lipid metabolism, regulation of vesicle transport, and cell signalling events.
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Affiliation(s)
- Markku Lehto
- Department of Molecular Medicine, National Public Health Institute, Biomedicum, PO Box 104, Haartmaninkatu 8, FIN-00251, Helsinki, Finland
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14
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Collier FM, Gregorio-King CC, Apostolopoulos J, Walder K, Kirkland MA. ORP3 splice variants and their expression in human tissues and hematopoietic cells. DNA Cell Biol 2003; 22:1-9. [PMID: 12590732 DOI: 10.1089/104454903321112442] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
ORP3 is a member of the newly described family of oxysterol-binding protein (OSBP)-related proteins (ORPs). We previously demonstrated that this gene is highly expressed in CD34(+) hematopoietic progenitor cells, and deduced that the "full-length" ORP3 gene comprises 23 exons and encodes a predicted protein of 887 amino acids with a C-terminal OSBP domain and an N-terminal pleckstrin homology domain. To further characterize the gene, we cloned ORP3 cDNA from PCR products and identified multiple splice variants. A total of eight isoforms were demonstrated with alternative splicing of exons 9, 12, and 15. Isoforms with an extension to exon 15 truncate the OSBP domain of the predicted protein sequence. In human tissues there was specific isoform distribution, with most tissues expressing varied levels of isoforms with the complete OSBP domain; while only whole brain, kidney, spleen, thymus, and thyroid expressed high levels of the isoforms associated with the truncated OSBP domain. Interestingly, the expression in cerebellum, heart, and liver of most isoforms was negligible. These data suggest that differential mRNA splicing may have resulted in functionally distinct forms of the ORP3 gene.
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Affiliation(s)
- F M Collier
- Stem Cell Laboratory, Douglas Hocking Research Institute, Barwon Health, The Geelong Hospital, Geelong, VIC, Australia.
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15
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16
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Abstract
Oxysterols are oxygenated derivatives of cholesterol that are intermediates or even end products in cholesterol excretion pathways. Because of their ability to pass cell membranes and the blood-brain barrier at a faster rate than cholesterol itself, they are also important as transport forms of cholesterol. In addition, oxysterols have been ascribed a number of important roles in connection with cholesterol turnover, atherosclerosis, apoptosis, necrosis, inflammation, immunosuppression, and the development of gallstones. According to current concepts, oxysterols are physiological mediators in connection with a number of cholesterol-induced metabolic effects. However, most of the evidence for this is still indirect, and there is a discrepancy between the documented potent effects of oxysterols under in vitro conditions and the studies demonstrating that they are of physiological importance in vivo. Oxysterol-binding proteins, such as liver X receptor-alpha (a nuclear receptor), do have a regulatory role in cholesterol turnover, but the physiological ligand of the protein has not yet been defined with certainty. Recently developed genetically engineered mouse models with markedly reduced or increased concentration of some of the oxysterols have exhibited surprisingly small changes in cholesterol turnover and homeostasis. The present review is a critical evaluation of the literature on oxysterols, in particular, the in vivo evidence for a role of oxysterols as physiological regulators of cholesterol homeostasis and as atherogenic factors.
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Affiliation(s)
- Ingemar Björkhem
- Division of Clinical Chemistry, Karolinska Institutet, Huddinge University Hospital, Huddinge, Sweden.
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17
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Kandutsch AA. A model scientist. Biochem Biophys Res Commun 2002; 292:1227-9. [PMID: 11969218 DOI: 10.1006/bbrc.2002.2014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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18
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Moreira EF, Jaworski C, Li A, Rodriguez IR. Molecular and biochemical characterization of a novel oxysterol-binding protein (OSBP2) highly expressed in retina. J Biol Chem 2001; 276:18570-8. [PMID: 11278871 DOI: 10.1074/jbc.m011259200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We are interested in understanding the possible function(s) of the oxysterol-binding proteins in mediating oxysterol cytotoxicity in the retina. In this study we describe the cloning, localization, and biological activity of a novel oxysterol-binding protein (OSBP2), and complete the molecular characterization of the previously known OSBP1. Both OSBP genes contain 14 exons and have similar exon sizes and splice sites suggesting they may have arisen from a gene duplication event. OSBP1 is located in chromosome 11q12.1, and OSBP2 is located in 22q12. At the protein level they share 63% overall similarity and although they have unique N termini, both have similar pleckstrin homology domains within the N terminus region. Northern blot analyses indicate that OSBP1 is broadly expressed in human and monkey tissues. OSBP2 is detected mainly in retina, testis, and fetal liver. Western blot analysis using peptide antibodies specific to OSBP1 and OSBP2 detected the proteins in different subcellular fractions in the retinal monkey tissue. OSBP1 is detected mainly in the soluble or cytosolic fraction and nuclei whereas OSBP2 is detected exclusively in the detergent soluble fraction suggesting association with membranes. Immunohistochemical localization of OSBP1 and OSBP2 in the monkey retina placed these two proteins in similar but distinct areas of the inner retina. OSBP2 was found to bind 7-ketocholesterol but to have very little affinity for cholesterol or 25-hydroxycholesterol.
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Affiliation(s)
- E F Moreira
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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19
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Abstract
Oxygenated derivatives of cholesterol (oxysterols) present a remarkably diverse profile of biological activities, including effects on sphingolipid metabolism, platelet aggregation, apoptosis, and protein prenylation. The most notable oxysterol activities center around the regulation of cholesterol homeostasis, which appears to be controlled in part by a complex series of interactions of oxysterol ligands with various receptors, such as the oxysterol binding protein, the cellular nucleic acid binding protein, the sterol regulatory element binding protein, the LXR nuclear orphan receptors, and the low-density lipoprotein receptor. Identification of the endogenous oxysterol ligands and elucidation of their enzymatic origins are topics of active investigation. Except for 24, 25-epoxysterols, most oxysterols arise from cholesterol by autoxidation or by specific microsomal or mitochondrial oxidations, usually involving cytochrome P-450 species. Oxysterols are variously metabolized to esters, bile acids, steroid hormones, cholesterol, or other sterols through pathways that may differ according to the type of cell and mode of experimentation (in vitro, in vivo, cell culture). Reliable measurements of oxysterol levels and activities are hampered by low physiological concentrations (approximately 0.01-0.1 microM plasma) relative to cholesterol (approximately 5,000 microM) and by the susceptibility of cholesterol to autoxidation, which produces artifactual oxysterols that may also have potent activities. Reports describing the occurrence and levels of oxysterols in plasma, low-density lipoproteins, various tissues, and food products include many unrealistic data resulting from inattention to autoxidation and to limitations of the analytical methodology. Because of the widespread lack of appreciation for the technical difficulties involved in oxysterol research, a rigorous evaluation of the chromatographic and spectroscopic methods used in the isolation, characterization, and quantitation of oxysterols has been included. This review comprises a detailed and critical assessment of current knowledge regarding the formation, occurrence, metabolism, regulatory properties, and other activities of oxysterols in mammalian systems.
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Affiliation(s)
- G J Schroepfer
- Departments of Biochemistry, Rice University, Houston, Texas, USA.
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20
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Abstract
By using classical methods of organic synthesis, the introduction of chemical modifications into the saturated side-chains of steroids usually requires a multistep synthesis to construct new side-chains to be added to the steroid nucleus. In order to circumvent these earlier methods, new procedures have been developed to directly introduce functionality onto the steroid side-chain to produce useful products. These initial products may also provide an entry toward the further modification of the side-chain to produce steroids which could previously be obtained only with great difficulty.
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Affiliation(s)
- E J Parish
- Department of Chemistry, Auburn University, Alabama 36849, USA.
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21
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LY295427, a novel hypocholesterolemic agent, enhances [3H]25-hydroxycholesterol binding to liver cytosolic proteins. J Lipid Res 1996. [DOI: 10.1016/s0022-2275(20)37462-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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22
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Morel DW, Lin CY. Cellular biochemistry of oxysterols derived from the diet or oxidation in vivo. J Nutr Biochem 1996. [DOI: 10.1016/0955-2863(96)00101-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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23
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Axelson M, Larsson O. 27-hydroxylated low density lipoprotein (LDL) cholesterol can be converted to 7alpha,27-dihydroxy-4-cholesten-3-one (cytosterone) before suppressing cholesterol production in normal human fibroblasts. Evidence that an altered metabolism of ldl cholesterol can underlie a defective feedback control in malignant cells. J Biol Chem 1996; 271:12724-36. [PMID: 8662693 DOI: 10.1074/jbc.271.22.12724] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The formation of oxysterols in cultured human fibroblasts and their physiological roles as intracellular regulators of cholesterol production have been investigated. In the presence of low density lipoproteins (LDL), normal fibroblasts converted LDL cholesterol to 27hydroxycholesterol, which was further metabolized to 7alpha, 27-dihydroxycholesterol, 7alpha,27-dihydroxy-4-cholesten-3-one, and 7alpha-hydroxy-3-oxo-4-cholestenoic acid. Autooxidation products of cholesterol contaminating the lipoproteins were also metabolized in the cells. 7alpha-Hydroxycholesterol was converted to 7alpha-hydroxy-4-cholesten-3-one prior to 27-hydroxylation and further oxidation to 7alpha-hydroxy-3-oxo-4-cholestenoic acid. 7beta-Hydroxycholesterol and 7-oxocholesterol were 27-hydroxylated and then oxidized to C27-acids. Oxidation of the 7beta-hydroxy group also occurred. 25-Hydroxycholesterol was 7alpha-hydroxylated and further oxidized to 7alpha,25-dihydroxy-4-cholesten-3-one. 25-Hydroxylation of sterols was observed only under specific conditions. In contrast, only small amounts of oxysterols were formed in virus-transformed human fibroblasts when incubated with lipoproteins. This was due to very low activities of the 27- and 7alpha-hydroxylating enzymes. The rate of oxidation at C-3 was also decreased moderately. A defective suppression of 3-hydroxy-3-methylglutaryl coenzyme A reductase by LDL and autooxidation products of cholesterol observed in the transformed fibroblasts could be caused by the deficiencies of the sterol-metabolizing enzymes, since these cells responded normally to the sterol metabolites 7alpha,27-dihydroxy-4-cholesten-3-one, 7alpha, 25-dihydroxy-4-cholesten-3-one, and 27-hydroxy-7-oxo-cholesterol. These metabolites, which all possessed an oxo group with a conjugated double bond in the steroid nucleus and a hydroxyl group in the side chain, did not seem to require further metabolism in order to be active. An impaired response to LDL was also seen in other human tumor cells, including breast carcinoma, colonic carcinoma, and malignant melanoma cells. Common to all the malignant cells was an intracellular shortage of 7alpha, 27-dihydroxy-4-cholesten-3-one caused by a decreased formation or an increased metabolism.
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Affiliation(s)
- M Axelson
- Department of Clinical Chemistry and the Department of Tumor Pathology, Karolinska Hospital, S-171 76 Stockholm, Sweden
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24
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Ridgway ND, Lagace TA. Brefeldin A renders Chinese hamster ovary cells insensitive to transcriptional suppression by 25-hydroxycholesterol. J Biol Chem 1995; 270:8023-31. [PMID: 7713903 DOI: 10.1074/jbc.270.14.8023] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The effect of disruption of the Golgi apparatus on 25-hydroxycholesterol-mediated transcriptional suppression and activation of acyl-CoA:cholesterol acyltransferase was examined. In Chinese hamster ovary (CHO) cells, brefeldin A (BFA) caused dose-dependent inhibition of 25-hydroxycholesterol-mediated suppression of mRNAs for four sterol-regulated genes: 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase, HMG-CoA synthase, farnesyl-diphosphate synthase, and the low density lipoprotein receptor. BFA prevented suppression whether added prior to or following a 4-h pretreatment with 25-hydroxycholesterol. In the presence of BFA (1 microgram/ml), 25-hydroxycholesterol-mediated suppression of mRNAs for HMG-CoA reductase, the low density lipoprotein receptor, and farnesyl-diphosphate synthase was almost completely blocked. HMG-CoA synthase mRNA was 80-90% suppressed by 25-hydroxycholesterol compared with 50-60% suppression in the presence of BFA. These effects of BFA were not due to alterations in mRNA stability. Disruption of the Golgi apparatus, as assessed by staining with a fluorescent lectin, correlated with concentrations of BFA that reversed mRNA suppression. Monensin was also found to block the effects of 25-hydroxycholesterol on suppression of HMG-CoA reductase. However, this ionophore decreased the other three sterol-regulated mRNAs to a similar degree as 25-hydroxycholesterol. In contrast to CHO cells, BFA-resistant PtK1 cells displayed normal down-regulation of HMG-CoA reductase and an intact Golgi apparatus in the presence of BFA and 25-hydroxycholesterol. Cholesterol esterification in CHO cells was stimulated to a similar extent by BFA (1 microgram/ml) and 25-hydroxycholesterol, and simultaneous treatment of CHO cells with both compounds was 60-70% additive. These results suggest that an intact Golgi apparatus is required for 25-hydroxycholesterol-mediated suppression of mRNA.
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Affiliation(s)
- N D Ridgway
- Department of Pediatrics and Biochemistry, Dalhousie University, Halifax, Nova Scotia, Canada
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25
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Parish EJ, Parish SC, Li S. Side-chain oxysterol regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. Lipids 1995; 30:247-51. [PMID: 7791533 DOI: 10.1007/bf02537828] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Side-chain oxysterols are known to be potent inhibitors of 3-hydroxy-3-methylglutaryl CoA reductase, a key regulatory enzyme in the biosynthesis of sterols. Structural variations in the side-chain oxysterols influence enzyme inhibition. Under certain conditions, biological systems have been induced to produce side-chain oxysterols, adding support to the hypothesis that oxysterols may be natural regulators of sterol biosynthesis in the intact cell. Specific inhibition of sterol biosynthesis is of interest as it may prove useful in the prevention or reversal of various cardiovascular disease states, as well as in the control of normal and abnormal cell growth.
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Affiliation(s)
- E J Parish
- Department of Chemistry, Auburn University, Alabama 36849, USA
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26
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Axelson M, Larsson O, Zhang J, Shoda J, Sjövall J. Structural specificity in the suppression of HMG-CoA reductase in human fibroblasts by intermediates in bile acid biosynthesis. J Lipid Res 1995. [DOI: 10.1016/s0022-2275(20)39905-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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27
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Ayala-Torres S, Johnson BH, Thompson EB. Oxysterol sensitive and resistant lymphoid cells: correlation with regulation of cellular nucleic acid binding protein mRNA. J Steroid Biochem Mol Biol 1994; 48:307-15. [PMID: 8142309 DOI: 10.1016/0960-0760(94)90070-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Oxygenated derivatives of cholesterol inhibit cholesterol synthesis, prevent lymphoid cell growth, and evoke cell death. We have employed a novel selection method to isolate M10 cells, a line of oxysterol-resistant cells, from the sensitive clone CEM C7. Concentrations of the potent sterol 25-hydroxycholesterol that occupy the oxysterol binding protein cause cell death in CEM C7, but not in M10 cells. Both cell lines have similar amounts of the oxysterol binding protein with similar affinities for oxysterol. However, in neither line are the levels of oxysterol binding protein mRNA affected by 1 microM 25-hydroxycholesterol. Furthermore, both cells express the cellular nucleic acid binding protein (CNBP), a 7 zinc finger, DNA-binding protein of unknown function, regulated by oxysterols. The levels of CNBP mRNA are significantly reduced by 25-hydroxycholesterol in the sensitive CEM C7 cells, in which the dose response and time course are consistent with occupancy of the oxysterol binding protein by oxysterol and with subsequent cell kill. However, in the resistant M10 cells, CNBP mRNA levels are unaffected by these concentrations of the 25-hydroxycholesterol. Our results suggest a role for CNBP in oxysterol-induced regulation of cell viability and growth.
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Affiliation(s)
- S Ayala-Torres
- Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77555-0645
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28
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Bakos JT, Johnson BH, Thompson EB. Oxysterol-induced cell death in human leukemic T-cells correlates with oxysterol binding protein occupancy and is independent of glucocorticoid-induced apoptosis. J Steroid Biochem Mol Biol 1993; 46:415-26. [PMID: 8217873 DOI: 10.1016/0960-0760(93)90096-f] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In eukaryotic cells oxysterols inhibit cholesterol biosynthesis and cell growth. A potent oxysterol, 25-hydroxycholesterol, was used to investigate the biological effects of oxysterols on three clonal lines of either glucocorticoid-sensitive or -resistant CEM cells, human leukemic T-lymphocytes. In addition, the glucocorticoid sensitivity of an oxysterol-resistant CEM cell line was tested. Oxysterols blocked growth and caused the lysis of cells regardless of their glucocorticoid response. All cells studied herein possessed an oxysterol binding protein with high affinity for 25-hydroxycholesterol. For all clones grown in serum-free medium, the half-maximal cytolytic concentration of 25-hydroxycholesterol (20-40 nM) correlated with its affinity (Kd = approximately 31 nM) for this oxysterol binding protein. Both cholesterol and mevalonate reversed 25-hydroxycholesterol cytotoxicity; 3-6 microM cholesterol or 0.1 mM mevalonate decreased 60 nM 25-hydroxycholesterol cytotoxicity by 50%. This cholesterol or mevalonate reversal appeared possible even after several days of 60 nM oxysterol treatment. The protective effect of cholesterol could be overcome by increasing 25-hydroxycholesterol concentrations. Cholesterol and mevalonate did not prevent glucocorticoid-mediated lymphocytolysis. Furthermore, the oxysterol-resistant line was sensitive to dexamethasone lysis. These data support the hypothesis that oxysterols and glucocorticoids act independently to block the growth of human leukemic lymphoblasts.
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Affiliation(s)
- J T Bakos
- University of Texas Medical Branch, Department of Human Biological Chemistry and Genetics, Galveston 77555
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29
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Stone BG, Evans CD. Evidence for a common biliary cholesterol and VLDL cholesterol precursor pool in rat liver. J Lipid Res 1992. [DOI: 10.1016/s0022-2275(20)41389-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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30
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Herz JE, Wilson WK, Pinkerton FD, Schroepfer GJ. Inhibitors of sterol synthesis. Synthesis and spectral properties of 3 beta-hydroxy-24-dimethylamino-5 alpha-chol-8(14)-en-15-one and its effects on HMG-CoA reductase activity in CHO-K1 cells. Chem Phys Lipids 1991; 60:61-9. [PMID: 1813179 DOI: 10.1016/0009-3084(91)90015-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A simple, three-step synthesis of the 25-aza analog of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (I) is described. Treatment of 3 beta-acetoxy-24-hydroxy-5 alpha-chol-8(14)-en-15-one (III) with 1.75 equivalents of tosyl chloride in pyridine for 24 h at 5 degrees C gave 3 beta-acetoxy-24-tosyloxy-5 alpha-chol-8(14)-en-15-one (IV). In contrast, treatment of III with 3.95 equivalents of tosyl chloride in pyridine for 12 h at 48 degrees C gave 3 beta-acetoxy-24-chloro-5 alpha-chol-8(14)-en-15-one (V). Treatment of IV with dimethylamine in dioxane yielded 3 beta-acetoxy-24-dimethylamino-5 alpha-chol-8(14)-en-15-one (VI). Hydrolysis of VI with LiOH.H2O in methanol gave 3 beta-hydroxy-24-dimethylamino-5 alpha-chol-8(14)-en-15-one (VII). 1H- and 13C-NMR assignments are presented for compounds IV-VII. The 25-aza analog (VII) of the 15-ketosterol (I), at a concentration of 1.0 microM, caused a 47% lowering of the level of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in Chinese hamster ovary cells.
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Affiliation(s)
- J E Herz
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251-1892
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31
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Taylor FR, Shown EP, Kandutsch AA. A proteolytic fragment of the oxysterol receptor which retains oxysterol binding activity. Arch Biochem Biophys 1991; 288:567-71. [PMID: 1898049 DOI: 10.1016/0003-9861(91)90237-d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The structural organization of the oxysterol receptor, postulated to be involved in the regulation of 3-hydroxy-3-methylglutaryl CoA reductase and cholesterol biosynthesis in mammalian cells, has been explored by limited proteolysis with trypsin, alpha-chymotrypsin, and endoproteinase GluC. Treatment with each of these proteases converts the receptor from a homodimer of approximately 95 kDa subunits to a 44-kDa form, based on hydrodynamic measurements by sucrose density gradient centrifugation and gel filtration chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of photoaffinity-labeled preparations indicates that the oxysterol binding site is on a 28-kDa fragment within the 44-kDa limit form of the receptor. The limit proteolytic form exhibits the high affinity and structural specificity for oxysterols of the native dimeric receptor with an increase in the rate constant of association for 25-hydroxycholesterol. The proteolytic form also shows an increased binding affinity for nonspecific DNA, but no sequence specificity for the oxysterol regulatory element from the reductase gene was detected.
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Affiliation(s)
- F R Taylor
- Jackson Laboratory, Bar Harbor, Maine 04609
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32
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Lin L, Hwang PL. Antiproliferative effects of oxygenated sterols: positive correlation with binding affinities for the antiestrogen-binding sites. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1082:177-84. [PMID: 2007181 DOI: 10.1016/0005-2760(91)90192-k] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Oxygenated derivatives of cholesterol have long been known to exhibit antiproliferative properties but the mechanism of this effect remains incompletely understood. Following up on a recent observation in our laboratory that certain oxysterols bind with high affinity to the microsomal antiestrogen-binding site, we attempted to determine if a relationship existed between the antiproliferative effect of oxysterols and their binding affinities for the antiestrogen-binding site. Using the human breast cancer cell line, MCF7, and 14 different compounds (4 nonsteroidal antiestrogens, 6 oxysterols with appreciable binding affinities for the antiestrogen-binding site, and 4 other sterols with little or no affinity for this site), we showed that for compounds which bound to the antiestrogen-binding site, there was a clear positive correlation between their relative cytotoxic potencies and their affinities for this binding site. Two sterols, namely 25-hydroxycholesterol and 20 alpha-hydroxycholesterol, were exceptions to this general pattern, both clearly inhibited cell proliferation without having significant binding affinity for the antiestrogen-binding site. The same general order of antiproliferative potency of the oxysterols seen with MCF7 cells was also observed with the murine lymphoma cell line EL4. These findings suggest the possibility that the antiestrogen-binding site may be involved in mediating the antiproliferative effects of nonsteroidal antiestrogens and oxygenated sterols.
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Affiliation(s)
- L Lin
- Department of Physiology, National University of Singapore
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33
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Taylor FR, Shown EP, Thompson EB, Kandutsch AA. Purification, subunit structure, and DNA binding properties of the mouse oxysterol receptor. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)51484-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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34
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Kupferberg A, Teller G, Behr P, Leray C, Urban PF, Vincendon G, Mersel M. Effect of 7 beta-hydroxycholesterol on astrocyte primary cultures and derived spontaneously transformed cell lines: cytotoxicity and metabolism. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 1013:231-8. [PMID: 2804084 DOI: 10.1016/0167-4889(89)90140-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The lethal effect of 7 beta-hydroxycholesterol (7 beta-OHC) on neonatal rat astrocyte primary cultures and spontaneously transformed cell lines derived from them was investigated. Confluent astrocyte primary cultures were not affected by 30 microM 7 beta-OHC over a period of 72 h. In contrast, spontaneously transformed cells were killed by 20 microM 7 beta-OHC within the first 48 h. Further studies indicated that the cell lines metabolized 7 beta-OHC to a product the polarity of which was less than that of 7 beta-OHC. The metabolite was identified as 7 beta-OHC esterified on C-3 by naturally occurring fatty acids. Incubation of the cell lines with 0.5 microM metabolite markedly affected the cells within 24 h. These observations suggest that the 7 beta-OHC metabolite is implicated in the mechanism of action of 7 beta-OHC cytotoxicity on spontaneously transformed cells.
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Affiliation(s)
- A Kupferberg
- Centre de Neurochimie du CNRS and INSERM U-44, Strasbourg, France
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35
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Denis M, Wilhelmsson A, Cuthill S, Poellinger L, Gustafsson JA. Structural differences between the glucocorticoid, dioxin and oxysterol receptors from rat liver cytosol. Biochem Biophys Res Commun 1989; 163:444-51. [PMID: 2549994 DOI: 10.1016/0006-291x(89)92156-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The rat hepatic glucocorticoid, dioxin and oxysterol receptors were subjected to high performance liquid chromatography on size-exclusion and anion-exchange columns. Both the glucocorticoid receptor and the dioxin receptor had a Stokes radius Rs approximately 7.5 nm, expected value for heteromeric complexes containing a dimer of the Mr approximately 90,000 heat shock protein, hsp90 (Rs approximately 7.0 nm). The oxysterol receptor represented a much smaller entity (Rs approximately 6.0 nm). When analyzed on a Mono Q anion-exchange column, the molybdate-stabilized glucocorticoid receptor and dioxin receptor eluted as single peaks at approximately 0.30 M and 0.26-0.28 M NaCl, respectively, whereas the oxysterol receptor represented a less negatively charged species (0.11-0.14 M NaCl). Following washing of the Mono Q column with molybdate-free buffer, the activated monomeric glucocorticoid receptor was detected (0.10-0.12 M NaCl). In contrast, no modification in the elution pattern of the dioxin receptor and the oxysterol receptor was observed. These data demonstrate differences in the physico-chemical properties of the glucocorticoid, dioxin and oxysterol receptors, respectively, which might reflect structural differences.
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Affiliation(s)
- M Denis
- Department of Medical Nutrition, Karolinska Institute, Huddinge University Hospital, Sweden
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36
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Wilson WK, Pinkerton FD, Kirkpatrick ND, Schroepfer GJ. Inhibitors of sterol synthesis. Chemical synthesis of 5 beta-cholest-8-ene-3 beta,15 alpha-diol and its effects on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells. J Lipid Res 1989. [DOI: 10.1016/s0022-2275(20)38318-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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37
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von Gunten CF, Sinensky M. Treatment of CHO-K1 cells with 25-hydroxycholesterol produces a more rapid loss of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity than can be accounted for by enzyme turnover. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 1001:218-24. [PMID: 2917146 DOI: 10.1016/0005-2760(89)90151-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A key enzyme in the regulation of mammalian cellular cholesterol biosynthesis is 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase). It is well established that treatment with the compound 25-hydroxycholesterol lowers HMG-CoA reductase activity in cultured Chinese hamster ovary (CHO-K1) cells. After brief incubation (0-4 h) with 25-hydroxycholesterol (0.5 microgram/ml), cellular HMG-CoA reductase activity is decreased to 40% of its original level. This also occurs in the presence of exogenous mevinolin, a competitive inhibitor of HMG-CoA reductase which has previously been shown to inhibit its degradation. The inhibition of HMG-CoA reductase activity by 25-hydroxycholesterol is complete after 2 h. Radio-immune precipitation analysis of the native enzyme under these conditions shows a degradation half-life which is considerably longer than that of the observed inhibition. Studies with sodium fluoride, phosphatase 2A, bacterial alkaline phosphatase and calf alkaline phosphatase indicate that the observed loss of activity is not due to phosphorylation. These data are not consistent with described mechanisms of HMG-CoA reductase activity regulation by phosphorylation or degradation but are consistent with a novel mechanism that regulates the catalytic efficiency of this enzyme.
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Affiliation(s)
- C F von Gunten
- Eleanor Roosevelt Institute for Cancer Research, Denver, CO 80206
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38
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3-Hydroxy-3-methylglutaryl-coenzyme A reductase of the sea urchin embryo. Deduced structure and regulatory properties. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)81374-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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39
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Pajewski TN, Pinkerton FD, Miller LR, Schroepfer GJ. Inhibitors of sterol synthesis. Studies of the metabolism of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one in Chinese hamster ovary cells and its effects on activities of early enzymes in cholesterol biosynthesis. Chem Phys Lipids 1988; 48:153-68. [PMID: 2907421 DOI: 10.1016/0009-3084(88)90086-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The metabolism of [2,4-3H]5 alpha-cholest-8(14)-en-3 beta-ol-15-one (I) has been studied in Chinese hamster ovary (CHO-K1) cells which were maintained in a lipid-deficient medium. The incorporation of I into the cells was linear with respect to sterol concentration in the medium over the ranges of concentrations studied and was more than 3.5 times that of the uptake of cholesterol. The results of detailed chromatographic analyses of the lipids recovered from the cells after 6 h of incubation with [2,4-3H]I (0.5 microM or 6.0 microM) indicated that most of the 3H was associated with free I. Considerably lesser amounts of the 3H was associated with esters of I. No formation of [3H]cholesterol or [3H]cholesteryl esters (or other C27 monohydroxysterols) from labeled I was observed. The labeled material with the chromatographic behavior of the esters of I gave, after mild alkaline hydrolysis, the free 15-ketosterol which was characterized by the results of chromatographic and cocrystallization studies. Upon transfer of the CHO-K1 cells from a culture medium containing 8% newborn calf serum to the same medium containing 8% lipid-deficient newborn calf serum, increases in the levels of activity of cytosolic acetoacetyl-CoA thiolase and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase and of HMG-CoA reductase were observed. These increases were blocked by the addition of I at a concentration of 1.0 microM. I (1.0 microM) also caused a decrease in the levels of activity of the three enzymes in cells previously grown in medium containing lipid-deficient serum. These results demonstrate that I not only affects the enzymatic reduction of HMG-CoA but also the enzymatic formation of this key intermediate in cholesterol biosynthesis.
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Affiliation(s)
- T N Pajewski
- Department of Biochemistry and Chemistry, Rice University, Houston, TX 77251
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Miller LR, Raulston DL, Schroepfer GJ. Inhibitors of sterol synthesis. Effects of dietary 5 alpha-cholest-8(14)-en-3 beta-ol-15-one on early enzymes in hepatic cholesterol biosynthesis. Chem Phys Lipids 1988; 47:177-86. [PMID: 2901919 DOI: 10.1016/0009-3084(88)90011-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effects of dietary administration (0.1% in diet for 8 days) of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one on the levels of activity of cytosolic acetoacetyl coenzyme A thiolase, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase, and microsomal HMG-CoA reductase in liver have been studied in male Sprague-Dawley rats. Significant increases in the levels of activity of acetoacetyl-CoA thiolase and of HMG-CoA synthase were observed. The levels of microsomal HMG-CoA reductase activity were increased, relative to pair-fed control animals, in three experiments and increased, relative to ad libitum control animals, in one of three experiments. When compared with other agents for which the primary mode of action is an inhibition of the intestinal absorption of cholesterol, the magnitude of the increases in the levels of hepatic microsomal HMG-CoA reductase activity in the 15-ketosterol-fed rats was considerably smaller. In view of the previously described marked activity of the 15-ketosterol in the inhibition of the intestinal absorption of cholesterol, as well as its known effects in lowering HMG-CoA reductase activity in mammalian cells in culture, it is proposed that the 15-ketosterol may suppress the elevated levels of hepatic microsomal HMG-CoA reductase activity induced by the reduced delivery of cholesterol to liver as a consequence of the inhibition of the intestinal absorption of cholesterol.
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Affiliation(s)
- L R Miller
- Department of Biochemistry, Rice University, Houston, TX 77251
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Schroepfer GJ, Parish EJ, Tsuda M, Kandutsch AA. Inhibitors of sterol synthesis. Chemical syntheses, properties and effects of 4,4-dimethyl-15-oxygenated sterols on sterol synthesis and on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in cultured mammalian cells. Chem Phys Lipids 1988; 47:187-207. [PMID: 3168085 DOI: 10.1016/0009-3084(88)90012-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The chemical syntheses of a number of 4,4-dimethyl substituted 15-oxygenated sterols have been pursued to permit evaluation of their activity in the inhibition of the biosynthesis of cholesterol and other biological effects. Described herein are the first chemical syntheses of 4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-en-3 beta-ol-15-one, 3 beta,15 alpha-diacetoxy-4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-ene, 3 beta-acetoxy-4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-en-15 beta-ol, 4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-ene-3 beta,15 alpha-diol, 4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-ene-3 beta,15 beta-diol, 4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-en-15 alpha-ol-3-one, 3 beta-benzoyloxy-4,4-dimethyl-5 alpha-cholest-8(14)-ene-7 alpha,15 alpha-diol, 7 alpha,15 alpha-diacetoxy-3 beta-benzoyloxy-4,4-dimethyl-5 alpha-cholest-8(14)-ene, 4,4-dimethyl-5 alpha-cholest-8(14)-en-3 beta-ol-15-one and 3 beta,7 alpha,15 alpha-tri-o-bromobenzoyloxy-5 alpha-cholest-8(14)-ene. Also prepared for use in the biological experiments were 4,4-dimethyl-5 alpha-cholest-7-ene-3 beta,15 alpha-diol, 4,4-dimethyl-5 alpha-cholest-8-ene-3 beta,15 alpha-diol and 4,4-dimethyl-5 alpha-cholest-8(14)-ene-3 beta,7 alpha,15 alpha-triol. The effects of twelve 4,4-dimethyl substituted 15-oxygenated sterols and of four 4,4-dimethyl substituted 32-oxygenated sterols on sterol synthesis and on the level of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity were evaluated in mouse L cells. With the exception of 4,4-dimethyl-5 alpha-cholest-8(14)-ene-3 beta,7 alpha,15 alpha-triol, all of the 4,4-dimethyl substituted 15-oxygenated sterols caused a 50% inhibition of sterol synthesis at less than 10(-6) M and six of the 4,4-dimethyl substituted 15-oxygenated sterols caused a 50% inhibition of sterol synthesis at less than 10(-7) M. 4,4-Dimethyl-14 alpha-ethyl-5 alpha-cholest-7-ene-3 beta,15 alpha-diol caused a 50% decrease in sterol synthesis at 10(-8) M. The potencies of the 4,4-dimethyl substituted 15-oxygenated and C-32-oxygenated sterols with respect to inhibition of sterol synthesis and suppression of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity have been compared with those of the corresponding sterols lacking the 4,4-dimethyl substitution.
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Affiliation(s)
- G J Schroepfer
- Department of Biochemistry, Rice University, Houston, TX 77251
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Lahoua Z, Astruc ME, Crastes de Paulet A. Serum-induced arachidonic acid release and prostaglandin biosynthesis are potentiated by oxygenated sterols in NRK 49F cells. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 958:396-404. [PMID: 3124881 DOI: 10.1016/0005-2760(88)90225-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Fetal calf serum is able to activate arachidonic acid release from phospholipids in NRK 49F cells. We showed that this phenomenon can be potentiated by adding oxysterols to the culture medium. The oxysterol effect was dose-dependent and was not observed in the absence of fetal calf serum. Greater amounts of prostaglandin E2 and prostaglandin F2 alpha were released into the medium in the presence of oxysterols without apparent modification of the cyclooxygenase activity. The most effective oxysterols, in descending order, were the following: calcitriol greater than 7 alpha-hydroxycholesterol greater than 7 beta-hydroxycholesterol greater than 25-hydroxycholesterol. Cholesterol and 7-ketocholesterol were unable to activate phospholipase activity. The mechanism of this activation by oxysterols is still unknown.
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Affiliation(s)
- Z Lahoua
- INSERM U.58, Montpellier, France
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Taylor FR, Kandutsch AA, Anzalone L, Phirwa S, Spencer TA. Photoaffinity labeling of the oxysterol receptor. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)69200-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Favata MF, Trzaskos JM, Chen HW, Fischer RT, Greenberg RS. Modulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase by azole antimycotics requires lanosterol demethylation, but not 24,25-epoxylanosterol formation. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)45344-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Abstract
Literature published between 1980 and 1986 dealing broadly with the topic of cholesterol autoxidation is reviewed. The review builds on the detailed 1981 monographic treatment of the topic by the author and covers new items of chemistry, analysis, and metabolism.
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Affiliation(s)
- L L Smith
- Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77550
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Chapter 8 Cellular regulation of cholesterol metabolism. ACTA ACUST UNITED AC 1987. [DOI: 10.1016/s0167-7306(08)60202-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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47
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Beseme F, Astruc ME, Defay R, Crastes de Paulet A. Rat liver cytosol oxysterol-binding protein. Characterization and comparison with the HTC cell protein. FEBS Lett 1987; 210:97-103. [PMID: 3803583 DOI: 10.1016/0014-5793(87)81305-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A cytosol protein that specifically binds cholesterol derivatives oxygenated on the side chain has been demonstrated in rat liver and transformed HTC cells. This protein, of which the sedimentation coefficient is about 8 S, was saturable and showed a high binding affinity (Kd about 5 X 10(-9) M) for 25-hydroxycholesterol. Its molecular mass is about 160 kDa. The physicochemical characteristics of this protein were identical whether the model was normal or transformed. This oxysterol-binding protein differs from the well-known sterol carrier proteins.
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Richert L, Beck JP, Shinitzky M. Inhibition of IL-2 secretion and IL-2 receptor appearance of activated lymphocytes pretreated with hydroxylated sterols. Immunol Lett 1986; 13:329-34. [PMID: 3096880 DOI: 10.1016/0165-2478(86)90067-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
When murine BALB/c splenocytes are pretreated for 2 h with different concentrations of 25-hydroxycholesterol (25-HC) or 7 beta-hydroxycholesterol (7-HC), washed and stimulated either with irradiated C57BL/6 splenocytes or with Con A, IL-2 secretion is inhibited in a dose-dependent way as well as the subsequent cell proliferation. Using the same treatment and stimulation conditions, IL-2 receptor appearance on human T lymphocytes, as characterized by anti-Tac antibody binding, is also inhibited in a dose-dependent way. In contrast, the hydrophilic derivative of 7 beta-hydroxycholesterol, the 3.7 bishemisuccinate sodium salt (7-HC BHS), did not influence any of the 3 tested parameters.
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Besème F, Astruc ME, Defay R, Descomps B, Crastes de Paulet A. Characterization of oxysterol-binding protein in rat embryo fibroblasts and variations as a function of the cell cycle. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 886:96-108. [PMID: 3955082 DOI: 10.1016/0167-4889(86)90215-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A cell-free system assay involving cell freeze-thawing and protein fractionation by ammonium sulfate precipitation was developed to characterize a cytosol binding protein specific for oxysterols in rat embryo fibroblasts. This protein shared common characteristics with the oxysterol-binding protein described in L cells and in normal human lymphocytes: 8 S sedimentation coefficient, sterol-protein complex of Mr 160 600, saturability, high affinity (Kd in the range of 10(-9) M) and specificity for cholesterol derivatives oxidized on the side chain. These compounds were better inhibitors of DNA synthesis than the compounds oxidized on the nucleus, whereas no difference was found between sterols oxygenated either on the side chain or on the nucleus, as far as inhibition of hydroxymethylglutaryl-CoA reductase (HMG-CoA reductase) was concerned. Macromolecular components capable of specifically binding 25-hydroxycholesterol were also detected in the fibroblast nucleus. The cytosol oxysterol-binding protein showed a sharp increase (5-fold) in the G2M phase of the cell cycle and in exponentially growing cells (maximal binding site number/cell: 43 500, versus 8850 in confluent cells). Neither the affinity nor the sedimentation coefficient of the protein changed in either situation. The quantitative (but not qualitative) variations of oxysterol-binding protein could be related to the inhibitory effect of 25-hydroxycholesterol on DNA synthesis, which becomes critical when this sterol is added in the G2M phase of the cell cycle.
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Heiniger HJ, Chen HW, Boissonneault GA, Hess M, Cottier H, Stoner RD. The role of cholesterol and its biosynthesis in lymphocyte proliferation and differentiation. Ann N Y Acad Sci 1985; 459:111-28. [PMID: 3868313 DOI: 10.1111/j.1749-6632.1985.tb20820.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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