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T Ishida C, Kubota CS, Carlyle E, Tsukamoto T, Espenshade PJ. A High-Throughput Screening Platform Identifies FDA-Approved Drugs That Inhibit SREBP Pathway Activation. ACS Chem Biol 2024; 19:1695-1704. [PMID: 39106256 DOI: 10.1021/acschembio.4c00354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/09/2024]
Abstract
Sterol regulatory element-binding protein (SREBP) transcription factors are central regulators of lipid homeostasis and are essential for lipid metabolic reprogramming that supports tumor growth in multiple cancers. SREBP pathway inhibitors have been identified, but bioavailable compounds are lacking. To address this need, we designed a novel approach for screening a collection of 4,474 FDA-approved drugs. SREBPs are conditionally essential and required under low lipid conditions. Leveraging this property, we screened for drugs that inhibited pancreatic cancer cell growth in lipid-poor, but not lipid-rich, medium. The primary screen identified 83 drugs that inhibited cell growth in a lipid-dependent manner. Secondary assays examining SREBP target gene expression, SREBP proteolytic cleavage, and effects on human breast cancer cells identified 13 FDA-approved drugs that inhibit SREBP pathway activation. Taken together, we demonstrated that our screening approach can identify SREBP inhibitors from a small library of compounds. This high-throughput screening platform enables screening of large compound collections to discover novel small molecule SREBP inhibitors.
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Affiliation(s)
- Chiaki T Ishida
- Department of Cell Biology, Johns Hopkins University, Baltimore, Maryland 21205 United States
| | - Casie S Kubota
- Department of Cell Biology, Johns Hopkins University, Baltimore, Maryland 21205 United States
| | - Evan Carlyle
- Johns Hopkins Drug Discovery and Department of Neurology, Johns Hopkins University, Baltimore, Maryland 21205 United States
| | - Takashi Tsukamoto
- Johns Hopkins Drug Discovery and Department of Neurology, Johns Hopkins University, Baltimore, Maryland 21205 United States
| | - Peter J Espenshade
- Department of Cell Biology, Johns Hopkins University, Baltimore, Maryland 21205 United States
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University,Baltimore, Maryland 21205 United States
- Giovanis Institute for Translational Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205 United States
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2
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Bu G, Chen G, Li J, Wu D, Liao J. Bifidobacterium bifidum BGN4 fractions ameliorate palmitic acid-induced hepatocyte ferroptosis by inhibiting SREBP1-CYP2E1 pathway. J Investig Med 2024; 72:67-79. [PMID: 37723650 DOI: 10.1177/10815589231204058] [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] [Indexed: 09/20/2023]
Abstract
Metabolic dysfunction-associated fatty liver disease (MAFLD) is strongly associated with disturbances in the intestinal microbiota. Herein, the biological effects and mechanism of Bifidobacterium bifidum BGN4 fractions in regulating hepatocyte ferroptosis during MAFLD progression were investigated. To establish an in vitro model of MAFLD, LO2 cells were subjected to palmitic acid (PA). The mRNA and protein expressions were assessed using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot, respectively. LO2 cell proliferation was examined using 5-diphenyltetrazolium bromide (MTT) and ethynyl-2'-deoxyuridine (EdU) assays, whereas its apoptosis was evaluated by flow cytometry. Furthermore, level of reactive oxygen species (ROS) was measured using 2', 7,-Dichlorodihydrofluorescein diacetate (DCFH-DA) staining. Additionally, the levels of Fe2+, malondialdehyde (MDA), and glutathione (GSH), as well as the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX) were detected using corresponding kits. Chromatin immunoprecipitation and dual-luciferase reporter gene assays were performed to analyze the interaction between sterol-regulatory element binding protein 1 (SREBP1) and cytochrome P450-2E1 (CYP2E1) promoter. Our results revealed that Bifidobacterium bifidum BGN4 fractions effectively ameliorated PA-induced hepatocyte injury, oxidative stress, and ferroptosis. However, these beneficial effects of BGN4 fractions on PA-induced hepatocyte were dramatically reversed by SREBP1 overexpression, suggesting that BGN4 attenuated MAFLD by acting on SREBP1. Moreover, we observed that BGN4 fractions inhibited CYP2E1 transcription by suppressing SREBP1 nuclear translocation. In addition, CYP2E1 overexpression eliminated the inhibitory effect of BGN4 fractions on PA-induced hepatocyte oxidative stress and ferroptosis. These findings collectively indicated that BGN4 fractions reduced CYP2E1 expression by inhibiting SREBP1 nuclear translocation, thereby suppressing hepatocyte oxidative stress and ferroptosis during the development of MAFLD.
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Affiliation(s)
- Guangkui Bu
- Department of Gastroenterology, Hunan Provincial People's Hospital The First-Affiliated Hospital of Hunan Normal University, Changsha, P.R. China
| | - Gang Chen
- Department of Gastroenterology, Hunan Provincial People's Hospital The First-Affiliated Hospital of Hunan Normal University, Changsha, P.R. China
| | - Juan Li
- Department of Gastroenterology, Hunan Provincial People's Hospital The First-Affiliated Hospital of Hunan Normal University, Changsha, P.R. China
| | - Dan Wu
- Department of Gastroenterology, Hunan Provincial People's Hospital The First-Affiliated Hospital of Hunan Normal University, Changsha, P.R. China
| | - Jiangtao Liao
- Department of Gastroenterology, Hunan Provincial People's Hospital The First-Affiliated Hospital of Hunan Normal University, Changsha, P.R. China
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3
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Bolshette N, Ezagouri S, Dandavate V, Karavaeva I, Golik M, Wang H, Espenshade PJ, Osborne TF, Han X, Asher G. Carbon dioxide regulates cholesterol levels through SREBP2. PLoS Biol 2023; 21:e3002367. [PMID: 37967106 PMCID: PMC10651039 DOI: 10.1371/journal.pbio.3002367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 10/06/2023] [Indexed: 11/17/2023] Open
Abstract
In mammals, O2 and CO2 levels are tightly regulated and are altered under various pathological conditions. While the molecular mechanisms that participate in O2 sensing are well characterized, little is known regarding the signaling pathways that participate in CO2 signaling and adaptation. Here, we show that CO2 levels control a distinct cellular transcriptional response that differs from mere pH changes. Unexpectedly, we discovered that CO2 regulates the expression of cholesterogenic genes in a SREBP2-dependent manner and modulates cellular cholesterol accumulation. Molecular dissection of the underlying mechanism suggests that CO2 triggers SREBP2 activation through changes in endoplasmic reticulum (ER) membrane cholesterol levels. Collectively, we propose that SREBP2 participates in CO2 signaling and that cellular cholesterol levels can be modulated by CO2 through SREBP2.
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Affiliation(s)
- Nityanand Bolshette
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Saar Ezagouri
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Vaishnavi Dandavate
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Iuliia Karavaeva
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Marina Golik
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Hu Wang
- The Sam & Ann Barshop Institute for Longevity & Aging Studies, University of Texas Health Science Center, San Antonio, Texas, United States of America
| | - Peter J. Espenshade
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Timothy F. Osborne
- Institute for Fundamental Biomedical Research, Johns Hopkins All Children’s Hospital, and Medicine in the Division of Endocrinology, Diabetes and Metabolism of the Johns Hopkins University School of Medicine, Petersburg, Florida, United States of America
| | - Xianlin Han
- The Sam & Ann Barshop Institute for Longevity & Aging Studies, University of Texas Health Science Center, San Antonio, Texas, United States of America
| | - Gad Asher
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
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4
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Heisler DB, Johnson KA, Ma DH, Ohlson MB, Zhang L, Tran M, Corley CD, Abrams ME, McDonald JG, Schoggins JW, Alto NM, Radhakrishnan A. A concerted mechanism involving ACAT and SREBPs by which oxysterols deplete accessible cholesterol to restrict microbial infection. eLife 2023; 12:e83534. [PMID: 36695568 PMCID: PMC9925056 DOI: 10.7554/elife.83534] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Accepted: 01/25/2023] [Indexed: 01/26/2023] Open
Abstract
Most of the cholesterol in the plasma membranes (PMs) of animal cells is sequestered through interactions with phospholipids and transmembrane domains of proteins. However, as cholesterol concentration rises above the PM's sequestration capacity, a new pool of cholesterol, called accessible cholesterol, emerges. The transport of accessible cholesterol between the PM and the endoplasmic reticulum (ER) is critical to maintain cholesterol homeostasis. This pathway has also been implicated in the suppression of both bacterial and viral pathogens by immunomodulatory oxysterols. Here, we describe a mechanism of depletion of accessible cholesterol from PMs by the oxysterol 25-hydroxycholesterol (25HC). We show that 25HC-mediated activation of acyl coenzyme A: cholesterol acyltransferase (ACAT) in the ER creates an imbalance in the equilibrium distribution of accessible cholesterol between the ER and PM. This imbalance triggers the rapid internalization of accessible cholesterol from the PM, and this depletion is sustained for long periods of time through 25HC-mediated suppression of SREBPs and continued activation of ACAT. In support of a physiological role for this mechanism, 25HC failed to suppress Zika virus and human coronavirus infection in ACAT-deficient cells, and Listeria monocytogenes infection in ACAT-deficient cells and mice. We propose that selective depletion of accessible PM cholesterol triggered by ACAT activation and sustained through SREBP suppression underpins the immunological activities of 25HC and a functionally related class of oxysterols.
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Affiliation(s)
- David B Heisler
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Kristen A Johnson
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Duo H Ma
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Maikke B Ohlson
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Lishu Zhang
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Michelle Tran
- 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
| | - Michael E Abrams
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Jeffrey G McDonald
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
| | - John W Schoggins
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Neal M Alto
- Department of Microbiology, The University of Texas Southwestern Medical CenterDallasUnited States
| | - Arun Radhakrishnan
- Department of Molecular Genetics, The University of Texas Southwestern Medical CenterDallasUnited States
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5
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Ishida CT, Shao W, Espenshade PJ. Assaying Sterol-Regulated ER-to-Golgi Transport of SREBP Cleavage-Activating Protein Using Immunofluorescence Microscopy. Methods Mol Biol 2023; 2557:755-764. [PMID: 36512249 PMCID: PMC10494790 DOI: 10.1007/978-1-0716-2639-9_45] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Sterol regulatory element-binding proteins (SREBPs) are a family of membrane-bound transcription factors that regulate the uptake and synthesis of cholesterol and fatty acids in mammalian cells. SREBP cleavage-activating protein (SCAP) is an endoplasmic reticulum (ER) protein that binds newly synthesized SREBP, retaining it in the ER where SREBP is inactive. SCAP binds cholesterol and functions as the cholesterol sensor in this regulatory system. Under low cholesterol conditions, SCAP escorts SREBP from the ER to the Golgi apparatus where two proteases sequentially cleave and activate SREBP. Given their central importance in maintaining cellular lipid homeostasis, other mechanisms exist to regulate SREBP activity, such as control of protein synthesis and degradation. Here, we describe methods to assay ER-to-Golgi transport of SCAP in vitro using immunofluorescence microscopy and two different cell systems, Chinese hamster ovary (CHO) cells stably expressing hamster GFP-SCAP and human HeLa cells transiently expressing human GFP-SCAP. These methods will permit investigators to determine if cellular perturbations act by affecting the ER-to-Golgi transport of SCAP.
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Affiliation(s)
- Chiaki T Ishida
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Wei Shao
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Peter J Espenshade
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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6
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Li X, Zhang M, Liu M, Liu TH, Hemba-Waduge RUS, Ji JY. Cdk8 attenuates lipogenesis by inhibiting SREBP-dependent transcription in Drosophila. Dis Model Mech 2022; 15:dmm049650. [PMID: 36305265 PMCID: PMC9702540 DOI: 10.1242/dmm.049650] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 10/14/2022] [Indexed: 10/10/2023] Open
Abstract
Fine-tuning of lipogenic gene expression is important for the maintenance of long-term homeostasis of intracellular lipids. The SREBP family of transcription factors are master regulators that control the transcription of lipogenic and cholesterogenic genes, but the mechanisms modulating SREBP-dependent transcription are still not fully understood. We previously reported that CDK8, a subunit of the transcription co-factor Mediator complex, phosphorylates SREBP at a conserved threonine residue. Here, using Drosophila as a model system, we observed that the phosphodeficient SREBP proteins (SREBP-Thr390Ala) were more stable and more potent in stimulating the expression of lipogenic genes and promoting lipogenesis in vivo than wild-type SREBP. In addition, starvation blocked the effects of wild-type SREBP-induced lipogenic gene transcription, whereas phosphodeficient SREBP was resistant to this effect. Furthermore, our biochemical analyses identified six highly conserved amino acid residues in the N-terminus disordered region of SREBP that are required for its interactions with both Cdk8 and the MED15 subunit of the small Mediator complex. These results support that the concerted actions of Cdk8 and MED15 are essential for the tight regulation of SREBP-dependent transcription. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Xiao Li
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M University Health Science Center, College Station, TX 77843, USA
| | - Meng Zhang
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, Louisiana Cancer Research Center, 1700 Tulane Avenue, New Orleans, LA 70112, USA
| | - Mengmeng Liu
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, Louisiana Cancer Research Center, 1700 Tulane Avenue, New Orleans, LA 70112, USA
| | - Tzu-Hao Liu
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, Louisiana Cancer Research Center, 1700 Tulane Avenue, New Orleans, LA 70112, USA
| | - Rajitha-Udakara-Sampath Hemba-Waduge
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, Louisiana Cancer Research Center, 1700 Tulane Avenue, New Orleans, LA 70112, USA
| | - Jun-Yuan Ji
- Department of Molecular and Cellular Medicine, College of Medicine, Texas A&M University Health Science Center, College Station, TX 77843, USA
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, Louisiana Cancer Research Center, 1700 Tulane Avenue, New Orleans, LA 70112, USA
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7
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Zhang Y, Wan C, Song Z, Meng W, Wang S, Lan Z. Pectolinarigenin reduces the expression of sterol regulatory element-binding proteins and cellular lipid levels. Biosci Biotechnol Biochem 2022; 86:1220-1230. [PMID: 35723236 DOI: 10.1093/bbb/zbac095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 06/13/2022] [Indexed: 11/13/2022]
Abstract
Sterol regulatory element-binding proteins (SREBPs) are transcription factors that act important roles in the genes involved in lipid biosynthesis. In this study, it was found that the flavonoid pectolinarigenin, reduced the activity of SRE-containing fatty acid synthase (FAS) promoter and the mRNA expressions of SREBP target genes in human hepatoma (Huh-7) cells. Moreover, compared to other flavonoids, pectolinarigenin reduced the mature forms of SREBPs in a dose-dependent manner. The insulin-induced gene (INSIG) and proteasome were not involved in the pectolinarigenin-mediated reduction of mature forms of SREBPs. Pectolinarigenin also reduced the lipid contents in vitro. These results suggest that pectolinarigenin may inhibit lipogenesis through suppressing SREBP activity, at least partially, via the formation of SREBPs mature forms, thereby reducing the expression of their downstream genes related to lipogenesis. To the best of our knowledge, this is the first work that shows how pectolinarigenin affects cellular lipid levels by affecting SREBPs.
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Affiliation(s)
- Yutao Zhang
- Jiangxi Provincial Key Laboratory of Drug Design and Evaluation, Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang, China
| | - Changjian Wan
- Jiangxi Provincial Key Laboratory of Drug Design and Evaluation, Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang, China
| | - Zijie Song
- Jiangxi Provincial Key Laboratory of Drug Design and Evaluation, Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang, China
| | - Wei Meng
- Jiangxi Provincial Key Laboratory of Drug Design and Evaluation, Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang, China
| | - Songhua Wang
- Jiangxi Provincial Key Laboratory of Drug Design and Evaluation, Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang, China
| | - Zhou Lan
- Jiangxi Provincial Key Laboratory of Drug Design and Evaluation, Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang, China
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8
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Miyata S, Kodaka M, Kikuchi A, Matsunaga Y, Shoji K, Kuan YC, Iwase M, Takeda K, Katsuta R, Ishigami K, Matsumoto Y, Suzuki T, Yamamoto Y, Sato R, Inoue J. Sulforaphane suppresses the activity of sterol regulatory element-binding proteins (SREBPs) by promoting SREBP precursor degradation. Sci Rep 2022; 12:8715. [PMID: 35610278 PMCID: PMC9130306 DOI: 10.1038/s41598-022-12347-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Accepted: 05/09/2022] [Indexed: 12/26/2022] Open
Abstract
Sterol regulatory element-binding proteins (SREBPs) are transcription factors that regulate various genes involved in cholesterol and fatty acid synthesis. In this study, we describe that naturally occurring isothiocyanate sulforaphane (SFaN) impairs fatty acid synthase promoter activity and reduces SREBP target gene (e.g., fatty acid synthase and acetyl-CoA carboxylase 1) expression in human hepatoma Huh-7 cells. SFaN reduced SREBP proteins by promoting the degradation of the SREBP precursor. Amino acids 595–784 of SREBP-1a were essential for SFaN-mediated SREBP-1a degradation. We also found that such SREBP-1 degradation occurs independently of the SREBP cleavage-activating protein and the Keap1-Nrf2 pathway. This study identifies SFaN as an SREBP inhibitor and provides evidence that SFaN could have major potential as a pharmaceutical preparation against hepatic steatosis and obesity.
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Affiliation(s)
- Shingo Miyata
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-8657, Japan
| | - Manami Kodaka
- Department of Agricultural Chemistry, Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Akito Kikuchi
- Department of Agricultural Chemistry, Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Yuki Matsunaga
- Department of Agricultural Chemistry, Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Kenta Shoji
- Department of Agricultural Chemistry, Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Yen-Chou Kuan
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-8657, Japan.,Department of Horticulture and Landscape Architecture, College of Bioresources and Agriculture, National Taiwan University, Taipei, Taiwan
| | - Masamori Iwase
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-8657, Japan
| | - Keita Takeda
- Department of Chemistry for Life Sciences and Agriculture, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Ryo Katsuta
- Department of Chemistry for Life Sciences and Agriculture, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Ken Ishigami
- Department of Chemistry for Life Sciences and Agriculture, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Yu Matsumoto
- Department of Agricultural Chemistry, Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Tsukasa Suzuki
- Department of Agricultural Chemistry, Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Yuji Yamamoto
- Department of Agricultural Chemistry, Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo, 156-8502, Japan
| | - Ryuichiro Sato
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-8657, Japan.
| | - Jun Inoue
- Department of Agricultural Chemistry, Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo, 156-8502, Japan.
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9
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Tiscione SA, Casas M, Horvath JD, Lam V, Hino K, Ory DS, Santana LF, Simó S, Dixon RE, Dickson EJ. IP 3R-driven increases in mitochondrial Ca 2+ promote neuronal death in NPC disease. Proc Natl Acad Sci U S A 2021; 118:e2110629118. [PMID: 34580197 PMCID: PMC8501836 DOI: 10.1073/pnas.2110629118] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2021] [Indexed: 01/05/2023] Open
Abstract
Ca2+ is the most ubiquitous second messenger in neurons whose spatial and temporal elevations are tightly controlled to initiate and orchestrate diverse intracellular signaling cascades. Numerous neuropathologies result from mutations or alterations in Ca2+ handling proteins; thus, elucidating molecular pathways that shape Ca2+ signaling is imperative. Here, we report that loss-of-function, knockout, or neurodegenerative disease-causing mutations in the lysosomal cholesterol transporter, Niemann-Pick Type C1 (NPC1), initiate a damaging signaling cascade that alters the expression and nanoscale distribution of IP3R type 1 (IP3R1) in endoplasmic reticulum membranes. These alterations detrimentally increase Gq-protein coupled receptor-stimulated Ca2+ release and spontaneous IP3R1 Ca2+ activity, leading to mitochondrial Ca2+ cytotoxicity. Mechanistically, we find that SREBP-dependent increases in Presenilin 1 (PS1) underlie functional and expressional changes in IP3R1. Accordingly, expression of PS1 mutants recapitulate, while PS1 knockout abrogates Ca2+ phenotypes. These data present a signaling axis that links the NPC1 lysosomal cholesterol transporter to the damaging redistribution and activity of IP3R1 that precipitates cell death in NPC1 disease and suggests that NPC1 is a nanostructural disease.
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Affiliation(s)
- Scott A Tiscione
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Maria Casas
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Jonathan D Horvath
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Vincent Lam
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Keiko Hino
- Department of Cell Biology and Human Anatomy, University of California, Davis, CA 95616
| | - Daniel S Ory
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Sergi Simó
- Department of Cell Biology and Human Anatomy, University of California, Davis, CA 95616
| | - Rose E Dixon
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616
| | - Eamonn J Dickson
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616;
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10
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Škara L, Huđek Turković A, Pezelj I, Vrtarić A, Sinčić N, Krušlin B, Ulamec M. Prostate Cancer-Focus on Cholesterol. Cancers (Basel) 2021; 13:4696. [PMID: 34572923 PMCID: PMC8469848 DOI: 10.3390/cancers13184696] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 09/08/2021] [Accepted: 09/15/2021] [Indexed: 12/24/2022] Open
Abstract
Prostate cancer (PC) is the most common malignancy in men. Common characteristic involved in PC pathogenesis are disturbed lipid metabolism and abnormal cholesterol accumulation. Cholesterol can be further utilized for membrane or hormone synthesis while cholesterol biosynthesis intermediates are important for oncogene membrane anchoring, nucleotide synthesis and mitochondrial electron transport. Since cholesterol and its biosynthesis intermediates influence numerous cellular processes, in this review we have described cholesterol homeostasis in a normal cell. Additionally, we have illustrated how commonly deregulated signaling pathways in PC (PI3K/AKT/MTOR, MAPK, AR and p53) are linked with cholesterol homeostasis regulation.
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Affiliation(s)
- Lucija Škara
- Department of Medical Biology, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
- Group for Research on Epigenetic Biomarkers (Epimark), School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
- Centre of Excellence for Reproductive and Regenerative Medicine, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
| | - Ana Huđek Turković
- Faculty of Food Technology and Biotechnology, University of Zagreb, 10000 Zagreb, Croatia;
| | - Ivan Pezelj
- Department of Urology, University Clinical Hospital Center Sestre Milosrdnice, 10000 Zagreb, Croatia;
| | - Alen Vrtarić
- Department of Clinical Chemistry, University Clinical Hospital Center Sestre Milosrdnice, 10000 Zagreb, Croatia;
| | - Nino Sinčić
- Department of Medical Biology, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
- Group for Research on Epigenetic Biomarkers (Epimark), School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
- Centre of Excellence for Reproductive and Regenerative Medicine, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
| | - Božo Krušlin
- Centre of Excellence for Reproductive and Regenerative Medicine, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
- Ljudevit Jurak Clinical Department of Pathology and Cytology, Sestre Milosrdnice University Hospital Center, 10000 Zagreb, Croatia
- Department of Pathology, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia
| | - Monika Ulamec
- Group for Research on Epigenetic Biomarkers (Epimark), School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
- Centre of Excellence for Reproductive and Regenerative Medicine, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
- Ljudevit Jurak Clinical Department of Pathology and Cytology, Sestre Milosrdnice University Hospital Center, 10000 Zagreb, Croatia
- Department of Pathology, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia
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11
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Watanabe Y, Sasaki T, Miyoshi S, Shimizu M, Yamauchi Y, Sato R. Insulin-induced genes INSIG1 and INSIG2 mediate oxysterol-dependent activation of the PERK-eIF2α-ATF4 axis. J Biol Chem 2021; 297:100989. [PMID: 34298014 PMCID: PMC8363831 DOI: 10.1016/j.jbc.2021.100989] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 07/12/2021] [Accepted: 07/19/2021] [Indexed: 11/06/2022] Open
Abstract
Insulin-induced genes (INSIGs) encode endoplasmic reticulum–resident proteins that regulate intracellular cholesterol metabolism. Oxysterols are oxygenated derivatives of cholesterol, some of which orchestrate lipid metabolism via interaction with INSIGs. Recently, it was reported that expression of activating transcription factor-4 (ATF4) was induced by certain oxysterols; the precise of mechanism is unclear. Herein, we show that INSIGs mediate ATF4 upregulation upon interaction with oxysterol. Oxysterols that possess a high affinity for INSIG, such as 27- and 25-hydroxycholesterol (25HC), markedly induced the increase of ATF4 protein when compared with other oxysterols. In addition, ATF4 upregulation by these oxysterols was attenuated in INSIG1/2-deficient Chinese hamster ovary cells and recovered by either INSIG1 or INSIG2 rescue. Mechanistic studies revealed that the binding of 25HC to INSIG is critical for increased ATF4 protein via activation of protein kinase RNA-activated–like ER kinase and eukaryotic translation initiation factor 2α. Knockout of INSIG1 or INSIG2 in human hepatoma Huh7 cells attenuated ATF4 protein upregulation, indicating that only one of the endogenous INSIGs, unlike overexpression of intrinsic INSIG1 or INSIG2, was insufficient for ATF4 induction. Furthermore, ATF4 proactively upregulated the cell death–inducible gene expression, such as Chop, Chac1, and Trb3, thereby markedly reducing cell viability with 25HC. These findings support a model whereby that INSIGs sense an increase in oxysterol in the endoplasmic reticulum and induce an increase of ATF4 protein via the protein kinase RNA-activated–like ER kinase–eukaryotic translation initiation factor 2α pathway, thereby promoting cell death.
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Affiliation(s)
- Yuichi Watanabe
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Takashi Sasaki
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Shoko Miyoshi
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Makoto Shimizu
- Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Yoshio Yamauchi
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Ryuichiro Sato
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan; 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.
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12
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Kober DL, Radhakrishnan A, Goldstein JL, Brown MS, Clark LD, Bai XC, Rosenbaum DM. Scap structures highlight key role for rotation of intertwined luminal loops in cholesterol sensing. Cell 2021; 184:3689-3701.e22. [PMID: 34139175 PMCID: PMC8277531 DOI: 10.1016/j.cell.2021.05.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 04/08/2021] [Accepted: 05/14/2021] [Indexed: 11/26/2022]
Abstract
The cholesterol-sensing protein Scap induces cholesterol synthesis by transporting membrane-bound transcription factors called sterol regulatory element-binding proteins (SREBPs) from the endoplasmic reticulum (ER) to the Golgi apparatus for proteolytic activation. Transport requires interaction between Scap's two ER luminal loops (L1 and L7), which flank an intramembrane sterol-sensing domain (SSD). Cholesterol inhibits Scap transport by binding to L1, which triggers Scap's binding to Insig, an ER retention protein. Here we used cryoelectron microscopy (cryo-EM) to elucidate two structures of full-length chicken Scap: (1) a wild-type free of Insigs and (2) mutant Scap bound to chicken Insig without cholesterol. Strikingly, L1 and L7 intertwine tightly to form a globular domain that acts as a luminal platform connecting the SSD to the rest of Scap. In the presence of Insig, this platform undergoes a large rotation accompanied by rearrangement of Scap's transmembrane helices. We postulate that this conformational change halts Scap transport of SREBPs and inhibits cholesterol synthesis.
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Affiliation(s)
- Daniel L Kober
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Molecular Genetics, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Arun Radhakrishnan
- Department of Molecular Genetics, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Joseph L Goldstein
- Department of Molecular Genetics, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Michael S Brown
- Department of Molecular Genetics, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Lindsay D Clark
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xiao-Chen Bai
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Daniel M Rosenbaum
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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13
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Kutchukian C, Vivas O, Casas M, Jones JG, Tiscione SA, Simó S, Ory DS, Dixon RE, Dickson EJ. NPC1 regulates the distribution of phosphatidylinositol 4-kinases at Golgi and lysosomal membranes. EMBO J 2021; 40:e105990. [PMID: 34019311 PMCID: PMC8246069 DOI: 10.15252/embj.2020105990] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 03/11/2021] [Accepted: 03/19/2021] [Indexed: 12/15/2022] Open
Abstract
Cholesterol and phosphoinositides (PI) are two critically important lipids that are found in cellular membranes and dysregulated in many disorders. Therefore, uncovering molecular pathways connecting these essential lipids may offer new therapeutic insights. We report that loss of function of lysosomal Niemann-Pick Type C1 (NPC1) cholesterol transporter, which leads to neurodegenerative NPC disease, initiates a signaling cascade that alters the cholesterol/phosphatidylinositol 4-phosphate (PtdIns4P) countertransport cycle between Golgi-endoplasmic reticulum (ER), as well as lysosome-ER membrane contact sites (MCS). Central to these disruptions is increased recruitment of phosphatidylinositol 4-kinases-PI4KIIα and PI4KIIIβ-which boosts PtdIns4P metabolism at Golgi and lysosomal membranes. Aberrantly increased PtdIns4P levels elevate constitutive anterograde secretion from the Golgi complex, and mTORC1 recruitment to lysosomes. NPC1 disease mutations phenocopy the transporter loss of function and can be rescued by inhibition or knockdown of either key phosphoinositide enzymes or their recruiting partners. In summary, we show that the lysosomal NPC1 cholesterol transporter tunes the molecular content of Golgi and lysosome MCS to regulate intracellular trafficking and growth signaling in health and disease.
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Affiliation(s)
- Candice Kutchukian
- Department of Physiology and Membrane BiologyUniversity of CaliforniaDavisCAUSA
| | - Oscar Vivas
- Department of Physiology and Membrane BiologyUniversity of CaliforniaDavisCAUSA
- Present address:
Department of Physiology and BiophysicsUniversity of WashingtonSeattleWAUSA
| | - Maria Casas
- Department of Physiology and Membrane BiologyUniversity of CaliforniaDavisCAUSA
| | - Julia G Jones
- Department of Physiology and Membrane BiologyUniversity of CaliforniaDavisCAUSA
| | - Scott A Tiscione
- Department of Physiology and Membrane BiologyUniversity of CaliforniaDavisCAUSA
| | - Sergi Simó
- Department of Cell Biology & Human AnatomyUniversity of CaliforniaDavisCAUSA
| | - Daniel S Ory
- Department of Internal MedicineWashington University School of MedicineSt. LouisMOUSA
| | - Rose E Dixon
- Department of Physiology and Membrane BiologyUniversity of CaliforniaDavisCAUSA
| | - Eamonn J Dickson
- Department of Physiology and Membrane BiologyUniversity of CaliforniaDavisCAUSA
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14
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Yan R, Cao P, Song W, Li Y, Wang T, Qian H, Yan C, Yan N. Structural basis for sterol sensing by Scap and Insig. Cell Rep 2021; 35:109299. [PMID: 34192549 DOI: 10.1016/j.celrep.2021.109299] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 04/29/2021] [Accepted: 06/03/2021] [Indexed: 11/30/2022] Open
Abstract
The sterol regulatory element-binding protein (SREBP) pathway monitors the cellular cholesterol level through sterol-regulated association between the SREBP cleavage-activating protein (Scap) and the insulin-induced gene (Insig). Despite structural determination of the Scap and Insig-2 complex bound to 25-hydroxycholesterol, the luminal domains of Scap remain unresolved. In this study, combining cryogenic electron microscopy (cryo-EM) analysis and artificial intelligence-facilitated structural prediction, we report the structure of the human Scap/Insig-2 complex purified in digitonin. The luminal domain loop 1 and a co-folded segment in loop 7 of Scap resemble those of the luminal/extracellular domain in NPC1 and related proteins, providing clues to the cholesterol-regulated interaction of loop 1 and loop 7. An additional luminal interface is observed between Scap and Insig. We also show that Scap(D428A), which inhibits SREBP activation even under sterol depletion, exhibits an identical conformation with the wild-type protein when complexed with Insig-2, and its constitutive suppression of the SREBP pathway may also involve a later step in protein trafficking.
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Affiliation(s)
- Renhong Yan
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China; Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China.
| | - Pingping Cao
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Wenqi Song
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yaning Li
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Tongtong Wang
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hongwu Qian
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Chuangye Yan
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
| | - Nieng Yan
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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15
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Wakana Y, Hayashi K, Nemoto T, Watanabe C, Taoka M, Angulo-Capel J, Garcia-Parajo MF, Kumata H, Umemura T, Inoue H, Arasaki K, Campelo F, Tagaya M. The ER cholesterol sensor SCAP promotes CARTS biogenesis at ER-Golgi membrane contact sites. J Cell Biol 2021; 220:211521. [PMID: 33156328 PMCID: PMC7654440 DOI: 10.1083/jcb.202002150] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 09/15/2020] [Accepted: 10/12/2020] [Indexed: 12/13/2022] Open
Abstract
In response to cholesterol deprivation, SCAP escorts SREBP transcription factors from the endoplasmic reticulum to the Golgi complex for their proteolytic activation, leading to gene expression for cholesterol synthesis and uptake. Here, we show that in cholesterol-fed cells, ER-localized SCAP interacts through Sac1 phosphatidylinositol 4-phosphate (PI4P) phosphatase with a VAP-OSBP complex, which mediates counter-transport of ER cholesterol and Golgi PI4P at ER-Golgi membrane contact sites (MCSs). SCAP knockdown inhibited the turnover of PI4P, perhaps due to a cholesterol transport defect, and altered the subcellular distribution of the VAP-OSBP complex. As in the case of perturbation of lipid transfer complexes at ER-Golgi MCSs, SCAP knockdown inhibited the biogenesis of the trans-Golgi network-derived transport carriers CARTS, which was reversed by expression of wild-type SCAP or a Golgi transport-defective mutant, but not of cholesterol sensing-defective mutants. Altogether, our findings reveal a new role for SCAP under cholesterol-fed conditions in the facilitation of CARTS biogenesis via ER-Golgi MCSs, depending on the ER cholesterol.
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Affiliation(s)
- Yuichi Wakana
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Kaito Hayashi
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Takumi Nemoto
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Chiaki Watanabe
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Masato Taoka
- Faculty of Science, Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
| | - Jessica Angulo-Capel
- Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Maria F Garcia-Parajo
- Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain
| | - Hidetoshi Kumata
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Tomonari Umemura
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Hiroki Inoue
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Kohei Arasaki
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Felix Campelo
- Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Mitsuo Tagaya
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
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16
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Yan R, Cao P, Song W, Qian H, Du X, Coates HW, Zhao X, Li Y, Gao S, Gong X, Liu X, Sui J, Lei J, Yang H, Brown AJ, Zhou Q, Yan C, Yan N. A structure of human Scap bound to Insig-2 suggests how their interaction is regulated by sterols. Science 2021; 371:science.abb2224. [PMID: 33446483 DOI: 10.1126/science.abb2224] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Revised: 07/31/2020] [Accepted: 01/06/2021] [Indexed: 12/22/2022]
Abstract
The sterol regulatory element-binding protein (SREBP) pathway controls cellular homeostasis of sterols. The key players in this pathway, Scap and Insig-1 and -2, are membrane-embedded sterol sensors. The 25-hydroxycholesterol (25HC)-dependent association of Scap and Insig acts as the master switch for the SREBP pathway. Here, we present cryo-electron microscopy analysis of the human Scap and Insig-2 complex in the presence of 25HC, with the transmembrane (TM) domains determined at an average resolution of 3.7 angstrom. The sterol-sensing domain in Scap and all six TMs in Insig-2 were resolved. A 25HC molecule is sandwiched between the S4 to S6 segments in Scap and TMs 3 and 4 in Insig-2 in the luminal leaflet of the membrane. Unwinding of the middle of the Scap-S4 segment is crucial for 25HC binding and Insig association.
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Affiliation(s)
- Renhong Yan
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, Hangzhou 310024, Zhejiang Province, China
| | - Pingping Cao
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Wenqi Song
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hongwu Qian
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Ximing Du
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW 2052, Australia
| | - Hudson W Coates
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW 2052, Australia
| | - Xin Zhao
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yaning Li
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Shuai Gao
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Xin Gong
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Ximing Liu
- National Institute of Biological Sciences (NIBS), Beijing 102206, China
| | - Jianhua Sui
- National Institute of Biological Sciences (NIBS), Beijing 102206, China.,Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 102206, China
| | - Jianlin Lei
- Technology Center for Protein Sciences, Ministry of Education Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW 2052, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW 2052, Australia
| | - Qiang Zhou
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, Hangzhou 310024, Zhejiang Province, China
| | - Chuangye Yan
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
| | - Nieng Yan
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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17
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Identification of a degradation signal at the carboxy terminus of SREBP2: A new role for this domain in cholesterol homeostasis. Proc Natl Acad Sci U S A 2020; 117:28080-28091. [PMID: 33106423 DOI: 10.1073/pnas.2018578117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Lipid homeostasis in animal cells is maintained by sterol regulatory element-binding proteins (SREBPs), membrane-bound transcription factors whose proteolytic activation requires the cholesterol-sensing membrane protein Scap. In endoplasmic reticulum (ER) membranes, the carboxyl-terminal domain (CTD) of SREBPs binds to the CTD of Scap. When cholesterol levels are low, Scap escorts SREBPs from the ER to the Golgi, where the actions of two proteases release the amino-terminal domains of SREBPs that travel to the nucleus to up-regulate expression of lipogenic genes. The CTD of SREBP remains bound to Scap but must be eliminated so that Scap can be recycled to bind and transport additional SREBPs. Here, we provide insights into how this occurs by performing a detailed molecular dissection of the CTD of SREBP2, one of three SREBP isoforms expressed in mammals. We identify a degradation signal comprised of seven noncontiguous amino acids encoded in exon 19 that mediates SREBP2's proteasomal degradation in the absence of Scap. When bound to the CTD of Scap, this signal is masked and SREBP2 is stabilized. Binding to Scap requires an arginine residue in exon 18 of SREBP2. After SREBP2 is cleaved in Golgi, its CTD remains bound to Scap and returns to the ER with Scap where it is eliminated by proteasomal degradation. The Scap-binding motif, but not the degradation signal, is conserved in SREBP1. SREBP1's stability is determined by a degradation signal in a different region of its CTD. These findings highlight a previously unknown role for the CTD of SREBPs in regulating SREBP activity.
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18
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Gesto DS, Pereira CMS, Cerqueira NMFS, Sousa SF. An Atomic-Level Perspective of HMG-CoA-Reductase: The Target Enzyme to Treat Hypercholesterolemia. Molecules 2020; 25:molecules25173891. [PMID: 32859023 PMCID: PMC7503714 DOI: 10.3390/molecules25173891] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 08/23/2020] [Accepted: 08/24/2020] [Indexed: 12/19/2022] Open
Abstract
This review provides an updated atomic-level perspective regarding the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoAR), linking the more recent data on this enzyme with a structure/function interpretation. This enzyme catalyzes one of the most important steps in cholesterol biosynthesis and is regarded as one of the most important drug targets in the treatment of hypercholesterolemia. Taking this into consideration, we review in the present article several aspects of this enzyme, including its structure and biochemistry, its catalytic mechanism and different reported and proposed approaches for inhibiting this enzyme, including the commercially available statins or the possibility of using dimerization inhibitors.
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Affiliation(s)
- Diana S. Gesto
- UCIBIO, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal;
| | - Carlos M. S. Pereira
- UCIBIO/REQUIMTE, BioSIM, Departamento de Biomedicina, Faculdade de Medicina da Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal; (C.M.S.P.); (N.M.F.S.C.)
| | - Nuno M. F. S. Cerqueira
- UCIBIO/REQUIMTE, BioSIM, Departamento de Biomedicina, Faculdade de Medicina da Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal; (C.M.S.P.); (N.M.F.S.C.)
| | - Sérgio F. Sousa
- UCIBIO/REQUIMTE, BioSIM, Departamento de Biomedicina, Faculdade de Medicina da Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal; (C.M.S.P.); (N.M.F.S.C.)
- Correspondence:
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19
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Abstract
Cholesterol is an important component of lipids in animal membranes. All living cells can synthesize cholesterol, but the amount of synthesis is not sufficient, and therefore cholesterol synthesized in the liver is delivered to extrahepatic tissues as a form of LDL. The liver is a primary organ to not only synthesize but also catabolize cholesterol into bile acids, which ends up to excrete with the feces. The synthetic and catabolic pathways are precisely regulated under the negative-feedback control system under the transcriptional regulation driven by several transcription factors such as the sterol regulatory element-binding proteins (SREBPs), the liver x receptor, and the farnesoid x receptor. This review summarizes various findings including our recent discoveries in the molecular mechanism of activation of SREBP that is involved in the regulation of hepatic cholesterol biosynthesis, and a novel function of the metabolic end product of cholesterol, bile acids, in skeletal muscles.
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Affiliation(s)
- Ryuichiro Sato
- Department of Applied Biological Chemistry, The University of Tokyo , Tokyo, Japan
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20
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Levental KR, Malmberg E, Symons JL, Fan YY, Chapkin RS, Ernst R, Levental I. Lipidomic and biophysical homeostasis of mammalian membranes counteracts dietary lipid perturbations to maintain cellular fitness. Nat Commun 2020; 11:1339. [PMID: 32165635 PMCID: PMC7067841 DOI: 10.1038/s41467-020-15203-1] [Citation(s) in RCA: 105] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 02/21/2020] [Indexed: 11/29/2022] Open
Abstract
Proper membrane physiology requires maintenance of biophysical properties, which must be buffered from external perturbations. While homeostatic adaptation of membrane fluidity to temperature variation is a ubiquitous feature of ectothermic organisms, such responsive membrane adaptation to external inputs has not been directly observed in mammals. Here, we report that challenging mammalian membranes by dietary lipids leads to robust lipidomic remodeling to preserve membrane physical properties. Specifically, exogenous polyunsaturated fatty acids are rapidly incorporated into membrane lipids, inducing a reduction in membrane packing. These effects are rapidly compensated both in culture and in vivo by lipidome-wide remodeling, most notably upregulation of saturated lipids and cholesterol, resulting in recovery of membrane packing and permeability. Abrogation of this response results in cytotoxicity when membrane homeostasis is challenged by dietary lipids. These results reveal an essential mammalian mechanism for membrane homeostasis wherein lipidome remodeling in response to dietary lipid inputs preserves functional membrane phenotypes. Proper membrane physiology requires maintenance of a narrow range of physicochemical properties, which must be buffered from external perturbations. Here, authors report lipidomic remodeling to preserve membrane physical properties upon exogenous polyunsaturated fatty acids exposure.
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Affiliation(s)
- Kandice R Levental
- Department of Integrative Biology & Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA.
| | - Eric Malmberg
- Department of Integrative Biology & Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Jessica L Symons
- Department of Integrative Biology & Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Yang-Yi Fan
- Program in Integrative Nutrition & Complex Diseases and Department of Nutrition, Texas A&M University, College Station, TX, USA
| | - Robert S Chapkin
- Program in Integrative Nutrition & Complex Diseases and Department of Nutrition, Texas A&M University, College Station, TX, USA
| | - Robert Ernst
- Department of Medical Biochemistry & Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany
| | - Ilya Levental
- Department of Integrative Biology & Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA.
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21
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Loregger A, Raaben M, Nieuwenhuis J, Tan JME, Jae LT, van den Hengel LG, Hendrix S, van den Berg M, Scheij S, Song JY, Huijbers IJ, Kroese LJ, Ottenhoff R, van Weeghel M, van de Sluis B, Brummelkamp T, Zelcer N. Haploid genetic screens identify SPRING/C12ORF49 as a determinant of SREBP signaling and cholesterol metabolism. Nat Commun 2020; 11:1128. [PMID: 32111832 PMCID: PMC7048761 DOI: 10.1038/s41467-020-14811-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 02/03/2020] [Indexed: 02/07/2023] Open
Abstract
The sterol-regulatory element binding proteins (SREBP) are central transcriptional regulators of lipid metabolism. Using haploid genetic screens we identify the SREBP Regulating Gene (SPRING/C12ORF49) as a determinant of the SREBP pathway. SPRING is a glycosylated Golgi-resident membrane protein and its ablation in Hap1 cells, Hepa1-6 hepatoma cells, and primary murine hepatocytes reduces SREBP signaling. In mice, Spring deletion is embryonic lethal yet silencing of hepatic Spring expression also attenuates the SREBP response. Mechanistically, attenuated SREBP signaling in SPRINGKO cells results from reduced SREBP cleavage-activating protein (SCAP) and its mislocalization to the Golgi irrespective of the cellular sterol status. Consistent with limited functional SCAP in SPRINGKO cells, reintroducing SCAP restores SREBP-dependent signaling and function. Moreover, in line with the role of SREBP in tumor growth, a wide range of tumor cell lines display dependency on SPRING expression. In conclusion, we identify SPRING as a previously unrecognized modulator of SREBP signaling.
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Affiliation(s)
- Anke Loregger
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Matthijs Raaben
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Joppe Nieuwenhuis
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Josephine M E Tan
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Lucas T Jae
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands.,Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor Lynen-Str. 25, 81377, Munich, Germany
| | - Lisa G van den Hengel
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Sebastian Hendrix
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Marlene van den Berg
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Saskia Scheij
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Ji-Ying Song
- Division of Experimental Animal Pathology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Ivo J Huijbers
- Mouse Clinic for Cancer and Aging (MCCA) Transgenic Facility, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Lona J Kroese
- Mouse Clinic for Cancer and Aging (MCCA) Transgenic Facility, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands
| | - Roelof Ottenhoff
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Michel van Weeghel
- Laboratory of Genetic and Metabolic Diseases and Core Facility Metabolomics, Academic Medical Center of the University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands
| | - Bart van de Sluis
- Department of Pediatrics, University Medical Center Groningen, Antonius Deusinglaan 1, 9713AV, Groningen, The Netherlands.,iPSC/CRISPR Center Groningen, University Medical Center Groningen, Antonius Deusinglaan 1, 9713AV, Groningen, The Netherlands
| | - Thijn Brummelkamp
- Oncode Institute, Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066CX, Amsterdam, The Netherlands. .,CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, A-1090, Vienna, Austria. .,Cancer Genomics Center, Amsterdam, The Netherlands.
| | - Noam Zelcer
- Department of Medical Biochemistry, Amsterdam UMC, Amsterdam Cardiovascular Sciences and Gastroenterology and Metabolism, University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands.
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22
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Kuan YC, Takahashi Y, Maruyama T, Shimizu M, Yamauchi Y, Sato R. Ring finger protein 5 activates sterol regulatory element-binding protein 2 (SREBP2) to promote cholesterol biosynthesis via inducing polyubiquitination of SREBP chaperone SCAP. J Biol Chem 2020; 295:3918-3928. [PMID: 32054686 DOI: 10.1074/jbc.ra119.011849] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 02/04/2020] [Indexed: 12/13/2022] Open
Abstract
Sterol regulatory element-binding protein 2 (SREBP2) is the master transcription factor that regulates cholesterol metabolism. SREBP2 activation is regulated by SREBP chaperone SCAP. Here we show that ring finger protein 5 (RNF5), an endoplasmic reticulum-anchored E3 ubiquitin ligase, mediates the Lys-29-linked polyubiquitination of SCAP and thereby activates SREBP2. RNF5 knockdown inhibited SREBP2 activation and reduced cholesterol biosynthesis in human hepatoma cells, and RNF5 overexpression activated SREBP2. Mechanistic studies revealed that RNF5 binds to the transmembrane domain of SCAP and ubiquitinates the Lys-305 located in cytosolic loop 2 of SCAP. Moreover, the RNF5-mediated ubiquitination enhanced an interaction between SCAP luminal loop 1 and loop 7, a crucial event for SREBP2 activation. Notably, an overexpressed K305R SCAP variant failed to restore the SREBP2 pathway in SCAP-deficient cell lines. These findings define a new mechanism by which an ubiquitination-induced SCAP conformational change regulates cholesterol biosynthesis.
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Affiliation(s)
- Yen-Chou Kuan
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
| | - Yu Takahashi
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
| | - Takashi Maruyama
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
| | - Makoto Shimizu
- Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
| | - Yoshio Yamauchi
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
| | - Ryuichiro Sato
- Food Biochemistry Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan .,Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan.,AMED-CREST, Japan Agency for Medical Research and Development, Chiyoda-ku, Tokyo 100-0004, Japan
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23
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Lipidomic profiling analysis of the phospholipid molecules in SCAP-induced lipid droplet formation in bovine mammary epithelial cells. Prostaglandins Other Lipid Mediat 2020; 149:106420. [PMID: 31953015 DOI: 10.1016/j.prostaglandins.2020.106420] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 12/15/2019] [Accepted: 01/10/2020] [Indexed: 12/12/2022]
Abstract
The accumulation of lipid droplets (LDs) in the cytoplasm plays an important role in energy balance, membrane synthesis and cell signal transduction. The aim of this study was to investigate the profile of phospholipids after SCAP-induced LD formation in bovine mammary epithelial cells (BMECs). A shRNA-SCAP vector and a SCAP/SREBP vector were used to knock down and overexpress the SCAP gene in BMECs prior to evaluating the effects on LDs using Western blotting, real-time PCR, LD staining and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The average LD diameter was determined following oil red O staining. The overexpression of SCAP increased the abundance of SCD, ACACA and FASN genes and nuclear SREBP1a. In contrast, knocking down SCAP decreased the abundance of the nuclear SREBP1a protein and downregulated the abundance of target genes. Lipid droplet staining revealed that knocking down SCAP reduced LD formation and average LD diameter. In contrast, overexpression of SCAP increased the formation and size of the LDs. The results from an analysis of cellular lipids revealed that phospholipids are the predominant species in the profile of cell lipids. phosphatidylethanolamine (PE) and phosphatidylcholine (PC) are important for determining the size of LDs. The LD formation induced by SCAP gene overexpression and knockdown underscored the role of phospholipids involved in lipid droplet formation and fusion.
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24
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Tiscione SA, Vivas O, Ginsburg KS, Bers DM, Ory DS, Santana LF, Dixon RE, Dickson EJ. Disease-associated mutations in Niemann-Pick type C1 alter ER calcium signaling and neuronal plasticity. J Cell Biol 2019; 218:4141-4156. [PMID: 31601621 PMCID: PMC6891088 DOI: 10.1083/jcb.201903018] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 08/12/2019] [Accepted: 09/06/2019] [Indexed: 11/22/2022] Open
Abstract
Niemann-Pick type C1 (NPC1) protein is essential for the transport of externally derived cholesterol from lysosomes to other organelles. Deficiency of NPC1 underlies the progressive NPC1 neurodegenerative disorder. Currently, there are no curative therapies for this fatal disease. Given the Ca2+ hypothesis of neurodegeneration, which posits that altered Ca2+ dynamics contribute to neuropathology, we tested if disease mutations in NPC1 alter Ca2+ signaling and neuronal plasticity. We determine that NPC1 inhibition or disease mutations potentiate store-operated Ca2+ entry (SOCE) due to a presenilin 1 (PSEN1)-dependent reduction in ER Ca2+ levels alongside elevated expression of the molecular SOCE components ORAI1 and STIM1. Associated with this dysfunctional Ca2+ signaling is destabilization of neuronal dendritic spines. Knockdown of PSEN1 or inhibition of the SREBP pathway restores Ca2+ homeostasis, corrects differential protein expression, reduces cholesterol accumulation, and rescues spine density. These findings highlight lysosomes as a crucial signaling platform responsible for tuning ER Ca2+ signaling, SOCE, and synaptic architecture in health and disease.
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Affiliation(s)
- Scott A Tiscione
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Oscar Vivas
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | | | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, CA
| | - Daniel S Ory
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO
| | - Luis F Santana
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Rose E Dixon
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Eamonn J Dickson
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
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25
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Jin U, Park SJ, Park SM. Cholesterol Metabolism in the Brain and Its Association with Parkinson's Disease. Exp Neurobiol 2019; 28:554-567. [PMID: 31698548 PMCID: PMC6844833 DOI: 10.5607/en.2019.28.5.554] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/18/2019] [Accepted: 10/21/2019] [Indexed: 12/11/2022] Open
Abstract
Parkinson’s disease (PD) is the second most progressive neurodegenerative disorder of the aging population after Alzheimer’s disease (AD). Defects in the lysosomal systems and mitochondria have been suspected to cause the pathogenesis of PD. Nevertheless, the pathogenesis of PD remains obscure. Abnormal cholesterol metabolism is linked to numerous disorders, including atherosclerosis. The brain contains the highest level of cholesterol in the body and abnormal cholesterol metabolism links also many neurodegenerative disorders such as AD, PD, Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS). The blood brain barrier effectively prevents uptake of lipoprotein-bound cholesterol from blood circulation. Accordingly, cholesterol level in the brain is independent from that in peripheral tissues. Because cholesterol metabolism in both peripheral tissue and the brain are quite different, cholesterol metabolism associated with neurodegeneration should be examined separately from that in peripheral tissues. Here, we review and compare cholesterol metabolism in the brain and peripheral tissues. Furthermore, the relationship between alterations in cholesterol metabolism and PD pathogenesis is reviewed.
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Affiliation(s)
- Uram Jin
- Department of Pharmacology, Ajou University School of Medicine, Suwon 16499, Korea.,Center for Convergence Research of Neurological Disorders, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Cardiology, Ajou University School of Medicine, Suwon 16499, Korea
| | - Soo Jin Park
- Department of Pharmacology, Ajou University School of Medicine, Suwon 16499, Korea.,Center for Convergence Research of Neurological Disorders, Ajou University School of Medicine, Suwon 16499, Korea.,Department of Thoracic and Cardiovascular Surgery, Ajou University School of Medicine, Suwon 16499, Korea
| | - Sang Myun Park
- Department of Pharmacology, Ajou University School of Medicine, Suwon 16499, Korea.,Center for Convergence Research of Neurological Disorders, Ajou University School of Medicine, Suwon 16499, Korea.,BK21 Plus Program, Department of Biomedical Sciences, Ajou University School of Medicine, Suwon 16499, Korea
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26
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Furuta T, Mizukami Y, Asano L, Kotake K, Ziegler S, Yoshida H, Watanabe M, Sato SI, Waldmann H, Nishikawa M, Uesugi M. Nutrient-Based Chemical Library as a Source of Energy Metabolism Modulators. ACS Chem Biol 2019; 14:1860-1865. [PMID: 31436407 DOI: 10.1021/acschembio.9b00444] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Covalent conjugates of multiple nutrients often exhibit greater biological activities than each individual nutrient and more predictable safety profiles than completely unnatural chemical entities. Here, we report the construction and application of a focused chemical library of 308 covalent conjugates of a variety of small-molecule nutrients. Screening of the library with a reporter gene of sterol regulatory element-binding protein (SREBP), a master regulator of mammalian lipogenesis, led to the discovery of a conjugate of docosahexaenoic acid (DHA), glucosamine, and amino acids as an inhibitor of SREBP (molecule 1, DHG). Mechanistic analyses indicate that molecule 1 impairs the SREBP activity by inhibiting glucose transporters and thereby activating AMP-activated protein kinase (AMPK). Oral administration of molecule 1 suppressed the intestinal absorption of glucose in mice. These results suggest that such synthetic libraries of nutrient conjugates serve as a source of novel chemical tools and pharmaceutical seeds that modulate energy metabolism.
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Affiliation(s)
- Tomoyuki Furuta
- Institute for Chemical Research and Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Yuya Mizukami
- Department of Biopharmaceutics and Drug Metabolism, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Lisa Asano
- Institute for Chemical Research and Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Kenjiro Kotake
- Institute for Chemical Research and Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Slava Ziegler
- Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Hiroki Yoshida
- Institute for Chemical Research and Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Mizuki Watanabe
- Institute for Chemical Research and Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Shin-ichi Sato
- Institute for Chemical Research and Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Herbert Waldmann
- Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
| | - Makiya Nishikawa
- Department of Biopharmaceutics and Drug Metabolism, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
- Laboratory of Biopharmaceutics, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Motonari Uesugi
- Institute for Chemical Research and Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto, 611-0011, Japan
- RIKEN-Max Planck Joint Research Division for Systems Chemical Biology, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- School of Pharmacy, Fudan University, Shanghai 201203, China
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27
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Han Y, Hu Z, Cui A, Liu Z, Ma F, Xue Y, Liu Y, Zhang F, Zhao Z, Yu Y, Gao J, Wei C, Li J, Fang J, Li J, Fan JG, Song BL, Li Y. Post-translational regulation of lipogenesis via AMPK-dependent phosphorylation of insulin-induced gene. Nat Commun 2019; 10:623. [PMID: 30733434 PMCID: PMC6367348 DOI: 10.1038/s41467-019-08585-4] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 01/07/2019] [Indexed: 12/20/2022] Open
Abstract
Insulin-induced gene (Insig) negatively regulates SREBP-mediated de novo fatty acid synthesis in the liver. However, the upstream regulation of Insig is incompletely understood. Here we report that AMPK interacts with and mediates phosphorylation of Insig. Thr222 phosphorylation following AMPK activation is required for protein stabilization of Insig-1, inhibition of cleavage and processing of SREBP-1, and lipogenic gene expression in response to metformin or A769662. AMPK-dependent phosphorylation ablates Insig’s interaction with E3 ubiquitin ligase gp78 and represses its ubiquitination and degradation, whereas AMPK deficiency shows opposite effects. Interestingly, activation of AMPK by metformin causes an augmentation of Insig stability and reduction of lipogenic gene expression, and leads to the attenuation of hepatic steatosis in HFHS diet-fed mice. Moreover, hepatic overexpression of Insig-1 rescues hepatic steatosis in liver-specific AMPKα2 knockout mice fed with HFHS diet. These findings uncover a novel effector of AMPK. Targeting Insig may have the therapeutic potential for treating fatty liver disease and related disorders. Insulin-related gene (Insig) negatively regulates hepatic fatty acid synthesis, a process involved in development of non-alcoholic fatty liver disease (NAFLD). Here, the authors show that AMPK activation by metformin promotes Insig phosphorylation, stabilizing it and inhibiting lipogenic gene expression. This is protective against steatosis in diabetic mice.
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Affiliation(s)
- Yamei Han
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Zhimin Hu
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Aoyuan Cui
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Zhengshuai Liu
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Fengguang Ma
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Yaqian Xue
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Yuxiao Liu
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Feifei Zhang
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Zehua Zhao
- Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, 200092, Shanghai, China
| | - Yanyan Yu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 201203, Shanghai, China
| | - Jing Gao
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Chun Wei
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, 310014, Hangzhou, China
| | - Jingya Li
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 201203, Shanghai, China
| | - Jing Fang
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China
| | - Jia Li
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 201203, Shanghai, China
| | - Jian-Gao Fan
- Department of Gastroenterology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, 200092, Shanghai, China
| | - Bao-Liang Song
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Institute for Advanced Studies, Wuhan University, 430072, Wuhan, China
| | - Yu Li
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031, Shanghai, China.
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28
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Kondo Y, Fu J, Wang H, Hoover C, McDaniel JM, Steet R, Patra D, Song J, Pollard L, Cathey S, Yago T, Wiley G, Macwana S, Guthridge J, McGee S, Li S, Griffin C, Furukawa K, James JA, Ruan C, McEver RP, Wierenga KJ, Gaffney PM, Xia L. Site-1 protease deficiency causes human skeletal dysplasia due to defective inter-organelle protein trafficking. JCI Insight 2018; 3:121596. [PMID: 30046013 PMCID: PMC6124414 DOI: 10.1172/jci.insight.121596] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 06/08/2018] [Indexed: 01/18/2023] Open
Abstract
Site-1 protease (S1P), encoded by MBTPS1, is a serine protease in the Golgi. S1P regulates lipogenesis, endoplasmic reticulum (ER) function, and lysosome biogenesis in mice and in cultured cells. However, how S1P differentially regulates these diverse functions in humans has been unclear. In addition, no human disease with S1P deficiency has been identified. Here, we report a pediatric patient with an amorphic and a severely hypomorphic mutation in MBTPS1. The unique combination of these mutations results in a frequency of functional MBTPS1 transcripts of approximately 1%, a finding that is associated with skeletal dysplasia and elevated blood lysosomal enzymes. We found that the residually expressed S1P is sufficient for lipid homeostasis but not for ER and lysosomal functions, especially in chondrocytes. The defective S1P function specifically impairs activation of the ER stress transducer BBF2H7, leading to ER retention of collagen in chondrocytes. S1P deficiency also causes abnormal secretion of lysosomal enzymes due to partial impairment of mannose-6-phosphate-dependent delivery to lysosomes. Collectively, these abnormalities lead to apoptosis of chondrocytes and lysosomal enzyme-mediated degradation of the bone matrix. Correction of an MBTPS1 variant or reduction of ER stress mitigated collagen-trafficking defects. These results define a new congenital human skeletal disorder and, more importantly, reveal that S1P is particularly required for skeletal development in humans. Our findings may also lead to new therapies for other genetic skeletal diseases, as ER dysfunction is common in these disorders.
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Affiliation(s)
- Yuji Kondo
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Jianxin Fu
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA.,Jiangsu Institute of Hematology, MOH Key Laboratory of Thrombosis and Hemostasis, Collaborative Innovation Center of Hematology, The First Affiliated Hospital of Soochow University, Suzhou, China
| | | | - Christopher Hoover
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA.,Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - J Michael McDaniel
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Richard Steet
- Complex Carbohydrate Research Center, University of Georgia, Georgia, Athens, USA
| | - Debabrata Patra
- Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Jianhua Song
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Laura Pollard
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | - Sara Cathey
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | - Tadayuki Yago
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Graham Wiley
- Division of Genomics and Data Sciences, Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Susan Macwana
- Division of Genomics and Data Sciences, Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Joel Guthridge
- Division of Genomics and Data Sciences, Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Samuel McGee
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | | | - Courtney Griffin
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Koichi Furukawa
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Judith A James
- Division of Genomics and Data Sciences, Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Changgeng Ruan
- Jiangsu Institute of Hematology, MOH Key Laboratory of Thrombosis and Hemostasis, Collaborative Innovation Center of Hematology, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Rodger P McEver
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA.,Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | | | - Patrick M Gaffney
- Division of Genomics and Data Sciences, Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Lijun Xia
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA.,Jiangsu Institute of Hematology, MOH Key Laboratory of Thrombosis and Hemostasis, Collaborative Innovation Center of Hematology, The First Affiliated Hospital of Soochow University, Suzhou, China.,Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
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29
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Inoue J, Miyata S, Shimizu M, Sato R. Isoxanthohumol stimulates ubiquitin-proteasome-dependent degradation of precursor forms of sterol regulatory element-binding proteins. Biosci Biotechnol Biochem 2018; 82:1591-1598. [PMID: 29804513 DOI: 10.1080/09168451.2018.1478715] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Sterol regulatory element-binding proteins (SREBPs) are transcription factors that regulate a wide variety of genes involved in fatty acid and cholesterol synthesis. In the present study, we identified that isoxanthohumol (IXN) suppressed SREBP activity. Low concentrations of IXN (10 and 30 μM) reduced the amount of mature forms of SREBPs, while high concentration of IXN (100 μM) reduced both precursor and mature forms of SREBPs in Huh-7 cells. The IXN-mediated decrease in the precursor forms of SREBPs in Huh-7 cells was completely abolished by culturing cells under sterol-supplemented conditions and was partly abolished by treatment with a proteasome inhibitor, MG132, but not a lysosome inhibitor, NH4Cl. Moreover, IXN accelerated the ubiquitination of the precursor forms of SREBP-1a. These results suggest that IXN suppresses SREBP activity, at least in part, via ubiquitin-proteasome-dependent degradation of the precursor forms of SREBPs. ABBREVIATIONS ACC1: acetyl-CoA carboxylase 1; DMEM: Dulbecco's modified Eagle's medium; ER: endoplasmic reticulum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; 25-HC: 25-hydroxycholesterol; HMGCR: HMG-CoA reductase; HMGCS: HMG-CoA synthase; Insig: insulin-induced gene; IXN: isoxanthohumol; LPDS: lipoprotein-deficient serum; SCAP: SREBP cleavage-activating protein; SCD1: stearoyl-CoA desaturase; SREBPs: sterol regulatory element-binding proteins; XN: xanthohumol.
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Affiliation(s)
- Jun Inoue
- a Department of Agricultural Chemistry, Faculty of Applied Biosciences , Tokyo University of Agriculture , Tokyo , Japan.,b Food Biochemistry laboratory, Department of Applied Biological Chemistry , Graduate School of Agricultural and Life Sciences, The University of Tokyo , Tokyo , Japan
| | - Shingo Miyata
- b Food Biochemistry laboratory, Department of Applied Biological Chemistry , Graduate School of Agricultural and Life Sciences, The University of Tokyo , Tokyo , Japan
| | - Makoto Shimizu
- b Food Biochemistry laboratory, Department of Applied Biological Chemistry , Graduate School of Agricultural and Life Sciences, The University of Tokyo , Tokyo , Japan
| | - Ryuichiro Sato
- b Food Biochemistry laboratory, Department of Applied Biological Chemistry , Graduate School of Agricultural and Life Sciences, The University of Tokyo , Tokyo , Japan.,c Nutri-Life Science laboratory, Department of Applied Biological Chemistry , Graduate School of Agricultural and Life Sciences, The University of Tokyo , Tokyo , Japan
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30
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Han LQ, Gao TY, Yang GY, Loor JJ. Overexpression of SREBF chaperone (SCAP) enhances nuclear SREBP1 translocation to upregulate fatty acid synthase (FASN) gene expression in bovine mammary epithelial cells. J Dairy Sci 2018; 101:6523-6531. [PMID: 29680640 DOI: 10.3168/jds.2018-14382] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 03/04/2018] [Indexed: 11/19/2022]
Abstract
Fatty acid synthase is a key enzyme for the synthesis of milk fat in the ruminant mammary gland. In nonruminants, sterol regulatory element binding protein 1 (SREBP1) is a regulator of FASN gene expression, and SREBF chaperone (SCAP) is essential for SREBP1 maturation and activity. However, the role of SCAP on the regulation of FASN gene expression in ruminants is unknown. The objective of this study was to investigate the transcriptional regulation of FASN by overexpressing SCAP in bovine mammary epithelial cells. A bovine SCAP expression vector, SREBP1 expression vector, and the promoter of FASN were cloned. The transcription factor binding sites of FASN promoter were predicted using bioinformatics analysis. After transfection with FASN promoter vectors in the immortalized bovine mammary epithelial cell line MAC-T, we co-overexpressed the SCAP + SREBP1 expression vector with pcDNA3.1 vector as control. The effect of SCAP + SREBP1 overexpression on the regulation of FASN was investigated using luciferase assay, immunofluorescence, Western blot, real-time PCR, and lipid droplet staining. We observed that co-overexpression of SCAP + SREBP1 significantly increased activity of the FASN promoter containing a sterol response element binding site. The FASN mRNA abundance and lipid droplet formation increased due to co-overexpression of SCAP + SREBP1. Compared with overexpression of SREBP1 alone, co-overexpression of SCAP + SREBP1 enhanced the nuclear translocation and nuclear SREBP1 protein abundance. Overall, as in nonruminants cells, results indicate that SCAP is essential for promoting nuclear translocation of SREBP1 and activation of FASN gene transcription, leading to lipid droplet formation in bovine mammary epithelial cells.
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Affiliation(s)
- L Q Han
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou 450002, P.R. China; Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois, Urbana 61801
| | - T Y Gao
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou 450002, P.R. China
| | - G Y Yang
- College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou 450002, P.R. China.
| | - J J Loor
- Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois, Urbana 61801.
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31
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Abstract
Cellular lipid metabolism and homeostasis are controlled by sterol regulatory-element binding proteins (SREBPs). In addition to performing canonical functions in the transcriptional regulation of genes involved in the biosynthesis and uptake of lipids, genome-wide system analyses have revealed that these versatile transcription factors act as important nodes of convergence and divergence within biological signalling networks. Thus, they are involved in myriad physiological and pathophysiological processes, highlighting the importance of lipid metabolism in biology. Changes in cell metabolism and growth are reciprocally linked through SREBPs. Anabolic and growth signalling pathways branch off and connect to multiple steps of SREBP activation and form complex regulatory networks. In addition, SREBPs are implicated in numerous pathogenic processes such as endoplasmic reticulum stress, inflammation, autophagy and apoptosis, and in this way, they contribute to obesity, dyslipidaemia, diabetes mellitus, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, chronic kidney disease, neurodegenerative diseases and cancers. This Review aims to provide a comprehensive understanding of the role of SREBPs in physiology and pathophysiology at the cell, organ and organism levels.
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Affiliation(s)
- Hitoshi Shimano
- Department of Internal Medicine (Endocrinology and Metabolism), Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
- International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
- Life Science Center, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, Tsukuba 305-8577, Japan
- AMED-CREST, Japan Agency for Medical Research and Development, Chiyoda-ku, Tokyo 100-0004, Japan
| | - Ryuichiro Sato
- AMED-CREST, Japan Agency for Medical Research and Development, Chiyoda-ku, Tokyo 100-0004, Japan
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan
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32
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Gao Y, Zhou Y, Goldstein JL, Brown MS, Radhakrishnan A. Cholesterol-induced conformational changes in the sterol-sensing domain of the Scap protein suggest feedback mechanism to control cholesterol synthesis. J Biol Chem 2017; 292:8729-8737. [PMID: 28377508 DOI: 10.1074/jbc.m117.783894] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/03/2017] [Indexed: 01/28/2023] Open
Abstract
Scap is a polytopic protein of endoplasmic reticulum (ER) membranes that transports sterol regulatory element-binding proteins to the Golgi complex for proteolytic activation. Cholesterol accumulation in ER membranes prevents Scap transport and decreases cholesterol synthesis. Previously, we provided evidence that cholesterol inhibition is initiated when cholesterol binds to loop 1 of Scap, which projects into the ER lumen. Within cells, this binding causes loop 1 to dissociate from loop 7, another luminal Scap loop. However, we have been unable to demonstrate this dissociation when we added cholesterol to isolated complexes of loops 1 and 7. We therefore speculated that the dissociation requires a conformational change in the intervening polytopic sequence separating loops 1 and 7. Here we demonstrate such a change using a protease protection assay in sealed membrane vesicles. In the absence of cholesterol, trypsin or proteinase K cleaved cytosolic loop 4, generating a protected fragment that we visualized with a monoclonal antibody against loop 1. When cholesterol was added to these membranes, cleavage in loop 4 was abolished. Because loop 4 is part of the so-called sterol-sensing domain separating loops 1 and 7, these results support the hypothesis that cholesterol binding to loop 1 alters the conformation of the sterol-sensing domain. They also suggest that this conformational change helps transmit the cholesterol signal from loop 1 to loop 7, thereby allowing separation of the loops and facilitating the feedback inhibition of cholesterol synthesis. These insights suggest a new structural model for cholesterol-mediated regulation of Scap activity.
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Affiliation(s)
- Yansong Gao
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Yulian Zhou
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Joseph L Goldstein
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Michael S Brown
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Arun Radhakrishnan
- From the Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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Dhingra S, Cramer RA. Regulation of Sterol Biosynthesis in the Human Fungal Pathogen Aspergillus fumigatus: Opportunities for Therapeutic Development. Front Microbiol 2017; 8:92. [PMID: 28203225 PMCID: PMC5285346 DOI: 10.3389/fmicb.2017.00092] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 01/13/2017] [Indexed: 12/29/2022] Open
Abstract
Sterols are a major component of eukaryotic cell membranes. For human fungal infections caused by the filamentous fungus Aspergillus fumigatus, antifungal drugs that target sterol biosynthesis and/or function remain the standard of care. Yet, an understanding of A. fumigatus sterol biosynthesis regulatory mechanisms remains an under developed therapeutic target. The critical role of sterol biosynthesis regulation and its interactions with clinically relevant azole drugs is highlighted by the basic helix loop helix (bHLH) class of transcription factors known as Sterol Regulatory Element Binding Proteins (SREBPs). SREBPs regulate transcription of key ergosterol biosynthesis genes in fungi including A. fumigatus. In addition, other emerging regulatory pathways and target genes involved in sterol biosynthesis and drug interactions provide additional opportunities including the unfolded protein response, iron responsive transcriptional networks, and chaperone proteins such as Hsp90. Thus, targeting molecular pathways critical for sterol biosynthesis regulation presents an opportunity to improve therapeutic options for the collection of diseases termed aspergillosis. This mini-review summarizes our current understanding of sterol biosynthesis regulation with a focus on mechanisms of transcriptional regulation by the SREBP family of transcription factors.
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Affiliation(s)
- Sourabh Dhingra
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover NH, USA
| | - Robert A Cramer
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover NH, USA
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Asano L, Watanabe M, Ryoden Y, Usuda K, Yamaguchi T, Khambu B, Takashima M, Sato SI, Sakai J, Nagasawa K, Uesugi M. Vitamin D Metabolite, 25-Hydroxyvitamin D, Regulates Lipid Metabolism by Inducing Degradation of SREBP/SCAP. Cell Chem Biol 2017; 24:207-217. [PMID: 28132894 DOI: 10.1016/j.chembiol.2016.12.017] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 11/23/2016] [Accepted: 12/29/2016] [Indexed: 12/19/2022]
Abstract
Sterol regulatory element-binding proteins (SREBPs) are transcription factors that control lipid homeostasis. SREBP activation is regulated by a negative feedback loop in which sterols bind to SREBP cleavage-activating protein (SCAP), an escort protein essential for SREBP activation, or to insulin-induced genes (Insigs) (endoplasmic reticulum [ER] anchor proteins), sequestering the SREBP-SCAP-Insig complex in the ER. We screened a chemical library of endogenous molecules and identified 25-hydroxyvitamin D (25OHD) as an inhibitor of SREBP activation. Unlike sterols and other SREBP inhibitors, 25OHD impairs SREBP activation by inducing proteolytic processing and ubiquitin-mediated degradation of SCAP, thereby decreasing SREBP levels independently of the vitamin D receptor. Vitamin D supplementation has been proposed to reduce the risk of metabolic diseases, but the mechanisms are unknown. The present results suggest a previously unrecognized molecular mechanism of vitamin D-mediated lipid control that might be useful in the treatment of metabolic diseases.
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Affiliation(s)
- Lisa Asano
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto 611-0011, Japan; Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Mizuki Watanabe
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto 611-0011, Japan; Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Yuta Ryoden
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Kousuke Usuda
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Takuya Yamaguchi
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Bilon Khambu
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Megumi Takashima
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Shin-Ichi Sato
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Juro Sakai
- Division of Metabolic Medicine, Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Tokyo 153-8904, Japan; The Translational Systems Biology and Medicine Initiative, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Tokyo 113-8655, Japan
| | - Kazuo Nagasawa
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan; CREST, AMED.
| | - Motonari Uesugi
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Uji, Kyoto 611-0011, Japan; Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan; CREST, AMED.
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35
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García-Ruiz C, Ribas V, Baulies A, Fernández-Checa JC. Mitochondrial Cholesterol and the Paradox in Cell Death. Handb Exp Pharmacol 2017; 240:189-210. [PMID: 28035533 DOI: 10.1007/164_2016_110] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Mitochondria are considered cholesterol-poor organelles, and obtain their cholesterol load by the action of specialized proteins involved in its delivery from extramitochondrial sources and trafficking within mitochondrial membranes. Although mitochondrial cholesterol fulfills vital physiological functions, such as the synthesis of bile acids in the liver or the formation of steroid hormones in specialized tissues, recent evidence indicates that the accumulation of cholesterol in mitochondria may be a key event in prevalent human diseases, in particular in the development of steatohepatitis (SH) and its progression to hepatocellular carcinoma (HCC). Mitochondrial cholesterol accumulation promotes the transition from simple steatosis to SH due to the sensitization to oxidative stress and cell death. However, mitochondrial cholesterol loading in HCC determines apoptosis resistance and insensitivity to chemotherapy. These opposing functions of mitochondrial cholesterol in SH and HCC define its paradoxical role in cell death as a pro- and anti-apoptotic factor. Further understanding of this conundrum may be useful to modulate the progression from SH to HCC by targeting mitochondrial cholesterol trafficking.
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Affiliation(s)
- Carmen García-Ruiz
- Department of Cell Death and Proliferation, Instituto Investigaciones Biomedicas de Barcelona, CSIC, C/Rosello 161, 08036, Barcelona, Spain
- Liver Unit, Hospital Clinic, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red (CIBERehd), Barcelona, Spain
- Keck School of Medicine, USC, University of Southern California Research Center for Alcohol Liver and Pancreatic Diseases and Cirrhosis, Los Angeles, CA, USA
| | - Vicente Ribas
- Department of Cell Death and Proliferation, Instituto Investigaciones Biomedicas de Barcelona, CSIC, C/Rosello 161, 08036, Barcelona, Spain
- Liver Unit, Hospital Clinic, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red (CIBERehd), Barcelona, Spain
| | - Anna Baulies
- Department of Cell Death and Proliferation, Instituto Investigaciones Biomedicas de Barcelona, CSIC, C/Rosello 161, 08036, Barcelona, Spain
- Liver Unit, Hospital Clinic, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red (CIBERehd), Barcelona, Spain
| | - Jose C Fernández-Checa
- Department of Cell Death and Proliferation, Instituto Investigaciones Biomedicas de Barcelona, CSIC, C/Rosello 161, 08036, Barcelona, Spain.
- Liver Unit, Hospital Clinic, IDIBAPS, Barcelona, Spain.
- Centro de Investigación Biomédica en Red (CIBERehd), Barcelona, Spain.
- Keck School of Medicine, USC, University of Southern California Research Center for Alcohol Liver and Pancreatic Diseases and Cirrhosis, Los Angeles, CA, USA.
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36
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Abstract
Cellular cholesterol levels are intricately controlled to maintain homeostasis. Here, we describe ways in which cellular cholesterol status can be manipulated for the study of cholesterol homeostasis, including sterol starvation (by culturing cells in lipoprotein-deficient serum and pretreating/treating with the cholesterol-lowering drug, statin) and sterol enrichment (using cholesterol complexed to cyclodextrin, and low-density lipoprotein). We also describe how to prepare lipoprotein-deficient serum and complex cholesterol to cyclodextrin.
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Affiliation(s)
- Winnie Luu
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Biological Sciences Building D26, Sydney, NSW, 2052, Australia
| | - Ingrid C Gelissen
- Faculty of Pharmacy, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Biological Sciences Building D26, Sydney, NSW, 2052, Australia.
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37
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Kuan YC, Hashidume T, Shibata T, Uchida K, Shimizu M, Inoue J, Sato R. Heat Shock Protein 90 Modulates Lipid Homeostasis by Regulating the Stability and Function of Sterol Regulatory Element-binding Protein (SREBP) and SREBP Cleavage-activating Protein. J Biol Chem 2016; 292:3016-3028. [PMID: 28003358 DOI: 10.1074/jbc.m116.767277] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 12/14/2016] [Indexed: 12/18/2022] Open
Abstract
Sterol regulatory element-binding proteins (SREBPs) are the key transcription factors that modulate lipid biosynthesis. SREBPs are synthesized as endoplasmic reticulum-bound precursors that require proteolytic activation in the Golgi apparatus. The stability and maturation of precursor SREBPs depend on their binding to SREBP cleavage-activating protein (SCAP), which escorts the SCAP-SREBP complex to the Golgi apparatus. In this study, we identified heat shock protein (HSP) 90 as a novel SREBP regulator that binds to and stabilizes SCAP-SREBP. In HepG2 cells, HSP90 inhibition led to proteasome-dependent degradation of SCAP-SREBP, which resulted in the down-regulation of SREBP target genes and the reduction in intracellular triglyceride and cholesterol levels. We also demonstrated in vivo that HSP90 inhibition decreased SCAP-SREBP protein, down-regulated SREBP target genes, and reduced lipids levels in mouse livers. We propose that HSP90 plays an indispensable role in SREBP regulation by stabilizing the SCAP-SREBP complex, facilitating the activation of SREBP to maintain lipids homeostasis.
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Affiliation(s)
| | | | - Takahiro Shibata
- the Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan, and
| | - Koji Uchida
- the Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan, and
| | | | - Jun Inoue
- From the Food Biochemistry Laboratory and
| | - Ryuichiro Sato
- From the Food Biochemistry Laboratory and .,the Nutri-Life Science Laboratory, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan.,AMED-CREST, Japan Agency for Medical Research and Development, Chiyoda-ku, Tokyo 100-0004, Japan
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38
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Cheng C, Guo JY, Geng F, Wu X, Cheng X, Li Q, Guo D. Analysis of SCAP N-glycosylation and Trafficking in Human Cells. J Vis Exp 2016. [PMID: 27911384 DOI: 10.3791/54709] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Elevated lipogenesis is a common characteristic of cancer and metabolic diseases. Sterol regulatory element-binding proteins (SREBPs), a family of membrane-bound transcription factors controlling the expression of genes important for the synthesis of cholesterol, fatty acids and phospholipids, are frequently upregulated in these diseases. In the process of SREBP nuclear translocation, SREBP-cleavage activating protein (SCAP) plays a central role in the trafficking of SREBP from the endoplasmic reticulum (ER) to the Golgi and in subsequent proteolysis activation. Recently, we uncovered that glucose-mediated N-glycosylation of SCAP is a prerequisite condition for the exit of SCAP/SREBP from the ER and movement to the Golgi. N-glycosylation stabilizes SCAP and directs SCAP/SREBP trafficking. Here, we describe a protocol for the isolation of membrane fractions in human cells and for the preparation of the samples for the detection of SCAP N-glycosylation and total protein by using western blot. We further provide a method to monitor SCAP trafficking by using confocal microscopy. This protocol is appropriate for the investigation of SCAP N-glycosylation and trafficking in mammalian cells.
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Affiliation(s)
- Chunming Cheng
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Jeffrey Yunhua Guo
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Feng Geng
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Xiaoning Wu
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Xiang Cheng
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Qiyue Li
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine
| | - Deliang Guo
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center and College of Medicine;
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Shao W, Machamer CE, Espenshade PJ. Fatostatin blocks ER exit of SCAP but inhibits cell growth in a SCAP-independent manner. J Lipid Res 2016; 57:1564-73. [PMID: 27324795 DOI: 10.1194/jlr.m069583] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Indexed: 12/30/2022] Open
Abstract
Sterol regulatory element-binding protein (SREBP) transcription factors are central regulators of cellular lipid homeostasis and activate expression of genes required for fatty acid, triglyceride, and cholesterol synthesis and uptake. SREBP cleavage activating protein (SCAP) plays an essential role in SREBP activation by mediating endoplasmic reticulum (ER)-to-Golgi transport of SREBP. In the Golgi, membrane-bound SREBPs are cleaved sequentially by the site-1 and site-2 proteases. Recent studies have shown a requirement for the SREBP pathway in the development of fatty liver disease and tumor growth, making SCAP a target for drug development. Fatostatin is a chemical inhibitor of the SREBP pathway that directly binds SCAP and blocks its ER-to-Golgi transport. In this study, we determined that fatostatin blocks ER exit of SCAP and showed that inhibition is independent of insulin-induced gene proteins, which function to retain the SCAP-SREBP complex in the ER. Fatostatin potently inhibited cell growth, but unexpectedly exogenous lipids failed to rescue proliferation of fatostatin-treated cells. Furthermore, fatostatin inhibited growth of cells lacking SCAP Using a vesicular stomatitis virus glycoprotein (VSVG) trafficking assay, we demonstrated that fatostatin delays ER-to-Golgi transport of VSVG. In summary, fatostatin inhibited SREBP activation, but fatostatin additionally inhibited cell proliferation through both lipid-independent and SCAP-independent mechanisms, possibly by general inhibition of ER-to-Golgi transport.
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Affiliation(s)
- Wei Shao
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Carolyn E Machamer
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Peter J Espenshade
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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40
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Albert A, Alexander D, Boesze-Battaglia K. Cholesterol in the rod outer segment: A complex role in a "simple" system. Chem Phys Lipids 2016; 199:94-105. [PMID: 27216754 DOI: 10.1016/j.chemphyslip.2016.04.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 04/22/2016] [Accepted: 04/23/2016] [Indexed: 12/01/2022]
Abstract
The rod outer segment (ROS) of retinal photoreceptor cells consists of disk membranes surrounded by the plasma membrane. It is a relatively uncomplicated system in which to investigate cholesterol distribution and its functional consequences in biologically relevant membranes. The light sensitive protein, rhodopsin is the major protein in both membranes, but the lipid compositions are significantly different in the disk and plasma membranes. Cholesterol is high in the ROS plasma membrane. Disk membranes are synthesized at the base of the ROS and are also high in cholesterol. However, cholesterol is rapidly depleted as the disks are apically displaced. During this apical displacement the disk phospholipid fatty acyl chains become progressively more unsaturated, which creates an environment unfavorable to cholesterol. Membrane cholesterol has functional consequences. The high cholesterol found in the plasma membrane and in newly synthesized disks inhibits the activation of rhodopsin. As disks are apically displaced and cholesterol is depleted rhodopsin becomes more responsive to light. This effect of cholesterol on rhodopsin activation has been shown in both native and reconstituted membranes. The modulation of activity can be at least partially explained by the effect of cholesterol on bulk lipid properties. Cholesterol decreases the partial free volume of the hydrocarbon region of the bilayer and thereby inhibits rhodopsin conformational changes required for activation. However, cholesterol binds to rhodopsin and may directly affect the protein also. Furthermore, cholesterol stabilizes rhodopsin to thermal denaturation. The membrane must provide an environment that allows rhodopsin conformational changes required for activation while also stabilizing the protein to thermal denaturation. Cholesterol thus plays a complex role in modulating the activity and stability of rhodopsin, which have implications for other G-protein coupled receptors.
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41
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Cheng C, Ru P, Geng F, Liu J, Yoo JY, Wu X, Cheng X, Euthine V, Hu P, Guo JY, Lefai E, Kaur B, Nohturfft A, Ma J, Chakravarti A, Guo D. Glucose-Mediated N-glycosylation of SCAP Is Essential for SREBP-1 Activation and Tumor Growth. Cancer Cell 2015; 28:569-581. [PMID: 26555173 PMCID: PMC4643405 DOI: 10.1016/j.ccell.2015.09.021] [Citation(s) in RCA: 189] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 08/04/2015] [Accepted: 09/27/2015] [Indexed: 12/17/2022]
Abstract
Tumorigenesis is associated with increased glucose consumption and lipogenesis, but how these pathways are interlinked is unclear. Here, we delineate a pathway in which EGFR signaling, by increasing glucose uptake, promotes N-glycosylation of sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP) and consequent activation of SREBP-1, an ER-bound transcription factor with central roles in lipid metabolism. Glycosylation stabilizes SCAP and reduces its association with Insig-1, allowing movement of SCAP/SREBP to the Golgi and consequent proteolytic activation of SREBP. Xenograft studies reveal that blocking SCAP N-glycosylation ameliorates EGFRvIII-driven glioblastoma growth. Thus, SCAP acts as key glucose-responsive protein linking oncogenic signaling and fuel availability to SREBP-dependent lipogenesis. Targeting SCAP N-glycosylation may provide a promising means of treating malignancies and metabolic diseases.
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Affiliation(s)
- Chunming Cheng
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Peng Ru
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Feng Geng
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Junfeng Liu
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA; College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, PR China
| | - Ji Young Yoo
- Department of Neurosurgery, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Xiaoning Wu
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Xiang Cheng
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Vanessa Euthine
- CarMeN Laboratory, INSERM U1060, INRA 1397, Faculté de Médecine Lyon Sud BP 12, Université de Lyon, 69921 Oullins Cedex, France
| | - Peng Hu
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Jeffrey Yunhua Guo
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Etienne Lefai
- CarMeN Laboratory, INSERM U1060, INRA 1397, Faculté de Médecine Lyon Sud BP 12, Université de Lyon, 69921 Oullins Cedex, France
| | - Balveen Kaur
- Department of Neurosurgery, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Axel Nohturfft
- Vascular Biology Research Centre, St. George's University of London, London SW17 0RE, UK
| | - Jianjie Ma
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Medical Center, Columbus, OH 43210, USA
| | - Arnab Chakravarti
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Deliang Guo
- Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA.
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Inoue K, Imai Y. Fatostatin, an SREBP inhibitor, prevented RANKL-induced bone loss by suppression of osteoclast differentiation. Biochim Biophys Acta Mol Basis Dis 2015; 1852:2432-41. [DOI: 10.1016/j.bbadis.2015.08.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 07/31/2015] [Accepted: 08/24/2015] [Indexed: 11/27/2022]
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Kim H, Rodriguez-Navas C, Kollipara RK, Kapur P, Pedrosa I, Brugarolas J, Kittler R, Ye J. Unsaturated Fatty Acids Stimulate Tumor Growth through Stabilization of β-Catenin. Cell Rep 2015; 13:495-503. [PMID: 26456834 DOI: 10.1016/j.celrep.2015.09.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 08/17/2015] [Accepted: 09/02/2015] [Indexed: 11/15/2022] Open
Abstract
Some cancer cells exhibit elevated levels of free fatty acids (FAs) as well as high levels of β-catenin, a transcriptional co-activator that promotes their growth. Here, we link these two phenomena by showing that unsaturated FAs inhibit degradation of β-catenin. Unsaturated FAs bind to the UAS domain of Fas-associated factor 1 (FAF1), a protein known to bind β-catenin, accelerating its degradation. FA binding disrupts the FAF1/β-catenin complex, preventing proteasomal degradation of ubiquitinated β-catenin. This mechanism for stabilization of β-catenin differs from that of Wnt signaling, which blocks ubiquitination of β-catenin. In clear cell renal cell carcinoma (ccRCC) cells, unsaturated FAs stimulated cell proliferation through stabilization of β-catenin. In tissues from biopsies of human ccRCC, elevated levels of unsaturated FAs correlated with increased levels of β-catenin. Thus, targeting FAF1 may be an effective approach to treat cancers that exhibit elevated FAs and β-catenin.
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Affiliation(s)
- Hyeonwoo Kim
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Carlos Rodriguez-Navas
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Rahul K Kollipara
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Payal Kapur
- Kidney Cancer Program in Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ivan Pedrosa
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - James Brugarolas
- Kidney Cancer Program in Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Hematology-Oncology Division, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ralf Kittler
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jin Ye
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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PAQR3 modulates cholesterol homeostasis by anchoring Scap/SREBP complex to the Golgi apparatus. Nat Commun 2015; 6:8100. [PMID: 26311497 PMCID: PMC4560833 DOI: 10.1038/ncomms9100] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Accepted: 07/17/2015] [Indexed: 01/18/2023] Open
Abstract
Cholesterol biosynthesis is regulated by transcription factors SREBPs and their escort protein Scap. On sterol depletion, Scap/SREBP complex is transported from endoplasmic reticulum (ER) to the Golgi apparatus where SREBP is activated. Under cholesterol sufficient condition, Insigs act as anchor proteins to retain Scap/SREBP in the ER. However, the anchor protein of Scap/SREBP in the Golgi is unknown. Here we report that a Golgi-localized membrane protein progestin and adipoQ receptors 3 (PAQR3) interacts with Scap and SREBP and tethers them to the Golgi. PAQR3 promotes Scap/SREBP complex formation, potentiates SREBP processing and enhances lipid synthesis. The mutually exclusive interaction between Scap and PAQR3 or Insig-1 is regulated by cholesterol level. PAQR3 knockdown in liver blunts SREBP pathway and decreases hepatic cholesterol content. Disrupting the interaction of PAQR3 with Scap/SREBP by a synthetic peptide inhibits SREBP processing and activation. Thus, PAQR3 regulates cholesterol homeostasis by anchoring Scap/SREBP to the Golgi and disruption of such function reduces cholesterol biosynthesis. Under conditions of sterol depletion, the Scap/SREBP complex is transported from the endoplasmic reticulum to the Golgi apparatus. Here Xu and Wang et al. show that the Golgi protein PAQR3 interacts with Scap and SREBP in a cholesterol regulated manner to help regulate sterol homeostasis.
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Haploid Genetic Screen Reveals a Profound and Direct Dependence on Cholesterol for Hantavirus Membrane Fusion. mBio 2015; 6:e00801. [PMID: 26126854 PMCID: PMC4488941 DOI: 10.1128/mbio.00801-15] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
UNLABELLED Hantaviruses cause hemorrhagic fever with renal syndrome (HFRS) in the Old World and a highly fatal hantavirus cardiopulmonary syndrome (HCPS) in the New World. No vaccines or antiviral therapies are currently available to prevent or treat hantavirus disease, and gaps in our understanding of how hantaviruses enter cells challenge the search for therapeutics. We performed a haploid genetic screen in human cells to identify host factors required for entry by Andes virus, a highly virulent New World hantavirus. We found that multiple genes involved in cholesterol sensing, regulation, and biosynthesis, including key components of the sterol response element-binding protein (SREBP) pathway, are critical for Andes virus entry. Genetic or pharmacological disruption of the membrane-bound transcription factor peptidase/site-1 protease (MBTPS1/S1P), an SREBP control element, dramatically reduced infection by virulent hantaviruses of both the Old World and New World clades but not by rhabdoviruses or alphaviruses, indicating that this pathway is broadly, but selectively, required by hantaviruses. These results could be fully explained as arising from the modest depletion of cellular membrane cholesterol that accompanied S1P disruption. Mechanistic studies of cells and with protein-free liposomes suggested that high levels of cholesterol are specifically needed for hantavirus membrane fusion. Taken together, our results indicate that the profound dependence on target membrane cholesterol is a fundamental, and unusual, biophysical property of hantavirus glycoprotein-membrane interactions during entry. IMPORTANCE Although hantaviruses cause important human diseases worldwide, no specific antiviral treatments are available. One of the major obstacles to the development of new therapies is a lack of understanding of how hantaviruses hijack our own host factors to enter cells. Here, we identified multiple cellular genes that control the levels of cholesterol in cellular membranes to be important for hantavirus entry. Our findings suggest that high concentrations of cholesterol in cellular membranes are required at a specific step in the entry process-fusion between viral and cellular membranes-that allows escape of the hantavirus genome into the host cell cytoplasm to initiate infection. Our findings uncover a fundamental feature of the hantavirus infection mechanism and point to cholesterol-lowering drugs as a potential new treatment of hantaviral infections.
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Mitsche MA, McDonald JG, Hobbs HH, Cohen JC. Flux analysis of cholesterol biosynthesis in vivo reveals multiple tissue and cell-type specific pathways. eLife 2015; 4:e07999. [PMID: 26114596 PMCID: PMC4501332 DOI: 10.7554/elife.07999] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 06/25/2015] [Indexed: 01/22/2023] Open
Abstract
Two parallel pathways produce cholesterol: the Bloch and Kandutsch-Russell pathways. Here we used stable isotope labeling and isotopomer analysis to trace sterol flux through the two pathways in mice. Surprisingly, no tissue used the canonical K–R pathway. Rather, a hybrid pathway was identified that we call the modified K–R (MK–R) pathway. Proportional flux through the Bloch pathway varied from 8% in preputial gland to 97% in testes, and the tissue-specificity observed in vivo was retained in cultured cells. The distribution of sterol isotopomers in plasma mirrored that of liver. Sterol depletion in cultured cells increased flux through the Bloch pathway, whereas overexpression of 24-dehydrocholesterol reductase (DHCR24) enhanced usage of the MK–R pathway. Thus, relative use of the Bloch and MK–R pathways is highly variable, tissue-specific, flux dependent, and epigenetically fixed. Maintenance of two interdigitated pathways permits production of diverse bioactive sterols that can be regulated independently of cholesterol. DOI:http://dx.doi.org/10.7554/eLife.07999.001 Cholesterol is important for animals, both as an essential component of the membrane that surrounds cells and as a building block to make hormones and other biologically important molecules. However, cells limit how much cholesterol they make because an excess of this fatty molecule can cause serious health problems, including heart disease and stroke. Cholesterol is made via a complex process that involves more than 30 different steps, which can be organized into two biochemical pathways (named the Bloch pathway and the Kandutsch–Russell pathway). The enzymes that carry out the steps in these pathways have been characterized in detail. Less is known about which of the two pathways is actually used in different cells and tissues, or how much cholesterol each pathway produces. This is partly because it is difficult to distinguish between the closely related intermediate molecules that are formed in each pathway. Mitsche et al. have now used mass spectrometry and isotope labeling techniques to analyze the relative contributions of the two cholesterol-making pathways in both cells grown in the laboratory and in mice. The experiments show that many cells use the Bloch pathway. However, no cells were found to use the Kandutsch–Russell pathway as it was originally described. Rather, some of the cells used a hybrid pathway where the production of cholesterol was started using the Bloch pathway and then after a certain number of steps, the process switched to using part of the Kandutsch–Russell pathway. Mitsche et al. referred to this mixed system as the ‘modified Kandutsch–Russell pathway’. Mitsche et al. next examined the flow of molecules through these two pathways in different tissues and observed that the Bloch pathway is exclusively used in the testes and adrenal glands, which produce high levels of cholesterol. In contrast, the skin and brain use the modified Kandutsch–Russell pathway. In some tissues, a fraction of the building blocks that can be used to make cholesterol were instead diverted to make other products. This suggests that animals have maintained the two pathways over the course of evolution to enable them to generate a variety of products, which can be used to carry out different biological processes. One challenge following this work will be to use the newly developed methods to analyze other complex biochemical pathways. DOI:http://dx.doi.org/10.7554/eLife.07999.002
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Affiliation(s)
- Matthew A Mitsche
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States
| | - Jeffrey G McDonald
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States
| | - Helen H Hobbs
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States
| | - Jonathan C Cohen
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, United States
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McFarlane MR, Cantoria MJ, Linden AG, January BA, Liang G, Engelking LJ. Scap is required for sterol synthesis and crypt growth in intestinal mucosa. J Lipid Res 2015; 56:1560-71. [PMID: 25896350 DOI: 10.1194/jlr.m059709] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Indexed: 11/20/2022] Open
Abstract
SREBP cleavage-activating protein (Scap) is an endoplasmic reticulum membrane protein required for cleavage and activation of sterol regulatory element-binding proteins (SREBPs), which activate the transcription of genes in sterol and fatty acid biosynthesis. Liver-specific loss of Scap is well tolerated; hepatic synthesis of sterols and fatty acids is reduced, but mice are otherwise healthy. To determine whether Scap loss is tolerated in the intestine, we generated a mouse model (Vil-Scap(-)) in which tamoxifen-inducible Cre-ER(T2), a fusion protein of Cre recombinase with a mutated ligand binding domain of the human estrogen receptor, ablates Scap in intestinal mucosa. After 4 days of tamoxifen, Vil-Scap(-) mice succumb with a severe enteropathy and near-complete collapse of intestinal mucosa. Organoids grown ex vivo from intestinal crypts of Vil-Scap(-) mice are readily killed when Scap is deleted by 4-hydroxytamoxifen. Death is prevented when culture medium is supplemented with cholesterol and oleate. These data show that, unlike the liver, the intestine requires Scap to sustain tissue integrity by maintaining the high levels of lipid synthesis necessary for proliferation of intestinal crypts.
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Affiliation(s)
- Matthew R McFarlane
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Mary Jo Cantoria
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Albert G Linden
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Brandon A January
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Guosheng Liang
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
| | - Luke J Engelking
- Department of Molecular Genetics University of Texas Southwestern Medical Center, Dallas, TX 75390-9046 Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046
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Meaney S. Epigenetic regulation of cholesterol homeostasis. Front Genet 2014; 5:311. [PMID: 25309573 PMCID: PMC4174035 DOI: 10.3389/fgene.2014.00311] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 08/20/2014] [Indexed: 01/15/2023] Open
Abstract
Although best known as a risk factor for cardiovascular disease, cholesterol is a vital component of all mammalian cells. In addition to key structural roles, cholesterol is a vital biochemical precursor for numerous biologically important compounds including oxysterols and bile acids, as well as acting as an activator of critical morphogenic systems (e.g., the Hedgehog system). A variety of sophisticated regulatory mechanisms interact to coordinate the overall level of cholesterol in cells, tissues and the entire organism. Accumulating evidence indicates that in additional to the more “traditional” regulatory schemes, cholesterol homeostasis is also under the control of epigenetic mechanisms such as histone acetylation and DNA methylation. The available evidence supporting a role for these mechanisms in the control of cholesterol synthesis, elimination, transport and storage are the focus of this review.
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Affiliation(s)
- Steve Meaney
- School of Biological Sciences, College of Sciences and Health, Dublin Institute of Technology Dublin, Ireland ; Environmental Sustainability and Health Institute, Dublin Institute of Technology Dublin, Ireland
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Prabhu AV, Sharpe LJ, Brown AJ. The sterol-based transcriptional control of human 7-dehydrocholesterol reductase (DHCR7): Evidence of a cooperative regulatory program in cholesterol synthesis. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1842:1431-9. [PMID: 25048193 DOI: 10.1016/j.bbalip.2014.07.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 06/20/2014] [Accepted: 07/07/2014] [Indexed: 02/01/2023]
Abstract
The enzyme 7-dehydrocholesterol reductase (DHCR7) catalyzes the final step of cholesterol synthesis via the Kandutsch-Russell pathway, and is crucial in maintaining cellular cholesterol levels. Its absence leads to the devastating fetal developmental disorder Smith-Lemli-Opitz Syndrome (SLOS). How this enzyme is regulated has implications in controlling not only cholesterol synthesis, but also the synthesis of Vitamin D - another product of 7-dehydrocholesterol. In this study, we look specifically at how DHCR7 is regulated by the sterol regulatory element-binding protein-2 (SREBP-2) transcription factor. Sterol regulation has previously been studied in the rat DHCR7 promoter, but we have found that its regulatory elements are not all conserved in humans. Rather, the human promoter contains two binding sites for SREBP-2 (at -155 and -55) and a binding site for the nuclear factor-Y (NF-Y) cofactor (at -136). The -155 site is a particularly responsive sterol regulatory element (SRE) which is well conserved in mammals, and was possibly overlooked in the rat promoter study. The exact location of the weaker -55 site (close to the known rat SRE) may have shifted during evolution. Furthermore, we established that the two SREs that bind SREBP-2 work in cooperation to synergistically activate DHCR7. We have previously characterized the SREs in DHCR24, the final enzyme in the alternate Bloch pathway of cholesterol synthesis. Here, comparison of the sterol regulation of these terminal enzymes demonstrates the unique cooperative system that helps to control cholesterol synthesis.
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Affiliation(s)
- Anika V Prabhu
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Laura J Sharpe
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Andrew J Brown
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia.
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50
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Morris LL, Hartman IZ, Jun DJ, Seemann J, DeBose-Boyd RA. Sequential actions of the AAA-ATPase valosin-containing protein (VCP)/p97 and the proteasome 19 S regulatory particle in sterol-accelerated, endoplasmic reticulum (ER)-associated degradation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase. J Biol Chem 2014; 289:19053-66. [PMID: 24860107 DOI: 10.1074/jbc.m114.576652] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Accelerated endoplasmic reticulum (ER)-associated degradation (ERAD) of the cholesterol biosynthetic enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase results from its sterol-induced binding to ER membrane proteins called Insig-1 and Insig-2. This binding allows for subsequent ubiquitination of reductase by Insig-associated ubiquitin ligases. Once ubiquitinated, reductase becomes dislocated from ER membranes into the cytosol for degradation by 26 S proteasomes through poorly defined reactions mediated by the AAA-ATPase valosin-containing protein (VCP)/p97 and augmented by the nonsterol isoprenoid geranylgeraniol. Here, we report that the oxysterol 25-hydroxycholesterol and geranylgeraniol combine to trigger extraction of reductase across ER membranes prior to its cytosolic release. This conclusion was drawn from studies utilizing a novel assay that measures membrane extraction of reductase by determining susceptibility of a lumenal epitope in the enzyme to in vitro protease digestion. Susceptibility of the lumenal epitope to protease digestion and thus membrane extraction of reductase were tightly regulated by 25-hydroxycholesterol and geranylgeraniol. The reaction was inhibited by RNA interference-mediated knockdown of either Insigs or VCP/p97. In contrast, reductase continued to become membrane-extracted, but not cytosolically dislocated, in cells deficient for AAA-ATPases of the proteasome 19 S regulatory particle. These findings establish sequential roles for VCP/p97 and the 19 S regulatory particle in the sterol-accelerated ERAD of reductase that may be applicable to the ERAD of other substrates.
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Affiliation(s)
| | | | | | | | - Russell A DeBose-Boyd
- From the Departments of Molecular Genetics and the Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9046
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