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Arabiotorre A, Bankaitis VA, Grabon A. Regulation of phosphoinositide metabolism in Apicomplexan parasites. Front Cell Dev Biol 2023; 11:1163574. [PMID: 37791074 PMCID: PMC10543664 DOI: 10.3389/fcell.2023.1163574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 07/11/2023] [Indexed: 10/05/2023] Open
Abstract
Phosphoinositides are a biologically essential class of phospholipids that contribute to organelle membrane identity, modulate membrane trafficking pathways, and are central components of major signal transduction pathways that operate on the cytosolic face of intracellular membranes in eukaryotes. Apicomplexans (such as Toxoplasma gondii and Plasmodium spp.) are obligate intracellular parasites that are important causative agents of disease in animals and humans. Recent advances in molecular and cell biology of Apicomplexan parasites reveal important roles for phosphoinositide signaling in key aspects of parasitosis. These include invasion of host cells, intracellular survival and replication, egress from host cells, and extracellular motility. As Apicomplexans have adapted to the organization of essential signaling pathways to accommodate their complex parasitic lifestyle, these organisms offer experimentally tractable systems for studying the evolution, conservation, and repurposing of phosphoinositide signaling. In this review, we describe the regulatory mechanisms that control the spatial and temporal regulation of phosphoinositides in the Apicomplexan parasites Plasmodium and T. gondii. We further discuss the similarities and differences presented by Apicomplexan phosphoinositide signaling relative to how these pathways are regulated in other eukaryotic organisms.
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Affiliation(s)
- Angela Arabiotorre
- Department of Cell Biology and Genetics, College of Medicine Texas A&M Health Sciences Center College Station, Bryan, TX, United States
| | - Vytas A. Bankaitis
- Department of Cell Biology and Genetics, College of Medicine Texas A&M Health Sciences Center College Station, Bryan, TX, United States
- Department of Biochemistry and Biophysics Texas A&M University College Station, College Station, TX, United States
- Department of Chemistry Texas A&M University College Station, College Station, TX, United States
| | - Aby Grabon
- Department of Cell Biology and Genetics, College of Medicine Texas A&M Health Sciences Center College Station, Bryan, TX, United States
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Fang R, Jiang Q, Jia X, Jiang Z. ARMH3-mediated recruitment of PI4KB directs Golgi-to-endosome trafficking and activation of the antiviral effector STING. Immunity 2023; 56:500-515.e6. [PMID: 36921576 DOI: 10.1016/j.immuni.2023.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 11/30/2022] [Accepted: 01/26/2023] [Indexed: 03/15/2023]
Abstract
The cGAS-STING pathway mediates cytoplasmic DNA-triggered innate immunity. STING activation is initiated by cyclic-GMP-AMP (cGAMP)-induced translocation from the endoplasmic reticulum and sulfated glycosaminoglycans-induced polymerization at the Golgi. Here, we examine the mechanisms underlying STING transport and activation beyond the Golgi. A genome-wide CRISPR-Cas9 screen identified Armadillo-like helical domain-containing protein 3 (ARMH3) as critical for STING activation. Upon cGAMP-triggered translocation, ARMH3 interacted with STING at the Golgi and recruited phosphatidylinositol 4-kinase beta (PI4KB) to synthesize PI4P, which directed STING Golgi-to-endosome trafficking via PI4P-binding proteins AP-1 and GGA2. Disrupting PI4P-dependent lipid transport through RNAi of other PI4P-binding proteins impaired STING activation. Consistently, disturbed lipid composition inhibited STING activation, whereas aberrantly elevated cellular PI4P led to cGAS-independent STING activation. Armh3fl/fllLyzCre/Cre mice were susceptible to DNA virus challenge in vivo. Thus, ARMH3 bridges STING and PIK4B to generate PI4P for STING transportation and activation, an interaction conserved in all eukaryotes.
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Affiliation(s)
- Run Fang
- Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking University, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - Qifei Jiang
- Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking University, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - Xinying Jia
- Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking University, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - Zhengfan Jiang
- Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking University, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China.
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3
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Membrane pools of phosphatidylinositol-4-phosphate regulate KCNQ1/KCNE1 membrane expression. Commun Biol 2021; 4:1392. [PMID: 34907346 PMCID: PMC8671492 DOI: 10.1038/s42003-021-02909-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 11/24/2021] [Indexed: 11/23/2022] Open
Abstract
Plasma membrane phosphatidylinositol 4-phosphate (PI4P) is a precursor of PI(4,5)P2, an important regulator of a large number of ion channels. Although the role of the phospholipid PI(4,5)P2 in stabilizing ion channel function is well established, little is known about the role of phospholipids in channel membrane localization and specifically the role of PI4P in channel function and localization. The phosphatidylinositol 4-kinases (PI4Ks) synthesize PI4P. Our data show that inhibition of PI4K and prolonged decrease of levels of plasma membrane PI4P lead to a decrease in the KCNQ1/KCNE1 channel membrane localization and function. In addition, we show that mutations linked to Long QT syndrome that affect channel interactions with phospholipids lead to a decrease in membrane expression. We show that expression of a LQT1-associated C-terminal deletion mutant abolishes PI4Kinase-mediated decrease in membrane expression and rescues membrane expression for phospholipid-targeting mutations. Our results indicate a novel role for PI4P on ion channel regulation. Our data suggest that decreased membrane PI4P availability to the channel, either due to inhibition of PI4K or as consequence of mutations, dramatically inhibits KCNQ1/KCNE1 channel membrane localization and current. Our results may have implications to regulation of other PI4P binding channels.
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Luo Y, Jiang Q, Zhu Z, Sattar H, Wu J, Huang W, Su S, Liang Y, Wang P, Meng X. Phosphoproteomics and Proteomics Reveal Metabolism as a Key Node in LPS-Induced Acute Inflammation in RAW264.7. Inflammation 2021; 43:1667-1679. [PMID: 32488682 DOI: 10.1007/s10753-020-01240-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To better understand the acute inflammatory mechanisms, the modulation, and to investigate the key node in predicting inflammatory diseases, high-sensitivity LC-MS/MS-based proteomics and phosphoproteomics approaches were used to identify differential proteins in RAW264.7 macrophages with lipopolysaccharide (LPS). Furthermore, differential proteins and their main biological process, as well as signaling pathways, were analyzed through bioinformatics techniques. The biological process comparison revealed 219 differential proteins and 405 differential phosphorylation proteins, including major regulatory factors of metabolism (PFKL, PGK1, GYS1, ACC, HSL, LDHA, RAB14, PRKAA1), inflammatory signaling transduction (IKKs, NF-κB, IRAK, IKBkb, PI3K, AKT), and apoptosis (MCL-1, BID, NOXA, SQSTM1). Label-free proteome demonstrated canonical inflammation signaling pathways such as the TNF signaling pathway, NF-κB signaling pathway, and NOD-like receptor signaling pathway. Meanwhile, phosphoproteome revealed new areas of acute inflammation. Phosphoproteomics profiled that glycolysis was enhanced and lipid synthesis was increased. Overall, the AMPK signaling pathway is the key regulatory part in macrophages. These revealed that the early initiation phase of acute inflammation primarily regulated the phosphoproteins of glucose metabolic pathway and lipid synthesis to generate energy and molecules, along with the enhancement of pro-inflammatory factors, and further induced apoptosis. Phosphoproteomics provides new evidence for a complex network of specific but synergistically acting mechanisms confirming that metabolism has a key role in acute inflammation.
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Affiliation(s)
- Yu Luo
- College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China
| | - Qing Jiang
- College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China
| | - Zhengwen Zhu
- College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China
| | - Haseeb Sattar
- International School of Clinical Medicine, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China
| | - Jiasi Wu
- College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China
| | - Wenge Huang
- College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China
| | - Siyu Su
- College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China
| | - Yusheng Liang
- College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China
| | - Ping Wang
- College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China.
| | - Xianli Meng
- College of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu, 611137, People's Republic of China.
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5
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Zhang H, Zhou J, Xiao P, Lin Y, Gong X, Liu S, Xu Q, Wang M, Ren H, Lu M, Wang Y, Zhu J, Xie Z, Li H, Lu K. PtdIns4P restriction by hydrolase SAC1 decides specific fusion of autophagosomes with lysosomes. Autophagy 2020; 17:1907-1917. [PMID: 32693712 DOI: 10.1080/15548627.2020.1796321] [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: 02/08/2023] Open
Abstract
Biogenesis of autophagosomes is the early step of macroautophagy/autophagy and requires membrane acquisition mainly from ER-Golgi-sourced precursor vesicles. Matured autophagosomes fuse with lysosomes for final degradation. However, how this selective fusion is determined remains elusive. Here, we identified Sac1 by a high throughput screen in Saccharomyces cerevisiae to show it was critical for autophagosome-lysosome fusion through its PtdIns4P phosphatase activity. Sac1 deficiency caused a dramatic increase of PtdIns4P at early Golgi apparatus and abnormal incorporation of PtdIns4P into Atg9 vesicles and autophagosomes, which caused failure to recruit SNARE proteins for autophagosome fusion with vacuoles. Sac1 function in autophagy was highly conserved from yeast to mammalian cells. Our work thus suggested that correct upstream lipid incorporation was important for downstream fusion step of autophagy and that Sac1 played a critical and ancient role in this surveillance of lipid integration.Abbreviations: Ape1: aminopeptidase Ι; ATG: autophagy related; EBSS: Earle's balanced salt solution; ER: endoplasmic reticulum; ERGIC: Golgi apparatus and ER-Golgi intermediate compartment; HOPS: homotypic fusion and protein sorting complex; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; PtdIns3P: phosphatidylinositol-3-phosphate; PtdIns4K: phosphoinositide-4-kinase; PtdIns4P: phosphatidylinositol-4-phosphate; SD-N: nitrogen starvation medium; SNARE: soluble N-ethylamide-sensitive factor attachment protein receptor.
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Affiliation(s)
- Hongjun Zhang
- Department of Neurosurgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Jiao Zhou
- Department of Neurosurgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Peng Xiao
- Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Yong Lin
- Key Laboratory of Molecular Biology for Infectious Diseases, Ministry of Education, Chongqing Medical University, Chongqing, China
| | - Xin Gong
- Department of Respiratory, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Shiyan Liu
- Department of Neurosurgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Qingjia Xu
- Department of Neurosurgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Minjin Wang
- Department of Clinical Laboratory, West China Hospital, Sichuan University, Chengdu, China
| | - Haiyan Ren
- Department of Respiratory, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Mengji Lu
- Institute of Virology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Yuan Wang
- Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Jing Zhu
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Zhiping Xie
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Huihui Li
- West China Second University Hospital, Sichuan University, Chengdu, China
| | - Kefeng Lu
- Department of Neurosurgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
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Makowski SL, Kuna RS, Field SJ. Induction of membrane curvature by proteins involved in Golgi trafficking. Adv Biol Regul 2019; 75:100661. [PMID: 31668661 PMCID: PMC7056495 DOI: 10.1016/j.jbior.2019.100661] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 09/25/2019] [Accepted: 09/30/2019] [Indexed: 12/22/2022]
Abstract
The Golgi apparatus serves a key role in processing and sorting lipids and proteins for delivery to their final cellular destinations. Vesicle exit from the Golgi initiates with directional deformation of the lipid bilayer to produce a bulge. Several mechanisms have been described by which lipids and proteins can induce directional membrane curvature to promote vesicle budding. Here we review some of the mechanisms implicated in inducing membrane curvature at the Golgi to promote vesicular trafficking to various cellular destinations.
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Affiliation(s)
- Stefanie L Makowski
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Ramya S Kuna
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Seth J Field
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA, 92093, USA.
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7
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Clarke BP, Logeman BL, Hale AT, Luka Z, York JD. A synthetic biological approach to reconstitution of inositide signaling pathways in bacteria. Adv Biol Regul 2019; 73:100637. [PMID: 31378699 DOI: 10.1016/j.jbior.2019.100637] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/01/2019] [Accepted: 07/04/2019] [Indexed: 11/19/2022]
Abstract
Inositide lipid (PIP) and soluble (IP) signaling pathways produce essential cellular codes conserved in eukaryotes. In many cases, deconvoluting metabolic and functional aspects of individual pathways are confounded by promiscuity and multiplicity of PIP and IP kinases and phosphatases. We report a molecular genetic approach that reconstitutes eukaryotic inositide lipid and soluble pathways in a prokaryotic cell which inherently lack inositide kinases and phosphatases in their genome. By expressing synthetic cassettes of eukaryotic genes, we have reconstructed the heterologous formation of a range of inositide lipids, including PI(3)P, PI(4,5)P2 and PIP3. In addition, we report the reconstruction of lipid-dependent production of inositol hexakisphosphate (IP6). Our synthetic system is scalable, reduces confounding metabolic issues, for example it is devoid of inositide phosphatases and orthologous kinases, and enables accurate characterization gene product enzymatic activity and substrate selectivity. This genetically engineered tool is designed to help interpret metabolic pathways and may facilitate in vivo testing of regulators and small molecule inhibitors. In summary, heterologous expression of inositide pathways in bacteria provide a malleable experimental platform for aiding signaling biologists and offers new insights into metabolism of these essential pathways.
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Affiliation(s)
- Bradley P Clarke
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Brandon L Logeman
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC, USA
| | - Andrew T Hale
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Zigmund Luka
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - John D York
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Pharmacology and Cancer Biology, Duke University, Durham, NC, USA.
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8
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Structural Basis for Regulation of Phosphoinositide Kinases and Their Involvement in Human Disease. Mol Cell 2018; 71:653-673. [DOI: 10.1016/j.molcel.2018.08.005] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 06/22/2018] [Accepted: 07/30/2018] [Indexed: 01/09/2023]
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9
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Del Bel LM, Brill JA. Sac1, a lipid phosphatase at the interface of vesicular and nonvesicular transport. Traffic 2018; 19:301-318. [PMID: 29411923 DOI: 10.1111/tra.12554] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 02/02/2018] [Accepted: 02/02/2018] [Indexed: 12/14/2022]
Abstract
The lipid phosphatase Sac1 dephosphorylates phosphatidylinositol 4-phosphate (PI4P), thereby holding levels of this crucial membrane signaling molecule in check. Sac1 regulates multiple cellular processes, including cytoskeletal organization, membrane trafficking and cell signaling. Here, we review the structure and regulation of Sac1, its roles in cell signaling and development and its links to health and disease. Remarkably, many of the diverse roles attributed to Sac1 can be explained by the recent discovery of its requirement at membrane contact sites, where its consumption of PI4P is proposed to drive interorganelle transfer of other cellular lipids, thereby promoting normal lipid homeostasis within cells.
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Affiliation(s)
- Lauren M Del Bel
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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10
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Daniotti JL, Pedro MP, Valdez Taubas J. The role of S-acylation in protein trafficking. Traffic 2017; 18:699-710. [DOI: 10.1111/tra.12510] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 08/16/2017] [Accepted: 08/20/2017] [Indexed: 12/13/2022]
Affiliation(s)
- Jose L. Daniotti
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET; Universidad Nacional de Córdoba; Córdoba Argentina
- Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas; Universidad Nacional de Córdoba; Córdoba Argentina
| | - Maria P. Pedro
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET; Universidad Nacional de Córdoba; Córdoba Argentina
- Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas; Universidad Nacional de Córdoba; Córdoba Argentina
| | - Javier Valdez Taubas
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET; Universidad Nacional de Córdoba; Córdoba Argentina
- Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas; Universidad Nacional de Córdoba; Córdoba Argentina
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Jain A, Holthuis JCM. Membrane contact sites, ancient and central hubs of cellular lipid logistics. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:1450-1458. [PMID: 28554771 DOI: 10.1016/j.bbamcr.2017.05.017] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 05/10/2017] [Accepted: 05/17/2017] [Indexed: 12/26/2022]
Abstract
Membrane contact sites (MCSs) are regions where two organelles are closely apposed to facilitate molecular communication and promote a functional integration of compartmentalized cellular processes. There is growing evidence that MCSs play key roles in controlling intracellular lipid flows and distributions. Strikingly, even organelles connected by vesicular trafficking exchange lipids en bulk via lipid transfer proteins that operate at MCSs. Herein, we describe how MCSs developed into central hubs of lipid logistics during the evolution of eukaryotic cells. We then focus on how modern eukaryotes exploit MCSs to help solve a major logistical problem, namely to preserve the unique lipid mixtures of their early and late secretory organelles in the face of extensive vesicular trafficking. This article is part of a Special Issue entitled: Membrane Contact Sites edited by Christian Ungermann and Benoit Kornmann.
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Affiliation(s)
- Amrita Jain
- Molecular Cell Biology Division, Department of Biology/Chemistry, University of Osnabrück, D-49076 Osnabrück, Germany
| | - Joost C M Holthuis
- Molecular Cell Biology Division, Department of Biology/Chemistry, University of Osnabrück, D-49076 Osnabrück, Germany; Membrane Biochemistry & Biophysics, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands.
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Ceramide Transport from the Endoplasmic Reticulum to the Trans Golgi Region at Organelle Membrane Contact Sites. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 997:69-81. [PMID: 28815522 DOI: 10.1007/978-981-10-4567-7_5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Lipids are the major constituents of all cell membranes and play dynamic roles in organelle structure and function. Although the spontaneous transfer of lipids between different membranes rarely occurs, lipids are appropriately transported between different organelles for their metabolism and to exert their functions in living cells. Proteins that have the biochemical capability to catalyze the intermembrane transfer of lipids are called lipid transfer proteins (LTPs). All organisms possess many types of LTPs. Recent studies revealed that LTPs are key players in the interorganelle transport of lipids at organelle membrane contact sites (MCSs). This chapter depicts how LTPs rationally operate at MCSs by using the ceramide transport protein CERT as a typical model for the LTP-mediated interorganelle transport of lipids.
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13
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Mutations in Encephalomyocarditis Virus 3A Protein Uncouple the Dependency of Genome Replication on Host Factors Phosphatidylinositol 4-Kinase IIIα and Oxysterol-Binding Protein. mSphere 2016; 1:mSphere00068-16. [PMID: 27303747 PMCID: PMC4888891 DOI: 10.1128/msphere.00068-16] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 04/25/2016] [Indexed: 12/18/2022] Open
Abstract
Positive-strand RNA viruses modulate lipid homeostasis to generate unique, membranous “replication organelles” (ROs) where viral genome replication takes place. Hepatitis C virus, encephalomyocarditis virus (EMCV), and enteroviruses have convergently evolved to hijack host phosphatidylinositol 4-kinases (PI4Ks), which produce PI4P lipids, to recruit oxysterol-binding protein (OSBP), a PI4P-binding protein that shuttles cholesterol to ROs. Consistent with the proposed coupling between PI4K and OSBP, enterovirus mutants resistant to PI4KB inhibitors are also resistant to OSBP inhibitors. Here, we show that EMCV can replicate without accumulating PI4P/cholesterol at ROs, by acquiring point mutations in nonstructural protein 3A. Remarkably, the mutations conferred resistance to PI4K but not OSBP inhibitors, thereby uncoupling the levels of dependency of EMCV RNA replication on PI4K and OSBP. This work may contribute to a deeper understanding of the roles of PI4K/PI4P and OSBP/cholesterol in membrane modifications induced by positive-strand RNA viruses. Positive-strand RNA [(+)RNA] viruses are true masters of reprogramming host lipid trafficking and synthesis to support virus genome replication. Via their membrane-associated 3A protein, picornaviruses of the genus Enterovirus (e.g., poliovirus, coxsackievirus, and rhinovirus) subvert Golgi complex-localized phosphatidylinositol 4-kinase IIIβ (PI4KB) to generate “replication organelles” (ROs) enriched in phosphatidylinositol 4-phosphate (PI4P). PI4P lipids serve to accumulate oxysterol-binding protein (OSBP), which subsequently transfers cholesterol to the ROs in a PI4P-dependent manner. Single-point mutations in 3A render enteroviruses resistant to both PI4KB and OSBP inhibition, indicating coupled dependency on these host factors. Recently, we showed that encephalomyocarditis virus (EMCV), a picornavirus that belongs to the Cardiovirus genus, also builds PI4P/cholesterol-enriched ROs. Like the hepatitis C virus (HCV) of the Flaviviridae family, it does so by hijacking the endoplasmic reticulum (ER)-localized phosphatidylinositol 4-kinase IIIα (PI4KA). Here we provide genetic evidence for the critical involvement of EMCV protein 3A in this process. Using a genetic screening approach, we selected EMCV mutants with single amino acid substitutions in 3A, which rescued RNA virus replication upon small interfering RNA (siRNA) knockdown or pharmacological inhibition of PI4KA. In the presence of PI4KA inhibitors, the mutants no longer induced PI4P, OSBP, or cholesterol accumulation at ROs, which aggregated into large cytoplasmic clusters. In contrast to the enterovirus escape mutants, we observed little if any cross-resistance of EMCV mutants to OSBP inhibitors, indicating an uncoupled level of dependency of their RNA replication on PI4KA and OSBP activities. This report may contribute to a better understanding of the roles of PI4KA and OSBP in membrane modifications induced by (+)RNA viruses. IMPORTANCE Positive-strand RNA viruses modulate lipid homeostasis to generate unique, membranous “replication organelles” (ROs) where viral genome replication takes place. Hepatitis C virus, encephalomyocarditis virus (EMCV), and enteroviruses have convergently evolved to hijack host phosphatidylinositol 4-kinases (PI4Ks), which produce PI4P lipids, to recruit oxysterol-binding protein (OSBP), a PI4P-binding protein that shuttles cholesterol to ROs. Consistent with the proposed coupling between PI4K and OSBP, enterovirus mutants resistant to PI4KB inhibitors are also resistant to OSBP inhibitors. Here, we show that EMCV can replicate without accumulating PI4P/cholesterol at ROs, by acquiring point mutations in nonstructural protein 3A. Remarkably, the mutations conferred resistance to PI4K but not OSBP inhibitors, thereby uncoupling the levels of dependency of EMCV RNA replication on PI4K and OSBP. This work may contribute to a deeper understanding of the roles of PI4K/PI4P and OSBP/cholesterol in membrane modifications induced by positive-strand RNA viruses.
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