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Wnętrzak A, Chachaj-Brekiesz A, Kobierski J, Dynarowicz-Latka P. The Structure of Oxysterols Determines Their Behavior at Phase Boundaries: Implications for Model Membranes and Structure-Activity Relationships. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1440:3-29. [PMID: 38036872 DOI: 10.1007/978-3-031-43883-7_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
The presence of an additional polar group in the cholesterol backbone increases the hydrophilicity of resulting compounds (oxysterols), determines their arrangement at the phase boundary, and interactions with other lipids and proteins. As a result, physicochemical properties of biomembranes (i.e., elasticity, permeability, and ability to bind proteins) are modified, which in turn may affect their functioning. The observed effect depends on the type of oxysterol and its concentration and can be both positive (e.g., antiviral activity) or negative (disturbance of cholesterol homeostasis, signal transduction, and protein segregation). The membrane activity of oxysterols has been successfully studied using membrane models (vesicles, monolayers, and solid supported films). Membrane models, in contrast to the natural systems, provide the possibility to selectively examine the specific aspect of biomolecule-membrane interactions. Moreover, the gradual increase in the complexity of the used model allows to understand the molecular phenomena occurring at the membrane level. The interest in research on artificial membranes has increased significantly in recent years, mainly due to the development of modern and sophisticated physicochemical methods (static and dynamic) in both the micro- and nanoscale, which are applied with the assistance of powerful theoretical calculations. This review provides an overview of the most important findings on this topic in the current literature.
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Affiliation(s)
- Anita Wnętrzak
- Faculty of Chemistry, Jagiellonian University, Kraków, Poland.
| | | | - Jan Kobierski
- Department of Pharmaceutical Biophysics, Faculty of Pharmacy, Jagiellonian University Medical College, Kraków, Poland
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2
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Microglia and Cholesterol Handling: Implications for Alzheimer's Disease. Biomedicines 2022; 10:biomedicines10123105. [PMID: 36551857 PMCID: PMC9775660 DOI: 10.3390/biomedicines10123105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 11/24/2022] [Accepted: 11/29/2022] [Indexed: 12/04/2022] Open
Abstract
Cholesterol is essential for brain function and structure, however altered cholesterol metabolism and transport are hallmarks of multiple neurodegenerative conditions, including Alzheimer's disease (AD). The well-established link between apolipoprotein E (APOE) genotype and increased AD risk highlights the importance of cholesterol and lipid transport in AD etiology. Whereas more is known about the regulation and dysregulation of cholesterol metabolism and transport in neurons and astrocytes, less is known about how microglia, the immune cells of the brain, handle cholesterol, and the subsequent implications for the ability of microglia to perform their essential functions. Evidence is emerging that a high-cholesterol environment, particularly in the context of defects in the ability to transport cholesterol (e.g., expression of the high-risk APOE4 isoform), can lead to chronic activation, increased inflammatory signaling, and reduced phagocytic capacity, which have been associated with AD pathology. In this narrative review we describe how cholesterol regulates microglia phenotype and function, and discuss what is known about the effects of statins on microglia, as well as highlighting areas of future research to advance knowledge that can lead to the development of novel therapies for the prevention and treatment of AD.
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3
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Suzuki A, Urano Y, Ishida T, Noguchi N. Different functions of vitamin E homologues in the various types of cell death induced by oxysterols. Free Radic Biol Med 2021; 176:356-365. [PMID: 34648906 DOI: 10.1016/j.freeradbiomed.2021.10.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 10/06/2021] [Accepted: 10/08/2021] [Indexed: 01/18/2023]
Abstract
24(S)-Hydroxycholesterol (24S-OHC) and 25-hydroxycholesterol (25-OHC) are produced by cholesterol 24-hydroxylase and cholesterol 25-hydroxylase, respectively. The purpose of the present study was to determine the type of cell death induced by these oxysterols in neuronal cells, hepatic cells, and keratinocytes, and to elucidate the inhibitory effect of vitamin E homologues on various types of cell death. In human neuronal cells (SH-SY5Y cells), 24S-OHC and 25-OHC caused a cell death that was independent of caspase activation. We reported previously that the esterification of 24S-OHC by acyl-CoA:cholesterol acyltransferase 1 (ACAT1) and the resulting formation of a lipid droplet (LD)-like structure are responsible for the 24S-OHC-induced neuronal cell death. Here, we found that 25-OHC also induced ACAT1-mediated 25-OHC esterification and LD formation in neuronal cells. 25-OHC-induced cell death was inhibited by α-tocopherol (α-Toc) but not by α-tocotrienol (α-Toc3), as observed for 24S-OHC-induced cell death in SH-SY5Y cells. In human hepatic cells (HepG2 cells), these oxysterols caused a cell death that was caspase- and oxysterol-esterification-independent. This cell death was suppressed by both α-Toc and α-Toc3, suggesting the involvement of free-radical-mediated lipid peroxidation in the cell death induced by these oxysterols in hepatic cells. In human keratinocytes (HaCaT cells), these oxysterols caused a caspase-dependent but oxysterol-esterification-independent cell death that was inhibited by α-Toc but not by α-Toc3. These results suggest that α-Toc and α-Toc3 act as radical-scavenging antioxidants against oxysterol-induced cell death in the same way in hepatic cells, whereas their behavior is different in inhibition of cell death in neuronal cells and keratinocytes. Collectively, these results demonstrated that 24S-OHC and 25-OHC induced the same type of cell death in each of the cell types examined, and that α-Toc and α-Toc3 exerted different effects, depending on the type of cell death.
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Affiliation(s)
- Atsuki Suzuki
- Systems Life Sciences Laboratory, Graduate School of Life and Medical Sciences, Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe, Kyoto, 610-0394, Japan
| | - Yasuomi Urano
- Systems Life Sciences Laboratory, Graduate School of Life and Medical Sciences, Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe, Kyoto, 610-0394, Japan
| | - Tomohisa Ishida
- Systems Life Sciences Laboratory, Graduate School of Life and Medical Sciences, Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe, Kyoto, 610-0394, Japan
| | - Noriko Noguchi
- Systems Life Sciences Laboratory, Graduate School of Life and Medical Sciences, Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe, Kyoto, 610-0394, Japan.
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4
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Elkins MR, Bandara A, Pantelopulos GA, Straub JE, Hong M. Direct Observation of Cholesterol Dimers and Tetramers in Lipid Bilayers. J Phys Chem B 2021; 125:1825-1837. [DOI: 10.1021/acs.jpcb.0c10631] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Matthew R. Elkins
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Asanga Bandara
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - George A. Pantelopulos
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - John E. Straub
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
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5
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Kwon B, Mandal T, Elkins MR, Oh Y, Cui Q, Hong M. Cholesterol Interaction with the Trimeric HIV Fusion Protein gp41 in Lipid Bilayers Investigated by Solid-State NMR Spectroscopy and Molecular Dynamics Simulations. J Mol Biol 2020; 432:4705-4721. [PMID: 32592698 PMCID: PMC7781112 DOI: 10.1016/j.jmb.2020.06.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 06/07/2020] [Accepted: 06/18/2020] [Indexed: 12/13/2022]
Abstract
HIV-1 entry into cells is mediated by the fusion protein gp41. Cholesterol plays an important role in this virus-cell fusion, but molecular structural information about cholesterol-gp41 interaction is so far absent. Here, we present experimental and computational data about cholesterol complexation with gp41 in lipid bilayers. We focus on the C-terminal region of the protein, which comprises a membrane-proximal external region (MPER) and the transmembrane domain (TMD). We measured peptide-cholesterol contacts in virus-mimetic lipid bilayers using solid-state NMR spectroscopy, and augmented these experimental data with all-atom molecular dynamics simulations. 2D 19F NMR spectra show correlation peaks between MPER residues and the cholesterol isooctyl tail, indicating that cholesterol is in molecular contact with the MPER-TMD trimer. 19F-13C distance measurements between the peptide and 13C-labeled cholesterol show that C17 on the D ring and C9 at the intersection of B and C rings are ~7.0 Å from the F673 side-chain 4-19F. At high peptide concentrations in the membrane, the 19F-13C distance data indicate three cholesterol molecules bound near F673 in each trimer. Mutation of a cholesterol recognition amino acid consensus motif did not change these distances, indicating that cholesterol binding does not require this sequence motif. Molecular dynamics simulations further identify two hotspots for cholesterol interactions. Taken together, these experimental data and simulations indicate that the helix-turn-helix conformation of the MPER-TMD is responsible for sequestering cholesterol. We propose that this gp41-cholesterol interaction mediates virus-cell fusion by recruiting gp41 to the boundary of the liquid-disordered and liquid-ordered phases to incur membrane curvature.
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Affiliation(s)
- Byungsu Kwon
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, USA
| | - Taraknath Mandal
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA
| | - Matthew R Elkins
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, USA
| | - Younghoon Oh
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA
| | - Qiang Cui
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA; Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA; Department of Biomedical Engineering, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, USA.
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6
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Wnętrzak A, Chachaj-Brekiesz A, Kobierski J, Karwowska K, Petelska AD, Dynarowicz-Latka P. Unusual Behavior of the Bipolar Molecule 25-Hydroxycholesterol at the Air/Water Interface-Langmuir Monolayer Approach Complemented with Theoretical Calculations. J Phys Chem B 2020; 124:1104-1114. [PMID: 31972080 PMCID: PMC7497659 DOI: 10.1021/acs.jpcb.9b10938] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 01/14/2020] [Indexed: 12/29/2022]
Abstract
In this study, 25-hydroxycholesterol (25-OH), a biamphiphilic compound with a wide range of biological activities, has been investigated at the air/water interface. We were interested in how two hydroxyl groups attached at distal positions of the 25-OH molecule (namely, at C(3) in the sterane system and at C(25) in the side chain) influence its surface behavior. Apart from traditional Langmuir monolayers, other complementary surface-sensitive techniques, such as electric surface potential measurements, Brewster angle microscopy (BAM, enabling texture visualization and film thickness measurements), and polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS), were applied. Experimental data have been interpreted with the aid of theoretical study. Our results show that 25-OH molecules in the monomolecular layer are anchored to the water surface alternatively with C(3) or C(25) hydroxyl groups. Theoretical calculations revealed that the populations of these alternative orientations were not equal and molecules anchored with C(3) hydroxyl groups were found to be in excess. As a consequence of such an arrangement, surface films of 25-OH are of lower stability as compared to cholesterol (considered as a non-oxidized analogue of 25-OH). Moreover, it was found that, upon compression, the transition from mono- to bilayer occurred. The molecular mechanism and interactions stabilizing bilayer structure were proposed. The explanation of the observed unusual surface behavior of 25-OH may contribute to an understanding of differences in biological activity between chain- and ring-oxidized sterols.
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Affiliation(s)
- Anita Wnętrzak
- Faculty
of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland
| | - Anna Chachaj-Brekiesz
- Faculty
of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland
| | - Jan Kobierski
- Department
of Pharmaceutical Biophysics, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, 30-688 Kraków, Poland
| | - Katarzyna Karwowska
- Faculty
of Chemistry, University of Bialystok, Ciolkowskiego 1K, 15-425 Bialystok, Poland
| | - Aneta D. Petelska
- Faculty
of Chemistry, University of Bialystok, Ciolkowskiego 1K, 15-425 Bialystok, Poland
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7
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Zhou W, Fisher PM, Vanderloop BH, Shen Y, Shi H, Maldonado AJ, Leaver DJ, Nes WD. A nematode sterol C4α-methyltransferase catalyzes a new methylation reaction responsible for sterol diversity. J Lipid Res 2019; 61:192-204. [PMID: 31548366 PMCID: PMC6997595 DOI: 10.1194/jlr.ra119000317] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Revised: 09/22/2019] [Indexed: 11/28/2022] Open
Abstract
Primitive sterol evolution plays an important role in fossil record interpretation and offers potential therapeutic avenues for human disease resulting from nematode infections. Recognizing that C4-methyl stenol products [8(14)-lophenol] can be synthesized in bacteria while C4-methyl stanol products (dinosterol) can be synthesized in dinoflagellates and preserved as sterane biomarkers in ancient sedimentary rock is key to eukaryotic sterol evolution. In this regard, nematodes have been proposed to convert dietary cholesterol to 8(14)-lophenol by a secondary metabolism pathway that could involve sterol C4 methylation analogous to the C2 methylation of hopanoids (radicle-type mechanism) or C24 methylation of sterols (carbocation-type mechanism). Here, we characterized dichotomous cholesterol metabolic pathways in Caenorhabditis elegans that generate 3-oxo sterol intermediates in separate paths to lophanol (4-methyl stanol) and 8(14)-lophenol (4-methyl stenol). We uncovered alternate C3-sterol oxidation and Δ7 desaturation steps that regulate sterol flux from which branching metabolite networks arise, while lophanol/8(14)-lophenol formation is shown to be dependent on a sterol C4α-methyltransferse (4-SMT) that requires 3-oxo sterol substrates and catalyzes a newly discovered 3-keto-enol tautomerism mechanism linked to S-adenosyl-l-methionine-dependent methylation. Alignment-specific substrate-binding domains similarly conserved in 4-SMT and 24-SMT enzymes, despite minimal amino acid sequence identity, suggests divergence from a common, primordial ancestor in the evolution of methyl sterols. The combination of these results provides evolutionary leads to sterol diversity and points to cryptic C4-methyl steroidogenic pathways of targeted convergence that mediate lineage-specific adaptations.
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Affiliation(s)
- Wenxu Zhou
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Paxtyn M Fisher
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Boden H Vanderloop
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Yun Shen
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Huazhong Shi
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Adrian J Maldonado
- Department of Biology, Geology, and Physical Sciences, Sul Ross State University, Alpine, TX
| | - David J Leaver
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX.,Department of Biology, Geology, and Physical Sciences, Sul Ross State University, Alpine, TX
| | - W David Nes
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
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8
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Elkins MR, Hong M. Elucidating ligand-bound structures of membrane proteins using solid-state NMR spectroscopy. Curr Opin Struct Biol 2019; 57:103-109. [PMID: 30903830 PMCID: PMC6697555 DOI: 10.1016/j.sbi.2019.02.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 02/05/2019] [Accepted: 02/08/2019] [Indexed: 01/08/2023]
Abstract
Magic-angle-spinning (MAS) solid-state NMR spectroscopy is a versatile technique to elucidate functionally important protein-ligand interactions in lipid membranes. Here, we review recent solid-state NMR studies of membrane protein interactions with cholesterol, lipids, transported substrates, and peptide ligands. These studies are conducted in synthetic or native lipid bilayers to provide an accurate environment for ligand binding. The solid-state NMR approaches include multinuclear detection to gain comprehensive structural information, distance measurements to locate ligand-binding sites, and dynamic nuclear polarization and 1H detection to enhance spectral sensitivity. These studies provide novel insights into the mechanisms of virus budding, virus entry into cells, transmembrane signaling, substrate transport, antibacterial action, and many other biological processes.
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Affiliation(s)
- Matthew R Elkins
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, United States
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139, United States.
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9
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Crucial role of the hydroxyl group orientation in Langmuir monolayers organization–The case of 7-hydroxycholesterol epimers. Colloids Surf A Physicochem Eng Asp 2019. [DOI: 10.1016/j.colsurfa.2018.12.025] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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10
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Elkins MR, Williams JK, Gelenter MD, Dai P, Kwon B, Sergeyev IV, Pentelute BL, Hong M. Cholesterol-binding site of the influenza M2 protein in lipid bilayers from solid-state NMR. Proc Natl Acad Sci U S A 2017; 114:12946-12951. [PMID: 29158386 PMCID: PMC5724280 DOI: 10.1073/pnas.1715127114] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The influenza M2 protein not only forms a proton channel but also mediates membrane scission in a cholesterol-dependent manner to cause virus budding and release. The atomic interaction of cholesterol with M2, as with most eukaryotic membrane proteins, has long been elusive. We have now determined the cholesterol-binding site of the M2 protein in phospholipid bilayers using solid-state NMR spectroscopy. Chain-fluorinated cholesterol was used to measure cholesterol proximity to M2 while sterol-deuterated cholesterol was used to measure bound-cholesterol orientation in lipid bilayers. Carbon-fluorine distance measurements show that at a cholesterol concentration of 17 mol%, two cholesterol molecules bind each M2 tetramer. Cholesterol binds the C-terminal transmembrane (TM) residues, near an amphipathic helix, without requiring a cholesterol recognition sequence motif. Deuterium NMR spectra indicate that bound cholesterol is approximately parallel to the bilayer normal, with the rough face of the sterol rings apposed to methyl-rich TM residues. The distance- and orientation-restrained cholesterol-binding site structure shows that cholesterol is stabilized by hydrophobic interactions with the TM helix and polar and aromatic interactions with neighboring amphipathic helices. At the 1:2 binding stoichiometry, lipid 31P spectra show an isotropic peak indicative of high membrane curvature. This M2-cholesterol complex structure, together with previously observed M2 localization at phase boundaries, suggests that cholesterol mediates M2 clustering to the neck of the budding virus to cause the necessary curvature for membrane scission. The solid-state NMR approach developed here is generally applicable for elucidating the structural basis of cholesterol's effects on membrane protein function.
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Affiliation(s)
- Matthew R Elkins
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Jonathan K Williams
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Martin D Gelenter
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Peng Dai
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Byungsu Kwon
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | | | - Bradley L Pentelute
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139;
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11
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Kulig W, Cwiklik L, Jurkiewicz P, Rog T, Vattulainen I. Cholesterol oxidation products and their biological importance. Chem Phys Lipids 2016; 199:144-160. [DOI: 10.1016/j.chemphyslip.2016.03.001] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 03/02/2016] [Accepted: 03/03/2016] [Indexed: 12/14/2022]
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12
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Leaver DJ, Patkar P, Singha UK, Miller MB, Haubrich BA, Chaudhuri M, Nes WD. Fluorinated Sterols Are Suicide Inhibitors of Ergosterol Biosynthesis and Growth in Trypanosoma brucei. ACTA ACUST UNITED AC 2016; 22:1374-83. [PMID: 26496686 DOI: 10.1016/j.chembiol.2015.08.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/20/2015] [Accepted: 08/28/2015] [Indexed: 11/19/2022]
Abstract
Trypanosoma brucei, the causal agent for sleeping sickness, depends on ergosterol for growth. Here, we describe the effects of a mechanism-based inhibitor, 26-fluorolanosterol (26FL), which converts in vivo to a fluorinated substrate of the sterol C24-methyltransferase essential for sterol methylation and function of ergosterol, and missing from the human host. 26FL showed potent inhibition of ergosterol biosynthesis and growth of procyclic and bloodstream forms while having no effect on cholesterol biosynthesis or growth of human epithelial kidney cells. During exposure of cloned TbSMT to 26-fluorocholesta-5,7,24-trienol, the enzyme is gradually killed as a consequence of the covalent binding of the intermediate C25 cation to the active site (kcat/kinact = 0.26 min(-1)/0.24 min(-1); partition ratio of 1.08), whereas 26FL is non-productively bound. These results demonstrate that poisoning of ergosterol biosynthesis by a 26-fluorinated Δ(24)-sterol is a promising strategy for developing a new treatment for trypanosomiasis.
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Affiliation(s)
- David J Leaver
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA; Institute of Chemistry and Biomedical Sciences, Nanjing University, 22 Hankou Road, Nanjing, Jiangsu, 210093, P.R. China
| | - Presheet Patkar
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA
| | - Ujjal K Singha
- Department of Microbiology and Immunology, Meharry Medical College, 1005 Doctor D. B. Todd Jr. Boulevard, Nashville, TN 37208, USA
| | - Matthew B Miller
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA
| | - Brad A Haubrich
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA
| | - Minu Chaudhuri
- Department of Microbiology and Immunology, Meharry Medical College, 1005 Doctor D. B. Todd Jr. Boulevard, Nashville, TN 37208, USA
| | - W David Nes
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA.
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13
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Benesch MGK, McElhaney RN. A comparative differential scanning calorimetry study of the effects of cholesterol and various oxysterols on the thermotropic phase behavior of dipalmitoylphosphatidylcholine bilayer membranes. Chem Phys Lipids 2015; 195:21-33. [PMID: 26620814 DOI: 10.1016/j.chemphyslip.2015.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 11/12/2015] [Accepted: 11/14/2015] [Indexed: 01/19/2023]
Abstract
We have carried out a comparative differential scanning calorimetric (DSC) study of the effects of cholesterol (C) and the eight most physiologically relevant oxysterols on the thermotropic phase behavior of dipalmitoylphosphatidylcholine (DPPC) bilayer membranes. The structures of these oxysterols differ from that of C by the presence of additional hydroxyl, keto or epoxy groups on the steroid ring system or by the presence of a hydroxyl group in the alkyl side chain. In general, the progressive incorporation of these oxysterols reduces the temperature, cooperativity and enthalpy of the pretransition of DPPC to a greater extent than C, indicating that their presence thermally destabilizes and disorders the gel states of DPPC bilayers to a greater extent than C. Similarly, the incorporation of these oxysterols either increases the temperature of the broad component of the main phase transition to a smaller extent than C or actually decreases it. Again, this indicates that the presence of these compounds is less effective at thermally stabilizing and ordering the sterol-rich domains of DPPC bilayers than is C itself. Moreover, the incorporation of these oxysterols decrease the cooperativity and enthalpy of the main phase transition of DPPC to a smaller extent than C, indicating that they are somewhat less miscible in fluid DPPC bilayers than is C. Particularly notable in this regard is 25-hydroxycholesterol, which exhibits a markedly reduced miscibility in both gel and fluid DPPC bilayers compared to C itself. In general, the effectiveness of these oxysterols in stabilizing and ordering DPPC bilayers decreases as their rate of interbilayer exchange and the polarity of the oxysterol increases. We close by providing a tentative molecular explanation for the results of our DSC studies and of those of previous biophysical studies of the effects of various oxysterol on lipid bilayer model membranes.
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Affiliation(s)
- Matthew G K Benesch
- Department of Biochemistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - Ronald N McElhaney
- Department of Biochemistry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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14
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Stottrup BL, Hernandez-Balderrama LH, Kunz JC, Nguyen AH, Sonquist BJ. Comparison of Cholesterol and 25-Hydroxycholesterol in Phase-Separated Langmuir Monolayers at the Air–Water Interface. J Phys Chem B 2014; 118:11231-7. [DOI: 10.1021/jp506592k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Benjamin L. Stottrup
- Department of Physics, ‡Department of Chemistry, and §Department of Biology, Augsburg College, Minneapolis, Minnesota 55454, United States
| | - Luis H. Hernandez-Balderrama
- Department of Physics, ‡Department of Chemistry, and §Department of Biology, Augsburg College, Minneapolis, Minnesota 55454, United States
| | - Joan C. Kunz
- Department of Physics, ‡Department of Chemistry, and §Department of Biology, Augsburg College, Minneapolis, Minnesota 55454, United States
| | - Andrew H. Nguyen
- Department of Physics, ‡Department of Chemistry, and §Department of Biology, Augsburg College, Minneapolis, Minnesota 55454, United States
| | - Benjamin J. Sonquist
- Department of Physics, ‡Department of Chemistry, and §Department of Biology, Augsburg College, Minneapolis, Minnesota 55454, United States
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15
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Habib L, Khreich N, Jraij A, Abbas S, Magdalou J, Charcosset C, Greige-Gerges H. Preparation and characterization of liposomes incorporating cucurbitacin E, a natural cytotoxic triterpene. Int J Pharm 2013; 448:313-9. [DOI: 10.1016/j.ijpharm.2013.03.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 03/12/2013] [Accepted: 03/13/2013] [Indexed: 11/27/2022]
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16
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Paiva D, Brezesinski G, Pereira MDC, Rocha S. Langmuir monolayers of monocationic lipid mixed with cholesterol or fluorocholesterol: DNA adsorption studies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:1920-1925. [PMID: 23356402 DOI: 10.1021/la304012e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Monolayers of the cationic lipid DOTAP (1,2-dioleoyl-3-trimethylammonium-propane) and cholesterol or heptafluorocholesterol were prepared, and their interaction with DNA was characterized. The mixture of DOTAP with each of the sterols at 1:1 molar ratios leads to monolayers in a liquid expanded state, similarly to that of DOTAP alone. The area per molecule of the mixtures was smaller than that expected according to the additivity rule applicable if the two components are either completely miscible or immiscible within the monolayer. The observed negative deviation from the additivity indicates the existence of additional attractive interactions between the components. The surface potential of DOTAP monolayer is positive (+560 mV). It decreases only slightly after the addition of cholesterol (+540 mV) but drastically after the addition of heptafluorocholesterol (+20 mV) in the 1:1 mixtures at a surface pressure of 35 mN/m. This difference is attributed to the negative dipole moment of the fluorinated component. The adsorption of DNA is similar for both systems, which supports the possibility of using fluorinated cholesterol as helper lipid in DNA transfection vectors.
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Affiliation(s)
- Diana Paiva
- LEPAE, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
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17
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Cholesterol Organization in Phosphatidylcholine Liposomes: A Surface Plasmon Resonance Study. MATERIALS 2012. [PMCID: PMC5448994 DOI: 10.3390/ma5112306] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Models for the organization of sterols into regular arrays within phospholipid bilayers have been proposed previously. The existence of such arrays in real systems has been supported by the fact that concentration-dependent sterol properties show discontinuities at the cholesterol mole fractions corresponding to regular lattice arrangements. Experimental results presented here are based on a surface plasmon resonance assay that was used to analyze rates of cyclodextrin-mediated removal of cholesterol from adsorbed liposomes at cholesterol mole fractions up to χC = 0.55. Two kinetic pools of cholesterol were detected; there was a fast pool present at χC > 0.25, and a slow pool, with a removal rate that was dependent on the initial χC but that did not vary as χC decreased during the course of one experiment. The cholesterol activity therefore seems to be affected by sample history as well as local concentration, which could be explained in terms of the formation of superlattices that are stable for relatively long times. We also describe a variation on the traditional lattice models, with phosphatidylcholine (PC) being treated as an arrangement of hexagonal tiles; the cholesterol is then introduced at any vertex point, without increasing the total area occupied by all the lipid molecules. This model is consistent with Langmuir trough measurements of total lipid area and provides a simple explanation for the maximum solubility of cholesterol in the PC bilayer.
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18
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Kerdous R, Heuvingh J, Bonneau S. Photo-dynamic induction of oxidative stress within cholesterol-containing membranes: Shape transitions and permeabilization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2965-72. [DOI: 10.1016/j.bbamem.2011.08.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2011] [Revised: 07/15/2011] [Accepted: 08/02/2011] [Indexed: 11/16/2022]
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19
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Reuter S, Hofmann AM, Busse K, Frey H, Kressler J. Langmuir and Langmuir-Blodgett films of multifunctional, amphiphilic polyethers with cholesterol moieties. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:1978-1989. [PMID: 21175221 DOI: 10.1021/la104274d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Langmuir films of multifunctional, hydrophilic polyethers containing a hydrophobic cholesterol group (Ch) were studied by surface pressure-mean molecular area (π-mmA) measurements and Brewster angle microscopy (BAM). The polyethers were either homopolymers or diblock copolymers of linear poly(glycerol) (lPG), linear poly(glyceryl glycidyl ether) (lPGG), linear poly(ethylene glycol) (lPEG), or hyperbranched poly(glycerol) (hbPG). Surface pressure measurements revealed that the homopolymers lPG and hbPG did not stay at the water surface after spreading and solvent evaporation, in contrast to lPEG. Because of the incorporation of the Ch group in the polymer structure, stable Langmuir films were formed by Ch-lPG(n), Ch-lPGG(n), and Ch-hbPG(n). The Ch-hbPG(n), Ch-lPEG(n), Ch-lPEG(n)-b-lPG(m), Ch-lPEG(n)-b-lPGG(m), and Ch-lPEG(n)-b-hbPG(m) systems showed an extended plateau region assigned to a phase transition involving the Ch groups. Typical hierarchically ordered morphologies of the LB films on hydrophilic substrates were observed for all Ch-initiated polymers. All LB films showed that Ch of the Ch-initiated homopolymers is able to crystallize. This strong tendency of self-aggregation then triggers further dewetting effects of the respective polyether entities. Fingerlike morphologies are observed for Ch-lPEG(69), since the lPEG(69) entity is able to undergo crystallization after transfer onto the silicon substrate.
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Affiliation(s)
- Sascha Reuter
- Department of Chemistry, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
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20
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Yoda T, Vestergaard MC, Akazawa-Ogawa Y, Yoshida Y, Hamada T, Takagi M. Dynamic Response of a Cholesterol-containing Model Membrane to Oxidative Stress. CHEM LETT 2010. [DOI: 10.1246/cl.2010.1273] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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21
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Taking another look with fluorescence microscopy: Image processing techniques in Langmuir monolayers for the twenty-first century. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1289-300. [DOI: 10.1016/j.bbamem.2010.01.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 12/11/2009] [Accepted: 01/05/2010] [Indexed: 12/15/2022]
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22
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Interaction of two oxysterols, 7-ketocholesterol and 25-hydroxycholesterol, with phosphatidylcholine and sphingomyelin in model membranes. Chem Phys Lipids 2010; 163:586-93. [DOI: 10.1016/j.chemphyslip.2010.05.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 04/07/2010] [Accepted: 05/04/2010] [Indexed: 02/03/2023]
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23
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Ishii H, Shimanouchi T, Umakoshi H, Walde P, Kuboi R. Analysis of the 22-NBD-cholesterol transfer between liposome membranes and its relation to the intermembrane exchange of 25-hydroxycholesterol. Colloids Surf B Biointerfaces 2010; 77:117-21. [DOI: 10.1016/j.colsurfb.2010.01.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2009] [Revised: 01/06/2010] [Accepted: 01/07/2010] [Indexed: 10/20/2022]
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24
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Janout V, Turkyilmaz S, Wang M, Wang Y, Manaka Y, Regen SL. An upside down view of cholesterol's condensing effect: does surface occupancy play a role? LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:5316-5318. [PMID: 20329715 PMCID: PMC2858571 DOI: 10.1021/la100878s] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The condensing action of cholesterol has been compared with that of a structural isomer having its hydroxyl group located at the C-25 position (i.e., 25-OH'), that is, an isomer favoring an "upside down" orientation in lipid membranes. Surface pressure-area isotherms of mixed monolayers made from 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/cholesterol and DMPC/25-OH' have established that 25-OH' has a weaker condensing effect than cholesterol. Nearest-neighbor recognition measurements in liposomes made from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) have also shown that 25-OH' has a weaker condensing effect in the physiologically relevant fluid bilayer state. These findings provide support for surface occupancy playing a role in the condensing action of cholesterol.
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Affiliation(s)
- Vaclav Janout
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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25
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Abstract
Acoustic sensors probe the response of a thin layer to the mechanical displacement associated with an acoustic wave. Acoustic measurements provide two simultaneous time-resolved signals; one signal is related to the velocity or frequency of the acoustic wave and is mainly a function of adsorbed mass, while the second signal, related to the oscillation amplitude, is associated with energy dissipation and is a function of the viscoelastic properties of the adsorbed layer. The methods described in this chapter explore the relationship between the acoustic measurements of adsorbed liposomes and the mechanical properties of the lipid bilayer. This is carried out using a well-characterized model system consisting of liposomes prepared from an unsaturated phospholipid and a range of mole fractions of cholesterol. Real-time acoustic measurements are shown to be sensitive to changes in the liposome cholesterol content, regardless of the mode of attachment of the liposome to the device surface. This sensitivity is not due to changes in the density of the bilayer, or to changes in the extent of liposome-surface interactions, thus leaving the mechanical properties of the bilayer as the feature that is probably being measured. Some mechanisms by which the acoustic response could be generated are suggested in this chapter.
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26
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Subbaiah PV, Sircar D, Aizezi B, Mintzer E. Differential effects of conjugated linoleic acid isomers on the biophysical and biochemical properties of model membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1798:506-14. [PMID: 20004173 DOI: 10.1016/j.bbamem.2009.11.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 11/12/2009] [Accepted: 11/30/2009] [Indexed: 01/19/2023]
Abstract
Conjugated linoleic acids (CLA) are known to exert several isomer-specific biological effects, but their mechanisms of action are unclear. In order to determine whether the physicochemical effects of CLA on membranes play a role in their isomer-specific effects, we synthesized phosphatidylcholines (PCs) with 16:0 at sn-1 position and one of four CLA isomers (trans 10 cis 12 (A), trans 9 trans 11 (B), cis 9 trans 11 (C), and cis 9 cis 11 (D)) at sn-2, and determined their biophysical properties in monolayers and bilayers. The surface areas of the PCs with the two natural CLA (A and C) were similar at all pressures, but they differed significantly in the presence of cholesterol, with PC-A condensing more than PC-C. Liposomes of PC-A similarly showed increased binding of cholesterol compared to PC-C liposomes. PC-A liposomes were less permeable to carboxyfluorescein compared to PC-C liposomes. The PC with two trans double bonds (B) showed the highest affinity to cholesterol and lowest permeability. The two natural CLA-PCs (A and C) stimulated lecithin-cholesterol acyltransferase activity by 2-fold, whereas the unnatural CLA-PCs (B and D) were inhibitory. These results suggest that the differences in the biophysical properties of CLA isomers A and C may partly contribute to the known differences in their biological effects.
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Affiliation(s)
- Papasani V Subbaiah
- Department of Medicine, University of Illinois at Chicago, 1819 West Polk, Chicago, IL 60612, USA.
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27
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Mitomo H, Chen WH, Regen SL. Oxysterol-induced rearrangement of the liquid-ordered phase: a possible link to Alzheimer's disease? J Am Chem Soc 2009; 131:12354-7. [PMID: 19658396 DOI: 10.1021/ja904308y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Nearest-neighbor recognition measurements have been made for an exchangeable phospholipid (A) interacting with an exchangeable form of cholesterol (B) in host membranes derived from 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine and varying concentrations of cholesterol, 7beta-hydroxycholesterol (7beta-OH), and 25-hydroxycholesterol (25-OH). Whereas partial replacement of cholesterol with 7beta-OH strengthens the association between A and B, a similar substitution with 25-OH weakens this association. A model that accounts for this dichotomy, and the possible relevance of these findings to the cytotoxicity of 7beta-OH and to Alzheimer's disease are briefly discussed.
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Affiliation(s)
- Hideyuki Mitomo
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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28
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Olsen BN, Schlesinger PH, Baker NA. Perturbations of membrane structure by cholesterol and cholesterol derivatives are determined by sterol orientation. J Am Chem Soc 2009; 131:4854-65. [PMID: 19334779 DOI: 10.1021/ja8095224] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Cholesterol is essential for proper function and regulation of eukaryotic membranes, and significant amounts of metabolic energy are dedicated to controlling cellular cholesterol levels. Oxidation products of cholesterol, the oxysterols, are enzymatically produced molecules that play a major role in mediating cholesterol homeostasis through mechanisms which have not yet been fully elucidated. Certain oxysterols are known to have direct effects on membrane permeability and structure, effects that are strikingly different from that of cholesterol. We use molecular dynamics simulations of these oxysterols in 1-palmitoyl 2-oleoyl phosphatidylcholine (POPC) bilayers to explain the structural origins for the differing effects of cholesterol and 25-hydroxycholesterol on bilayer properties. In particular, we demonstrate that the source for these differing perturbations is the much wider range of molecular orientations accessible to 25-hydroxycholesterol when compared to cholesterol. This study shows that direct membrane perturbation by side-chain oxysterols is significant and suggests that these membrane perturbations may play a role in the oxysterol regulation of cholesterol homeostasis.
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Affiliation(s)
- Brett N Olsen
- Molecular Cell Biology Graduate Program, Center for Computational Biology, Washington University in St. Louis, 700 South Euclid Avenue, Campus Box 8036, St. Louis, Missouri 63110, USA
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29
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Oxysterol activation of phosphatidylcholine synthesis involves CTP:phosphocholine cytidylyltransferase α translocation to the nuclear envelope. Biochem J 2009; 418:209-17. [DOI: 10.1042/bj20081923] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In addition to suppressing cholesterol synthesis and uptake, oxysterols also activate glycerophospholipid and SM (sphingomyelin) synthesis, possibly to buffer cells from excess sterol accumulation. In the present study, we investigated the effects of oxysterols on the CDP-choline pathway for PtdCho (phosphatidylcholine) synthesis using wild-type and sterol-resistant CHO (Chinese-hamster ovary) cells expressing a mutant of SCAP [SREBP (sterol-regulatory-element-binding protein) cleavage-activating protein] (CHO-SCAP D443N). [3H]Choline-labelling experiments showed that 25OH (25-hydroxycholesterol), 22OH (22-hydroxycholesterol) and 27OH (27-hydroxycholesterol) increased PtdCho synthesis in CHO cells as a result of CCTα (CTP:phosphocholine cytidylyltransferase α) translocation and activation at the NE (nuclear envelope). These oxysterols also activate PtdCho synthesis in J774 macrophages. in vitro, CCTα activity was stimulated 2- to 2.5-fold by liposomes containing 5 mol% 25OH, 22OH or 27OH. Inclusion of up to 5 mol% cholesterol did not further activate CCTα. 25OH activated CCTα in CHO-SCAP D443N cells leading to a transient increase in PtdCho synthesis and accumulation of CDP-choline. CCTα translocation to the NE and intranuclear tubules in CHO-SCAP D443N cells was complete after 1 h exposure to 25OH compared with only partial translocation by 4–6 h in CHO-Mock cells. These enhanced responses in CHO-D443N cells were sterol-dependent since depletion with cyclodextrin or lovastatin resulted in reduced sensitivity to 25OH. However, the lack of effect of cholesterol on in vitro CCT activity indicates an indirect relationship or involvement of other sterols or oxysterol. We conclude that translocation and activation of CCTα at nuclear membranes by side-chain hydroxylated sterols are regulated by the cholesterol status of the cell.
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30
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Gale SE, Westover EJ, Dudley N, Krishnan K, Merlin S, Scherrer DE, Han X, Zhai X, Brockman HL, Brown RE, Covey DF, Schaffer JE, Schlesinger P, Ory DS. Side chain oxygenated cholesterol regulates cellular cholesterol homeostasis through direct sterol-membrane interactions. J Biol Chem 2008; 284:1755-64. [PMID: 18996837 DOI: 10.1074/jbc.m807210200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Side chain oxysterols exert cholesterol homeostatic effects by suppression of sterol regulatory element-binding protein maturation and promoting degradation of hydroxymethylglutaryl-CoA reductase. To examine whether oxysterol-membrane interactions contribute to the regulation of cellular cholesterol homeostasis, we synthesized the enantiomer of 25-hydroxycholesterol. Using this unique oxysterol probe, we provide evidence that oxysterol regulation of cholesterol homeostatic responses is not mediated by enantiospecific oxysterol-protein interactions. We show that side chain oxysterols, but not steroid ring-modified oxysterols, exhibit membrane expansion behavior in phospholipid monolayers and bilayers in vitro. This behavior is non-enantiospecific and is abrogated by increasing the saturation of phospholipid acyl chain constituents. Moreover, we extend these findings into cultured cells by showing that exposure to saturated fatty acids at concentrations that lead to endoplasmic reticulum membrane phospholipid remodeling inhibits oxysterol activity. These studies implicate oxysterol-membrane interactions in acute regulation of sterol homeostatic responses and provide new insights into the mechanism through which oxysterols regulate cellular cholesterol balance.
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Affiliation(s)
- Sarah E Gale
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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31
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Melzak KA, Bender F, Tsortos A, Gizeli E. Probing mechanical properties of liposomes using acoustic sensors. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:9172-9180. [PMID: 18642856 DOI: 10.1021/la800730s] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Acoustic devices were employed to characterize variations in the mechanical properties (density and viscoelasticity) of liposomes composed of 1-oleoyl-2-palmitoyl- sn-glycero-3-phosphocholine (POPC) and cholesterol. Liposome properties were modified in three ways. In some experiments, the POPC/cholesterol ratio was varied prior to deposition on the device surface. Alternatively, the ratio was changed in situ via either insertion of cholesterol or removal of cholesterol with beta-cyclodextrin. This was done for liposomes adsorbed directly on the device surface and for liposomes attached via a biotin-terminated poly(ethylene glycol) linker. The acoustic measurements make use of two simultaneous time-resolved signals: one signal is related to the velocity of the acoustic wave, while the second is related to dissipation of acoustic energy. Together, they provide information not only about the mass (or density) of the probed medium but also about its viscoelastic properties. The cholesterol-induced increase in the surface density of the lipid bilayer was indeed observed in the acoustic data, but the resulting change in signal was larger than expected from the change in surface density. In addition, increasing the bilayer resistance to stretching was found to lead to a greater dissipation of the acoustic energy. The acoustic response is assessed in terms of the possible distortions of the liposomes and the known effects of cholesterol on the mechanical properties of the lipid bilayer that encloses the aqueous core of the liposome. To aid the interpretation of the acoustic response, it is discussed how the above changes in the lipid bilayer will affect the effective viscoelastic properties of the entire liposome/solvent film on the scale of the acoustic wavelength. It was found that the acoustic device is very sensitive to the mechanical properties of lipid vesicles; the response of the acoustic device is explained, and the basic underlying mechanisms of interaction are identified.
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Affiliation(s)
- Kathryn A Melzak
- Institute of Molecular Biology and Biotechnology, FORTH, Vassilika Vouton, Heraklion/Crete, Greece
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32
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Matsumori N, Kasai Y, Oishi T, Murata M, Nomura K. Orientation of Fluorinated Cholesterol in Lipid Bilayers Analyzed by 19F Tensor Calculation and Solid-State NMR. J Am Chem Soc 2008; 130:4757-66. [DOI: 10.1021/ja077580l] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Nobuaki Matsumori
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan, and Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-Cho, Mishima-Gun, Osaka 618-8503, Japan
| | - Yusuke Kasai
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan, and Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-Cho, Mishima-Gun, Osaka 618-8503, Japan
| | - Tohru Oishi
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan, and Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-Cho, Mishima-Gun, Osaka 618-8503, Japan
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan, and Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-Cho, Mishima-Gun, Osaka 618-8503, Japan
| | - Kaoru Nomura
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan, and Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-Cho, Mishima-Gun, Osaka 618-8503, Japan
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33
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Kasai Y, Matsumori N, Umegawa Y, Matsuoka S, Ueno H, Ikeuchi H, Oishi T, Murata M. Self-Assembled Amphotericin B Is Probably Surrounded by Ergosterol: Bimolecular Interactions as Evidenced by Solid-State NMR and CD Spectra. Chemistry 2008; 14:1178-85. [DOI: 10.1002/chem.200701256] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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34
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Radhakrishnan A, Ikeda Y, Kwon HJ, Brown MS, Goldstein JL. Sterol-regulated transport of SREBPs from endoplasmic reticulum to Golgi: oxysterols block transport by binding to Insig. Proc Natl Acad Sci U S A 2007; 104:6511-8. [PMID: 17428920 PMCID: PMC1851665 DOI: 10.1073/pnas.0700899104] [Citation(s) in RCA: 443] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cholesterol synthesis in animals is controlled by the regulated transport of sterol regulatory element-binding proteins (SREBPs) from the endoplasmic reticulum to the Golgi, where the transcription factors are processed proteolytically to release active fragments. Transport is inhibited by either cholesterol or oxysterols, blocking cholesterol synthesis. Cholesterol acts by binding to the SREBP-escort protein Scap, thereby causing Scap to bind to anchor proteins called Insigs. Here, we show that oxysterols act by binding to Insigs, causing Insigs to bind to Scap. Mutational analysis of the six transmembrane helices of Insigs reveals that the third and fourth are important for Insig's binding to oxysterols and to Scap. These studies define Insigs as oxysterol-binding proteins, explaining the long-known ability of oxysterols to inhibit cholesterol synthesis in animal cells.
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Affiliation(s)
| | | | - Hyock Joo Kwon
- Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Michael S. Brown
- Departments of *Molecular Genetics and
- To whom correspondence may be addressed. E-mail: or
| | - Joseph L. Goldstein
- Departments of *Molecular Genetics and
- To whom correspondence may be addressed. E-mail: or
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35
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Expression of ATP binding cassette-transporter ABCG1 prevents cell death by transporting cytotoxic 7β-hydroxycholesterol. FEBS Lett 2007; 581:1673-80. [DOI: 10.1016/j.febslet.2007.03.038] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Revised: 03/09/2007] [Accepted: 03/15/2007] [Indexed: 11/22/2022]
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36
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Massey JB, Pownall HJ. Structures of biologically active oxysterols determine their differential effects on phospholipid membranes. Biochemistry 2006; 45:10747-58. [PMID: 16939227 DOI: 10.1021/bi060540u] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Oxysterols, derivatives of cholesterol that contain a second oxygen moiety, are intermediates in cholesterol catabolism, regulators of lipid metabolism, and toxic sterols with proatherogenic effects. In model membranes, cholesterol and eight selected oxysterols were compared by fluorescence probe techniques that measure changes in bilayer order and phase behavior and by the formation of detergent-resistant membranes (DRM). The oxysterols were modified on the sterol nucleus or on the isooctyl side chain. The model membranes consisted of dipalmitoyl phosphatidylcholine (DPPC) and mixtures of dioleoyl phosphatidylcholine with DPPC and with sphingomyelin. The different oxysterols induced changes in membrane properties according to the differences in their structures. Whereas the effects of some oxysterols on membrane order, fluorescence probe microenvironment, and DRM formation were similar to those of cholesterol, others had little or no effect. An empirical correlation ranking the oxysterols by their ability to modify membrane biophysical properties when compared to cholesterol led to a significant structure/function relationship between the biophysical measurements and an important cellular phenomenon, apoptosis. 7beta-Hydroxycholesterol, which is the most cytotoxic of the eight selected oxysterols, was one of the least cholesterol-like with respect to modification of membrane properties. The results suggest that an underlying mechanism for oxysterol-induced apoptosis in cells, e.g., monocyte/macrophages, should include their biophysical effects on membranes, such as the regulation of the formation and composition of sterol-rich membrane domains.
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Affiliation(s)
- John B Massey
- Section of Atherosclerosis and Lipoprotein Research, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.
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37
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Abstract
25-Hydroxycholesterol (25-HC) appears to play a role in several important biological processes, including regulating cellular cholesterol levels and promoting apoptosis. However, in most cases the mechanisms by which 25-HC elicits its biological effects are not known. Insights into mechanisms of 25-HC action can be gained by studying the activity of its enantiomer (ent-25-HC). ent-25-HC is physically and chemically identical to 25-HC; however, 25-HC and ent-25-HC can be distinguished in chiral environments, like a protein binding site. In order to probe the mechanisms of 25-HC action, we have synthesized the enantiomer of 25-HC (ent-25-HC).
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Affiliation(s)
- Emily J Westover
- Department of Molecular Biology and Pharmacology, Washington University School of Medicine, 660 S. Euclid, St. Louis, MO 63110, USA
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38
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Orädd G, Westerman PW, Lindblom G. Lateral diffusion coefficients of separate lipid species in a ternary raft-forming bilayer: a Pfg-NMR multinuclear study. Biophys J 2005; 89:315-20. [PMID: 15863478 PMCID: PMC1366530 DOI: 10.1529/biophysj.105.061762] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
By isotopical labeling lipid lateral diffusion coefficients for each of the membrane constituents, including cholesterol, have been measured by 1H, 2H, and 19F pulsed field gradient NMR spectroscopy in macroscopically oriented lipid bilayers. This provides a means of obtaining detailed dynamic and compositional information in raft-forming lipid bilayers without introducing foreign molecules into the systems. The raft systems studied contained dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DPPC)/cholesterol at the molar ratios of 42.5:42.5:15 and 35:35:30 in excess water. At temperatures below 30 degrees C the raft system forms large (>1 microm) domains of a liquid ordered (l(o)) phase, in which the lipid lateral diffusion was approximately 5 times slower than for the lipids in the surrounding liquid disordered (l(d)) phase. Within each domain all lipid species showed the same diffusion coefficient, despite the very different structures of cholesterol and phospholipids. DPPC partitions exclusively into the l(o) domains, whereas cholesterol and dioleoylphosphatidylcholine were distributed in both l(o) and l(d) phases. The cholesterol concentration was found to be 10-20 mol % in the l(d) domain and 30-40 mol % in the l(o) domain. Comparison of these results with data from sphingomyelin-containing systems suggests that DPPC interacts more weakly with cholesterol than does sphingomyelin.
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Affiliation(s)
- Greger Orädd
- Department of Chemistry: Biophysical Chemistry, Umeå University, Umeå, Sweden
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39
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Kauffman JM, Pellicciari R, Carey MC. Interfacial properties of most monofluorinated bile acids deviate markedly from the natural congeners: studies with the Langmuir-Pockels surface balance. J Lipid Res 2004; 46:571-81. [PMID: 15604514 DOI: 10.1194/jlr.m400439-jlr200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We characterized the air-water interfacial properties of four monofluorinated bile acids alone and in binary mixtures with a common lecithin, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), using an automated Langmuir-Pockels surface balance. We compared 7alpha-fluoromurocholic acid (FMCA), 7alpha-fluorohyodeoxycholic acid (FHDCA), 6alpha-fluoroursodeoxycholic acid (FUDCA), and 6alpha-fluorochenodeoxycholic acid (FCDCA) with their natural dihydroxy homologs, murocholic acid (MCA), hyodeoxycholic acid (HDCA), ursodeoxycholic acid (UDCA), and chenodeoxycholic acid (CDCA). For further comparison, two trihydroxy bile acids, 3alpha,6beta,7alpha-trihydroxycholanoic acid [alpha-muricholic acid (alpha-MCA)] and 3alpha,6alpha,7beta-trihydroxycholanoic acid [omega-muricholic acid (omega-MCA)], with isologous OH polar functions to FMCA and FUDCA were also studied. Pressure-area isotherms of MCA, HDCA, UDCA, CDCA, and FMCA displayed sharp collapse points. In contrast, FHDCA, FUDCA, and FCDCA formed monolayers that were less stable than the trihydroxy bile acids, displaying second-order phase transitions in their isotherms. All natural and fluorinated bile acids condensed mixed monolayers with POPC, with maximal effects at molar bile acid concentrations between 30 and 50 mol%. Examination of molecular models revealed that the 7alpha-F atom of the interfacially stable FMCA projects away from the 6beta-OH function, resulting in minimal steric interactions, whereas in FHDCA, FUDCA, and FCDCA, close vicinal interactions between OH and F polar functions result in progressive bulk solubility upon monolayer compression. These results provide a framework for designing F-modified bile acids to mimic or diverge from the natural compounds in vivo.
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Affiliation(s)
- John M Kauffman
- Department of Medicine, Harvard Medical School, Harvard Digestive Diseases Center, Brigham and Women's Hospital, Boston, MA, USA
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40
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Orädd G, Lindblom G. Lateral diffusion studied by pulsed field gradient NMR on oriented lipid membranes. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2004; 42:123-131. [PMID: 14745791 DOI: 10.1002/mrc.1338] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This mini-review focuses on the utilization of pulsed magnetic field gradients to measure diffusional motion in systems of macroscopically oriented lipid bilayers. The NMR diffusion technique is proposed to have appreciable potential for future biophysical investigations in the field of membrane biology. Topics such as transport of molecules both across and in the plane of the membrane can be successfully studied, and the formation of lipid domains and their intrinsic dynamics can also be scrutinized. First, a short introduction to the NMR technique is given together with a brief discussion on methods of obtaining a good bilayer orientation. Then, a number of recent results on biophysical/biological membrane systems of great interest is presented, in which some unique conclusions on so-called 'raft membranes' are reached. It is shown for systems with large two-phase areas of liquid disordered and liquid ordered phases that lipid lateral diffusion is faster in the former phase and has a smaller apparent activation energy. Further, on the time-scale of the experiments (50-250 ms), exchange between the two phases is fast in the phospholipid-cholesterol-water ternary system, whereas it is slow in the sphingomyelin-dioleoylphosphatidylcholine-cholesterol-water quaternary system.
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Affiliation(s)
- Greger Orädd
- Department of Biophysical Chemistry, Umeå University, Umeå, Sweden
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41
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Zitzer A, Westover EJ, Covey DF, Palmer M. Differential interaction of the two cholesterol-dependent, membrane-damaging toxins, streptolysin O and Vibrio cholerae cytolysin, with enantiomeric cholesterol. FEBS Lett 2003; 553:229-31. [PMID: 14572629 DOI: 10.1016/s0014-5793(03)01023-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Membrane cholesterol is essential to the activity of at least two structurally unrelated families of bacterial pore-forming toxins, represented by streptolysin O (SLO) and Vibrio cholerae cytolysin (VCC), respectively. Here, we report that SLO and VCC differ sharply in their interaction with liposome membranes containing enantiomeric cholesterol (ent-cholesterol). VCC had very low activity with ent-cholesterol, which is in line with a stereospecific mode of interaction of this toxin with cholesterol. In contrast, SLO was only slightly less active with ent-cholesterol than with cholesterol, suggesting a rather limited degree of structural specificity in the toxin-cholesterol interaction.
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Affiliation(s)
- Alexander Zitzer
- Department of Hematology and Oncology, Johannes Gutenberg University, D-55101 Mainz, Germany
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42
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Cho KH, An S, Lee WS, Paik YK, Kim YK, Jeong TS. Mass-production of human ACAT-1 and ACAT-2 to screen isoform-specific inhibitor: a different substrate specificity and inhibitory regulation. Biochem Biophys Res Commun 2003; 309:864-72. [PMID: 13679053 DOI: 10.1016/j.bbrc.2003.08.077] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Recently, acyl-CoA:cholesterol acyltransferase was found to be present as two isoforms, ACAT-1 and ACAT-2, in mammalian tissues with different metabolic functions and tissue-specific locations. In this study, the isoforms were mass-produced individually from insect cells to establish a more sensitive and reliable screening method for specific inhibitors against each isoform. The expressed hACAT-1 and hACAT-2 appeared as a 50 kDa- and a 46 kDa-band on SDS-PAGE, respectively, from Hi5 cells and they preferred to exist in oligomeric form, from dimer to tetramer, during the purification process. They also exhibited an approximate 3.4 to 3.7-fold increase in activities when compared to rat liver microsomal fractions at the same protein concentration. Known ACAT inhibitors, pyripyropene A, oleic acid anilide, and diethyl pyrocarbonate, were tested to evaluate the inhibitory specificity and sensitivity of the expressed enzymes. Interestingly, pyripyropene A inhibited only the hACAT-2 fraction with IC(50)=0.64 microM but not the hACAT-1 fraction; whereas the fatty acid anilide did not show a significant difference in inhibitory activity with either hACAT-1 or hACAT-2. Furthermore, cholesterol was more rapidly utilized by hACAT-1, but hACAT-2 esterified other cholic acid derivatives more efficiently. These results suggest that the specificity of each substrate and inhibitor was highly different, depending on each isoform from the viewpoint of the regulatory site and the substrate binding site location.
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Affiliation(s)
- Kyung-Hyun Cho
- Lipid Metabolism Research Laboratory, Korea Research Institute of Bioscience and Biotechnology, Daejon 305-333, South Korea
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43
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Zhang Y, Yu C, Liu J, Spencer TA, Chang CCY, Chang TY. Cholesterol is superior to 7-ketocholesterol or 7 alpha-hydroxycholesterol as an allosteric activator for acyl-coenzyme A:cholesterol acyltransferase 1. J Biol Chem 2003; 278:11642-7. [PMID: 12533546 DOI: 10.1074/jbc.m211559200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We compared the abilities of cholesterol versus various oxysterols as substrate and/or as activator for the enzyme acyl-coenzyme A:cholesterol acyltransferase (ACAT), by monitoring the activity of purified human ACAT1 in response to sterols solubilized in mixed micelles or in reconstituted vesicles. The results showed that 5 alpha,6 alpha-epoxycholesterol and 7 alpha-hydroxycholesterol are comparable with cholesterol as the favored substrates, whereas 7-ketocholesterol, 7 beta-hydroxycholesterol, 5 beta,6 beta-epoxycholesterol, and 24(S),25-epoxycholesterol are very poor substrates for the enzyme. We then tested the ability of 7-ketocholesterol as an activator when cholesterol was measured as the substrate, and vice versa. When cholesterol was measured as the substrate, the addition of 7-ketocholesterol could not activate the enzyme. In contrast, when 7-ketocholesterol was measured as the substrate, the addition of cholesterol significantly activated the enzyme and changed the shape of the substrate saturation curve from sigmoidal to essentially hyperbolic. Additional results show that, as an activator, cholesterol is much better than all the oxysterols tested. These results suggest that ACAT1 contains two types of sterol binding sites; the structural requirement for the ACAT activator site is more stringent than it is for the ACAT substrate site. Upon activation by cholesterol, ACAT1 becomes promiscuous toward various sterols as its substrate.
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Affiliation(s)
- Yi Zhang
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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44
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Meaney S, Bodin K, Diczfalusy U, Björkhem I. On the rate of translocation in vitro and kinetics in vivo of the major oxysterols in human circulation: critical importance of the position of the oxygen function. J Lipid Res 2002; 43:2130-5. [PMID: 12454275 DOI: 10.1194/jlr.m200293-jlr200] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Oxysterols possess powerful biological activities. Some of their effects on the regulation of key enzymes are similar to those of cholesterol, but are much more potent. One of the critical properties of oxysterols is their ability to pass lipophilic membranes at a high rate. Transfer of unesterified 25-hydroxycholesterol from red blood cells to plasma has been reported to occur more than 1,000 times faster than cholesterol. Here we have measured the relative rate of such translocation of the three major oxysterols in human circulation: 27-hydroxycholesterol, 24S-hydroxycholesterol, and 4beta-hydroxycholesterol. The distance from the 3beta-hydroxyl group to the additional hydroxyl group is the greatest possible in 27-hydroxycholesterol and the least possible in 4beta-hydroxycholesterol. The rate of exchange between erythrocytes and plasma was found to be high for 27-hydroxycholesterol and 24S-hydroxycholesterol, and hardly possible to measure for 4beta-hydroxycholesterol and cholesterol. When injected intravenously into humans, deuterium labeled 24- and 27-hydroxycholesterol caused an immediate high enrichment of the corresponding plasma sterols followed by a decay. After injection of labeled 4beta-hydroxycholesterol, the maximum deuterium enrichment occurred after 2-3 h, when secretion of the oxysterol from the liver is likely to be the limiting factor. When radiolabeled cholesterol was injected under the same conditions, maximum appearance of label occurred after about 2 days. The results illustrate the importance of the position of the additional oxygen in oxysterols and are discussed in relation to the rate of metabolism and biological effects of these oxysterols.
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Affiliation(s)
- Steve Meaney
- Division of Clinical Chemistry, Karolinska Institutet, Huddinge University Hospital, Stockholm, Sweden
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45
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Orädd G, Lindblom G, Westerman PW. Lateral diffusion of cholesterol and dimyristoylphosphatidylcholine in a lipid bilayer measured by pulsed field gradient NMR spectroscopy. Biophys J 2002; 83:2702-4. [PMID: 12414702 PMCID: PMC1302354 DOI: 10.1016/s0006-3495(02)75279-x] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The pulsed field gradient NMR method for measuring self-diffusion has been used for a direct determination of the lateral diffusion coefficient of cholesterol, fluorine labeled at the 6-position, for an oriented lamellar liquid-crystalline phase of dimyristoylphosphatidylcholine (DMPC)/cholesterol/water. It is found that the diffusion coefficients of DMPC and cholesterol are equal over a large temperature interval. The apparent energy of activation for the diffusion process (58 kJ/mol) is about the same as for a lamellar phase of DMPC/water, whereas the phospholipid lateral diffusion coefficient is approximately four times smaller in the presence of cholesterol.
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Affiliation(s)
- Greger Orädd
- Department of Biophysical Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
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46
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Mintzer EA, Waarts BL, Wilschut J, Bittman R. Behavior of a photoactivatable analog of cholesterol, 6-photocholesterol, in model membranes. FEBS Lett 2002; 510:181-4. [PMID: 11801250 DOI: 10.1016/s0014-5793(01)03271-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
6-Photocholesterol, a new photoactivatable analog of cholesterol in which a diazirine functionality replaces the 5,6-double bond in the steroid nucleus, was used recently to identify cholesterol-binding proteins in neuroendocrine cells [Thiele, C., Hannah, M.J., Farenholz, F. and Huttner, W.B. (2000) Nat. Cell Biol. 2, 42-49], to track the distribution and transport of cholesterol in Caenorhabditis elegans [Matyash, V., Geier, C., Henske, A., Mukherjee, S., Hirsh, D., Thiele, C., Grant, B., Maxfield, F.R. and Kurzchalia, T.V. (2001) Mol. Biol. Cell 12, 1725-1736], and to probe lipid-protein interactions in oligodendrocytes [Simons, M., Kramer, E.M., Thiele, C., Stoffel, W. and Trotter, J. (2000) J. Cell Biol. 151, 143-154]. To determine whether 6-photocholesterol is a faithful mimetic of cholesterol we analyzed the ability of this probe, under conditions in which it is not photoactivated to a carbene, to substitute for cholesterol in two unrelated assays: (1) to condense 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine monomolecular films and (2) to mediate the fusion of two alphaviruses (Semliki Forest and Sindbis) with liposomes. The results suggest that this analog is a suitable photoprobe of cholesterol.
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Affiliation(s)
- Evan A Mintzer
- Department of Chemistry and Biochemistry, Queens College of the City University of New York, Flushing, 13367, USA
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47
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Prosser RS, Luchette PA, Westerman PW, Rozek A, Hancock RE. Determination of membrane immersion depth with O(2): a high-pressure (19)F NMR study. Biophys J 2001; 80:1406-16. [PMID: 11222301 PMCID: PMC1301332 DOI: 10.1016/s0006-3495(01)76113-9] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Oxygen is known to partition with an increasing concentration gradient toward the hydrophobic membrane interior. At partial pressures (P(O2)) of 100 Atm or more, this concentration gradient is sufficient to induce paramagnetic effects that depend sensitively on membrane immersion depth. This effect is demonstrated for the fluorine nucleus by depth-dependent paramagnetic shifts and spin-lattice relaxation rates, using a fluorinated detergent, CF3(CF(2))(5)C(2)H(4)-O-maltose (TFOM), reconstituted into a lipid bilayer model membrane system. To interpret the spin-lattice relaxation rates (R) in terms of a precise immersion depth, two specifically fluorinated cholesterol species (6-fluorocholesterol and 25-fluorocholesterol), whose membrane immersion depths were independently estimated, were studied by (19)F NMR. The paramagnetic relaxation rates, R, of the cholesterol species were then used to parameterize a Gaussian profile that directly relates R to immersion depth z. This same Gaussian curve could then be used to determine the membrane immersion depth of all six fluorinated chain positions of TFOM and of two adjacent residues of specifically fluorinated analogs of the antibacterial peptide indolicidin. The potential of this method for determination of immersion depth and topology of membrane proteins is discussed.
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Affiliation(s)
- R S Prosser
- Department of Chemistry, Kent State University, Kent, Ohio 44242, USA.
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