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Lin S, Chang P, Tsao S, Aderinwale A, Sallapalli BT, He J, Zhang Y. Oxysterol binding protein (OSBP) contributes to hepatitis E virus replication. Virol J 2024; 21:161. [PMID: 39039546 PMCID: PMC11265327 DOI: 10.1186/s12985-024-02438-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Accepted: 07/16/2024] [Indexed: 07/24/2024] Open
Abstract
Hepatitis E virus (HEV) is a positive-sense, single-stranded RNA virus and causes primarily acute self-limiting infections. The ORF1 of the HEV genome encodes a polyprotein around 190 kDa, which contains several putative domains, including helicase and RNA-dependent RNA polymerase. The HEV-encoded helicase is a member of the superfamily 1 helicase family and possesses multiple enzymatic functions, such as RNA 5'-triphosphatase, RNA unwinding, and NTPase, which are thought to contribute to viral RNA synthesis. However, the helicase interaction with cellular proteins remains less known. Oxysterol binding protein (OSBP) is a lipid regulator that shuffles between the Golgi apparatus and the endoplasmic reticulum for cholesterol and phosphatidylinositol-4-phosphate exchange and controls the efflux of cholesterol from cells. In this study, the RNAi-mediated silencing of OSBP significantly reduced HEV replication. Further studies indicate that the HEV helicase interacted with OSBP, shown by co-immunoprecipitation and co-localization in co-transfected cells. The presence of helicase blocked OSBP preferential translocation to the Golgi apparatus. These results demonstrate that OSBP contributes to HEV replication and enrich our understanding of the HEV-cell interactions.
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Affiliation(s)
- Shaoli Lin
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Peixi Chang
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Shane Tsao
- National Cancer Institute, National Institute of Health, Bethesda, MD, USA
| | - Abigail Aderinwale
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Bhargava Teja Sallapalli
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Jia He
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA
| | - Yanjin Zhang
- Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
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2
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Doyle CP, Rectenwald A, Timple L, Hammond GRV. Orthogonal targeting of SAC1 to mitochondria implicates ORP2 as a major player in PM PI4P turnover. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.08.28.555163. [PMID: 37693626 PMCID: PMC10491111 DOI: 10.1101/2023.08.28.555163] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Oxysterol binding protein (OSBP)-related proteins (ORPs) 5 and 8 have been shown to deplete the lipid phosphatidylinositol 4-phosphate (PI4P) at sites of membrane contact between the endoplasmic reticulum (ER) and plasma membrane (PM). This is believed to be caused by transport of PI4P from the PM to the ER, where PI4P is degraded by an ER-localized SAC1 phosphatase. This is proposed to power the anti-port of phosphatidylserine (PS) lipids from ER to PM, up their concentration gradient. Alternatively, ORPs have been proposed to sequester PI4P, dependent on the concentration of their alternative lipid ligand. Here, we aimed to distinguish these possibilities in living cells by orthogonal targeting of PI4P transfer and degradation to PM-mitochondria contact sites. Surprisingly, we found that orthogonal targeting of SAC1 to mitochondria enhanced PM PI4P turnover independent of targeting to contact sites with the PM. This turnover could be slowed by knock-down of soluble ORP2, which also has a major impact on PM PI4P levels even without SAC1 over-expression. The data reveal a role for contact site-independent modulation of PM PI4P levels and lipid antiport.
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Affiliation(s)
- Colleen P Doyle
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Andrew Rectenwald
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Liz Timple
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Gerald R V Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
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3
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Doyle CP, Rectenwald A, Timple L, Hammond GRV. Orthogonal Targeting of SAC1 to Mitochondria Implicates ORP2 as a Major Player in PM PI4P Turnover. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2024; 7:25152564241229272. [PMID: 38327560 PMCID: PMC10848804 DOI: 10.1177/25152564241229272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 01/11/2024] [Accepted: 01/12/2024] [Indexed: 02/09/2024]
Abstract
Oxysterol-binding protein (OSBP)-related proteins (ORPs) 5 and 8 have been shown to deplete the lipid phosphatidylinositol 4-phosphate (PI4P) at sites of membrane contact between the endoplasmic reticulum (ER) and plasma membrane (PM). This is believed to be caused by transport of PI4P from the PM to the ER, where PI4P is degraded by an ER-localized SAC1 phosphatase. This is proposed to power the anti-port of phosphatidylserine (PS) lipids from ER to PM, up their concentration gradient. Alternatively, ORPs have been proposed to sequester PI4P, dependent on the concentration of their alternative lipid ligand. Here, we aimed to distinguish these possibilities in living cells by orthogonal targeting of PI4P transfer and degradation to PM-mitochondria contact sites. Surprisingly, we found that orthogonal targeting of SAC1 to mitochondria enhanced PM PI4P turnover independent of targeting to contact sites with the PM. This turnover could be slowed by knock-down of soluble ORP2, which also has a major impact on PM PI4P levels even without SAC1 over-expression. The data reveal a role for contact site-independent modulation of PM PI4P levels and lipid antiport.
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Affiliation(s)
- Colleen P. Doyle
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Andrew Rectenwald
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Liz Timple
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Gerald R. V. Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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4
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Taskinen JH, Ruhanen H, Matysik S, Käkelä R, Olkkonen VM. Systemwide effects of ER-intracellular membrane contact site disturbance in primary endothelial cells. J Steroid Biochem Mol Biol 2023; 232:106349. [PMID: 37321512 DOI: 10.1016/j.jsbmb.2023.106349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 06/09/2023] [Accepted: 06/11/2023] [Indexed: 06/17/2023]
Abstract
Membrane contact sites (MCS) make up a crucial route of inter-organelle non-vesicular transport within the cell. Multiple proteins are involved in this process, which includes the ER-resident proteins vesicle associated membrane protein associated protein A and -B (VAPA/B) that form MCS between the ER and other membrane compartments. Currently most functional data on VAP depleted phenotypes have shown alterations in lipid homeostasis, induction of ER stress, dysfunction of UPR and autophagy, as well as neurodegeneration. Literature on concurrent silencing of VAPA/B is still sparse; therefore, we investigated how it affects the macromolecule pools of primary endothelial cells. Our transcriptomics results showed significant upregulation in genes related to inflammation, ER and Golgi dysfunction, ER stress, cell adhesion, as well as Coat Protein Complex-I and -II (COP-I, COP-II) vesicle transport. Genes related to cellular division were downregulated, as well as key genes of lipid and sterol biosynthesis. Lipidomics analyses revealed reductions in cholesteryl esters, very long chain highly unsaturated and saturated lipids, whereas increases in free cholesterol and relatively short chain unsaturated lipids were evident. Furthermore, the knockdown resulted in an inhibition of angiogenesis in vitro. We speculate that ER MCS depletion has led to multifaceted outcomes, which include elevated ER free cholesterol content and ER stress, alterations in lipid metabolism, ER-Golgi function and vesicle transport, which have led to a reduction in angiogenesis. The silencing also induced an inflammatory response, consistent with upregulation of markers of early atherogenesis. To conclude, ER MCS mediated by VAPA/B play a crucial role in maintaining cholesterol traffic and sustain normal endothelial functions.
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Affiliation(s)
- Juuso H Taskinen
- Minerva Foundation Institute for Medical Research, Tukholmankatu 8, 00290 Helsinki, Finland
| | - Hanna Ruhanen
- Molecular and Integrative Biosciences Research Programme, University of Helsinki, Viikinkaari 1, PO BOX 65, 00014 University of Helsinki, Finland; Helsinki University Lipidomics Unit (HiLIPID), Helsinki Institute of Life Science (HiLIFE) and Biocenter Finland, University of Helsinki, Viikinkaari 1, PO BOX 65, 00014 University of Helsinki, Finland
| | - Silke Matysik
- Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Regensburg, Franz-Josef-Strauß-Allee 11, 93053 Regensburg, Germany
| | - Reijo Käkelä
- Molecular and Integrative Biosciences Research Programme, University of Helsinki, Viikinkaari 1, PO BOX 65, 00014 University of Helsinki, Finland; Helsinki University Lipidomics Unit (HiLIPID), Helsinki Institute of Life Science (HiLIFE) and Biocenter Finland, University of Helsinki, Viikinkaari 1, PO BOX 65, 00014 University of Helsinki, Finland
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Tukholmankatu 8, 00290 Helsinki, Finland; Department of Anatomy, Faculty of Medicine, University of Helsinki, Haartmaninkatu 8, 00290 Helsinki, Finland.
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5
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Lange Y, Tabei SMA, Steck TL. A basic model for the association of ligands with membrane cholesterol: application to cytolysin binding. J Lipid Res 2023; 64:100344. [PMID: 36791915 PMCID: PMC10119614 DOI: 10.1016/j.jlr.2023.100344] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/19/2023] [Accepted: 02/07/2023] [Indexed: 02/16/2023] Open
Abstract
Almost all the cholesterol in cellular membranes is associated with phospholipids in simple stoichiometric complexes. This limits the binding of sterol ligands such as filipin and Perfringolysin O (PFO) to a small fraction of the total. We offer a simple mathematical model that characterizes this complexity. It posits that the cholesterol accessible to ligands has two forms: active cholesterol, which is that not complexed with phospholipids; and extractable cholesterol, that which ligands can capture competitively from the phospholipid complexes. Simulations based on the model match published data for the association of PFO oligomers with liposomes, plasma membranes and the isolated endoplasmic reticulum. The model shows how the binding of a probe greatly underestimates cholesterol abundance when its affinity for the sterol is so weak that it competes poorly with the membrane phospholipids. Two examples are the under-staining of plasma membranes by filipin and the failure of domain D4 of PFO to label their cytoplasmic leaflets. Conversely, the exaggerated staining of endolysosomes suggests that their cholesterol, being uncomplexed, is readily available. The model is also applicable to the association of cholesterol with intrinsic membrane proteins. For example, it supports the hypothesis that the sharp threshold in the regulation of homeostatic ER proteins by cholesterol derives from the cooperativity of their binding to the sterol weakly held by the phospholipid. § Thus, the model explicates the complexity inherent in the binding of ligands like PFO and filipin to the small accessible fraction of membrane cholesterol.
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Affiliation(s)
- Yvonne Lange
- 1Department of Pathology, Rush University Medical Center, Chicago, Il 60612, USA.
| | - S M Ali Tabei
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614, USA
| | - Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Il 60637, USA
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6
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Singh RP, Poh YP, Sinha SD, Wideman JG. Evolutionary History of Oxysterol-Binding Proteins Reveals Complex History of Duplication and Loss in Animals and Fungi. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2023; 6:25152564221150428. [PMID: 37366416 PMCID: PMC10243569 DOI: 10.1177/25152564221150428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 12/17/2022] [Accepted: 12/21/2022] [Indexed: 06/28/2023]
Abstract
Cells maintain the specific lipid composition of distinct organelles by vesicular transport as well as non-vesicular lipid trafficking via lipid transport proteins. Oxysterol-binding proteins (OSBPs) are a family of lipid transport proteins that transfer lipids at various membrane contact sites (MCSs). OSBPs have been extensively investigated in human and yeast cells where 12 have been identified in Homo sapiens and 7 in Saccharomyces cerevisiae. The evolutionary relationship between these well-characterized OSBPs is still unclear. By reconstructing phylogenies of eukaryote OSBPs, we show that the ancestral Saccharomycotina had four OSBPs, the ancestral fungus had five OSBPs, and the ancestral animal had six OSBPs, whereas the shared ancestor of animals and fungi as well as the ancestral eukaryote had only three OSBPs. Our analyses identified three undescribed ancient OSBP orthologues, one fungal OSBP (Osh8) lost in the lineage leading to yeast, one animal OSBP (ORP12) lost in the lineage leading to vertebrates, and one eukaryotic OSBP (OshEu) lost in both the animal and fungal lineages.
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Affiliation(s)
- Rohan P. Singh
- Center for Mechanisms of Evolution, Biodesign Institute,
School of Life Sciences, Arizona State University, Tempe, USA
| | - Yu-Ping Poh
- Center for Mechanisms of Evolution, Biodesign Institute,
School of Life Sciences, Arizona State University, Tempe, USA
| | - Savar D. Sinha
- Center for Mechanisms of Evolution, Biodesign Institute,
School of Life Sciences, Arizona State University, Tempe, USA
| | - Jeremy G. Wideman
- Center for Mechanisms of Evolution, Biodesign Institute,
School of Life Sciences, Arizona State University, Tempe, USA
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7
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Weber-Boyvat M, Kroll J, Trimbuch T, Olkkonen VM, Rosenmund C. The lipid transporter ORP2 regulates synaptic neurotransmitter release via two distinct mechanisms. Cell Rep 2022; 41:111882. [PMID: 36577376 DOI: 10.1016/j.celrep.2022.111882] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 08/26/2022] [Accepted: 12/02/2022] [Indexed: 12/28/2022] Open
Abstract
Cholesterol is crucial for neuronal synaptic transmission, assisting in the molecular and structural organization of lipid rafts, ion channels, and exocytic proteins. Although cholesterol absence was shown to result in impaired neurotransmission, how cholesterol locally traffics and its route of action are still under debate. Here, we characterized the lipid transfer protein ORP2 in murine hippocampal neurons. We show that ORP2 preferentially localizes to the presynapse. Loss of ORP2 reduces presynaptic cholesterol levels by 50%, coinciding with a profoundly reduced release probability, enhanced facilitation, and impaired presynaptic calcium influx. In addition, ORP2 plays a cholesterol-transport-independent role in regulating vesicle priming and spontaneous release, likely by competing with Munc18-1 in syntaxin1A binding. To conclude, we identified a dual function of ORP2 as a physiological modulator of the synaptic cholesterol content and a regulator of neuronal exocytosis.
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Affiliation(s)
- Marion Weber-Boyvat
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Charitéplatz 1, 10117 Berlin, Germany.
| | - Jana Kroll
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Charitéplatz 1, 10117 Berlin, Germany
| | - Thorsten Trimbuch
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Charitéplatz 1, 10117 Berlin, Germany
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, 00290 Helsinki, Finland; Department of Anatomy, Faculty of Medicine, University of Helsinki, 00014 Helsinki, Finland
| | - Christian Rosenmund
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Charitéplatz 1, 10117 Berlin, Germany.
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8
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Li W, Shan B, Cheng X, He H, Qin J, Zhao H, Tian M, Zhang X, Jin G. circRNA Acbd6 promotes neural stem cell differentiation into cholinergic neurons via the miR-320-5p-Osbpl2 axis. J Biol Chem 2022; 298:101828. [PMID: 35305988 PMCID: PMC9018392 DOI: 10.1016/j.jbc.2022.101828] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Revised: 03/05/2022] [Accepted: 03/07/2022] [Indexed: 11/29/2022] Open
Abstract
Neural stem cells (NSCs) persist in the dentate gyrus of the hippocampus into adulthood and are essential for both neurogenesis and neural circuit integration. Exosomes have also been shown to play vital roles in regulating biological processes of receptor cells as a medium for cell-to-cell communication signaling molecules. The precise molecular mechanisms of exosome-mediated signaling, however, remain largely unknown. Here, we found that exosomes produced by denervated hippocampi following fimbria–fornix transection could promote the differentiation of hippocampal neural precursor cells into cholinergic neurons in coculture with NSCs. Furthermore, we found that 14 circular RNAs (circRNAs) were upregulated in hippocampal exosomes after fimbria–fornix transection using high-throughput RNA-Seq technology. We further characterized the function and mechanism by which the upregulated circRNA Acbd6 (acyl-CoA-binding domain–containing 6) promoted the differentiation of NSCs into cholinergic neurons using RT–quantitative PCR, Western blot, ELISA, flow cytometry, immunohistochemistry, and immunofluorescence assay. By luciferase reporter assay, we demonstrated that circAcbd6 functioned as an endogenous miR-320-5p sponge to inhibit miR-320-5p activity, resulting in increased oxysterol-binding protein–related protein 2 expression with subsequent facilitation of NSC differentiation. Taken together, our results suggest that circAcbd6 promotes differentiation of NSCs into cholinergic neurons via miR-320-5p/oxysterol-binding protein–related protein 2 axis, which contribute important insights to our understanding of how circRNAs regulate neurogenesis.
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Affiliation(s)
- Wen Li
- Department of Human Anatomy, Institute of Neurobiology, Medical School of Nantong University, Nantong, Jiangsu, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China; Key Laboratory of Neuroregeneration of Jiangsu Province and Ministry of Education, Nantong University, Nantong, Jiangsu, China
| | - Boquan Shan
- Department of Human Anatomy, Institute of Neurobiology, Medical School of Nantong University, Nantong, Jiangsu, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China; Key Laboratory of Neuroregeneration of Jiangsu Province and Ministry of Education, Nantong University, Nantong, Jiangsu, China
| | - Xiang Cheng
- Department of Human Anatomy, Institute of Neurobiology, Medical School of Nantong University, Nantong, Jiangsu, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China; Key Laboratory of Neuroregeneration of Jiangsu Province and Ministry of Education, Nantong University, Nantong, Jiangsu, China
| | - Hui He
- Department of Human Anatomy, Institute of Neurobiology, Medical School of Nantong University, Nantong, Jiangsu, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China; Key Laboratory of Neuroregeneration of Jiangsu Province and Ministry of Education, Nantong University, Nantong, Jiangsu, China
| | - Jianbing Qin
- Department of Human Anatomy, Institute of Neurobiology, Medical School of Nantong University, Nantong, Jiangsu, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China; Key Laboratory of Neuroregeneration of Jiangsu Province and Ministry of Education, Nantong University, Nantong, Jiangsu, China
| | - Heyan Zhao
- Department of Human Anatomy, Institute of Neurobiology, Medical School of Nantong University, Nantong, Jiangsu, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China; Key Laboratory of Neuroregeneration of Jiangsu Province and Ministry of Education, Nantong University, Nantong, Jiangsu, China
| | - Meiling Tian
- Department of Human Anatomy, Institute of Neurobiology, Medical School of Nantong University, Nantong, Jiangsu, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China; Key Laboratory of Neuroregeneration of Jiangsu Province and Ministry of Education, Nantong University, Nantong, Jiangsu, China
| | - Xinhua Zhang
- Department of Human Anatomy, Institute of Neurobiology, Medical School of Nantong University, Nantong, Jiangsu, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China; Key Laboratory of Neuroregeneration of Jiangsu Province and Ministry of Education, Nantong University, Nantong, Jiangsu, China.
| | - Guohua Jin
- Department of Human Anatomy, Institute of Neurobiology, Medical School of Nantong University, Nantong, Jiangsu, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China; Key Laboratory of Neuroregeneration of Jiangsu Province and Ministry of Education, Nantong University, Nantong, Jiangsu, China.
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9
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Olkkonen VM, Ikonen E. Cholesterol transport in the late endocytic pathway: Roles of ORP family proteins. J Steroid Biochem Mol Biol 2022; 216:106040. [PMID: 34864207 DOI: 10.1016/j.jsbmb.2021.106040] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 11/24/2021] [Accepted: 12/01/2021] [Indexed: 12/29/2022]
Abstract
Oxysterol-binding protein (OSBP) homologues, designated ORP or OSBPL proteins, constitute one of the largest families of intracellular lipid-binding/transfer proteins (LTP). This review summarizes the mounting evidence that several members of this family participate in the machinery facilitating cholesterol trafficking in the late endocytic pathway. There are indications that OSBP, besides acting as a cholesterol/phosphatidylinositol 4-phosphate (PI4P) exchanger at the endoplasmic reticulum (ER)-trans-Golgi network (TGN) membrane contact sites (MCS), also exchanges these lipids at ER-lysosome (Lys) contacts, increasing Lys cholesterol content. The long isoform of ORP1 (ORP1L), which also targets ER-late endosome (LE)/Lys MCS, has the capacity to mediate cholesterol transport either from ER to LE or in the opposite direction. Moreover, it regulates the motility, positioning and fusion of LE as well as autophagic flux. ORP2, the closest relative of ORP1, is mainly cytosolic, but also targets PI(4,5)P2-rich endosomal compartments. Our latest data suggest that ORP2 transfers cholesterol from LE to recycling endosomes (RE) in exchange for PI(4,5)P2, thus stimulating the recruitment of focal adhesion kinase (FAK) on the RE and cell adhesion. FAK activates phosphoinositide kinase on the RE to enhance PI(4,5)P2 synthesis. ORP2 in turn transfers PI(4,5)P2 from RE to LE, thus regulating LE tubule formation and transport activity.
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Affiliation(s)
- Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Helsinki, Finland; Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland.
| | - Elina Ikonen
- Minerva Foundation Institute for Medical Research, Helsinki, Finland; Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland; Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
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10
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Shi H, Wang H, Zhang C, Lu Y, Yao J, Chen Z, Xing G, Wei Q, Cao X. Mutations in OSBPL2 cause hearing loss associated with primary cilia defects via Sonic Hedgehog signaling. JCI Insight 2022; 7:149626. [PMID: 35041619 PMCID: PMC8876550 DOI: 10.1172/jci.insight.149626] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 01/12/2022] [Indexed: 11/17/2022] Open
Abstract
Defective primary cilia cause a range of diseases called ciliopathies, which include hearing loss (HL). Variants in the human oxysterol-binding protein like 2 (OSBPL2/ORP2) are responsible for autosomal dominant nonsyndromic HL (DFNA67). However, the pathogenesis of OSBPL2 deficiency has not been fully elucidated. In this study, we show that the Osbpl2-KO mice exhibited progressive HL and abnormal cochlear development with defective cilia. Further research revealed that OSBPL2 was located at the base of the kinocilia in hair cells (HCs) and primary cilia in supporting cells (SCs) and functioned in the maintenance of ciliogenesis by regulating the homeostasis of PI(4,5)P2 (phosphatidylinositol 4,5-bisphosphate) on the cilia membrane. OSBPL2 deficiency led to a significant increase of PI(4,5)P2 on the cilia membrane, which could be partially rescued by the overexpression of INPP5E. In addition, smoothened and GL13, the key molecules in the Sonic Hedgehog (Shh) signaling pathway, were detected to be downregulated in Osbpl2-KO HEI-OC1 cells. Our findings revealed that OSBPL2 deficiency resulted in ciliary defects and abnormal Shh signaling transduction in auditory cells, which helped to elucidate the underlying mechanism of OSBPL2 deficiency in HL.
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Affiliation(s)
- Hairong Shi
- Department of Medical Genetics, Nanjing Medical Univeristy, Nanjing, China
| | - Hongshun Wang
- Department of Medical Genetics, Nanjing Medical Univeristy, Nanjing, China
| | - Cheng Zhang
- Department of Medical Genetics, Nanjing Medical Univeristy, Nanjing, China
| | - Yajie Lu
- Department of Medical Genetics, Nanjing Medical Univeristy, Nanjing, China
| | - Jun Yao
- Department of Medical Genetics, Nanjing Medical Univeristy, Nanjing, China
| | - Zhibin Chen
- Department of Otolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Guangqian Xing
- Department of Otolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Qinjun Wei
- Department of Medical Genetics, Nanjing Medical Univeristy, Nanjing, China
| | - Xin Cao
- Department of Medical Genetics, Nanjing Medical Univeristy, Nanjing, China
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11
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Arora A, Taskinen JH, Olkkonen VM. Coordination of inter-organelle communication and lipid fluxes by OSBP-related proteins. Prog Lipid Res 2022; 86:101146. [PMID: 34999137 DOI: 10.1016/j.plipres.2022.101146] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 12/10/2021] [Accepted: 01/03/2022] [Indexed: 12/31/2022]
Abstract
Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute one of the largest families of lipid-binding/transfer proteins (LTPs) in eukaryotes. The current view is that many of them mediate inter-organelle lipid transfer over membrane contact sites (MCS). The transfer occurs in several cases in a 'counter-current' fashion: A lipid such as cholesterol or phosphatidylserine (PS) is transferred against its concentration gradient driven by transport of a phosphoinositide in the opposite direction. In this way ORPs are envisioned to maintain the distinct organelle lipid compositions, with impacts on multiple organelle functions. However, the functions of ORPs extend beyond lipid homeostasis to regulation of processes such as cell survival, proliferation and migration. Important expanding areas of mammalian ORP research include their roles in viral and bacterial infections, cancers, and neuronal function. The yeast OSBP homologue (Osh) proteins execute multifaceted functions in sterol and glycerophospholipid homeostasis, post-Golgi vesicle transport, phosphatidylinositol-4-phosphate, sphingolipid and target of rapamycin (TOR) signalling, and cell cycle control. These observations identify ORPs as lipid transporters and coordinators of signals with an unforeseen variety of cellular processes. Understanding their activities not only enlightens the biology of the living cell but also allows their employment as targets of new therapeutic approaches for disease.
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Affiliation(s)
- Amita Arora
- Minerva Foundation Institute for Medical Research, and Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland
| | - Juuso H Taskinen
- Minerva Foundation Institute for Medical Research, and Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, and Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland.
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12
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Yu Y, He L, Xu H, Zhang L, Zhang H, Li M. Mathematical model of the ratio of sucrose added to dangshan pear paste based on GC analysis of d-allose as the characteristic component. Lebensm Wiss Technol 2021. [DOI: 10.1016/j.lwt.2021.112363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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13
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Takahashi K, Kanerva K, Vanharanta L, Almeida‐Souza L, Lietha D, Olkkonen VM, Ikonen E. ORP2 couples LDL-cholesterol transport to FAK activation by endosomal cholesterol/PI(4,5)P 2 exchange. EMBO J 2021; 40:e106871. [PMID: 34124795 PMCID: PMC8281050 DOI: 10.15252/embj.2020106871] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 04/30/2021] [Accepted: 05/03/2021] [Indexed: 12/19/2022] Open
Abstract
Low-density lipoprotein (LDL)-cholesterol delivery from late endosomes to the plasma membrane regulates focal adhesion dynamics and cell migration, but the mechanisms controlling it are poorly characterized. Here, we employed auxin-inducible rapid degradation of oxysterol-binding protein-related protein 2 (ORP2/OSBPL2) to show that endogenous ORP2 mediates the transfer of LDL-derived cholesterol from late endosomes to focal adhesion kinase (FAK)-/integrin-positive recycling endosomes in human cells. In vitro, cholesterol enhances membrane association of FAK to PI(4,5)P2 -containing lipid bilayers. In cells, ORP2 stimulates FAK activation and PI(4,5)P2 generation in endomembranes, enhancing cell adhesion. Moreover, ORP2 increases PI(4,5)P2 in NPC1-containing late endosomes in a FAK-dependent manner, controlling their tubulovesicular trafficking. Together, these results provide evidence that ORP2 controls FAK activation and LDL-cholesterol plasma membrane delivery by promoting bidirectional cholesterol/PI(4,5)P2 exchange between late and recycling endosomes.
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Affiliation(s)
- Kohta Takahashi
- Department of Anatomy and Stem Cells and Metabolism Research ProgramFaculty of MedicineUniversity of HelsinkiHelsinkiFinland
- Minerva Foundation Institute for Medical ResearchHelsinkiFinland
- Present address:
Laboratory of Microbiology and ImmunologyGraduate School of Pharmaceutical SciencesChiba UniversityChibaJapan
| | - Kristiina Kanerva
- Department of Anatomy and Stem Cells and Metabolism Research ProgramFaculty of MedicineUniversity of HelsinkiHelsinkiFinland
- Minerva Foundation Institute for Medical ResearchHelsinkiFinland
| | - Lauri Vanharanta
- Department of Anatomy and Stem Cells and Metabolism Research ProgramFaculty of MedicineUniversity of HelsinkiHelsinkiFinland
- Minerva Foundation Institute for Medical ResearchHelsinkiFinland
| | - Leonardo Almeida‐Souza
- Helsinki Institute of Life Science, HiLIFEUniversity of HelsinkiHelsinkiFinland
- Faculty of Biological and Environmental SciencesUniversity of HelsinkiHelsinkiFinland
- Institute of BiotechnologyUniversity of HelsinkiHelsinkiFinland
| | - Daniel Lietha
- Centro de Investigaciones Biológicas Margarita Salas (CIB)Spanish National Research Council (CSIC)MadridSpain
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical ResearchHelsinkiFinland
| | - Elina Ikonen
- Department of Anatomy and Stem Cells and Metabolism Research ProgramFaculty of MedicineUniversity of HelsinkiHelsinkiFinland
- Minerva Foundation Institute for Medical ResearchHelsinkiFinland
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14
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Wang T, Zhang T, Tang Y, Wang H, Wei Q, Lu Y, Yao J, Qu Y, Cao X. Oxysterol-binding protein-like 2 contributes to the developmental progression of preadipocytes by binding to β-catenin. Cell Death Discov 2021; 7:109. [PMID: 34001864 PMCID: PMC8129138 DOI: 10.1038/s41420-021-00503-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Accepted: 04/28/2021] [Indexed: 02/06/2023] Open
Abstract
Oxysterol-binding protein-like 2 (OSBPL2), also known as oxysterol-binding protein-related protein (ORP) 2, is a member of lipid transfer protein well-known for its role in regulating cholesterol homeostasis. A recent study reported that OSBPL2/ORP2 localizes to lipid droplets (LDs) and is associated with energy metabolism and obesity. However, the function of OSBPL2/ORP2 in adipocyte differentiation is poorly understood. Here, we report that OSBPL2/ORP2 contributes to the developmental progression of preadipocytes. We found that OSBPL2/ORP2 binds to β-catenin, a key effector in the Wnt signaling pathway that inhibits adipogenesis. This complex plays a role in regulating the protein level of β-catenin only in preadipocytes, not in mature adipocytes. Our data further indicated that OSBPL2/ORP2 mediates the transport of β-catenin into the nucleus and thus regulates target genes related to adipocyte differentiation. Deletion of OSBPL2/ORP2 markedly reduces β-catenin both in the cytoplasm and in the nucleus, promotes preadipocytes maturation, and ultimately leads to obesity-related characteristics. Altogether, we provide novel insight into the function of OSBPL2/ORP2 in the developmental progression of preadipocytes and suggest OSBPL2/ORP2 may be a potential therapeutic target for the treatment of obesity-related diseases.
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Affiliation(s)
- Tianming Wang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Tianyu Zhang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Youzhi Tang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Hongshun Wang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Qinjun Wei
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Yajie Lu
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Jun Yao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Yuan Qu
- Jiangsu Cancer Hospital, Nanjing Medical University, Nanjing, China
| | - Xin Cao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China. .,Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China.
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15
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Interactions of Lipid Droplets with the Intracellular Transport Machinery. Int J Mol Sci 2021; 22:ijms22052776. [PMID: 33803444 PMCID: PMC7967230 DOI: 10.3390/ijms22052776] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 02/27/2021] [Accepted: 02/27/2021] [Indexed: 12/16/2022] Open
Abstract
Historically, studies of intracellular membrane trafficking have focused on the secretory and endocytic pathways and their major organelles. However, these pathways are also directly implicated in the biogenesis and function of other important intracellular organelles, the best studied of which are peroxisomes and lipid droplets. There is a large recent body of work on these organelles, which have resulted in the introduction of new paradigms regarding the roles of membrane trafficking organelles. In this review, we discuss the roles of membrane trafficking in the life cycle of lipid droplets. This includes the complementary roles of lipid phase separation and proteins in the biogenesis of lipid droplets from endoplasmic reticulum (ER) membranes, and the attachment of mature lipid droplets to membranes by lipidic bridges and by more conventional protein tethers. We also discuss the catabolism of neutral lipids, which in part results from the interaction of lipid droplets with cytosolic molecules, but with important roles for both macroautophagy and microautophagy. Finally, we address their eventual demise, which involves interactions with the autophagocytotic machinery. We pay particular attention to the roles of small GTPases, particularly Rab18, in these processes.
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16
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The emerging roles of OSBP-related proteins in cancer: Impacts through phosphoinositide metabolism and protein-protein interactions. Biochem Pharmacol 2021; 196:114455. [PMID: 33556339 DOI: 10.1016/j.bcp.2021.114455] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 01/26/2021] [Accepted: 01/28/2021] [Indexed: 01/04/2023]
Abstract
Oxysterol-binding protein -related proteins (ORPs) form a large family of intracellular lipid binding/transfer proteins. A number of ORPs are implicated in inter-organelle lipid transfer over membrane contacts sites, their mode of action involving in several cases the transfer of two lipids in opposite directions, termed countercurrent lipid transfer. A unifying feature appears to be the capacity to bind phosphatidylinositol polyphosphates (PIPs). These lipids are in some cases transported by ORPs from one organelle to another to drive the transfer of another lipid against its concentration gradient, while they in other cases may act as allosteric regulators of ORPs, or an ORP may introduce a PIP to an enzyme for catalysis. Dysregulation of several ORP family members is implicated in cancers, ORP3, -4, -5 and -8 being thus far the most studied examples. The most likely mechanisms underlying their associations with malignant growth are (i) impacts on PIP-mediated signaling events resulting in altered Ca2+ homeostasis, bioenergetics, cell survival, proliferation, and migration, (ii) protein-protein interactions affecting the activity of signaling factors, and (iii) modification of cellular lipid transport in a way that facilitates the proliferation of malignant cells. In this review I discuss the existing functional evidence for the involvement of ORPs in cancerous growth, discuss the findings in the light of the putative mechanisms outlined above and the possibility of employing ORPs as targets of anti-cancer therapy.
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17
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Monaco G, Percio S, Ting SB. Budgeting at the Ca 2+ store: a PIP (2)eline to starve LSCs? Cell Calcium 2020; 93:102309. [PMID: 33181424 DOI: 10.1016/j.ceca.2020.102309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 10/10/2020] [Accepted: 10/17/2020] [Indexed: 11/24/2022]
Abstract
The oxysterol-binding protein-related proteins (ORPs) have emerged as orchestrators of phosphatidylinositol-4,5-bisphosphate (PIP2) and cholesterol trafficking to the plasma membrane (PM). In this scenario, recent studies raised the prospect of ORPs cooperative behavior in sustaining leukemia stem cells (LSCs) survival by remotely enhancing ER-mitochondria Ca2+ communication. At the apex of the signaling cascade, the aberrantly upregulated LSC-ORP4L fosters PM-PIP2 extraction & cleavage, endoplasmic reticulum (ER)-Ca2+ release and mitochondrial energetics. The theoretical ember of draining fuel from the chemoresistant LSCs by restraining endoplasmic reticulum (ER)-mitochondria Ca2+ fluxes in a lipid-contingent fashion ensues. In light of relevant literature, this review briefly and critically discusses some key molecular ins & outs underlying such therapeutic opportunity in acute myeloid leukemia (AML).
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Affiliation(s)
- Giovanni Monaco
- Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium; Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Australia.
| | - Stefano Percio
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Australia; Department of Applied Research and Technological Development, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Stephen B Ting
- Australian Centre for Blood Diseases, Central Clinical School, Monash University, Melbourne, Australia; Faculty of Medicine, Nursing and Health Sciences, Monash University & Department of Haematology, Eastern Health, Box Hill Hospital, Melbourne, Australia
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18
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Koponen A, Pan G, Kivelä AM, Ralko A, Taskinen JH, Arora A, Kosonen R, Kari OK, Ndika J, Ikonen E, Cho W, Yan D, Olkkonen VM. ORP2, a cholesterol transporter, regulates angiogenic signaling in endothelial cells. FASEB J 2020; 34:14671-14694. [DOI: 10.1096/fj.202000202r] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 07/22/2020] [Accepted: 08/21/2020] [Indexed: 12/12/2022]
Affiliation(s)
- Annika Koponen
- Minerva Foundation Institute for Medical ResearchBiomedicum 2U Helsinki Finland
| | - Guoping Pan
- Department of Biology Jinan University Guangzhou China
| | - Annukka M. Kivelä
- Minerva Foundation Institute for Medical ResearchBiomedicum 2U Helsinki Finland
| | - Arthur Ralko
- Department of Chemistry University of Illinois at Chicago Chicago IL USA
| | - Juuso H. Taskinen
- Minerva Foundation Institute for Medical ResearchBiomedicum 2U Helsinki Finland
| | - Amita Arora
- Minerva Foundation Institute for Medical ResearchBiomedicum 2U Helsinki Finland
| | - Riikka Kosonen
- Minerva Foundation Institute for Medical ResearchBiomedicum 2U Helsinki Finland
| | - Otto K. Kari
- Drug Research Program Division of Pharmaceutical Biosciences Faculty of Pharmacy University of Helsinki Helsinki Finland
| | - Joseph Ndika
- Human Microbiome Research Faculty of Medicine University of Helsinki Helsinki Finland
| | - Elina Ikonen
- Minerva Foundation Institute for Medical ResearchBiomedicum 2U Helsinki Finland
- Department of Anatomy Faculty of Medicine University of Helsinki Helsinki Finland
| | - Wonhwa Cho
- Department of Chemistry University of Illinois at Chicago Chicago IL USA
| | - Daoguang Yan
- Department of Biology Jinan University Guangzhou China
| | - Vesa M. Olkkonen
- Minerva Foundation Institute for Medical ResearchBiomedicum 2U Helsinki Finland
- Department of Anatomy Faculty of Medicine University of Helsinki Helsinki Finland
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19
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Du X, Zhou L, Aw YC, Mak HY, Xu Y, Rae J, Wang W, Zadoorian A, Hancock SE, Osborne B, Chen X, Wu JW, Turner N, Parton RG, Li P, Yang H. ORP5 localizes to ER-lipid droplet contacts and regulates the level of PI(4)P on lipid droplets. J Cell Biol 2020; 219:jcb.201905162. [PMID: 31653673 PMCID: PMC7039201 DOI: 10.1083/jcb.201905162] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 09/17/2019] [Accepted: 10/03/2019] [Indexed: 12/22/2022] Open
Abstract
Lipid droplets (LDs) are important organelles for cell metabolism. Here, Du et al. show that phosphatidylinositol-4-phosphate produced by PI4K2A can exist on LDs and is used/consumed by ORP5, which localizes to ER–LD contacts during the growth of LDs. Lipid droplets (LDs) are evolutionarily conserved organelles that play important roles in cellular metabolism. Each LD is enclosed by a monolayer of phospholipids, distinct from bilayer membranes. During LD biogenesis and growth, this monolayer of lipids expands by acquiring phospholipids from the endoplasmic reticulum (ER) through nonvesicular mechanisms. Here, in a mini-screen, we find that ORP5, an integral membrane protein of the ER, can localize to ER–LD contact sites upon oleate loading. ORP5 interacts with LDs through its ligand-binding domain, and ORP5 deficiency enhances neutral lipid synthesis and increases the size of LDs. Importantly, there is significantly more phosphatidylinositol-4-phosphate (PI(4)P) and less phosphatidylserine (PS) on LDs in ORP5-deficient cells than in normal cells. The increased presence of PI(4)P on LDs in ORP5-deficient cells requires phosphatidylinositol 4-kinase 2-α. Our results thus demonstrate the existence of PI(4)P on LDs and suggest that LD-associated PI(4)P may be primarily used by ORP5 to deliver PS to LDs.
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Affiliation(s)
- Ximing Du
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
| | - Linkang Zhou
- State Key Laboratory of Membrane Biology and Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yvette Celine Aw
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
| | - Hoi Yin Mak
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
| | - Yanqing Xu
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
| | - James Rae
- Centre for Microscopy and Microanalysis, Institute of Molecular Bioscience, University of Queensland, St. Lucia, Australia
| | - Wenmin Wang
- State Key Laboratory of Membrane Biology and Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Armella Zadoorian
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
| | - Sarah E Hancock
- School of Medical Sciences, The University of New South Wales, Sydney, Australia
| | - Brenna Osborne
- School of Medical Sciences, The University of New South Wales, Sydney, Australia
| | - Xiang Chen
- Institute of Molecular Enzymology, Soochow University, Suzhou, Jiangsu, China
| | - Jia-Wei Wu
- Institute of Molecular Enzymology, Soochow University, Suzhou, Jiangsu, China
| | - Nigel Turner
- School of Medical Sciences, The University of New South Wales, Sydney, Australia
| | - Robert G Parton
- Centre for Microscopy and Microanalysis, Institute of Molecular Bioscience, University of Queensland, St. Lucia, Australia
| | - Peng Li
- State Key Laboratory of Membrane Biology and Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
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20
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Griffiths NW, Del Bel LM, Wilk R, Brill JA. Cellular homeostasis in the Drosophila retina requires the lipid phosphatase Sac1. Mol Biol Cell 2020; 31:1183-1199. [PMID: 32186963 PMCID: PMC7353163 DOI: 10.1091/mbc.e20-02-0161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The complex functions of cellular membranes, and thus overall cell physiology, depend on the distribution of crucial lipid species. Sac1 is an essential, conserved, ER-localized phosphatase whose substrate, phosphatidylinositol 4-phosphate (PI4P), coordinates secretory trafficking and plasma membrane function. PI4P from multiple pools is delivered to Sac1 by oxysterol-binding protein and related proteins in exchange for other lipids and sterols, which places Sac1 at the intersection of multiple lipid distribution pathways. However, much remains unknown about the roles of Sac1 in subcellular homeostasis and organismal development. Using a temperature-sensitive allele (Sac1ts), we show that Sac1 is required for structural integrity of the Drosophila retinal floor. The βps-integrin Myospheroid, which is necessary for basal cell adhesion, is mislocalized in Sac1ts retinas. In addition, the adhesion proteins Roughest and Kirre, which coordinate apical retinal cell patterning at an earlier stage, accumulate within Sac1ts retinal cells due to impaired endo-lysosomal degradation. Moreover, Sac1 is required for ER homeostasis in Drosophila retinal cells. Together, our data illustrate the importance of Sac1 in regulating multiple aspects of cellular homeostasis during tissue development.
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Affiliation(s)
- Nigel W Griffiths
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Lauren M Del Bel
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Ronit Wilk
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
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21
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Martello A, Platt FM, Eden ER. Staying in touch with the endocytic network: The importance of contacts for cholesterol transport. Traffic 2020; 21:354-363. [PMID: 32129938 PMCID: PMC8650999 DOI: 10.1111/tra.12726] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 02/21/2020] [Accepted: 03/02/2020] [Indexed: 12/16/2022]
Abstract
Cholesterol homeostasis is critical for cell function and human health. Cholesterol is heterogeneously distributed among cellular membranes, with the redistribution of endocytosed dietary cholesterol playing a pivotal role in the regulation of cholesterol homeostasis. While gaps remain in our understanding of intracellular dietary cholesterol transport, a highly complex network of pathways is starting to emerge, often involving inter‐dependent vesicular and non‐vesicular transport mechanisms. The last decade has seen a surge in interest in non‐vesicular transport and inter‐organellar communication at membrane contact sites. By providing platforms for protein interactions, signalling events, lipid exchange and calcium flux, membrane contact sites (MCS) are now appreciated as controlling the fate of large amounts of lipid and play central roles in the regulation and co‐ordination of endocytic trafficking. Here, we review the role of MCS in multiple pathways for cholesterol export from the endocytic pathway and highlight the intriguing interplay between vesicular and non‐vesicular transport mechanisms and relationship with neurodegenerative disease.
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Affiliation(s)
| | - Fran M Platt
- Department of Pharmacology, University of Oxford, Oxford, UK
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22
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Affiliation(s)
- Maria Bohnert
- Institute of Cell Dynamics and Imaging, University of Münster
- Cells-in-Motion Cluster of Excellence (EXC 1003—CiM), University of Münster
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23
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Zhao K, Foster J, Ridgway ND. Oxysterol-binding protein-related protein 1 variants have opposing cholesterol transport activities from the endolysosomes. Mol Biol Cell 2020; 31:793-802. [PMID: 32023146 PMCID: PMC7185962 DOI: 10.1091/mbc.e19-12-0697] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
OSBPL1 encodes the full-length oxysterol-binding protein-related protein ORP1L, which transports LDL-derived cholesterol at membrane contacts between the late endosomes/lysosomes (LEL) and the endoplasmic reticulum (ER). OSBPL1 also encodes the truncated variant ORP1S that contains only the C-terminal lipid binding domain. HeLa cells in which both variants were knocked out (ORP1-null) were used to determine the functional relationship between ORP1L and ORP1S with respect to cellular cholesterol localization and regulation. ORP1-null cells accumulated cholesterol in LEL and had reduced plasma membrane (PM) cholesterol. PM cholesterol was restored by expression of wild-type ORP1S or a phosphatidylinositol phosphate-binding mutant but not by a sterol-binding mutant. Expression of ORP2, another truncated variant, also restored PM cholesterol in ORP1-null cells. Consistent with a LEL-to-PM cholesterol transport activity, a small fraction of ORP1S was detected on the PM. As a consequence of reduced delivery of cholesterol to the PM in ORP1-null cells, cholesterol was diverted to the ER resulting in normalization of de novo cholesterol synthesis. The deficiency in PM cholesterol also reduced ABCA1-dependent cholesterol efflux and LDL receptor activity in ORP1-null cells. We conclude that ORP1S, which lacks discrete membrane-targeting motifs, transports cholesterol from LEL to the PM.
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Affiliation(s)
- Kexin Zhao
- Departments of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Jason Foster
- Departments of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Neale D Ridgway
- Departments of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
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24
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Hugenroth M, Bohnert M. Come a little bit closer! Lipid droplet-ER contact sites are getting crowded. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1867:118603. [PMID: 31733263 DOI: 10.1016/j.bbamcr.2019.118603] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/26/2019] [Accepted: 10/29/2019] [Indexed: 12/12/2022]
Abstract
Not so long ago, contact sites between the endoplasmic reticulum (ER) and lipid droplets (LDs) were largely unexplored on a molecular level. In recent years however, numerous proteins have been identified that are enriched or exclusively located at the interfaces between LDs and the ER. These comprise members of protein classes typically found in diverse types of contacts, such as organelle tethers and lipid transfer proteins, but also proteins that have no similarities to known contact site machineries. This structurally heterogeneous group of contact site residents might be required to fulfill unique aspects of LD-ER contact biology, such as de novo LD biogenesis, and maintenance of lipidic connections between LDs and ER. Here, we summarize the current knowledge on the molecular components of this special organelle contact site, and discuss their features and functions.
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Affiliation(s)
- Marie Hugenroth
- Institute of Cell Dynamics and Imaging, University of Münster, Von-Esmarch-Str. 56, 48149 Münster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Münster, Germany
| | - Maria Bohnert
- Institute of Cell Dynamics and Imaging, University of Münster, Von-Esmarch-Str. 56, 48149 Münster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Münster, Germany.
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25
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Shi H, Wang H, Yao J, Lin C, Wei Q, Lu Y, Cao X. Comparative transcriptome analysis of auditory OC-1 cells and zebrafish inner ear tissues in the absence of human OSBPL2 orthologues. Biochem Biophys Res Commun 2019; 521:42-49. [PMID: 31629475 DOI: 10.1016/j.bbrc.2019.10.061] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 10/05/2019] [Indexed: 12/16/2022]
Abstract
In our previous study, Oxysterol-binding protein-related protein 2 (OSBPL2) was first identified as a new deafness-causative gene contribute to non-syndromic hearing loss. However, the underlying mechanism of OSBPL2-induced hearing loss remains unknown. Here, we used hearing-specific cells and tissues OC-1 cells and zebrafish inner ear tissues as models to identify common transcriptome changes in genes and pathways in the absence of human OSBPL2 orthologues by RNA-seq analysis. In total, 2112 differentially expressed genes (DEGs) were identified between wild-type (WT) and Osbpl2-/- OC-1 cells, and 877 DEGs were identified between WT and osbpl2b-/- zebrafish inner ear tissues. Functional annotation implicated Osbpl2/osbpl2b in lipid metabolism, cell adhesion and the extracellular matrix in both OC-1 cells and zebrafish inner ear tissues. Protein-protein interaction (PPI) analysis indicated that Osbpl2/osbpl2b were also involved in ubiquitination. Further experiments showed that Osbpl2-/- OC-1 cells exhibited an abnormal focal adhesion morphology characterized by inhibited FAK activity and impaired cell adhesion. In conclusion, we identified novel pathways modulated by OSBPL2 orthologues, providing new insight into the mechanism of hearing loss induced by OSBPL2 deficiency.
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Affiliation(s)
- Hairong Shi
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Hongshun Wang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Jun Yao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China
| | - Changsong Lin
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Qinjun Wei
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China
| | - Yajie Lu
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China
| | - Xin Cao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China.
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Zhang C, Zhang H, Zhang M, Lin C, Wang H, Yao J, Wei Q, Lu Y, Chen Z, Xing G, Cao X. OSBPL2 deficiency upregulate SQLE expression increasing intracellular cholesterol and cholesteryl ester by AMPK/SP1 and SREBF2 signalling pathway. Exp Cell Res 2019; 383:111512. [PMID: 31356817 DOI: 10.1016/j.yexcr.2019.111512] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/25/2019] [Accepted: 07/26/2019] [Indexed: 12/12/2022]
Abstract
Previous studies have shown that oxysterol binding protein like 2 (OSBPL2) knockdown is closely related to cholesterol metabolism. However, whether there is a direct relation between OSBPL2 and cholesterol synthesis is unknown. This study explored the mechanism of OSBPL2 deficiency in the upregulation of squalene epoxidase (SQLE) and the subsequent accumulation of intracellular cholesterol and cholesteryl ester. Here, we constructed an OSBPL2-deleted HeLa cell line using CRISPR/Cas9 technology, screened differentially expressed genes and examined the transcriptional regulation of SQLE using a dual-luciferase reporter gene. RNA-seq analysis showed that SQLE was upregulated significantly and the dual luciferase reporter gene assay revealed that two new functional transcription factor binding sites of Sp1 transcription factor (SP1) and sterol regulatory element-binding transcription factor 2 (SREBF2) in the SQLE promoter participated in the SQLE transcription and expression. In addition, we also observed that OSBPL2 deletion inhibited the AMPK signalling pathway and that the inhibition of AMPK signalling promoted SP1 and SREBF2 entry into the nuclear to upregulate SQLE expression. Therefore, these data support that OSBPL2 deficiency upregulates SQLE expression and increases the accumulation of cholesterol and cholesteryl ester by suppressing AMPK signalling, which provides new evidence of the connection between OSBPL2 and cholesterol synthesis.
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Affiliation(s)
- Cui Zhang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Hongdu Zhang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Min Zhang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Changsong Lin
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Hongshun Wang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Jun Yao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China
| | - Qinjun Wei
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China; The Laboratory Center for Basic Medical Sciences, Nanjing Medical University, Nanjing, China
| | - Yajie Lu
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China
| | - Zhibin Chen
- Department of Otolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Guangqian Xing
- Department of Otolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Xin Cao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China; The Laboratory Center for Basic Medical Sciences, Nanjing Medical University, Nanjing, China.
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Olkkonen VM, Koponen A, Arora A. OSBP-related protein 2 (ORP2): Unraveling its functions in cellular lipid/carbohydrate metabolism, signaling and F-actin regulation. J Steroid Biochem Mol Biol 2019; 192:105298. [PMID: 30716465 DOI: 10.1016/j.jsbmb.2019.01.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 01/21/2019] [Accepted: 01/25/2019] [Indexed: 12/20/2022]
Abstract
Oxysterol-binding protein (OSBP)-related proteins (ORPs) constitute a family of intracellular lipid-binding/transport proteins (LTPs) in eukaryotes. They typically have a modular structure comprising a lipid-binding domain and membrane targeting determinants, being thus suited for function at membrane contact sites. Among the mammalian ORPs, ORP2/OSBPL2 is the only member that only exists as a 'short' variant lacking a membrane-targeting pleckstrin homology domain. ORP2 is expressed ubiquitously and has been assigned a multitude of functions. Its OSBP-related domain binds cholesterol, oxysterols, and phosphoinositides, and its overexpression enhances cellular cholesterol efflux. Consistently, the latest observations suggest a function of ORP2 in cholesterol transport to the plasma membrane (PM) in exchange for phosphatidylinositol 4,5-bisphosphate (PI4,5P2), with significant impacts on the concentrations of PM cholesterol and PI4,5P2. On the other hand, ORP2 localizes at the surface of cytoplasmic lipid droplets (LDs) and at endoplasmic-reticulum-LD contact sites, and its depletion modifies cellular triglyceride (TG) metabolism. Study in an adrenocortical cell line further suggested a function of ORP2 in the synthesis of steroid hormones. Our recent knock-out of ORP2 in human hepatoma cells revealed its function in hepatocellular PI3K/Akt signaling, glucose and triglyceride metabolism, as well as in actin cytoskeletal regulation, cell adhesion, migration and proliferation. ORP2 was shown to interact physically with F-actin regulators such as DIAPH1, ARHGAP12, SEPT9 and MLC12, as well as with IQGAP1 and the Cdc37-Hsp90 chaperone complex controlling the activity of Akt. Interestingly, mutations in OSBPL2 encoding ORP2 are associated with autosomal dominant non-syndromic hearing loss, and the protein was found to localize in cochlear hair cell stereocilia. The functions assigned to ORP2 suggest that this protein, in concert with other LTPs, controls the subcellular distribution of cholesterol in various cell types and steroid hormone synthesis in adrenocortical cells. However, it also impacts cellular TG and carbohydrate metabolism and F-actin-dependent functions, revealing a bewildering spectrum of activities.
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Affiliation(s)
- Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290, Helsinki, Finland; Department of Anatomy, Faculty of Medicine, FI-00014, University of Helsinki, Finland.
| | - Annika Koponen
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290, Helsinki, Finland; Department of Anatomy, Faculty of Medicine, FI-00014, University of Helsinki, Finland
| | - Amita Arora
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290, Helsinki, Finland; Department of Anatomy, Faculty of Medicine, FI-00014, University of Helsinki, Finland
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Wang H, Lin C, Yao J, Shi H, Zhang C, Wei Q, Lu Y, Chen Z, Xing G, Cao X. Deletion of OSBPL2 in auditory cells increases cholesterol biosynthesis and drives reactive oxygen species production by inhibiting AMPK activity. Cell Death Dis 2019; 10:627. [PMID: 31427568 PMCID: PMC6700064 DOI: 10.1038/s41419-019-1858-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 07/25/2019] [Accepted: 07/30/2019] [Indexed: 02/07/2023]
Abstract
Oxysterol-binding protein like 2 (OSBPL2) was identified as a novel causal gene for autosomal dominant nonsyndromic hearing loss. However, the pathogenesis of OSBPL2 deficits in ADNSHL was still unclear. The function of OSBPL2 as a lipid-sensing regulator in multiple cellular processes suggested that OSBPL2 might play an important role in the regulation of cholesterol-homeostasis, which was essential for inner ear. In this study the potential roles of OSBPL2 in cholesterol biosynthesis and ROS production were investigated in Osbpl2-KO OC1 cells and osbpl2b-KO zebrafish. RNA-seq-based analysis suggested that OSBPL2 was implicated in cholesterol biosynthesis and AMPK signaling pathway. Furthermore, Osbpl2/osbpl2b-KO resulted in a reduction of AMPK activity and up-regulation of Srebp2/srebp2, Hmgcr/hmgcr and Hmgcs1/hmgcs1, key genes in the sterol biosynthetic pathway and associated with AMPK signaling. In addition, OSBPL2 was also found to interact with ATIC, key activator of AMPK. The levels of total cholesterol and ROS in OC1 cells or zebrafish inner ear were both increased in Osbpl2/osbpl2b-KO mutants and the mitochondrial damage was detected in Osbpl2-KO OC1 cells. This study uncovered the regulatory roles of OSBPL2 in cellular cholesterol biosynthesis and ROS production. These founds might contribute to the deep understanding of the pathogenesis of OSBPL2 mutation in ADNSHL.
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Affiliation(s)
- Hongshun Wang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Changsong Lin
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Jun Yao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China.,Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China
| | - Hairong Shi
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Cui Zhang
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China
| | - Qinjun Wei
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China.,Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China.,The Laboratory Center for Basic Medical Sciences, Nanjing Medical University, Nanjing, China
| | - Yajie Lu
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China.,Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China
| | - Zhibin Chen
- Department of Otolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Guangqian Xing
- Department of Otolaryngology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Xin Cao
- Department of Medical Genetics, School of Basic Medical Science, Nanjing Medical University, Nanjing, China. .,Jiangsu Key Laboratory of Xenotransplantation, Nanjing Medical University, Nanjing, China. .,The Laboratory Center for Basic Medical Sciences, Nanjing Medical University, Nanjing, China.
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Phosphoinositides in the control of lysosome function and homeostasis. Biochem Soc Trans 2019; 47:1173-1185. [PMID: 31383818 DOI: 10.1042/bst20190158] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 07/12/2019] [Accepted: 07/15/2019] [Indexed: 12/11/2022]
Abstract
Lysosomes are the main degradative compartments of mammalian cells and serve as platforms for cellular nutrient signaling and sterol transport. The diverse functions of lysosomes and their adaptation to extracellular and intracellular cues are tightly linked to the spatiotemporally controlled synthesis, turnover and interconversion of lysosomal phosphoinositides, minor phospholipids that define membrane identity and couple membrane dynamics to cell signaling. How precisely lysosomal phosphoinositides act and which effector proteins within the lysosome membrane or at the lysosomal surface recognize them is only now beginning to emerge. Importantly, mutations in phosphoinositide metabolizing enzyme cause lysosomal dysfunction and are associated with numerous diseases ranging from neurodegeneration to cancer. Here, we discuss the phosphoinositides and phosphoinositide metabolizing enzymes implicated in lysosome function and homeostasis and outline perspectives for future research.
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Yang H. Extended synaptotagmins, peroxisome-endoplasmic reticulum contact and cholesterol transport. SCIENCE CHINA-LIFE SCIENCES 2019; 62:1266-1269. [DOI: 10.1007/s11427-019-9573-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 06/04/2019] [Indexed: 12/14/2022]
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Affiliation(s)
- Daniella M Schwartz
- Genetics and Pathogenesis of Allergy Section, Laboratory of Allergic Diseases, NIAID, NIH, Bethesda, MD, USA
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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Tong J, Tan L, Chun C, Im YJ. Structural basis of human ORP1-Rab7 interaction for the late-endosome and lysosome targeting. PLoS One 2019; 14:e0211724. [PMID: 30721249 PMCID: PMC6363164 DOI: 10.1371/journal.pone.0211724] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 01/20/2019] [Indexed: 02/07/2023] Open
Abstract
Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute a family of lipid transfer proteins conserved in eukaryotes. ORP1 transports cholesterol at the interface between the late endosomes/lysosomes (LELs) and the endoplasmic reticulum (ER). ORP1 is targeted to the endosomal membranes by forming a tripartite complex with the LE GTPase Rab7 and its effector RILP (Rab7-interacting lysosomal protein). Here, we determined the crystal structure of human ORP1 ANK domain in complex with the GTP-bound form of Rab7. ORP1 ANK binds to the helix α3 of Rab7 located away from the switching regions, which makes the interaction independent of the nucleotide-binding state of Rab7. Thus, the effector-interacting switch regions of Rab7 are accessible for RILP binding, allowing formation of the ORP1-Rab7-RILP complex. ORP1 ANK binds to Rab7 and the Rab7-RILP complex with similar micro-molar affinities, which is consistent with the independence binding of ORP1 and RILP to Rab7. The structural model of the ORP1-Rab7-RILP complex correlates with the recruitment of ORP1 at the LEL-ER interface and the role in lipid transport and regulation.
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Affiliation(s)
- Junsen Tong
- College of Pharmacy, Chonnam National University, Gwangju, Republic of Korea
| | - Lingchen Tan
- College of Pharmacy, Chonnam National University, Gwangju, Republic of Korea
| | - ChangJu Chun
- College of Pharmacy, Chonnam National University, Gwangju, Republic of Korea
| | - Young Jun Im
- College of Pharmacy, Chonnam National University, Gwangju, Republic of Korea
- * E-mail:
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