1
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Salloum Z, Dauner K, Li YF, Verma N, Valdivieso-González D, Almendro-Vedia V, Zhang JD, Nakka K, Chen MX, McDonald J, Corley CD, Sorisky A, Song BL, López-Montero I, Luo J, Dilworth JF, Zha X. Statin-mediated reduction in mitochondrial cholesterol primes an anti-inflammatory response in macrophages by upregulating Jmjd3. eLife 2024; 13:e85964. [PMID: 38602170 PMCID: PMC11186637 DOI: 10.7554/elife.85964] [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] [Received: 01/05/2023] [Accepted: 03/13/2024] [Indexed: 04/12/2024] Open
Abstract
Statins are known to be anti-inflammatory, but the mechanism remains poorly understood. Here, we show that macrophages, either treated with statin in vitro or from statin-treated mice, have reduced cholesterol levels and higher expression of Jmjd3, a H3K27me3 demethylase. We provide evidence that lowering cholesterol levels in macrophages suppresses the adenosine triphosphate (ATP) synthase in the inner mitochondrial membrane and changes the proton gradient in the mitochondria. This activates nuclear factor kappa-B (NF-κB) and Jmjd3 expression, which removes the repressive marker H3K27me3. Accordingly, the epigenome is altered by the cholesterol reduction. When subsequently challenged by the inflammatory stimulus lipopolysaccharide (M1), macrophages, either treated with statins in vitro or isolated from statin-fed mice, express lower levels proinflammatory cytokines than controls, while augmenting anti-inflammatory Il10 expression. On the other hand, when macrophages are alternatively activated by IL-4 (M2), statins promote the expression of Arg1, Ym1, and Mrc1. The enhanced expression is correlated with the statin-induced removal of H3K27me3 from these genes prior to activation. In addition, Jmjd3 and its demethylase activity are necessary for cholesterol to modulate both M1 and M2 activation. We conclude that upregulation of Jmjd3 is a key event for the anti-inflammatory function of statins on macrophages.
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Affiliation(s)
- Zeina Salloum
- Chronic Disease Program, Ottawa Hospital Research InstituteOttawaCanada
| | - Kristin Dauner
- Chronic Disease Program, Ottawa Hospital Research InstituteOttawaCanada
| | - Yun-feng Li
- College of Life Sciences, Wuhan UniversityWuhanChina
| | - Neha Verma
- Chronic Disease Program, Ottawa Hospital Research InstituteOttawaCanada
| | - David Valdivieso-González
- Departamento Química Física, Universidad Complutense de Madrid, AvdaMadridSpain
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12)MadridSpain
| | - Víctor Almendro-Vedia
- Departamento Química Física, Universidad Complutense de Madrid, AvdaMadridSpain
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12)MadridSpain
| | - John D Zhang
- Chronic Disease Program, Ottawa Hospital Research InstituteOttawaCanada
| | - Kiran Nakka
- Sprott Center for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research InstituteOttawaCanada
| | - Mei Xi Chen
- Sprott Center for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research InstituteOttawaCanada
- Department of Cell and Regenerative Biology, University of WisconsinMadisonUnited States
| | - Jeffrey McDonald
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Chase D Corley
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Alexander Sorisky
- Chronic Disease Program, Ottawa Hospital Research InstituteOttawaCanada
- Department of Cellular and Molecular Medicine, University of OttawaOttawaCanada
| | | | - Iván López-Montero
- Departamento Química Física, Universidad Complutense de Madrid, AvdaMadridSpain
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12)MadridSpain
| | - Jie Luo
- College of Life Sciences, Wuhan UniversityWuhanChina
| | - Jeffrey F Dilworth
- Sprott Center for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research InstituteOttawaCanada
- Department of Cell and Regenerative Biology, University of WisconsinMadisonUnited States
- Department of Cellular and Molecular Medicine, University of OttawaOttawaCanada
| | - Xiaohui Zha
- Chronic Disease Program, Ottawa Hospital Research InstituteOttawaCanada
- Departments of Medicine and of Biochemistry, Microbiology & Immunology, University of OttawaOttawaCanada
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2
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Saiioum Z, Dauner K, Li YF, Verma N, Almendro-Vedia V, Valdivieso Gonzalez D, Zhang DJ, Nakka K, McDonald J, Sorisky A, Song BL, Lopez Montero I, Luo J, Dilworth J, Zha X. Statin-mediated reduction in mitochondrial cholesterol primes an anti-inflammatory response in macrophages by upregulating JMJD3. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.01.09.523264. [PMID: 36711703 PMCID: PMC9881925 DOI: 10.1101/2023.01.09.523264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Stains are known to be anti-inflammatory, but the mechanism remains poorly understood. Here we show that macrophages, either treated with statin in vitro or from statin-treated mice, have reduced cholesterol levels and higher expression of Jmjd3, a H3K27me3 demethylase. We provide evidence that lowering cholesterol levels in macrophages suppresses the ATP synthase in the inner mitochondrial membrane (IMM) and changes the proton gradient in the mitochondria. This activates NFkB and Jmjd3 expression to remove the repressive marker H3K27me3. Accordingly, the epigenome is altered by the cholesterol reduction. When subsequently challenged by the inflammatory stimulus LPS (M1), both macrophages treated with statins in vitro or isolated from statin-treated mice in vivo, express lower levels pro-inflammatory cytokines than controls, while augmenting anti-inflammatory Il10 expression. On the other hand, when macrophages are alternatively activated by IL4 (M2), statins promote the expression of Arg1, Ym1, and Mrc1. The enhanced expression is correlated with the statin-induced removal of H3K27me3 from these genes prior to activation. In addition, Jmjd3 and its demethylase activity are necessary for cholesterol to modulate both M1 and M2 activation. We conclude that upregulation of Jmjd3 is a key event for the anti-inflammatory function of statins on macrophages.
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3
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Petrov AM. Oxysterols in Central and Peripheral Synaptic Communication. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1440:91-123. [PMID: 38036877 DOI: 10.1007/978-3-031-43883-7_6] [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
Cholesterol is a key molecule for synaptic transmission, and both central and peripheral synapses are cholesterol rich. During intense neuronal activity, a substantial portion of synaptic cholesterol can be oxidized by either enzymatic or non-enzymatic pathways to form oxysterols, which in turn modulate the activities of neurotransmitter receptors (e.g., NMDA and adrenergic receptors), signaling molecules (nitric oxide synthases, protein kinase C, liver X receptors), and synaptic vesicle cycling involved in neurotransmitters release. 24-Hydroxycholesterol, produced by neurons in the brain, could directly affect neighboring synapses and change neurotransmission. 27-Hydroxycholesterol, which can cross the blood-brain barrier, can alter both synaptogenesis and synaptic plasticity. Increased generation of 25-hydroxycholesterol by activated microglia and macrophages could link inflammatory processes to learning and neuronal regulation. Amyloids and oxidative stress can lead to an increase in the levels of ring-oxidized sterols and some of these oxysterols (4-cholesten-3-one, 5α-cholestan-3-one, 7β-hydroxycholesterol, 7-ketocholesterol) have a high potency to disturb or modulate neurotransmission at both the presynaptic and postsynaptic levels. Overall, oxysterols could be used as "molecular prototypes" for therapeutic approaches. Analogs of 24-hydroxycholesterol (SGE-301, SGE-550, SAGE718) can be used for correction of NMDA receptor hypofunction-related states, whereas inhibitors of cholesterol 24-hydroxylase, cholestane-3β,5α,6β-triol, and cholest-4-en-3-one oxime (olesoxime) can be utilized as potential anti-epileptic drugs and (or) protectors from excitotoxicity.
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Affiliation(s)
- Alexey M Petrov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", Kazan, RT, Russia.
- Kazan State Medial University, Kazan, RT, Russia.
- Kazan Federal University, Kazan, RT, Russia.
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4
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Wüstner D, Dupont Juhl A, Egebjerg JM, Werner S, McNally J, Schneider G. Kinetic modelling of sterol transport between plasma membrane and endo-lysosomes based on quantitative fluorescence and X-ray imaging data. Front Cell Dev Biol 2023; 11:1144936. [PMID: 38020900 PMCID: PMC10644255 DOI: 10.3389/fcell.2023.1144936] [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: 01/15/2023] [Accepted: 10/20/2023] [Indexed: 12/01/2023] Open
Abstract
Niemann Pick type C1 and C2 (NPC1 and NPC2) are two sterol-binding proteins which, together, orchestrate cholesterol transport through late endosomes and lysosomes (LE/LYSs). NPC2 can facilitate sterol exchange between model membranes severalfold, but how this is connected to its function in cells is poorly understood. Using fluorescent analogs of cholesterol and quantitative fluorescence microscopy, we have recently measured the transport kinetics of sterol between plasma membrane (PM), recycling endosomes (REs) and LE/LYSs in control and NPC2 deficient fibroblasts. Here, we use kinetic modeling of this data to determine rate constants for sterol transport between intracellular compartments. Our model predicts that sterol is trapped in intraluminal vesicles (ILVs) of LE/LYSs in the absence of NPC2, causing delayed sterol export from LE/LYSs in NPC2 deficient fibroblasts. Using soft X-ray tomography, we confirm, that LE/LYSs of NPC2 deficient cells but not of control cells contain enlarged, carbon-rich intraluminal vesicular structures, supporting our model prediction of lipid accumulation in ILVs. By including sterol export via exocytosis of ILVs as exosomes and by release of vesicles-ectosomes-from the PM, we can reconcile measured sterol efflux kinetics and show that both pathways can be reciprocally regulated by the intraluminal sterol transfer activity of NPC2 inside LE/LYSs. Our results thereby connect the in vitro function of NPC2 as sterol transfer protein between membranes with its in vivo function.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Alice Dupont Juhl
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Jacob Marcus Egebjerg
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Stephan Werner
- Department of X-Ray Microscopy, Helmholtz-Zentrum Berlin, Berlin, Germany
| | - James McNally
- Department of X-Ray Microscopy, Helmholtz-Zentrum Berlin, Berlin, Germany
| | - Gerd Schneider
- Department of X-Ray Microscopy, Helmholtz-Zentrum Berlin, Berlin, Germany
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5
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Steck TL, Lange Y. Is reverse cholesterol transport regulated by active cholesterol? J Lipid Res 2023; 64:100385. [PMID: 37169287 PMCID: PMC10279919 DOI: 10.1016/j.jlr.2023.100385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 05/02/2023] [Accepted: 05/05/2023] [Indexed: 05/13/2023] Open
Abstract
This review considers the hypothesis that a small portion of plasma membrane cholesterol regulates reverse cholesterol transport in coordination with overall cellular homeostasis. It appears that almost all of the plasma membrane cholesterol is held in stoichiometric complexes with bilayer phospholipids. The minor fraction of cholesterol that exceeds the complexation capacity of the phospholipids is called active cholesterol. It has an elevated chemical activity and circulates among the organelles. It also moves down its chemical activity gradient to plasma HDL, facilitated by the activity of ABCA1, ABCG1, and SR-BI. ABCA1 initiates this process by perturbing the organization of the plasma membrane bilayer, thereby priming its phospholipids for translocation to apoA-I to form nascent HDL. The active excess sterol and that activated by ABCA1 itself follow the phospholipids to the nascent HDL. ABCG1 similarly rearranges the bilayer and sends additional active cholesterol to nascent HDL, while SR-BI simply facilitates the equilibration of the active sterol between plasma membranes and plasma proteins. Active cholesterol also flows downhill to cytoplasmic membranes where it serves both as a feedback signal to homeostatic ER proteins and as the substrate for the synthesis of mitochondrial 27-hydroxycholesterol (27HC). 27HC binds the LXR and promotes the expression of the aforementioned transport proteins. 27HC-LXR also activates ABCA1 by competitively displacing its inhibitor, unliganded LXR. § Considerable indirect evidence suggests that active cholesterol serves as both a substrate and a feedback signal for reverse cholesterol transport. Direct tests of this novel hypothesis are proposed.
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Affiliation(s)
- Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, IL, USA.
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6
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Kennelly JP, Tontonoz P. Cholesterol Transport to the Endoplasmic Reticulum. Cold Spring Harb Perspect Biol 2023; 15:cshperspect.a041263. [PMID: 35940908 PMCID: PMC9899650 DOI: 10.1101/cshperspect.a041263] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Most cholesterol in mammalian cells is stored in the plasma membrane (PM). Cholesterol transport from the PM to low-sterol regulatory regions of the endoplasmic reticulum (ER) controls cholesterol synthesis and uptake, and thereby influences the rates of cholesterol flux between tissues of complex organisms. Cholesterol transfer to the ER is also required for steroidogenesis, oxysterol and bile acid synthesis, and cholesterol esterification. The ER-resident Aster proteins (Aster-A, -B, and -C) form contacts with the PM to move cholesterol to the ER in mammals. Mice lacking Aster-B have low adrenal cholesteryl ester stores and impaired steroidogenesis because of a defect in cholesterol transport from high-density lipoprotein (HDL) to the ER. This work reviews the molecular characteristics of Asters, their role in HDL- and low-density lipoprotein (LDL)-cholesterol movement, and how cholesterol transferred to the ER is utilized by cells. The roles of other lipid transporters and of membrane lipid organization in maintaining aspects of cholesterol homeostasis are also highlighted.
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Affiliation(s)
- John P Kennelly
- Department of Pathology and Laboratory Medicine, Department of Biological Chemistry, Molecular Biology Institute, University of California, Los Angeles, California 90095, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, Department of Biological Chemistry, Molecular Biology Institute, University of California, Los Angeles, California 90095, USA
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7
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Okada BY, Kuroiwa S, Noi A, Tanaka A, Nishikawa J, Kondo Y, Ishitsuka Y, Irie T, Higaki K, Matsuo M, Ichikawa A. Effects of 6-O-α-maltosyl-β cyclodextrin on lipid metabolism in Npc1-deficient Chinese hamster ovary cells. Mol Genet Metab 2022; 137:239-248. [PMID: 36182715 DOI: 10.1016/j.ymgme.2022.09.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 09/02/2022] [Accepted: 09/20/2022] [Indexed: 11/21/2022]
Abstract
Niemann-Pick disease Type C (NPC) is a lysosomal storage disorder caused by mutation of the NPC1/NPC2 genes, which ultimately results in the accumulation of unesterified cholesterol (UEC) in lysosomes, thereby inducing symptoms such as progressive neurodegeneration and hepatosplenomegaly. This study determines the effects of 6-O-α-maltosyl-β cyclodextrin (Mal-βCD) on lipid levels and synthesis in Npc1-deficient (Npc1-KO cells) and vehicle CHO cells. Compared to vehicle cells, Npc1-KO cells exhibited high level of UEC, and low levels of esterified cholesterols (ECs) and long-chain fatty acids (LCFAs). The difference in lipid levels between Npc1-KO and CHO cells was largely ameliorated by Mal-βCD administration. Moreover, the effects of Mal-βCD were reproduced in the lysosomes prepared from Npc1-KO cells. Stable isotope tracer analysis with extracellular addition of D4-deuterated palmitic acid (D4-PA) to Npc1-KO cells increased the synthesis of D4-deuterated LCFAs (D4-LCFAs) and D4-deuterated ECs (D4-ECs) in a Mal-βCD-dependent manner. Simultaneous addition of D6-deuterated UEC (D6-UEC) and D4-PA promoted the Mal-βCD-dependent synthesis of D6-/D4-ECs, consisting of D6-UEC and D4-PA, D4-deuterated stearic acid, or D4-deuterated myristic acid, in Npc1-KO cells. These results suggest that Mal-βCD helps to maintain normal lipid metabolism by restoring balance among UEC, ECs, and LCFAs through acting on behalf of NPC1 in Npc1-KO cells and may therefore be useful in designing effective therapies for NPC.
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Affiliation(s)
- By Yasuyo Okada
- School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Kyuban-cho, Koshien, Nishinomiya, Hyogo 663-8179, Japan.
| | - Sayako Kuroiwa
- School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Kyuban-cho, Koshien, Nishinomiya, Hyogo 663-8179, Japan
| | - Ayaka Noi
- School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Kyuban-cho, Koshien, Nishinomiya, Hyogo 663-8179, Japan
| | - Ayaka Tanaka
- School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Kyuban-cho, Koshien, Nishinomiya, Hyogo 663-8179, Japan
| | - Junichi Nishikawa
- School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Kyuban-cho, Koshien, Nishinomiya, Hyogo 663-8179, Japan
| | - Yuki Kondo
- Department of Clinical Chemistry and Informatics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto 862-0973, Japan
| | - Yoichi Ishitsuka
- Department of Clinical Chemistry and Informatics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto 862-0973, Japan
| | - Tetsumi Irie
- Department of Pharmaceutical Packaging Technology, Faculty of Life Sciences, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto 862-0973, Japan
| | - Katsumi Higaki
- Research Initiative Center, Organization for Research Initiative and Promotion, Tottori University, 86 Nishi-cho, Yonago 683-8503, Japan
| | - Muneaki Matsuo
- Department of Pediatrics, Faculty of Medicine, Saga University, 5-1-1, Nabeshima, Saga 849-8501, Japan
| | - Atsushi Ichikawa
- School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Kyuban-cho, Koshien, Nishinomiya, Hyogo 663-8179, Japan; Bio-Education Laboratory, Tawara Building #702, 1-21-33 Higashinakajima, Osaka 533-0033, Japan.
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8
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Thorne JL, Cioccoloni G. Nuclear Receptors and Lipid Sensing. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1390:83-105. [DOI: 10.1007/978-3-031-11836-4_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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9
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Steck TL, Tabei SMA, Lange Y. A basic model for cell cholesterol homeostasis. Traffic 2021; 22:471-481. [PMID: 34528339 DOI: 10.1111/tra.12816] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 08/26/2021] [Accepted: 09/13/2021] [Indexed: 11/30/2022]
Abstract
Cells manage their cholesterol by negative feedback using a battery of sterol-responsive proteins. How these activities are coordinated so as to specify the abundance and distribution of the sterol is unclear. We present a simple mathematical model that addresses this question. It assumes that almost all of the cholesterol is associated with phospholipids in stoichiometric complexes. A small fraction of the sterol is uncomplexed and thermodynamically active. It equilibrates among the organelles, setting their sterol level according to the affinity of their phospholipids. The activity of the homeostatic proteins in the cytoplasmic membranes is then set by their fractional saturation with uncomplexed cholesterol in competition with the phospholipids. The high-affinity phospholipids in the plasma membrane (PM) are filled to near stoichiometric equivalence, giving it most of the cell sterol. Notably, the affinity of the phospholipids in the endomembranes (EMs) is lower by orders of magnitude than that of the phospholipids in the PM. Thus, the small amount of sterol in the EMs rests far below stoichiometric capacity. Simulations match a variety of experimental data. The model captures the essence of cell cholesterol homeostasis, makes coherent a diverse set of experimental findings, provides a surprising prediction and suggests new experiments.
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Affiliation(s)
- Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - S M Ali Tabei
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa, USA
| | - Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois, USA
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10
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Juhl AD, Heegaard CW, Werner S, Schneider G, Krishnan K, Covey DF, Wüstner D. Quantitative imaging of membrane contact sites for sterol transfer between endo-lysosomes and mitochondria in living cells. Sci Rep 2021; 11:8927. [PMID: 33903617 PMCID: PMC8076251 DOI: 10.1038/s41598-021-87876-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 03/31/2021] [Indexed: 01/25/2023] Open
Abstract
Mitochondria receive cholesterol from late endosomes and lysosomes (LE/LYSs) or from the plasma membrane for production of oxysterols and steroid hormones. This process depends on the endo-lysosomal sterol transfer protein Niemann Pick C2 (NPC2). Using the intrinsically fluorescent cholesterol analog, cholestatrienol, we directly observe sterol transport to mitochondria in fibroblasts upon treating NPC2 deficient human fibroblasts with NPC2 protein. Soft X-ray tomography reveals the ultrastructure of mitochondria and discloses close contact to endosome-like organelles. Using fluorescence microscopy, we localize endo-lysosomes containing NPC2 relative to mitochondria based on the Euclidian distance transform and use statistical inference to show that about 30% of such LE/LYSs are in contact to mitochondria in human fibroblasts. Using Markov Chain Monte Carlo image simulations, we show that interaction between both organelle types, a defining feature of membrane contact sites (MCSs) can give rise to the observed spatial organelle distribution. We devise a protocol to determine the surface fraction of endo-lysosomes in contact with mitochondria and show that this fraction does not depend on functional NPC1 or NPC2 proteins. Finally, we localize MCSs between LE/LYSs containing NPC2 and mitochondria in time-lapse image sequences and show that they either form transiently or remain stable for tens of seconds. Lasting MCSs between endo-lysosomes containing NPC2 and mitochondria move by slow anomalous sub-diffusion, providing location and time for sterol transport between both organelles. Our quantitative imaging strategy will be of high value for characterizing the dynamics and function of MCSs between various organelles in living cells.
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Affiliation(s)
- Alice Dupont Juhl
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Christian W Heegaard
- Department of Molecular Biology and Genetics, University of Aarhus, 8000, Aarhus C, Denmark
| | - Stephan Werner
- Department of X-Ray Microscopy, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Gerd Schneider
- Department of X-Ray Microscopy, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Kathiresan Krishnan
- Department of Developmental Biology, Washington University, St. Louis, MO, 63110, USA
| | - Douglas F Covey
- Department of Developmental Biology, Washington University, St. Louis, MO, 63110, USA
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
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11
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Szomek M, Moesgaard L, Reinholdt P, Haarhøj Hald SB, Petersen D, Krishnan K, Covey DF, Kongsted J, Wüstner D. Membrane organization and intracellular transport of a fluorescent analogue of 27-hydroxycholesterol. Chem Phys Lipids 2020; 233:105004. [PMID: 33137329 DOI: 10.1016/j.chemphyslip.2020.105004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Revised: 09/29/2020] [Accepted: 10/24/2020] [Indexed: 11/30/2022]
Abstract
Oxysterols are cholesterol metabolites with multiple functions in controlling cellular homeostasis. In particular, 27-hydroxycholesterol (27-OH-Chol) has been shown to regulate a variety of physiological functions, but little is known about its uptake, intracellular trafficking, and efflux from cells. This is largely due to a lack of suitable analogs of 27-OH-Chol, which mimic this oxysterol closely. Here, we present the intrinsically fluorescent 27-hydroxy-cholestatrienol (27-OH-CTL), which differs from 27-OH-Chol only by having two additional double bonds in the steroid ring system. Based on molecular dynamics (MD) simulations, we show that 27-OH-CTL possesses almost identical membrane properties compared to 27-OH-Chol. By comparative imaging of 27-OH-CTL and of the cholesterol analogue cholestatrienol (CTL) in living cells, we assess the impact of a single hydroxy group on sterol trafficking. We find that human fibroblasts take up more CTL than 27-OH-CTL, but efflux the oxysterol analogue more efficiently. For both sterols, efflux includes shedding of vesicles from the plasma membrane. Intracellular, 27-OH-CTL accumulates primarily in lipid droplets (LDs), while CTL is mostly found in endosomes and lysosomes. Using fluorescence recovery after photobleaching (FRAP), we find for both sterols a rapidly exchanging pool, which moves orders of magnitude faster than sterol containing vesicles and LDs. In summary, by applying a new fluorescent derivative of 27-OH-Chol we demonstrate that human cells can distinguish sterols based on a single hydroxy group in the side chain, resulting in different transport itineraries, dynamics, and efflux kinetics. Both intrinsically fluorescent cholesterol and oxysterol analogues show rapid non-vesicular transport in human fibroblasts.
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Affiliation(s)
- Maria Szomek
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Laust Moesgaard
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Peter Reinholdt
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Sophia Bell Haarhøj Hald
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Daniel Petersen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Kathiresan Krishnan
- Department of Developmental Biology, Washington University, St. Louis, MO 63110, USA
| | - Douglas F Covey
- Department of Developmental Biology, Washington University, St. Louis, MO 63110, USA
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
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12
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Lange Y, Steck TL. Active cholesterol 20 years on. Traffic 2020; 21:662-674. [PMID: 32930466 DOI: 10.1111/tra.12762] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 09/08/2020] [Accepted: 09/10/2020] [Indexed: 12/13/2022]
Abstract
This review considers the following hypotheses, some well-supported and some speculative. Almost all of the sterol molecules in plasma membranes are associated with bilayer phospholipids in complexes of varied strength and stoichiometry. These complexes underlie many of the material properties of the bilayer. The small fraction of cholesterol molecules exceeding the binding capacity of the phospholipids is thermodynamically active and serves diverse functions. It circulates briskly among the cell membranes, particularly through contact sites linking the organelles. Active cholesterol provides the upstream feedback signal to multiple mechanisms governing plasma membrane homeostasis, pegging the sterol level to a threshold set by its phospholipids. Active cholesterol could also be the cargo for various inter-organelle transporters and the form excreted from cells by reverse transport. Furthermore, it is integral to the function of caveolae; a mediator of Hedgehog regulation; and a ligand for the binding of cytolytic toxins to membranes. Active cholesterol modulates a variety of plasma membrane proteins-receptors, channels and transporters-at least in vitro.
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Affiliation(s)
- Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois, USA
| | - Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
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13
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Revilla G, Pons MDP, Baila-Rueda L, García-León A, Santos D, Cenarro A, Magalhaes M, Blanco RM, Moral A, Ignacio Pérez J, Sabé G, González C, Fuste V, Lerma E, Faria MDS, de Leiva A, Corcoy R, Carles Escolà-Gil J, Mato E. Cholesterol and 27-hydroxycholesterol promote thyroid carcinoma aggressiveness. Sci Rep 2019; 9:10260. [PMID: 31311983 PMCID: PMC6635382 DOI: 10.1038/s41598-019-46727-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 07/04/2019] [Indexed: 01/16/2023] Open
Abstract
Cholesterol mediates its proliferative and metastatic effects via the metabolite 27-hydroxycholesterol (27-HC), at least in breast and endometrial cancer. We determined the serum lipoprotein profile, intratumoral cholesterol and 27-HC levels in a cohort of patients with well-differentiated papillary thyroid carcinoma (PTC; low/intermediate and high risk), advanced thyroid cancers (poorly differentiated, PDTC and anaplastic thyroid carcinoma, ATC) and benign thyroid tumors, as well as the expression of genes involved in cholesterol metabolism. We investigated the gene expression profile, cellular proliferation, and migration in Nthy-ori 3.1 and CAL-62 cell lines loaded with human low-density lipoprotein (LDL). Patients with more aggressive tumors (high-risk PTC and PDTC/ATC) showed a decrease in blood LDL cholesterol and apolipoprotein B. These changes were associated with an increase in the expression of the thyroid’s LDL receptor, whereas 3-hydroxy-3-methylglutaryl-CoA reductase and 25-hydroxycholesterol 7-alpha-hydroxylase were downregulated, with an intratumoral increase of the 27-HC metabolite. Furthermore, LDL promoted proliferation in both the Nthy-ori 3.1 and CAL-62 thyroid cellular models, but only in ATC cells was its cellular migration increased significantly. We conclude that cholesterol and intratumoral accumulation of 27-HC promote the aggressive behavior process of PTC. Targeting cholesterol metabolism could be a new therapeutic strategy in thyroid tumors with poor prognosis.
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Affiliation(s)
- Giovanna Revilla
- Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,Departament de Bioquímica, Biologia Molecular i Biomedicina, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Monica de Pablo Pons
- Department of Endocrinology-EDUAB-HSP, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Lucía Baila-Rueda
- Unidad Clínica y de Investigación en Lípidos y Arteriosclerosis, Hospital Universitario Miguel Servet, Instituto de Investigación Sanitaria Aragón (IIS Aragón), Zaragoza, Spain.,CIBER de Enfermedades Cardiovasculares, CIBERCV, Madrid, Spain
| | - Annabel García-León
- Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - David Santos
- Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,CIBER de Diabetes y Enfermedades Metabólicas Asociadas, CIBERDEM, Madrid, Spain
| | - Ana Cenarro
- CIBER de Enfermedades Cardiovasculares, CIBERCV, Madrid, Spain
| | - Marcelo Magalhaes
- Service of Endocrinology, Clinical Research Center (CEPEC), Hospital of the Federal University of Maranhão (HUUFMA), São Luís, Maranhão, Brazil
| | - R M Blanco
- CIBER Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Madrid, Spain
| | - Antonio Moral
- Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,Department of General Surgery-Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,Medicine Department, Autonomous University of Barcelona (UAB), Barcelona, Spain
| | - José Ignacio Pérez
- Department of General Surgery-Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Gerard Sabé
- Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Cintia González
- Department of Endocrinology-EDUAB-HSP, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,CIBER Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Madrid, Spain
| | - Victoria Fuste
- Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,Department of Anatomic Pathology-Hospital de la Santa Creu i Sant Pau, UAB, Barcelona, Spain
| | - Enrique Lerma
- Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,Department of Anatomic Pathology-Hospital de la Santa Creu i Sant Pau, UAB, Barcelona, Spain
| | - Manuel Dos Santos Faria
- Service of Endocrinology, Clinical Research Center (CEPEC), Hospital of the Federal University of Maranhão (HUUFMA), São Luís, Maranhão, Brazil
| | - Alberto de Leiva
- Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,CIBER Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Madrid, Spain
| | - Rosa Corcoy
- Department of Endocrinology-EDUAB-HSP, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.,CIBER Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Madrid, Spain.,Medicine Department, Autonomous University of Barcelona (UAB), Barcelona, Spain
| | - Joan Carles Escolà-Gil
- Institut d'Investigacions Biomèdiques (IIB) Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain. .,Departament de Bioquímica, Biologia Molecular i Biomedicina, Universitat Autònoma de Barcelona, Barcelona, Spain. .,CIBER de Diabetes y Enfermedades Metabólicas Asociadas, CIBERDEM, Madrid, Spain.
| | - Eugenia Mato
- Department of Endocrinology-EDUAB-HSP, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain. .,CIBER Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Madrid, Spain.
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14
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Caridis AM, Lightbody RJ, Tarlton JMR, Dolan S, Graham A. Genetic obesity increases pancreatic expression of mitochondrial proteins which regulate cholesterol efflux in BRIN-BD11 insulinoma cells. Biosci Rep 2019; 39:BSR20181155. [PMID: 30819824 PMCID: PMC6430727 DOI: 10.1042/bsr20181155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 01/29/2019] [Accepted: 02/26/2019] [Indexed: 11/24/2022] Open
Abstract
Pancreatic β-cells are sensitive to fluctuations in cholesterol content, which can damage the insulin secretion pathway, contributing to the aetiology of type 2 diabetes mellitus. Cholesterol efflux to (apo)lipoproteins, via ATP-binding cassette (ABC) transporter A1 (ABCA1), can prevent intracellular cholesterol accumulation; in some peripheral cells, ABCA1-dependent efflux is enhanced by promotion of cholesterol trafficking to, and generation of Liver X receptor (LXR) ligands by, mitochondrial sterol 27-hydroxylase (Cyp27A1 (cytochrome P450 27 A1/sterol 27-hydroxylase)) and its redox partners, adrenodoxin (ADX) and ADX reductase (ADXR). Despite this, the roles of mitochondrial cholesterol trafficking (steroidogenic acute regulatory protein [StAR] and 18-kDa translocator protein [TSPO]) and metabolising proteins in insulin-secreting cells remain wholly uncharacterised. Here, we demonstrate an increase in pancreatic expression of Cyp27A1, ADXR, TSPO and LXRα, but not ADX or StAR, in obese (fa/fa) rodents compared with lean (Fa/?) controls. Overexpression of Cyp27A1 alone in BRIN-BD11 cells increased INS2 expression, without affecting lipid metabolism; however, after exposure to low-density lipoprotein (LDL), cholesterol efflux to (apo)lipoprotein acceptors was enhanced in Cyp27A1-overexpressing cells. Co-transfection of Cyp27A1, ADX and ADXR, at a ratio approximating that in pancreatic tissue, stimulated cholesterol efflux to apolipoprotein A-I (apoA-I) in both basal and cholesterol-loaded cells; insulin release was stimulated equally by all acceptors in cholesterol-loaded cells. Thus, genetic obesity increases pancreatic expression of Cyp27A1, ADXR, TSPO and LXRα, while modulation of Cyp27A1 and its redox partners promotes cholesterol efflux from insulin-secreting cells to acceptor (apo)lipoproteins; this response may help guard against loss of insulin secretion caused by accumulation of excess intracellular cholesterol.
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Affiliation(s)
- Anna-Maria Caridis
- Department of Biological and Biomedical Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, United Kingdom
| | - Richard J Lightbody
- Department of Biological and Biomedical Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, United Kingdom
| | - Jamie M R Tarlton
- Department of Biological and Biomedical Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, United Kingdom
| | - Sharron Dolan
- Department of Biological and Biomedical Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, United Kingdom
| | - Annette Graham
- Department of Biological and Biomedical Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, United Kingdom
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15
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Kennedy BE, Charman M, Karten B. Measurement of Mitochondrial Cholesterol Import Using a Mitochondria-Targeted CYP11A1 Fusion Construct. Methods Mol Biol 2018; 1583:163-184. [PMID: 28205173 DOI: 10.1007/978-1-4939-6875-6_12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2023]
Abstract
All animal membranes require cholesterol as an essential regulator of biophysical properties and function, but the levels of cholesterol vary widely among different subcellular compartments. Mitochondria, and in particular the inner mitochondrial membrane, have the lowest levels of cholesterol in the cell. Nevertheless, mitochondria need cholesterol for membrane maintenance and biogenesis, as well as oxysterol, steroid, and hepatic bile acid production. Alterations in mitochondrial cholesterol have been associated with a range of pathological conditions, including cancer, hepatosteatosis, cardiac ischemia, Alzheimer's, and Niemann-Pick Type C Disease. The mechanisms of mitochondrial cholesterol import are not fully elucidated yet, and may vary in different cell types and environmental conditions. Measuring cholesterol trafficking to the mitochondrial membranes is technically challenging because of its low abundance; for example, traditional pulse-chase experiments with isotope-labeled cholesterol are not feasible. Here, we describe improvements to a method first developed by the Miller group at the University of California to measure cholesterol trafficking to the inner mitochondrial membrane (IMM) through the conversion of cholesterol to pregnenolone. This method uses a mitochondria-targeted, ectopically expressed fusion construct of CYP11A1, ferredoxin reductase and ferredoxin. Pregnenolone is formed exclusively from cholesterol at the IMM, and can be analyzed with high sensitivity and specificity through ELISA or radioimmunoassay of the medium/buffer to reflect mitochondrial cholesterol import. This assay can be used to investigate the effects of genetic or pharmacological interventions on mitochondrial cholesterol import in cultured cells or isolated mitochondria.
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Affiliation(s)
- Barry E Kennedy
- Department of Biochemistry and Molecular Biology, Dalhousie University, Sir Charles Tupper Medical Building 9G, 5850 College Street, Halifax, NS, Canada, B3H 4R2
| | - Mark Charman
- Department of Biochemistry and Molecular Biology, Dalhousie University, Sir Charles Tupper Medical Building 9G, 5850 College Street, Halifax, NS, Canada, B3H 4R2
| | - Barbara Karten
- Department of Biochemistry and Molecular Biology, Dalhousie University, Sir Charles Tupper Medical Building 9G, 5850 College Street, Halifax, NS, Canada, B3H 4R2.
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16
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Yamauchi Y, Rogers MA. Sterol Metabolism and Transport in Atherosclerosis and Cancer. Front Endocrinol (Lausanne) 2018; 9:509. [PMID: 30283400 PMCID: PMC6157400 DOI: 10.3389/fendo.2018.00509] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 08/14/2018] [Indexed: 01/22/2023] Open
Abstract
Cholesterol is a vital lipid molecule for mammalian cells, regulating fluidity of biological membranes, and serving as an essential constituent of lipid rafts. Mammalian cells acquire cholesterol from extracellular lipoproteins and from de novo synthesis. Cholesterol biosynthesis generates various precursor sterols. Cholesterol undergoes metabolic conversion into oxygenated sterols (oxysterols), bile acids, and steroid hormones. Cholesterol intermediates and metabolites have diverse and important cellular functions. A network of molecular machineries including transcription factors, protein modifiers, sterol transporters/carriers, and sterol sensors regulate sterol homeostasis in mammalian cells and tissues. Dysfunction in metabolism and transport of cholesterol, sterol intermediates, and oxysterols occurs in various pathophysiological settings such as atherosclerosis, cancers, and neurodegenerative diseases. Here we review the cholesterol, intermediate sterol, and oxysterol regulatory mechanisms and intracellular transport machineries, and discuss the roles of sterols and sterol metabolism in human diseases.
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Affiliation(s)
- Yoshio Yamauchi
- Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
- AMED-CREST, Japan Agency for Medical Research and Development, Tokyo, Japan
- *Correspondence: Yoshio Yamauchi
| | - Maximillian A. Rogers
- Division of Cardiovascular Medicine, Center for Interdisciplinary Cardiovascular Sciences, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States
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17
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Torres S, Balboa E, Zanlungo S, Enrich C, Garcia-Ruiz C, Fernandez-Checa JC. Lysosomal and Mitochondrial Liaisons in Niemann-Pick Disease. Front Physiol 2017; 8:982. [PMID: 29249985 PMCID: PMC5714892 DOI: 10.3389/fphys.2017.00982] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Accepted: 11/16/2017] [Indexed: 12/28/2022] Open
Abstract
Lysosomal storage disorders (LSD) are characterized by the accumulation of diverse lipid species in lysosomes. Niemann-Pick type A/B (NPA/B) and type C diseases Niemann-Pick type C (NPC) are progressive LSD caused by loss of function of distinct lysosomal-residing proteins, acid sphingomyelinase and NPC1, respectively. While the primary cause of these diseases differs, both share common biochemical features, including the accumulation of sphingolipids and cholesterol, predominantly in endolysosomes. Besides these alterations in lysosomal homeostasis and function due to accumulation of specific lipid species, the lysosomal functional defects can have far-reaching consequences, disrupting intracellular trafficking of sterols, lipids and calcium through membrane contact sites (MCS) of apposed compartments. Although MCS between endoplasmic reticulum and mitochondria have been well studied and characterized in different contexts, emerging evidence indicates that lysosomes also exhibit close proximity with mitochondria, which translates in their mutual functional regulation. Indeed, as best illustrated in NPC disease, alterations in the lysosomal-mitochondrial liaisons underlie the secondary accumulation of specific lipids, such as cholesterol in mitochondria, resulting in mitochondrial dysfunction and defective antioxidant defense, which contribute to disease progression. Thus, a better understanding of the lysosomal and mitochondrial interactions and trafficking may identify novel targets for the treatment of Niemann-Pick disease.
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Affiliation(s)
- Sandra Torres
- Department of Cell Death and Proliferation, Intituto de Investigaciones Biomédicas de Barcelona, Consejo Superior de Investigaciones Científicas, Barcelona, Spain.,Liver Unit and Hospital Clinc I Provincial, Centro de Investigación Biomédica en Red (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Elisa Balboa
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Silvana Zanlungo
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Carlos Enrich
- Departamento de Biomedicina, Unidad de Biología Celular, Centro de Investigación Biomédica CELLEX, Facultad de Medicina y Ciencias de la Salud, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universidad de Barcelona, Barcelona, Spain
| | - Carmen Garcia-Ruiz
- Department of Cell Death and Proliferation, Intituto de Investigaciones Biomédicas de Barcelona, Consejo Superior de Investigaciones Científicas, Barcelona, Spain.,Liver Unit and Hospital Clinc I Provincial, Centro de Investigación Biomédica en Red (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain.,Southern California Research Center for ALDP and Cirrhosis, Los Angeles, CA, United States
| | - Jose C Fernandez-Checa
- Department of Cell Death and Proliferation, Intituto de Investigaciones Biomédicas de Barcelona, Consejo Superior de Investigaciones Científicas, Barcelona, Spain.,Liver Unit and Hospital Clinc I Provincial, Centro de Investigación Biomédica en Red (CIBEREHD), Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain.,Southern California Research Center for ALDP and Cirrhosis, Los Angeles, CA, United States
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18
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Balboa E, Castro J, Pinochet MJ, Cancino GI, Matías N, Sáez PJ, Martínez A, Álvarez AR, Garcia-Ruiz C, Fernandez-Checa JC, Zanlungo S. MLN64 induces mitochondrial dysfunction associated with increased mitochondrial cholesterol content. Redox Biol 2017; 12:274-284. [PMID: 28282615 PMCID: PMC5344325 DOI: 10.1016/j.redox.2017.02.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 02/24/2017] [Accepted: 02/27/2017] [Indexed: 01/08/2023] Open
Abstract
MLN64 is a late endosomal cholesterol-binding membrane protein that has been implicated in cholesterol transport from endosomal membranes to the plasma membrane and/or mitochondria, in toxin-induced resistance, and in mitochondrial dysfunction. Down-regulation of MLN64 in Niemann-Pick C1 deficient cells decreased mitochondrial cholesterol content, suggesting that MLN64 functions independently of NPC1. However, the role of MLN64 in the maintenance of endosomal cholesterol flow and intracellular cholesterol homeostasis remains unclear. We have previously described that hepatic MLN64 overexpression increases liver cholesterol content and induces liver damage. Here, we studied the function of MLN64 in normal and NPC1-deficient cells and we evaluated whether MLN64 overexpressing cells exhibit alterations in mitochondrial function. We used recombinant-adenovirus-mediated MLN64 gene transfer to overexpress MLN64 in mouse liver and hepatic cells; and RNA interference to down-regulate MLN64 in NPC1-deficient cells. In MLN64-overexpressing cells, we found increased mitochondrial cholesterol content and decreased glutathione (GSH) levels and ATPase activity. Furthermore, we found decreased mitochondrial membrane potential and mitochondrial fragmentation and increased mitochondrial superoxide levels in MLN64-overexpressing cells and in NPC1-deficient cells. Consequently, MLN64 expression was increased in NPC1-deficient cells and reduction of its expression restore mitochondrial membrane potential and mitochondrial superoxide levels. Our findings suggest that MLN64 overexpression induces an increase in mitochondrial cholesterol content and consequently a decrease in mitochondrial GSH content leading to mitochondrial dysfunction. In addition, we demonstrate that MLN64 expression is increased in NPC cells and plays a key role in cholesterol transport into the mitochondria. MLN64 overexpression induces an increase in mitochondrial cholesterol content. MLN64 protein expression is increased in NPC cells. Down-regulation of MLN64 restores mitochondrial membrane potential and superoxide levels in NPC cells. MLN64 overexpression produces mitochondrial dysfunction.
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Affiliation(s)
- Elisa Balboa
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
| | - Juan Castro
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - María-José Pinochet
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Gonzalo I Cancino
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Center for Integrative Biology, Universidad Mayor
| | - Nuria Matías
- Liver Unit, Hospital Clínic i Provincial, Institut d'Investigacions Biomèdiques August Pi i Sunyer, and CIBEREHD, Barcelona, Spain
| | | | - Alexis Martínez
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alejandra R Álvarez
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Carmen Garcia-Ruiz
- Liver Unit, Hospital Clínic i Provincial, Institut d'Investigacions Biomèdiques August Pi i Sunyer, and CIBEREHD, Barcelona, Spain; Research Center for ALPD, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - José C Fernandez-Checa
- Liver Unit, Hospital Clínic i Provincial, Institut d'Investigacions Biomèdiques August Pi i Sunyer, and CIBEREHD, Barcelona, Spain; Research Center for ALPD, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Silvana Zanlungo
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
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19
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Wei X, Song H, Yin L, Rizzo MG, Sidhu R, Covey DF, Ory DS, Semenkovich CF. Fatty acid synthesis configures the plasma membrane for inflammation in diabetes. Nature 2016; 539:294-298. [PMID: 27806377 PMCID: PMC5671339 DOI: 10.1038/nature20117] [Citation(s) in RCA: 194] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 09/23/2016] [Indexed: 12/19/2022]
Abstract
Dietary fat promotes pathological insulin resistance through chronic inflammation. The inactivation of inflammatory proteins produced by macrophages improves diet-induced diabetes, but how nutrient-dense diets induce diabetes is unknown. Membrane lipids affect the innate immune response, which requires domains that influence high-fat-diet-induced chronic inflammation and alter cell function based on phospholipid composition. Endogenous fatty acid synthesis, mediated by fatty acid synthase (FAS), affects membrane composition. Here we show that macrophage FAS is indispensable for diet-induced inflammation. Deleting Fasn in macrophages prevents diet-induced insulin resistance, recruitment of macrophages to adipose tissue and chronic inflammation in mice. We found that FAS deficiency alters membrane order and composition, impairing the retention of plasma membrane cholesterol and disrupting Rho GTPase trafficking-a process required for cell adhesion, migration and activation. Expression of a constitutively active Rho GTPase, however, restored inflammatory signalling. Exogenous palmitate was partitioned to different pools from endogenous lipids and did not rescue inflammatory signalling. However, exogenous cholesterol, as well as other planar sterols, did rescue signalling, with cholesterol restoring FAS-induced perturbations in membrane order. Our results show that the production of endogenous fat in macrophages is necessary for the development of exogenous-fat-induced insulin resistance through the creation of a receptive environment at the plasma membrane for the assembly of cholesterol-dependent signalling networks.
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Affiliation(s)
- Xiaochao Wei
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Haowei Song
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Li Yin
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Michael G Rizzo
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Rohini Sidhu
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Douglas F Covey
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Daniel S Ory
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Clay F Semenkovich
- Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110, USA
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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20
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Elustondo P, Martin LA, Karten B. Mitochondrial cholesterol import. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:90-101. [PMID: 27565112 DOI: 10.1016/j.bbalip.2016.08.012] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 08/15/2016] [Accepted: 08/19/2016] [Indexed: 02/06/2023]
Abstract
All animal subcellular membranes require cholesterol, which influences membrane fluidity and permeability, fission and fusion processes, and membrane protein function. The distribution of cholesterol among subcellular membranes is highly heterogeneous and the cholesterol content of each membrane must be carefully regulated. Compared to other subcellular membranes, mitochondrial membranes are cholesterol-poor, particularly the inner mitochondrial membrane (IMM). As a result, steroidogenesis can be controlled through the delivery of cholesterol to the IMM, where it is converted to pregnenolone. The low basal levels of cholesterol also make mitochondria sensitive to changes in cholesterol content, which can have a relatively large impact on the biophysical and functional characteristics of mitochondrial membranes. Increased mitochondrial cholesterol levels have been observed in diverse pathological conditions including cancer, steatohepatitis, Alzheimer disease and Niemann-Pick Type C1-deficiency, and are associated with increased oxidative stress, impaired oxidative phosphorylation, and changes in the susceptibility to apoptosis, among other alterations in mitochondrial function. Mitochondria are not included in the vesicular trafficking network; therefore, cholesterol transport to mitochondria is mostly achieved through the activity of lipid transfer proteins at membrane contact sites or by cytosolic, diffusible lipid transfer proteins. Here we will give an overview of the main mechanisms involved in mitochondrial cholesterol import, focusing on the steroidogenic acute regulatory protein StAR/STARD1 and other members of the StAR-related lipid transfer (START) domain protein family, and we will discuss how changes in mitochondrial cholesterol levels can arise and affect mitochondrial function. This article is part of a Special Issue entitled: Lipids of Mitochondria edited by Guenther Daum.
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Affiliation(s)
- Pia Elustondo
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Laura A Martin
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Barbara Karten
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada.
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21
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Lange Y, Steck TL. Active membrane cholesterol as a physiological effector. Chem Phys Lipids 2016; 199:74-93. [PMID: 26874289 DOI: 10.1016/j.chemphyslip.2016.02.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 02/04/2016] [Accepted: 02/08/2016] [Indexed: 02/05/2023]
Abstract
Sterols associate preferentially with plasma membrane sphingolipids and saturated phospholipids to form stoichiometric complexes. Cholesterol in molar excess of the capacity of these polar bilayer lipids has a high accessibility and fugacity; we call this fraction active cholesterol. This review first considers how active cholesterol serves as an upstream regulator of cellular sterol homeostasis. The mechanism appears to utilize the redistribution of active cholesterol down its diffusional gradient to the endoplasmic reticulum and mitochondria, where it binds multiple effectors and directs their feedback activity. We have also reviewed a broad literature in search of a role for active cholesterol (as opposed to bulk cholesterol or lipid domains such as rafts) in the activity of diverse membrane proteins. Several systems provide such evidence, implicating, in particular, caveolin-1, various kinds of ABC-type cholesterol transporters, solute transporters, receptors and ion channels. We suggest that this larger role for active cholesterol warrants close attention and can be tested easily.
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Affiliation(s)
- Yvonne Lange
- Department of Pathology, Rush University Medical Center, 1653 W. Congress Parkway, Chicago, IL 60612, USA.
| | - Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
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22
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Pleiotropic effects of antitumour alkylphospholipids on cholesterol transport and metabolism. Exp Cell Res 2015; 340:81-90. [PMID: 26712518 DOI: 10.1016/j.yexcr.2015.12.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 12/15/2015] [Accepted: 12/18/2015] [Indexed: 11/20/2022]
Abstract
BACKGROUND Alkylphospholipid (APL) analogs are a new class of membrane-directed synthetic compounds with a variety of biological actions and clinical applications. In particular, these agents are promising candidates in cancer treatment. We have demonstrated that after prolonged treatment APLs alter intracellular cholesterol traffic and metabolism in human tumor-cell lines, leading to an accumulation of cholesterol inside the cell. After further investigation concerning the mode of action of APLs, we have explored the influence of several APLs on novel aspects of cholesterol and lipoprotein homeostasis using hepatoma HepG2 cells and THP1-derived macrophages. METHODS Quantitative real-time PCR analysis with a pathway-focused PCR array system was performed to measure relative changes in the mRNA expression of a number of genes related to cholesterol transport and metabolism. We compared the gene-expression profiles of HepG2 cells treated with miltefosine, edelfosine or perifosine for 6h and 24h with the profile of control cells. We also analysed particular genes of interest in both HepG2 and macrophage-like THP1 cells using specific PCR assays. Immunoblots were used to confirm protein-expression changes. Measurement of ABCA1-mediated cholesterol efflux was determined using apoA1 as cholesterol acceptor. RESULTS We found global changes in gene-expression patterns to maintain cholesterol homeostasis after exposure of cells to APLs. The pathways for cholesterol biosynthesis and LDL-cholesterol uptake were both transcriptionally upregulated by the three APLs assayed. Conversely, major pathways involved in the catabolism of cholesterol to bile acids and lipoprotein-associated cholesterol export were impaired after APL incubation, which may well contribute to the higher cell-cholesterol levels induced by these compounds. CONCLUSION Incubation of cells with different APLs stimulated cholesterol biosynthesis and uptake at the same time as it depressed common pathways for excess cholesterol removal in tumor cells, ultimately leading to altered cholesterol homeostasis.
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23
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Jinn S, Brandis KA, Ren A, Chacko A, Dudley-Rucker N, Gale SE, Sidhu R, Fujiwara H, Jiang H, Olsen BN, Schaffer JE, Ory DS. snoRNA U17 regulates cellular cholesterol trafficking. Cell Metab 2015; 21:855-67. [PMID: 25980348 PMCID: PMC4456254 DOI: 10.1016/j.cmet.2015.04.010] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 02/19/2015] [Accepted: 04/05/2015] [Indexed: 12/31/2022]
Abstract
Cholesterol is required for the growth and viability of mammalian cells and is an obligate precursor for steroid hormone synthesis. Using a loss-of-function screen for mutants with defects in intracellular cholesterol trafficking, a Chinese hamster ovary cell mutant with haploinsufficiency of the U17 snoRNA was isolated. U17 is an H/ACA orphan snoRNA, for which a function other than ribosomal processing has not previously been identified. Through expression profiling, we identified hypoxia-upregulated mitochondrial movement regulator (HUMMR) mRNA as a target that is negatively regulated by U17 snoRNA. Upregulation of HUMMR in U17 snoRNA-deficient cells promoted the formation of ER-mitochondrial contacts, decreasing esterification of cholesterol and facilitating cholesterol trafficking to mitochondria. U17 snoRNA and HUMMR regulate mitochondrial synthesis of steroids in vivo and are developmentally regulated in steroidogenic tissues, suggesting that the U17 snoRNA-HUMMR pathway may serve a previously unrecognized, physiological role in gonadal tissue maturation.
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Affiliation(s)
- Sarah Jinn
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Katrina A Brandis
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Aileen Ren
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Anita Chacko
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Nicole Dudley-Rucker
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Sarah E Gale
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Rohini Sidhu
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Hideji Fujiwara
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Hui Jiang
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Brett N Olsen
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Jean E Schaffer
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Daniel S Ory
- Diabetic Cardiovascular Disease Center and Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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24
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Mitochondrial cholesterol: mechanisms of import and effects on mitochondrial function. J Bioenerg Biomembr 2014; 48:137-51. [PMID: 25425472 DOI: 10.1007/s10863-014-9592-6] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 11/14/2014] [Indexed: 12/23/2022]
Abstract
Mitochondria require cholesterol for biogenesis and membrane maintenance, and for the synthesis of steroids, oxysterols and hepatic bile acids. Multiple pathways mediate the transport of cholesterol from different subcellular pools to mitochondria. In steroidogenic cells, the steroidogenic acute regulatory protein (StAR) interacts with a mitochondrial protein complex to mediate cholesterol delivery to the inner mitochondrial membrane for conversion to pregnenolone. In non-steroidogenic cells, several members of a protein family defined by the presence of a StAR-related lipid transfer (START) domain play key roles in the delivery of cholesterol to mitochondrial membranes. Subdomains of the endoplasmic reticulum (ER), termed mitochondria-associated ER membranes (MAM), form membrane contact sites with mitochondria and may contribute to the transport of ER cholesterol to mitochondria, either independently or in conjunction with lipid-transfer proteins. Model systems of mitochondria enriched with cholesterol in vitro and mitochondria isolated from cells with (patho)physiological mitochondrial cholesterol accumulation clearly demonstrate that mitochondrial cholesterol levels affect mitochondrial function. Increased mitochondrial cholesterol levels have been observed in several diseases, including cancer, ischemia, steatohepatitis and neurodegenerative diseases, and influence disease pathology. Hence, a deeper understanding of the mechanisms maintaining mitochondrial cholesterol homeostasis may reveal additional targets for therapeutic intervention. Here we give a brief overview of mitochondrial cholesterol import in steroidogenic cells, and then focus on cholesterol trafficking pathways that deliver cholesterol to mitochondrial membranes in non-steroidogenic cells. We also briefly discuss the consequences of increased mitochondrial cholesterol levels on mitochondrial function and their potential role in disease pathology.
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25
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Essentially all excess fibroblast cholesterol moves from plasma membranes to intracellular compartments. PLoS One 2014; 9:e98482. [PMID: 25014655 PMCID: PMC4094430 DOI: 10.1371/journal.pone.0098482] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 05/02/2014] [Indexed: 11/19/2022] Open
Abstract
It has been shown that modestly increasing plasma membrane cholesterol beyond its physiological set point greatly increases the endoplasmic reticulum and mitochondrial pools, thereby eliciting manifold feedback responses that return cell cholesterol to its resting state. The question arises whether this homeostatic mechanism reflects the targeting of cell surface cholesterol to specific intracellular sites or its general equilibration among the organelles. We now show that human fibroblast cholesterol can be increased as much as two-fold from 2-hydroxypropyl-β-cyclodextrin without changing the size of the cell surface pool. Rather, essentially all of the added cholesterol disperses rapidly among cytoplasmic membranes, increasing their overall cholesterol content by as much as five-fold. We conclude that the level of plasma membrane cholesterol is normally at capacity and that even small increments above this physiological set point redistribute essentially entirely to intracellular membranes, perhaps down their chemical activity gradients.
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26
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Olsen BN, Bielska AA, Lee T, Daily MD, Covey DF, Schlesinger PH, Baker NA, Ory DS. The structural basis of cholesterol accessibility in membranes. Biophys J 2014; 105:1838-47. [PMID: 24138860 DOI: 10.1016/j.bpj.2013.08.042] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 08/23/2013] [Accepted: 08/30/2013] [Indexed: 02/02/2023] Open
Abstract
Although the majority of free cellular cholesterol is present in the plasma membrane, cholesterol homeostasis is principally regulated through sterol-sensing proteins that reside in the cholesterol-poor endoplasmic reticulum (ER). In response to acute cholesterol loading or depletion, there is rapid equilibration between the ER and plasma membrane cholesterol pools, suggesting a biophysical model in which the availability of plasma membrane cholesterol for trafficking to internal membranes modulates ER membrane behavior. Previous studies have predominantly examined cholesterol availability in terms of binding to extramembrane acceptors, but have provided limited insight into the structural changes underlying cholesterol activation. In this study, we use both molecular dynamics simulations and experimental membrane systems to examine the behavior of cholesterol in membrane bilayers. We find that cholesterol depth within the bilayer provides a reasonable structural metric for cholesterol availability and that this is correlated with cholesterol-acceptor binding. Further, the distribution of cholesterol availability in our simulations is continuous rather than divided into distinct available and unavailable pools. This data provide support for a revised cholesterol activation model in which activation is driven not by saturation of membrane-cholesterol interactions but rather by bulk membrane remodeling that reduces membrane-cholesterol affinity.
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Affiliation(s)
- Brett N Olsen
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St. Louis, Missouri
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27
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Bielska AA, Olsen BN, Gale SE, Mydock-McGrane L, Krishnan K, Baker NA, Schlesinger PH, Covey DF, Ory DS. Side-chain oxysterols modulate cholesterol accessibility through membrane remodeling. Biochemistry 2014; 53:3042-51. [PMID: 24758724 PMCID: PMC4020583 DOI: 10.1021/bi5000096] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
![]()
Side-chain
oxysterols, such as 25-hydroxycholesterol (25-HC), are
key regulators of cholesterol homeostasis. New evidence suggests that
the alteration of membrane structure by 25-HC contributes to its regulatory
effects. We have examined the role of oxysterol membrane effects on
cholesterol accessibility within the membrane using perfringolysin
O (PFO), a cholesterol-dependent cytolysin that selectively binds
accessible cholesterol, as a sensor of membrane cholesterol accessibility.
We show that 25-HC increases cholesterol accessibility in a manner
dependent on the membrane lipid composition. Structural analysis of
molecular dynamics simulations reveals that increased cholesterol
accessibility is associated with membrane thinning, and that the effects
of 25-HC on cholesterol accessibility are driven by these changes
in membrane thickness. Further, we find that the 25-HC antagonist
LY295427 (agisterol) abrogates the membrane effects of 25-HC in a
nonenantioselective
manner, suggesting that agisterol antagonizes the cholesterol-homeostatic
effects of 25-HC indirectly through its membrane interactions. These
studies demonstrate that oxysterols regulate cholesterol accessibility,
and thus the availability of cholesterol to be sensed
and transported throughout the cell, by modulating the membrane environment.
This work
provides new insights into how alterations in membrane structure can
be used to relay cholesterol regulatory signals.
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Affiliation(s)
- Agata A Bielska
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine , St. Louis, Missouri 63110, United States
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28
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Bile acid synthesis precursors in familial combined hyperlipidemia: The oxysterols 24S-hydroxycholesterol and 27-hydroxycholesterol. Biochem Biophys Res Commun 2014; 446:731-5. [DOI: 10.1016/j.bbrc.2013.12.131] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 12/25/2013] [Indexed: 11/22/2022]
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29
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Sniderman AD, Qi Y, Ma CIJ, Wang RHL, Naples M, Baker C, Zhang J, Adeli K, Kiss RS. Hepatic cholesterol homeostasis: is the low-density lipoprotein pathway a regulatory or a shunt pathway? Arterioscler Thromb Vasc Biol 2013; 33:2481-90. [PMID: 23990208 DOI: 10.1161/atvbaha.113.301517] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE The hypothesis that cholesterol that enters the cell within low-density lipoprotein (LDL) particles rapidly equilibrates with the regulatory pool of intracellular cholesterol and maintains cholesterol homeostasis by reducing cholesterol and LDL receptor synthesis was validated in the fibroblast but not in the hepatocyte. Accordingly, the present studies were designed to compare the effects of cholesterol that enters the hepatocyte within an LDL particle with those of cholesterol that enters via other lipoprotein particles. APPROACH AND RESULTS We measured cholesterol synthesis and esterification in hamster hepatocytes treated with LDL and other lipoprotein particles, including chylomicron remnants and VLDL. Endogenous cholesterol synthesis was not significantly reduced by uptake of LDL, but cholesterol esterification (280%) and acyl CoA:cholesterol acyltransferase 2 expression (870%) were increased. In contrast, cholesterol synthesis was significantly reduced (70% decrease) with other lipoprotein particles. Furthermore, more cholesterol that entered the hepatocyte within LDL particles was secreted within VLDL particles (480%) compared with cholesterol from other sources. CONCLUSIONS Much of the cholesterol that enters the hepatocyte within LDL particles is shunted through the cell and resecreted within VLDL particles without reaching equilibrium with the regulatory pool.
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Affiliation(s)
- Allan D Sniderman
- From the Department of Medicine, Cardiovascular Research Laboratories, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada (A.D.S., Y.Q., C.J.M., R.H.L.W., R.S.K.); Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (M.N., C.B., J.Z., K.A.); and Department of Biochemistry and Laboratory Medicine, University of Toronto, Toronto, Ontario, Canada (M.N., C.B., J.Z., K.A.)
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30
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van der Kant R, Zondervan I, Janssen L, Neefjes J. Cholesterol-binding molecules MLN64 and ORP1L mark distinct late endosomes with transporters ABCA3 and NPC1. J Lipid Res 2013; 54:2153-2165. [PMID: 23709693 DOI: 10.1194/jlr.m037325] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cholesterol is an essential lipid in eukaryotic cells and is present in membranes of all intracellular compartments. A major source for cellular cholesterol is internalized lipoprotein particles that are transported toward acidic late endosomes (LE) and lysosomes. Here the lipoprotein particles are hydrolyzed, and free cholesterol is redistributed to other organelles. The LE can contain over half of the cellular cholesterol and, as a major sorting station, can contain many cholesterol-binding proteins from the ABCA, STARD, and ORP families. Here, we show that metastatic lymph node 64 (MLN64, STARD3) and oxysterol-binding protein-related protein 1L (ORP1L) define two subpopulations of LE. MLN64 is present on a LE containing the cholesterol transporter ABCA3, whereas ORP1L localizes to another population of LE containing Niemann Pick type C1 (NPC1), a cholesterol exporter. Endocytosed cargo passes through MLN64/ABCA3-positive compartments before it reaches ORP1L/NPC1-positive LE. The MLN64/ABCA3 compartments cycle between LE and plasma membrane and frequently contact "later" ORP1L/NPC1-containing LE. We propose two stages of cholesterol handling in late endosomal compartments: first, cholesterol enters MLN64/ABCA3-positive compartments from where it can be recycled to the plasma membrane, and later, cholesterol enters ORP1L/NPC1 endosomes that mediate cholesterol export to the endoplasmic reticulum.
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Affiliation(s)
- Rik van der Kant
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Ilse Zondervan
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Lennert Janssen
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Jacques Neefjes
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, Netherlands.
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31
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Bertolotti M, Del Puppo M, Corna F, Anzivino C, Gabbi C, Baldelli E, Carulli L, Loria P, Galli Kienle M, Carulli N. Increased appearance rate of 27-hydroxycholesterol in vivo in hypercholesterolemia: a possible compensatory mechanism. Nutr Metab Cardiovasc Dis 2012; 22:823-830. [PMID: 21546230 DOI: 10.1016/j.numecd.2011.02.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 02/19/2011] [Accepted: 02/20/2011] [Indexed: 10/18/2022]
Abstract
BACKGROUND AND AIMS The first step in the alternative pathway of bile acid biosynthesis is the 27-hydroxylation of cholesterol, which takes place both in liver and extrahepatic tissues. This pathway is believed to play a role in peripheral cholesterol degradation. Aim of this study was to investigate the impact of hyperlipidemia on 27-hydroxycholesterol appearance rate, and to assess the effects induced by treatment with statins. METHODS AND RESULTS Seven patients with familial hypercholesterolemia and eight patients with familial combined hyperlipidemia underwent determination of 27-hydroxylation rates in vivo by i.v. infusion of deuterated 27-hydroxycholesterol. Isotope enrichment was assayed by gas chromatography-mass spectrometry, allowing to calculate 27-hydroxycholesterol appearance rates. Six normocholesterolemic subjects were regarded as controls. In some hypercholesterolemic patients the infusions were repeated during treatment with atorvastatin or rosuvastatin. Hydroxylation rates were higher in hypercholesterolemic patients (8.7 ± 2.5 mg/h; controls, 3.4 ± 2.0 mg/h; combined hyperlipidemia, 4.4 ± 1.6 mg/h; mean ± SD, P < 0.01 vs both). After statin treatment, both plasma cholesterol levels and hydroxylation rates dropped by nearly 50%. No difference was detectable between the two statins. A linear correlation was shown between plasma cholesterol and 27-hydroxylation rates. CONCLUSION Hypercholesterolemia associates with increased 27-hydroxycholesterol appearance rates, which decrease during hypocholesterolemic treatment. The correlation with cholesterol levels supports the view that 27-hydroxylation may act as a compensatory mechanism in a condition of larger plasma cholesterol pool. A regulatory role for hepatic and extrahepatic nuclear receptors seems reasonable. These data prompt novel pharmacological approaches for the management of hypercholesterolemia and the prevention of atherosclerosis.
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Affiliation(s)
- M Bertolotti
- Dipartimento di Medicina, Endocrinologia, Metabolismo e Geriatria, Università degli Studi di Modena e Reggio Emilia, Nuovo Ospedale Civile, via Giardini 1355, 41100 Modena, Italy.
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32
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Kennedy BE, Charman M, Karten B. Niemann-Pick Type C2 protein contributes to the transport of endosomal cholesterol to mitochondria without interacting with NPC1. J Lipid Res 2012; 53:2632-42. [PMID: 22962690 DOI: 10.1194/jlr.m029942] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mitochondrial cholesterol is maintained within a narrow range to regulate steroid and oxysterol synthesis and to ensure mitochondrial function. Mitochondria acquire cholesterol through several pathways from different cellular pools. Here we have characterized mitochondrial import of endosomal cholesterol using Chinese hamster ovary cells expressing a CYP11A1 fusion protein that converts cholesterol to pregnenolone at the mitochondrial inner membrane. RNA interference-mediated depletion of the voltage-dependent anion channel 1 in the mitochondrial outer membrane or of Niemann-Pick Type C2 (NPC2) in the endosome lumen decreased arrival of cholesterol at the mitochondrial inner membrane. Expression of NPC2 mutants unable to transfer cholesterol to NPC1 still restored mitochondrial cholesterol import in NPC2-depleted cells. Transport assays in semi-permeabilized cells showed nonvesicular cholesterol trafficking directly from endosomes to mitochondria that did not require cytosolic transport proteins but that was reduced in the absence of NPC2. Our findings indicate that NPC2 delivers cholesterol to the perimeter membrane of late endosomes, where it becomes available for transport to mitochondria without requiring NPC1.
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Affiliation(s)
- Barry E Kennedy
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
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33
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Kristiana I, Luu W, Stevenson J, Cartland S, Jessup W, Belani JD, Rychnovsky SD, Brown AJ. Cholesterol through the looking glass: ability of its enantiomer also to elicit homeostatic responses. J Biol Chem 2012; 287:33897-904. [PMID: 22869373 DOI: 10.1074/jbc.m112.360537] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
How cholesterol is sensed to maintain homeostasis has been explained by direct binding to a specific protein, Scap, or through altering the physical properties of the membrane. The enantiomer of cholesterol (ent-cholesterol) is a valuable tool in distinguishing between these two models because it shares nonspecific membrane effects with native cholesterol (nat-cholesterol), but not specific binding interactions. This is the first study to compare ent- and nat-cholesterol directly on major molecular parameters of cholesterol homeostasis. We found that ent-cholesterol suppressed activation of the master transcriptional regulator of cholesterol metabolism, SREBP-2, almost as effectively as nat-cholesterol. Importantly, ent-cholesterol induced a conformational change in the cholesterol-sensing protein Scap in isolated membranes in vitro, even when steps were taken to eliminate potential confounding effects from endogenous cholesterol. Ent-cholesterol also accelerated proteasomal degradation of the key cholesterol biosynthetic enzyme, squalene monooxygenase. Together, these findings provide compelling evidence that cholesterol maintains its own homeostasis not only via direct protein interactions, but also by altering membrane properties.
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Affiliation(s)
- Ika Kristiana
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia
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34
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Tse A, Lee AK, Yan L, Tse FW. Influence of cholesterol on cellular signaling and fusion pore kinetics. J Mol Neurosci 2012; 48:395-401. [PMID: 22467040 DOI: 10.1007/s12031-012-9760-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2012] [Accepted: 03/19/2012] [Indexed: 12/12/2022]
Abstract
Cholesterol is an important lipid component of cellular membranes. Recent studies have shown that changes in cellular cholesterol level can affect cellular functions. Here, we summarize our recent findings on the impact of cholesterol on the glucose-stimulated Ca(2+) signaling in rat pancreatic β cells and the fusion pore kinetics of large dense core granules in rat chromaffin cells. In mouse pancreatic β cells, pharmacological elevation of cellular cholesterol (but not cholesterol extraction) reduced the current density of the delayed rectifier K(+) channels, the ATP-dependent K(+) channels, and voltage-gated Ca(2+) channels. Importantly, cholesterol enrichment impaired glucose-stimulated Ca(2+) signaling in mouse pancreatic β cells via a suppression of voltage-gated Ca(2+) channels and a decrease in mitochondrial ATP production, which in turn led to a reduction in the glucose-evoked depolarization. In rat chromaffin cells, we found that the persistence of the semi-stable fusion pore was increased by cholesterol enrichment, and acute cholesterol extraction from the cytosolic side of the cell destabilized the semi-stable fusion pore. Overall, our findings highlight the importance of cholesterol in the regulation of cellular signaling and exocytosis.
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Affiliation(s)
- Amy Tse
- Department of Pharmacology, University of Alberta, Edmonton, Canada T6G 2H7
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35
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Bielska AA, Schlesinger P, Covey DF, Ory DS. Oxysterols as non-genomic regulators of cholesterol homeostasis. Trends Endocrinol Metab 2012; 23:99-106. [PMID: 22244444 PMCID: PMC3294026 DOI: 10.1016/j.tem.2011.12.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 11/21/2011] [Accepted: 12/05/2011] [Indexed: 12/31/2022]
Abstract
Tight regulation of cellular and plasma cholesterol is crucial to proper cellular functioning because excess free cholesterol is toxic to cells and is associated with atherosclerosis and heart disease. Cellular cholesterol homeostasis is regulated by enzymatically formed oxygenated cholesterol derivatives termed oxysterols. Although the effects of oxysterols on transcriptional pathways are well described, the non-transcriptional mechanisms through which oxysterols acutely modulate cellular cholesterol levels are less well understood. We present emerging evidence suggesting that the membrane biophysical properties of oxysterols underlie their acute cholesterol-regulatory functions and discuss the relevance of these acute effects to cholesterol overload in physiological and pathophysiological states.
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Affiliation(s)
- Agata A Bielska
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St Louis, MO 63110, USA
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36
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Lange Y, Ye J, Steck TL. Activation mobilizes the cholesterol in the late endosomes-lysosomes of Niemann Pick type C cells. PLoS One 2012; 7:e30051. [PMID: 22276143 PMCID: PMC3262792 DOI: 10.1371/journal.pone.0030051] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 12/12/2011] [Indexed: 11/18/2022] Open
Abstract
A variety of intercalating amphipaths increase the chemical activity of plasma membrane cholesterol. To test whether intracellular cholesterol can be similarly activated, we examined NPC1 and NPC2 fibroblasts, since they accumulate large amounts of cholesterol in their late endosomes and lysosomes (LE/L). We gauged the mobility of intracellular sterol from its appearance at the surface of the intact cells, as determined by its susceptibility to cholesterol oxidase and its isotope exchange with extracellular 2-(hydroxypropyl)-β-cyclodextrin-cholesterol. The entire cytoplasmic cholesterol pool in these cells was mobile, exchanging with the plasma membrane with an apparent half-time of ∼3–4 hours, ∼4–5 times slower than that for wild type human fibroblasts (half-time ∼0.75 hours). The mobility of the intracellular cholesterol was increased by the membrane-intercalating amphipaths chlorpromazine and 1-octanol. Chlorpromazine also promoted the net transfer of LE/L cholesterol to serum and cyclodextrin. Surprisingly, the mobility of LE/L cholesterol was greatly stimulated by treating intact NPC cells with glutaraldehyde or formaldehyde. Similar effects were seen with wild type fibroblasts in which the LE/L cholesterol pool had been expanded using U18666A. We also showed that the cholesterol in the intracellular membranes of fixed wild-type fibroblasts was mobile; it was rapidly oxidized by cholesterol oxidase and was rapidly replenished by exogenous sterol. We conclude that a) the cholesterol in NPC cells can exit the LE/L (and the extensive membranous inclusions therein) over a few hours; b) this mobility is stimulated by the activation of the cholesterol with intercalating amphipaths; c) intracellular cholesterol is even more mobile in fixed cells; and d) amphipaths that activate cholesterol might be useful in treating NPC disease.
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Affiliation(s)
- Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois, United States of America.
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37
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Clayton PT. Disorders of bile acid synthesis. J Inherit Metab Dis 2011; 34:593-604. [PMID: 21229319 DOI: 10.1007/s10545-010-9259-3] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 11/30/2010] [Accepted: 12/01/2010] [Indexed: 12/14/2022]
Abstract
Inborn errors of bile acid synthesis can produce life-threatening cholestatic liver disease (which usually presents in infancy) and progressive neurological disease presenting later in childhood or in adult life. Both types of disease can often be treated very effectively with bile acid replacement therapy and it is therefore important to diagnose these disorders as early as possible. The cholestatic disease in infancy is characterised by conjugated hyperbilirubinaemia with raised transaminases but normal γ-glutamyl transpeptidase and a biopsy showing a giant cell hepatitis. There is usually evidence of fat-soluble vitamin malabsorption. The neurological presentation often includes signs of upper motor neurone damage (spastic paraparesis). The most useful screening test for many of these disorders is analysis of urinary cholanoids (bile acids and bile alcohols); this is usually now achieved by electrospray ionisation tandem mass spectrometry. The disorders that are discussed in this review are: 3β-hydroxysteroid-Δ5-C27-steroid dehydrogenase deficiency, Δ4-3-oxosteroid 5β-reductase deficiency, sterol 27-hydroxylase deficiency (cerberotendinous xanthomatosis, CTX), oxysterol 7α-hydroxylase deficiency (including one form of hereditary spastic paraparesis) and the amidation defects, bile acid-CoA: aminoacid N-acyltransferase (BAAT) deficiency and bile acid-CoA ligase deficiency. The disorders of peroxisome biogenesis and peroxisomal β-oxidation that affect bile acid synthesis will be covered in the review by Ferdinandusse et al.
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Affiliation(s)
- Peter Theodore Clayton
- Biochemistry Research Group, Clinical and Molecular Genetics Unit, UCL Institute of Child Health (and Great Ormond Street Hospital for Children), 30 Guilford Street, London WC1N 1EH, UK.
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38
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Steck TL, Lange Y. Cell cholesterol homeostasis: mediation by active cholesterol. Trends Cell Biol 2010; 20:680-7. [PMID: 20843692 DOI: 10.1016/j.tcb.2010.08.007] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 08/03/2010] [Accepted: 08/12/2010] [Indexed: 12/15/2022]
Abstract
Recent evidence suggests that the major pathways mediating cell cholesterol homeostasis respond to a common signal: active membrane cholesterol. Active cholesterol is the fraction that exceeds the complexing capacity of the polar bilayer lipids. Increments in plasma membrane cholesterol exceeding this threshold have an elevated chemical activity (escape tendency) and redistribute via diverse transport proteins to both circulating plasma lipoproteins and intracellular organelles. Active cholesterol thereby prompts several feedback responses. It is the substrate for its own esterification and for the synthesis of regulatory side-chain oxysterols. It also stimulates manifold pathways that down-regulate the biosynthesis, curtail the ingestion and increase the export of cholesterol. Thus, the abundance of cell cholesterol is tightly coupled to that of its polar lipid partners through active cholesterol.
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Affiliation(s)
- Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.
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Cruz P, Torres C, Ramírez ME, Epuñán MJ, Valladares LE, Sierralta WD. Proliferation of human mammary cancer cells exposed to 27-hydroxycholesterol. Exp Ther Med 2010; 1:531-536. [PMID: 22993572 DOI: 10.3892/etm_00000084] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 03/22/2010] [Indexed: 12/25/2022] Open
Abstract
The aim of the present study was to identify the possible mechanisms by which certain estradiol receptor (ER)-positive mammary tumor cells remain resistant to treatment with anti-estrogens or inhibitors of local estradiol (E(2)) production. To this end, we compared the proliferative effects on mammary cancer cells of the novel selective ER modulator 27-hydroxycholesterol (27OHC) to those of E(2), and evaluated their inhibition by ICI 182,780 (ICI). Analysis of the effects on the cell cycle of 27OHC and E(2) in the absence or presence of ICI was conducted. In ER-positive mammary tumor cells, we detected the blocking of 27OHC proliferation-stimulatory activity by simvastatin, as well as the inhibition of E(2)-stimulated proliferation by an α-fetoprotein-derived cyclic nonapeptide. The effects reported herein may be extrapolated to infiltrating mammary cancer, where the activity of local macrophages may stimulate tumor growth. We suggest that increased breast cancer growth in obese patients may be related to increased 27OHC circulatory levels.
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Affiliation(s)
- Pamela Cruz
- Laboratorio de Nutrición y Regulación Metabólica, INTA-Universidad de Chile , Santiago 7830489
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40
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Abstract
Diets rich in saturated fatty acids have long been associated with increased plasma cholesterol concentrations and hence increased risk of cardiovascular disease. More recently, they have also been suggested to promote the development of non-alcoholic fatty liver disease. While there is now considerable evidence to suggest that polyunsaturated fatty acids exert many of their effects through regulating the activity of transcription factors, including peroxisome proliferator activated receptors, sterol regulatory binding proteins (SREBPs) and liver X receptor, our understanding of how saturated fatty acids act is still limited. Here we review the potential mechanisms whereby saturated fatty acids modulate hepatic lipid metabolism thereby impacting on the synthesis, storage and secretion of lipids. Evidence is presented that their effects are, at least partly, mediated through modulation of the activity of the SREBP family of transcription factors.
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Affiliation(s)
| | - A.M. Salter
- Corresponding author. Tel.: +44 115 9516120.
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Charman M, Kennedy BE, Osborne N, Karten B. MLN64 mediates egress of cholesterol from endosomes to mitochondria in the absence of functional Niemann-Pick Type C1 protein. J Lipid Res 2009; 51:1023-34. [PMID: 19965586 DOI: 10.1194/jlr.m002345] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Niemann-Pick Type C (NPC) disease is a fatal, neurodegenerative disorder, caused in most cases by mutations in the late endosomal protein NPC1. A hallmark of NPC disease is endosomal cholesterol accumulation and an impaired cholesterol homeostatic response, which might affect cholesterol transport to mitochondria and, thus, mitochondrial and cellular function. This study aimed to characterize mitochondrial cholesterol homeostasis in NPC disease. Using wild-type and NPC1-deficient Chinese hamster ovary cells, stably transfected with a CYP11A1 complex to assess mitochondrial cholesterol import by pregnenolone production, we show that cholesterol transport to the mitochondrial inner membrane is not affected by loss of NPC1. However, mitochondrial cholesterol content was higher in NPC1-deficient than in wild-type cells. Cholesterol transport to the mitochondrial inner membrane increased markedly upon exposure of cholesterol-deprived cells to lipoproteins, indicating transport of endosomal cholesterol to mitochondria. Reduction of endosomal metastatic lymph node protein 64 (MLN64) by RNA interference decreased cholesterol transport to the mitochondrial inner membrane and reduced mitochondrial cholesterol levels in NPC1-deficient cells, suggesting that MLN64 transported cholesterol to mitochondria even in the absence of NPC1. In summary, this study describes a transport pathway for endosomal cholesterol to mitochondria that requires MLN64, but not NPC1, and that may be responsible for increased mitochondrial cholesterol in NPC disease.
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Affiliation(s)
- Mark Charman
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 1X5, Canada
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Lange Y, Ye J, Duban ME, Steck TL. Activation of membrane cholesterol by 63 amphipaths. Biochemistry 2009; 48:8505-15. [PMID: 19655814 DOI: 10.1021/bi900951r] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A few membrane-intercalating amphipaths have been observed to stimulate the interaction of cholesterol with cholesterol oxidase, saponin and cyclodextrin, presumably by displacing cholesterol laterally from its phospholipid complexes. We now report that this effect, referred to as cholesterol activation, occurs with dozens of other amphipaths, including alkanols, saturated and cis- and trans-unsaturated fatty acids, fatty acid methyl esters, sphingosine derivatives, terpenes, alkyl ethers, ketones, aromatics and cyclic alkyl derivatives. The apparent potency of the agents tested ranged from 3 microM to 7 mM and generally paralleled their octanol/water partition coefficients, except that relative potency declined for compounds with >10 carbons. Some small amphipaths activated cholesterol at a membrane concentration of approximately 3 mol per 100 mol of bilayer lipids, about equimolar with the cholesterol they displaced. Lysophosphatidylserine countered the effects of all these agents, consistent with its ability to reduce the pool of active membrane cholesterol. Various amphipaths stabilized red cells against the hemolysis elicited by cholesterol depletion, presumably by substituting for the extracted sterol. The number and location of cis and trans fatty acid unsaturations and the absolute stereochemistry of enantiomer pairs had only small effects on amphipath potency. Nevertheless, potency varied approximately 7-fold within a group of diverse agents with similar partition coefficients. We infer that a wide variety of amphipaths can displace membrane cholesterol by competing stoichiometrically but with only limited specificity for weak association with phospholipids. Any number of other drugs and experimental agents might do the same.
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Affiliation(s)
- Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois 60612, USA.
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