1
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Talandashti R, van Ek L, Gehin C, Xue D, Moqadam M, Gavin AC, Reuter N. Membrane specificity of the human cholesterol transfer protein STARD4. J Mol Biol 2024; 436:168572. [PMID: 38615744 DOI: 10.1016/j.jmb.2024.168572] [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: 01/26/2024] [Revised: 03/28/2024] [Accepted: 04/09/2024] [Indexed: 04/16/2024]
Abstract
STARD4 regulates cholesterol homeostasis by transferring cholesterol between the plasma membrane and endoplasmic reticulum. The STARD4 structure features a helix-grip fold surrounding a large hydrophobic cavity holding the sterol. Its access is controlled by a gate formed by the Ω1 and Ω4 loops and the C-terminal α-helix. Little is known about the mechanisms by which STARD4 binds to membranes and extracts/releases cholesterol. All available structures of STARD4 are without a bound sterol and display the same closed conformation of the gate. The cholesterol transfer activity of the mouse STARD4 is enhanced in the presence of anionic lipids, and in particular of phosphatidylinositol biphosphates (PIP2) for which two binding sites were proposed on the mouse STARD4 surface. Yet only one of these sites is conserved in human STARD4. We here report the results of a liposome microarray-based assay and microseconds-long molecular dynamics simulations of human STARD4 with complex lipid bilayers mimicking the composition of the donor and acceptor membranes. We show that the binding of apo form of human STARD4 is sensitive to the presence of PIP2 through two specific binding sites, one of which was not identified on mouse STARD4. We report two novel conformations of the gate in holo-STARD4: a yet-unobserved close conformation and an open conformation of Ω4 shedding light on the opening/closure mechanism needed for cholesterol uptake/release. Overall, the modulation of human STARD4 membrane-binding by lipid composition, and by the presence of the cargo supports the capacity of human STARD4 to achieve directed transfer between specific organelle membranes.
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Affiliation(s)
- Reza Talandashti
- Department of Chemistry, University of Bergen, Bergen 5020, Norway; Computational Biology Unit, Department of Informatics, University of Bergen, Bergen 5020, Norway
| | - Larissa van Ek
- Department of Cellular Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland; Diabetes Center, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Charlotte Gehin
- École Polytechnique Fédérale de Lausanne EPFL, Lausanne, Switzerland
| | - Dandan Xue
- Department of Chemistry, University of Bergen, Bergen 5020, Norway; Computational Biology Unit, Department of Informatics, University of Bergen, Bergen 5020, Norway
| | - Mahmoud Moqadam
- Department of Chemistry, University of Bergen, Bergen 5020, Norway; Computational Biology Unit, Department of Informatics, University of Bergen, Bergen 5020, Norway
| | - Anne-Claude Gavin
- Department of Cellular Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland; Diabetes Center, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Nathalie Reuter
- Department of Chemistry, University of Bergen, Bergen 5020, Norway; Computational Biology Unit, Department of Informatics, University of Bergen, Bergen 5020, Norway.
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2
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Sun S, Zhao G, Jia M, Jiang Q, Li S, Wang H, Li W, Wang Y, Bian X, Zhao YG, Huang X, Yang G, Cai H, Pastor-Pareja JC, Ge L, Zhang C, Hu J. Stay in touch with the endoplasmic reticulum. SCIENCE CHINA. LIFE SCIENCES 2024; 67:230-257. [PMID: 38212460 DOI: 10.1007/s11427-023-2443-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 08/28/2023] [Indexed: 01/13/2024]
Abstract
The endoplasmic reticulum (ER), which is composed of a continuous network of tubules and sheets, forms the most widely distributed membrane system in eukaryotic cells. As a result, it engages a variety of organelles by establishing membrane contact sites (MCSs). These contacts regulate organelle positioning and remodeling, including fusion and fission, facilitate precise lipid exchange, and couple vital signaling events. Here, we systematically review recent advances and converging themes on ER-involved organellar contact. The molecular basis, cellular influence, and potential physiological functions for ER/nuclear envelope contacts with mitochondria, Golgi, endosomes, lysosomes, lipid droplets, autophagosomes, and plasma membrane are summarized.
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Affiliation(s)
- Sha Sun
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China
| | - Gan Zhao
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China
| | - Mingkang Jia
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China
| | - Qing Jiang
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China
| | - Shulin Li
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Haibin Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China
| | - Wenjing Li
- Laboratory of Computational Biology & Machine Intelligence, School of Artificial Intelligence, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yunyun Wang
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Xin Bian
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China.
| | - Yan G Zhao
- Brain Research Center, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, 518055, China.
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Ge Yang
- Laboratory of Computational Biology & Machine Intelligence, School of Artificial Intelligence, University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Huaqing Cai
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Jose C Pastor-Pareja
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
- Institute of Neurosciences, Consejo Superior de Investigaciones Cientfflcas-Universidad Miguel Hernandez, San Juan de Alicante, 03550, Spain.
| | - Liang Ge
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
| | - Chuanmao Zhang
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China.
| | - Junjie Hu
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China.
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3
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Koh DHZ, Naito T, Na M, Yeap YJ, Rozario P, Zhong FL, Lim KL, Saheki Y. Visualization of accessible cholesterol using a GRAM domain-based biosensor. Nat Commun 2023; 14:6773. [PMID: 37880244 PMCID: PMC10600248 DOI: 10.1038/s41467-023-42498-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Accepted: 10/12/2023] [Indexed: 10/27/2023] Open
Abstract
Cholesterol is important for membrane integrity and cell signaling, and dysregulation of the distribution of cellular cholesterol is associated with numerous diseases, including neurodegenerative disorders. While regulated transport of a specific pool of cholesterol, known as "accessible cholesterol", contributes to the maintenance of cellular cholesterol distribution and homeostasis, tools to monitor accessible cholesterol in live cells remain limited. Here, we engineer a highly sensitive accessible cholesterol biosensor by taking advantage of the cholesterol-sensing element (the GRAM domain) of an evolutionarily conserved lipid transfer protein, GRAMD1b. Using this cholesterol biosensor, which we call GRAM-W, we successfully visualize in real time the distribution of accessible cholesterol in many different cell types, including human keratinocytes and iPSC-derived neurons, and show differential dependencies on cholesterol biosynthesis and uptake for maintaining levels of accessible cholesterol. Furthermore, we combine GRAM-W with a dimerization-dependent fluorescent protein (ddFP) and establish a strategy for the ultrasensitive detection of accessible plasma membrane cholesterol. These tools will allow us to obtain important insights into the molecular mechanisms by which the distribution of cellular cholesterol is regulated.
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Affiliation(s)
- Dylan Hong Zheng Koh
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Tomoki Naito
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Minyoung Na
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Yee Jie Yeap
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Pritisha Rozario
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Franklin L Zhong
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
- Skin Research Institute of Singapore (SRIS), Singapore, 308232, Singapore
| | - Kah-Leong Lim
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
- National Neuroscience Institute, Singapore, 308433, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore.
- Institute of Resource Development and Analysis, Kumamoto University, Kumamoto, 860-0811, Japan.
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4
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Naito T, Yang H, Koh DHZ, Mahajan D, Lu L, Saheki Y. Regulation of cellular cholesterol distribution via non-vesicular lipid transport at ER-Golgi contact sites. Nat Commun 2023; 14:5867. [PMID: 37735529 PMCID: PMC10514280 DOI: 10.1038/s41467-023-41213-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 08/28/2023] [Indexed: 09/23/2023] Open
Abstract
Abnormal distribution of cellular cholesterol is associated with numerous diseases, including cardiovascular and neurodegenerative diseases. Regulated transport of cholesterol is critical for maintaining its proper distribution in the cell, yet the underlying mechanisms remain unclear. Here, we show that lipid transfer proteins, namely ORP9, OSBP, and GRAMD1s/Asters (GRAMD1a/GRAMD1b/GRAMD1c), control non-vesicular cholesterol transport at points of contact between the ER and the trans-Golgi network (TGN), thereby maintaining cellular cholesterol distribution. ORP9 localizes to the TGN via interaction between its tandem α-helices and ORP10/ORP11. ORP9 extracts PI4P from the TGN to prevent its overaccumulation and suppresses OSBP-mediated PI4P-driven cholesterol transport to the Golgi. By contrast, GRAMD1s transport excess cholesterol from the Golgi to the ER, thereby preventing its build-up. Cells lacking ORP9 exhibit accumulation of cholesterol at the Golgi, which is further enhanced by additional depletion of GRAMD1s with major accumulation in the plasma membrane. This is accompanied by chronic activation of the SREBP-2 signalling pathway. Our findings reveal the importance of regulated lipid transport at ER-Golgi contacts for maintaining cellular cholesterol distribution and homeostasis.
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Affiliation(s)
- Tomoki Naito
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Haoning Yang
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Dylan Hong Zheng Koh
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Divyanshu Mahajan
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore
| | - Lei Lu
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore.
- Institute of Resource Development and Analysis, Kumamoto University, Kumamoto, 860-0811, Japan.
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5
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Choy HL, Gaylord EA, Doering TL. Ergosterol distribution controls surface structure formation and fungal pathogenicity. mBio 2023; 14:e0135323. [PMID: 37409809 PMCID: PMC10470819 DOI: 10.1128/mbio.01353-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 06/01/2023] [Indexed: 07/07/2023] Open
Abstract
Ergosterol, the major sterol in fungal membranes, is critical for defining membrane fluidity and regulating cellular processes. Although ergosterol synthesis has been well defined in model yeast, little is known about sterol organization in the context of fungal pathogenesis. We identified a retrograde sterol transporter, Ysp2, in the opportunistic fungal pathogen Cryptococcus neoformans. We found that the lack of Ysp2 under host-mimicking conditions leads to abnormal accumulation of ergosterol at the plasma membrane, invagination of the plasma membrane, and malformation of the cell wall, which can be functionally rescued by inhibiting ergosterol synthesis with the antifungal drug fluconazole. We also observed that cells lacking Ysp2 mislocalize the cell surface protein Pma1 and have abnormally thin and permeable capsules. As a result of perturbed ergosterol distribution and its consequences, ysp2∆ cells cannot survive in physiologically relevant environments such as host phagocytes and are dramatically attenuated in virulence. These findings expand our knowledge of cryptococcal biology and underscore the importance of sterol homeostasis in fungal pathogenesis. IMPORTANCE Cryptococcus neoformans is an opportunistic fungal pathogen that kills over 100,000 people worldwide each year. Only three drugs are available to treat cryptococcosis, and these are variously limited by toxicity, availability, cost, and resistance. Ergosterol is the most abundant sterol in fungi and a key component in modulating membrane behavior. Two of the drugs used for cryptococcal infection, amphotericin B and fluconazole, target this lipid and its synthesis, highlighting its importance as a therapeutic target. We discovered a cryptococcal ergosterol transporter, Ysp2, and demonstrated its key roles in multiple aspects of cryptococcal biology and pathogenesis. These studies demonstrate the role of ergosterol homeostasis in C. neoformans virulence, deepen our understanding of a pathway with proven therapeutic importance, and open a new area of study.
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Affiliation(s)
- Hau Lam Choy
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Elizabeth A. Gaylord
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Tamara L. Doering
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
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6
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Xie H, Weinstein H. Allosterically coupled conformational dynamics in solution prepare the sterol transfer protein StarD4 to release its cargo upon interaction with target membranes. Front Mol Biosci 2023; 10:1197154. [PMID: 37275961 PMCID: PMC10232897 DOI: 10.3389/fmolb.2023.1197154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 05/04/2023] [Indexed: 06/07/2023] Open
Abstract
Complex mechanisms regulate the cellular distribution of cholesterol, a critical component of eukaryote membranes involved in regulation of membrane protein functions directly and through the physiochemical properties of membranes. StarD4, a member of the steroidogenic acute regulator-related lipid-transfer (StART) domain (StARD)-containing protein family, is a highly efficient sterol-specific transfer protein involved in cholesterol homeostasis. Its mechanism of cargo loading and release remains unknown despite recent insights into the key role of phosphatidylinositol phosphates in modulating its interactions with target membranes. We have used large-scale atomistic Molecular dynamics (MD) simulations to study how the dynamics of cholesterol bound to the StarD4 protein can affect interaction with target membranes, and cargo delivery. We identify the two major cholesterol (CHL) binding modes in the hydrophobic pocket of StarD4, one near S136&S147 (the Ser-mode), and another closer to the putative release gate located near W171, R92&Y117 (the Trp-mode). We show that conformational changes of StarD4 associated directly with the transition between these binding modes facilitate the opening of the gate. To understand the dynamics of this connection we apply a machine-learning algorithm for the detection of rare events in MD trajectories (RED), which reveals the structural motifs involved in the opening of a front gate and a back corridor in the StarD4 structure occurring together with the spontaneous transition of CHL from the Ser-mode of binding to the Trp-mode. Further analysis of MD trajectory data with the information-theory based NbIT method reveals the allosteric network connecting the CHL binding site to the functionally important structural components of the gate and corridor. Mutations of residues in the allosteric network are shown to affect the performance of the allosteric connection. These findings outline an allosteric mechanism which prepares the CHL-bound StarD4 to release and deliver the cargo when it is bound to the target membrane.
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Affiliation(s)
- Hengyi Xie
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, United States
| | - Harel Weinstein
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, United States
- Institute for Computational Biomedicine, Weill Cornell Medicine, New York, NY, United States
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7
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Choy HL, Gaylord EA, Doering TL. Ergosterol distribution controls surface structure formation and fungal pathogenicity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.17.528979. [PMID: 36824733 PMCID: PMC9949117 DOI: 10.1101/2023.02.17.528979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Ergosterol, the major sterol in fungal membranes, is critical for defining membrane fluidity and regulating cellular processes. Although ergosterol synthesis has been well defined in model yeast, little is known about sterol organization in the context of fungal pathogenesis. We identified a retrograde sterol transporter, Ysp2, in the opportunistic fungal pathogen Cryptococcus neoformans . We found that the lack of Ysp2 under host-mimicking conditions leads to abnormal accumulation of ergosterol at the plasma membrane, invagination of the plasma membrane, and malformation of the cell wall, which can be functionally rescued by inhibiting ergosterol synthesis with the antifungal drug fluconazole. We also observed that cells lacking Ysp2 mislocalize the cell surface protein Pma1 and have thinner and more permeable capsules. As a result of perturbed ergosterol distribution and its consequences, ysp2 Î" cells cannot survive in physiologically-rele-vant environments such as host phagocytes and are dramatically attenuated in virulence. These findings expand our knowledge of cryptococcal biology and underscore the importance of sterol homeostasis in fungal pathogenesis. IMPORTANCE Cryptococcus neoformans is an opportunistic fungal pathogen that kills over 100,000 people worldwide each year. Only three drugs are available to treat cryptococcosis, and these are variously limited by toxicity, availability, cost, and resistance. Ergosterol is the most abundant sterol in fungi and a key component in modulating membrane behavior. Two of the drugs used for cryptococcal infection, amphotericin B and fluconazole, target this lipid and its synthesis, highlighting its importance as a therapeutic target. We discovered a cryptococcal ergosterol transporter, Ysp2, and demonstrated its key roles in multiple aspects of cryptococcal biology and pathogenesis. These studies demonstrate the role of ergosterol homeostasis in C. neoformans virulence, deepen our understanding of a pathway with proven therapeutic importance, and open a new area of study.
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Affiliation(s)
- Hau Lam Choy
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Elizabeth A. Gaylord
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Tamara L. Doering
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
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8
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Kennelly JP, Tontonoz P. Cholesterol Transport to the Endoplasmic Reticulum. Cold Spring Harb Perspect Biol 2023; 15:cshperspect.a041263. [PMID: 35940908 PMCID: PMC9899650 DOI: 10.1101/cshperspect.a041263] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Most cholesterol in mammalian cells is stored in the plasma membrane (PM). Cholesterol transport from the PM to low-sterol regulatory regions of the endoplasmic reticulum (ER) controls cholesterol synthesis and uptake, and thereby influences the rates of cholesterol flux between tissues of complex organisms. Cholesterol transfer to the ER is also required for steroidogenesis, oxysterol and bile acid synthesis, and cholesterol esterification. The ER-resident Aster proteins (Aster-A, -B, and -C) form contacts with the PM to move cholesterol to the ER in mammals. Mice lacking Aster-B have low adrenal cholesteryl ester stores and impaired steroidogenesis because of a defect in cholesterol transport from high-density lipoprotein (HDL) to the ER. This work reviews the molecular characteristics of Asters, their role in HDL- and low-density lipoprotein (LDL)-cholesterol movement, and how cholesterol transferred to the ER is utilized by cells. The roles of other lipid transporters and of membrane lipid organization in maintaining aspects of cholesterol homeostasis are also highlighted.
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Affiliation(s)
- John P Kennelly
- Department of Pathology and Laboratory Medicine, Department of Biological Chemistry, Molecular Biology Institute, University of California, Los Angeles, California 90095, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, Department of Biological Chemistry, Molecular Biology Institute, University of California, Los Angeles, California 90095, USA
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9
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Hong Z, Adlakha J, Wan N, Guinn E, Giska F, Gupta K, Melia TJ, Reinisch KM. Mitoguardin-2-mediated lipid transfer preserves mitochondrial morphology and lipid droplet formation. J Cell Biol 2022; 221:e202207022. [PMID: 36282247 PMCID: PMC9597353 DOI: 10.1083/jcb.202207022] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 09/12/2022] [Accepted: 10/04/2022] [Indexed: 12/15/2022] Open
Abstract
Lipid transport proteins at membrane contacts, where organelles are closely apposed, are critical in redistributing lipids from the endoplasmic reticulum (ER), where they are made, to other cellular membranes. Such protein-mediated transfer is especially important for maintaining organelles disconnected from secretory pathways, like mitochondria. We identify mitoguardin-2, a mitochondrial protein at contacts with the ER and/or lipid droplets (LDs), as a lipid transporter. An x-ray structure shows that the C-terminal domain of mitoguardin-2 has a hydrophobic cavity that binds lipids. Mass spectrometry analysis reveals that both glycerophospholipids and free-fatty acids co-purify with mitoguardin-2 from cells, and that each mitoguardin-2 can accommodate up to two lipids. Mitoguardin-2 transfers glycerophospholipids between membranes in vitro, and this transport ability is required for roles both in mitochondrial and LD biology. While it is not established that protein-mediated transfer at contacts plays a role in LD metabolism, our findings raise the possibility that mitoguardin-2 functions in transporting fatty acids and glycerophospholipids at mitochondria-LD contacts.
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Affiliation(s)
- Zhouping Hong
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Jyoti Adlakha
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Neng Wan
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Emily Guinn
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Fabian Giska
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
- Nanobiology Institute, Yale University, West Haven, CT
| | - Kallol Gupta
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
- Nanobiology Institute, Yale University, West Haven, CT
- Aligning Science Across Parkinson’s Collaborative Research Network, Chevy Chase, MD
| | - Thomas J. Melia
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Karin M. Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
- Aligning Science Across Parkinson’s Collaborative Research Network, Chevy Chase, MD
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10
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Overduin M, Tran A, Eekels DM, Overduin F, Kervin TA. Transmembrane Membrane Readers form a Novel Class of Proteins That Include Peripheral Phosphoinositide Recognition Domains and Viral Spikes. MEMBRANES 2022; 12:1161. [PMID: 36422153 PMCID: PMC9692390 DOI: 10.3390/membranes12111161] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 11/11/2022] [Accepted: 11/15/2022] [Indexed: 06/16/2023]
Abstract
Membrane proteins are broadly classified as transmembrane (TM) or peripheral, with functions that pertain to only a single bilayer at a given time. Here, we explicate a class of proteins that contain both transmembrane and peripheral domains, which we dub transmembrane membrane readers (TMMRs). Their transmembrane and peripheral elements anchor them to one bilayer and reversibly attach them to another section of bilayer, respectively, positioning them to tether and fuse membranes while recognizing signals such as phosphoinositides (PIs) and modifying lipid chemistries in proximity to their transmembrane domains. Here, we analyze full-length models from AlphaFold2 and Rosetta, as well as structures from nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography, using the Membrane Optimal Docking Area (MODA) program to map their membrane-binding surfaces. Eukaryotic TMMRs include phospholipid-binding C1, C2, CRAL-TRIO, FYVE, GRAM, GTPase, MATH, PDZ, PH, PX, SMP, StART and WD domains within proteins including protrudin, sorting nexins and synaptotagmins. The spike proteins of SARS-CoV-2 as well as other viruses are also TMMRs, seeing as they are anchored into the viral membrane while mediating fusion with host cell membranes. As such, TMMRs have key roles in cell biology and membrane trafficking, and include drug targets for diseases such as COVID-19.
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Affiliation(s)
- Michael Overduin
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Anh Tran
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | | | - Finn Overduin
- Institute of Nutritional Science, University of Potsdam, 14476 Potsdam, Germany
| | - Troy A. Kervin
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
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11
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Ogasawara F, Ueda K. ABCA1 and cholesterol transfer protein Aster-A promote an asymmetric cholesterol distribution in the plasma membrane. J Biol Chem 2022; 298:102702. [PMID: 36395885 PMCID: PMC9747601 DOI: 10.1016/j.jbc.2022.102702] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 10/31/2022] [Accepted: 11/04/2022] [Indexed: 11/16/2022] Open
Abstract
Cholesterol is a major and essential component of the mammalian cell plasma membrane (PM), and the loss of cholesterol homeostasis leads to various pathologies. Cellular cholesterol uptake and synthesis are regulated by a cholesterol sensor in the endoplasmic reticulum (ER). However, it remains unclear how changes in the cholesterol level of the PM are recognized. Here, we show that the sensing of cholesterol in the PM depends on ABCA1 and the cholesterol transfer protein Aster-A, which cooperatively maintain the asymmetric transbilayer cholesterol distribution in the PM. We demonstrate that ABCA1 translocates (flops) cholesterol from the inner leaflet of the PM to the outer leaflet of the PM to maintain a low inner leaflet cholesterol level. We also found that when inner cholesterol levels were increased, Aster-A was recruited to the PM-ER contact site to transfer cholesterol to the ER. These results suggest that ABCA1 could promote an asymmetric cholesterol distribution to suppress Aster-A recruitment to the PM-ER contact site to maintain intracellular cholesterol homeostasis.
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12
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Sokolov SS, Volynsky PE, Zangieva OT, Severin FF, Glagoleva ES, Knorre DA. Cytostatic effects of structurally different ginsenosides on yeast cells with altered sterol biosynthesis and transport. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183993. [PMID: 35724740 DOI: 10.1016/j.bbamem.2022.183993] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 05/16/2022] [Accepted: 06/13/2022] [Indexed: 06/15/2023]
Abstract
Triterpene glycosides are a diverse group of plant secondary metabolites, consisting of a sterol-like aglycon and one or several sugar groups. A number of triterpene glycosides show membranolytic activity, and, therefore, are considered to be promising antimicrobial drugs. However, the interrelation between their structure, biological activities, and target membrane lipid composition remains elusive. Here we studied the antifungal effects of four Panax triterpene glycosides (ginsenosides) with sugar moieties at the C-3 (ginsenosides Rg3, Rh2), C-20 (compound K), and both (ginsenoside F2) positions in Saccharomyces cerevisiae mutants with altered sterol plasma membrane composition. We observed reduced cytostatic activity of the Rg3 and compound K in the UPC2-1 strain with high membrane sterol content. Moreover, LAM gene deletion reduced yeast resistance to Rg3 and digitonin, another saponin with glycosylated aglycon in the C-3 position. LAM genes encode plasma membrane-anchored StARkin superfamily-member sterol transporters. We also showed that the deletion of the ERG6 gene that inhibits ergosterol biosynthesis at the stage of zymosterol increased the cytostatic effects of Rg3 and Rh2, but not the other two tested ginsenosides. At the same time, in silico simulation revealed that the substitution of ergosterol with zymosterol in the membrane changes the spatial orientation of Rg3 and Rh2 in the membranes. These results imply that the plasma membrane sterol composition defines its interaction with triterpene glycoside depending on their glycoside group position. Our results also suggest that the biological role of membrane-anchored StARkin family protein is to protect eukaryotic cells from triterpenes glycosylated at the C-3 position.
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Affiliation(s)
- Svyatoslav S Sokolov
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Leninskie Gory 1-40, Moscow, Russia
| | - Pavel E Volynsky
- Laboratory of Biomolecular Modeling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997, Miklukho-Maklaya Str., 16/10, Moscow, Russia
| | - Olga T Zangieva
- Federal State Budgetary Institution "National Medical and Surgical Center named after N.I.Pirogov" of the Ministry of Healthcare of the Russian Federation, 105203, Nizhnyaya Pervomayskaya str., 70, Moscow, Russia
| | - Fedor F Severin
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Leninskie Gory 1-40, Moscow, Russia
| | - Elena S Glagoleva
- Faculty of Biology, Lomonosov Moscow State University, 119991, Leninskie Gory 1-12, Moscow, Russia
| | - Dmitry A Knorre
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Leninskie Gory 1-40, Moscow, Russia.
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13
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Zhang Y, Ge J, Bian X, Kumar A. Quantitative Models of Lipid Transfer and Membrane Contact Formation. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2022; 5:1-21. [PMID: 36120532 DOI: 10.1177/25152564221096024] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Lipid transfer proteins (LTPs) transfer lipids between different organelles, and thus play key roles in lipid homeostasis and organelle dynamics. The lipid transfer often occurs at the membrane contact sites (MCS) where two membranes are held within 10-30 nm. While most LTPs act as a shuttle to transfer lipids, recent experiments reveal a new category of eukaryotic LTPs that may serve as a bridge to transport lipids in bulk at MCSs. However, the molecular mechanisms underlying lipid transfer and MCS formation are not well understood. Here, we first review two recent studies of extended synaptotagmin (E-Syt)-mediated membrane binding and lipid transfer using novel approaches. Then we describe mathematical models to quantify the kinetics of lipid transfer by shuttle LTPs based on a lipid exchange mechanism. We find that simple lipid mixing among membranes of similar composition and/or lipid partitioning among membranes of distinct composition can explain lipid transfer against a concentration gradient widely observed for LTPs. We predict that selective transport of lipids, but not membrane proteins, by bridge LTPs leads to osmotic membrane tension by analogy to the osmotic pressure across a semipermeable membrane. A gradient of such tension and the conventional membrane tension may drive bulk lipid flow through bridge LTPs at a speed consistent with the fast membrane expansion observed in vivo. Finally, we discuss the implications of membrane tension and lipid transfer in organelle biogenesis. Overall, the quantitative models may help clarify the mechanisms of LTP-mediated MCS formation and lipid transfer.
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Affiliation(s)
- Yongli Zhang
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Jinghua Ge
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Xin Bian
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA.,Present address: State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, China
| | - Avinash Kumar
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
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14
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Depta L, Whitmarsh-Everiss T, Laraia L. Structure, function and small molecule modulation of intracellular sterol transport proteins. Bioorg Med Chem 2022; 68:116856. [PMID: 35716590 DOI: 10.1016/j.bmc.2022.116856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 05/23/2022] [Indexed: 11/02/2022]
Abstract
Intracellular sterol transport proteins (STPs) are crucial for maintaining cellular lipid homeostasis by regulating local sterol pools. Despite structural similarities in their sterol binding domains, STPs have different substrate specificities, intracellular localisation and biological functions. In this review, we highlight recent advances in the determination of STP structures and how this regulates their lipid specificities. Furthermore, we cover the important discoveries relating to the intracellular localisation of STPs, and the organelles between which lipid transport is carried out, giving rise to specific functions in health and disease. Finally, serendipitous and targeted efforts to identify small molecule modulators of STPs, as well as their ability to act as tool compounds and potential therapeutics, will be discussed.
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Affiliation(s)
- Laura Depta
- Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800 Kgs Lyngby, Denmark
| | - Thomas Whitmarsh-Everiss
- Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800 Kgs Lyngby, Denmark
| | - Luca Laraia
- Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800 Kgs Lyngby, Denmark.
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15
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Kim H, Lee S, Jun Y, Lee C. Structural basis for mitoguardin-2 mediated lipid transport at ER-mitochondrial membrane contact sites. Nat Commun 2022; 13:3702. [PMID: 35764626 PMCID: PMC9239997 DOI: 10.1038/s41467-022-31462-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 06/17/2022] [Indexed: 11/10/2022] Open
Abstract
The endoplasmic reticulum (ER)-mitochondria contact site (ERMCS) is crucial for exchanging biological molecules such as phospholipids and Ca2+ ions between these organelles. Mitoguardin-2 (MIGA2), a mitochondrial outer membrane protein, forms the ERMCS in higher eukaryotic cells. Here, we report the crystal structures of the MIGA2 Lipid Droplet (LD) targeting domain and the ER membrane protein VAPB bound to the phosphorylated FFAT motif of MIGA2. These structures reveal that the MIGA2 LD targeting domain has a large internal hydrophobic pocket that accommodates phospholipids and that two phosphorylations of the FFAT motif are required for tight interaction of MIGA2 with VAPB, which enhances the rate of lipid transport. Further biochemical studies show that MIGA2 transports phospholipids between membranes with a strong preference for binding and trafficking phosphatidylserine (PS). These results provide a structural and molecular basis for understanding how MIGA2 mediates the formation of ERMCS and facilitates lipid trafficking at the ERMCS. The ER-mitochondria contact sites are crucial for exchanging phospholipids. Here, Kim et al. present crystal structures of mitoguardin-2 (MIGA2) which reveal that MIGA2 directly binds phospholipids and transfers them between the ER and mitochondria.
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Affiliation(s)
- Hyunwoo Kim
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan, Korea.,Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju, Korea
| | - Seowhang Lee
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan, Korea
| | - Youngsoo Jun
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju, Korea.,School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Korea
| | - Changwook Lee
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan, Korea. .,Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju, Korea.
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16
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Sotillos S, von der Decken I, Domenech Mercadé I, Srinivasan S, Sirokha D, Livshits L, Vanni S, Nef S, Biason-Lauber A, Rodríguez Gutiérrez D, Castelli-Gair Hombría J. A conserved function of Human DLC3 and Drosophila Cv-c in testis development. eLife 2022; 11:82343. [PMID: 36326091 PMCID: PMC9678365 DOI: 10.7554/elife.82343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 10/25/2022] [Indexed: 11/23/2022] Open
Abstract
The identification of genes affecting gonad development is essential to understand the mechanisms causing Variations/Differences in Sex Development (DSD). Recently, a DLC3 mutation was associated with male gonadal dysgenesis in 46,XY DSD patients. We have studied the requirement of Cv-c, the Drosophila ortholog of DLC3, in Drosophila gonad development, as well as the functional capacity of DLC3 human variants to rescue cv-c gonad defects. We show that Cv-c is required to maintain testis integrity during fly development. We find that Cv-c and human DLC3 can perform the same function in fly embryos, as flies carrying wild type but not patient DLC3 variations can rescue gonadal dysgenesis, suggesting functional conservation. We also demonstrate that the StART domain mediates Cv-c's function in the male gonad independently from the GAP domain's activity. This work demonstrates a role for DLC3/Cv-c in male gonadogenesis and highlights a novel StART domain mediated function required to organize the gonadal mesoderm and maintain its interaction with the germ cells during testis development.
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Affiliation(s)
- Sol Sotillos
- Centro Andaluz de Biología del DesarrolloSevilleSpain
| | - Isabel von der Decken
- Department of Endocrinology, Metabolism and Cardiovascular research, University of FribourgFribourgSwitzerland
| | - Ivan Domenech Mercadé
- Department of Endocrinology, Metabolism and Cardiovascular research, University of FribourgFribourgSwitzerland
| | | | - Dmytro Sirokha
- Institute of Molecular Biology and Genetics, National Academy of Sciences of UkraineKyivUkraine
| | - Ludmila Livshits
- Institute of Molecular Biology and Genetics, National Academy of Sciences of UkraineKyivUkraine
| | - Stefano Vanni
- Department of Biology, University of FribourgFribourgSwitzerland
| | - Serge Nef
- Department of Genetic Medicine and Development, Faculty of Medicine, University of GenevaGenevaSwitzerland
| | - Anna Biason-Lauber
- Department of Endocrinology, Metabolism and Cardiovascular research, University of FribourgFribourgSwitzerland
| | - Daniel Rodríguez Gutiérrez
- Department of Endocrinology, Metabolism and Cardiovascular research, University of FribourgFribourgSwitzerland
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17
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Egea PF. Mechanisms of Non-Vesicular Exchange of Lipids at Membrane Contact Sites: Of Shuttles, Tunnels and, Funnels. Front Cell Dev Biol 2021; 9:784367. [PMID: 34912813 PMCID: PMC8667587 DOI: 10.3389/fcell.2021.784367] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 11/08/2021] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic cells are characterized by their exquisite compartmentalization resulting from a cornucopia of membrane-bound organelles. Each of these compartments hosts a flurry of biochemical reactions and supports biological functions such as genome storage, membrane protein and lipid biosynthesis/degradation and ATP synthesis, all essential to cellular life. Acting as hubs for the transfer of matter and signals between organelles and throughout the cell, membrane contacts sites (MCSs), sites of close apposition between membranes from different organelles, are essential to cellular homeostasis. One of the now well-acknowledged function of MCSs involves the non-vesicular trafficking of lipids; its characterization answered one long-standing question of eukaryotic cell biology revealing how some organelles receive and distribute their membrane lipids in absence of vesicular trafficking. The endoplasmic reticulum (ER) in synergy with the mitochondria, stands as the nexus for the biosynthesis and distribution of phospholipids (PLs) throughout the cell by contacting nearly all other organelle types. MCSs create and maintain lipid fluxes and gradients essential to the functional asymmetry and polarity of biological membranes throughout the cell. Membrane apposition is mediated by proteinaceous tethers some of which function as lipid transfer proteins (LTPs). We summarize here the current state of mechanistic knowledge of some of the major classes of LTPs and tethers based on the available atomic to near-atomic resolution structures of several "model" MCSs from yeast but also in Metazoans; we describe different models of lipid transfer at MCSs and analyze the determinants of their specificity and directionality. Each of these systems illustrate fundamental principles and mechanisms for the non-vesicular exchange of lipids between eukaryotic membrane-bound organelles essential to a wide range of cellular processes such as at PL biosynthesis and distribution, lipid storage, autophagy and organelle biogenesis.
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Affiliation(s)
- Pascal F Egea
- Department of Biological Chemistry, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States
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18
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Jamecna D, Antonny B. Intrinsically disordered protein regions at membrane contact sites. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1866:159020. [PMID: 34352388 DOI: 10.1016/j.bbalip.2021.159020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 06/30/2021] [Accepted: 07/01/2021] [Indexed: 12/14/2022]
Abstract
Membrane contact sites (MCS) are regions of close apposition between membrane-bound organelles. Proteins that occupy MCS display various domain organisation. Among them, lipid transfer proteins (LTPs) frequently contain both structured domains as well as regions of intrinsic disorder. In this review, we discuss the various roles of intrinsically disordered protein regions (IDPRs) in LTPs as well as in other proteins that are associated with organelle contact sites. We distinguish the following functions: (i) to act as flexible tethers between two membranes; (ii) to act as entropic barriers to prevent protein crowding and regulate membrane tethering geometry; (iii) to define the action range of catalytic domains. These functions are added to other functions of IDPRs in membrane environments, such as mediating protein-protein and protein-membrane interactions. We suggest that the overall efficiency and fidelity of contact sites might require fine coordination between all these IDPR activities.
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Affiliation(s)
- Denisa Jamecna
- Université Côte d'Azur et CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, 660 route des lucioles, 06560 Valbonne, France; Biochemistry Center (BZH), Heidelberg, Germany
| | - Bruno Antonny
- Université Côte d'Azur et CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, 660 route des lucioles, 06560 Valbonne, France.
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19
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Schoop V, Martello A, Eden ER, Höglinger D. Cellular cholesterol and how to find it. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1866:158989. [PMID: 34118431 DOI: 10.1016/j.bbalip.2021.158989] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/01/2021] [Accepted: 06/02/2021] [Indexed: 01/06/2023]
Abstract
Cholesterol is an essential component of eukaryotic cellular membranes. Information about its subcellular localization and transport pathways inside cells are key for the understanding and treatment of cholesterol-related diseases. In this review we give an overview over the most commonly used methods that contributed to our current understanding of subcellular cholesterol localization and transport routes. First, we discuss methods that provide insights into cholesterol metabolism based on readouts of downstream effects such as esterification. Subsequently, we focus on the use of cholesterol-binding molecules as probes that facilitate visualization and quantification of sterols inside of cells. Finally, we explore different analogues of cholesterol which, when taken up by living cells, are integrated and transported in a similar fashion as endogenous sterols. Taken together, we highlight the challenges and advantages of each method such that researchers studying aspects of cholesterol transport may choose the most pertinent approach for their problem.
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Affiliation(s)
- Valentin Schoop
- Heidelberg University Biochemistry Center (BZH), 69120 Heidelberg, Germany
| | - Andrea Martello
- University College London (UCL), Institute of Ophthalmology, EC1V 9EL London, United Kingdom
| | - Emily R Eden
- University College London (UCL), Institute of Ophthalmology, EC1V 9EL London, United Kingdom
| | - Doris Höglinger
- Heidelberg University Biochemistry Center (BZH), 69120 Heidelberg, Germany.
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20
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Fenech EJ, Ben-Dor S, Schuldiner M. Double the Fun, Double the Trouble: Paralogs and Homologs Functioning in the Endoplasmic Reticulum. Annu Rev Biochem 2021; 89:637-666. [PMID: 32569522 DOI: 10.1146/annurev-biochem-011520-104831] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The evolution of eukaryotic genomes has been propelled by a series of gene duplication events, leading to an expansion in new functions and pathways. While duplicate genes may retain some functional redundancy, it is clear that to survive selection they cannot simply serve as a backup but rather must acquire distinct functions required for cellular processes to work accurately and efficiently. Understanding these differences and characterizing gene-specific functions is complex. Here we explore different gene pairs and families within the context of the endoplasmic reticulum (ER), the main cellular hub of lipid biosynthesis and the entry site for the secretory pathway. Focusing on each of the ER functions, we highlight specificities of related proteins and the capabilities conferred to cells through their conservation. More generally, these examples suggest why related genes have been maintained by evolutionary forces and provide a conceptual framework to experimentally determine why they have survived selection.
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Affiliation(s)
- Emma J Fenech
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel;
| | - Shifra Ben-Dor
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel;
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21
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GRAMD1-mediated accessible cholesterol sensing and transport. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1866:158957. [PMID: 33932585 DOI: 10.1016/j.bbalip.2021.158957] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 04/09/2021] [Accepted: 04/19/2021] [Indexed: 01/19/2023]
Abstract
Cholesterol, an essential lipid for cell signaling and structural integrity of cellular membranes, is highly enriched in the plasma membrane (PM). However, the regulatory mechanisms that control its biosynthesis and uptake both reside in the endoplasmic reticulum (ER). Thus, the ER needs to constantly monitor the levels of PM cholesterol. This is in part mediated by regulated transport of a biochemically defined pool of cholesterol, termed "accessible" cholesterol, from the PM to the ER via evolutionarily conserved ER-anchored lipid transfer proteins, the GRAMD1s/Asters (GRAMD1a/1b/1c) (Lam/Ltc proteins in yeast). GRAMD1s possess cytosolically exposed GRAM domain and StART-like domain followed by a transmembrane ER anchor. They form homo- and hetero-meric complexes and move to the contacts formed between the ER and the PM by sensing a transient expansion of the accessible pool of cholesterol in the PM via the GRAM domain and facilitate its extraction and transport to the ER via the StART-like domain. The GRAMD1b GRAM domain possesses distinct, but synergistic sites, for recognizing accessible cholesterol and anionic lipids, including phosphatidylserine, within the PM. This property of the GRAM domain contributes to regulated tethering of the PM to ER membrane where GRAMD1s are anchored and fine-tunes StART-like domain-dependent accessible cholesterol transport. Thus, cells use GRAMD1s to sense the levels of cholesterol in the PM and regulate transport of accessible PM cholesterol to the ER in order to maintain cholesterol homeostasis.
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22
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Zhou Y, Zhong T, Wei W, Wu Z, Yang A, Liu N, Wang M, Zhang X. Single START-domain protein Mtsp17 is involved in transcriptional regulation in Mycobacterium smegmatis. PLoS One 2021; 16:e0249379. [PMID: 33857164 PMCID: PMC8049324 DOI: 10.1371/journal.pone.0249379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 03/17/2021] [Indexed: 11/19/2022] Open
Abstract
Tuberculosis caused by the pathogen Mycobacterium tuberculosis (MTB), remains a significant threat to global health. Elucidating the mechanisms of essential MTB genes provides an important theoretical basis for drug exploitation. Gene mtsp17 is essential and is conserved in the Mycobacterium genus. Although Mtsp17 has a structure closely resembling typical steroidogenic acute regulatory protein-related lipid transfer (START) family proteins, its biological function is different. This study characterizes the transcriptomes of Mycobacterium smegmatis to explore the consequences of mtsp17 downregulation on gene expression. Suppression of the mtsp17 gene resulted in significant down-regulation of 3% and upregulation of 1% of all protein-coding genes. Expression of desA1, an essential gene involved in mycolic acid synthesis, and the anti-SigF antagonist MSMEG_0586 were down-regulated in the conditional Mtsp17 knockout mutant and up-regulated in the Mtsp17 over-expression strain. Trends in the changes of 70 of the 79 differentially expressed genes (Log2 fold change > 1.5) in the conditional Mtsp17 knockout strain were the same as in the SigF knockout strain. Our data suggest that Mtsp17 is likely an activator of desA1 and Mtsp17 regulates the SigF regulon by SigF regulatory pathways through the anti-SigF antagonist MSMEG_0586. Our findings indicate the role of Mtsp17 may be in transcriptional regulation, provide new insights into the molecular mechanisms of START family proteins, and uncover a new node in the regulatory network of mycobacteria.
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Affiliation(s)
- Ying Zhou
- Department of Bone and Joint Surgery, The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Tianying Zhong
- Guangdong Province Green and High Performance Novel Materials Engineering Research Center, Jiangmen Polytechnic, Jiangmen, China
| | - Wenjing Wei
- Center for Tuberculosis Control of Guangdong Province, Guangzhou, China
| | - Zhuhua Wu
- Center for Tuberculosis Control of Guangdong Province, Guangzhou, China
| | - Anping Yang
- School of Medicine, Foshan University, Foshan, Guangdong, China
| | - Ning Liu
- Department of Bone and Joint Surgery, The First Affiliated Hospital of Jinan University, Guangzhou, China
- * E-mail: (NL); (MW); (XZ)
| | - Ming Wang
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- * E-mail: (NL); (MW); (XZ)
| | - Xiaoli Zhang
- School of Medicine, Foshan University, Foshan, Guangdong, China
- * E-mail: (NL); (MW); (XZ)
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23
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Ercan B, Naito T, Koh DHZ, Dharmawan D, Saheki Y. Molecular basis of accessible plasma membrane cholesterol recognition by the GRAM domain of GRAMD1b. EMBO J 2021; 40:e106524. [PMID: 33604931 PMCID: PMC7957428 DOI: 10.15252/embj.2020106524] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 12/16/2020] [Accepted: 01/08/2021] [Indexed: 12/25/2022] Open
Abstract
Cholesterol is essential for cell physiology. Transport of the "accessible" pool of cholesterol from the plasma membrane (PM) to the endoplasmic reticulum (ER) by ER-localized GRAMD1 proteins (GRAMD1a/1b/1c) contributes to cholesterol homeostasis. However, how cells detect accessible cholesterol within the PM remains unclear. We show that the GRAM domain of GRAMD1b, a coincidence detector for anionic lipids, including phosphatidylserine (PS), and cholesterol, possesses distinct but synergistic sites for sensing accessible cholesterol and anionic lipids. We find that a mutation within the GRAM domain of GRAMD1b that is associated with intellectual disability in humans specifically impairs cholesterol sensing. In addition, we identified another point mutation within this domain that enhances cholesterol sensitivity without altering its PS sensitivity. Cell-free reconstitution and cell-based assays revealed that the ability of the GRAM domain to sense accessible cholesterol regulates membrane tethering and determines the rate of cholesterol transport by GRAMD1b. Thus, cells detect the codistribution of accessible cholesterol and anionic lipids in the PM and fine-tune the non-vesicular transport of PM cholesterol to the ER via GRAMD1s.
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Affiliation(s)
- Bilge Ercan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
| | - Tomoki Naito
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
| | | | - Dennis Dharmawan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore.,Institute of Resource Development and Analysis, Kumamoto University, Kumamoto, Japan
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24
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Hewlett B, Singh NP, Vannier C, Galli T. ER-PM Contact Sites - SNARING Actors in Emerging Functions. Front Cell Dev Biol 2021; 9:635518. [PMID: 33681218 PMCID: PMC7928305 DOI: 10.3389/fcell.2021.635518] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 01/21/2021] [Indexed: 11/13/2022] Open
Abstract
The compartmentalisation achieved by confining cytoplasm into membrane-enclosed organelles in eukaryotic cells is essential for maintaining vital functions including ATP production, synthetic and degradative pathways. While intracellular organelles are highly specialised in these functions, the restricting membranes also impede exchange of molecules responsible for the synchronised and responsive cellular activities. The initial identification of contact sites between the ER and plasma membrane (PM) provided a potential candidate structure for communication between organelles without mixing by fusion. Over the past decades, research has revealed a far broader picture of the events. Membrane contact sites (MCSs) have been recognized as increasingly important actors in cell differentiation, plasticity and maintenance, and, upon dysfunction, responsible for pathological conditions such as cancer and neurodegenerative diseases. Present in multiple organelles and cell types, MCSs promote transport of lipids and Ca2+ homoeostasis, with a range of associated protein families. Interestingly, each MCS displays a unique molecular signature, adapted to organelle functions. This review will explore the literature describing the molecular components and interactions taking place at ER-PM contact sites, their functions, and implications in eukaryotic cells, particularly neurons, with emphasis on lipid transfer proteins and emerging function of SNAREs.
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Affiliation(s)
- Bailey Hewlett
- INSERM U1266, Institut de Psychiatrie et Neurosciences de Paris, Université de Paris, Paris, France
| | - Neha Pratap Singh
- INSERM U1266, Institut de Psychiatrie et Neurosciences de Paris, Université de Paris, Paris, France
| | - Christian Vannier
- INSERM U1266, Institut de Psychiatrie et Neurosciences de Paris, Université de Paris, Paris, France
| | - Thierry Galli
- INSERM U1266, Institut de Psychiatrie et Neurosciences de Paris, Université de Paris, Paris, France.,GHU PARIS Psychiatrie and Neurosciences, Paris, France
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25
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Zheng Koh DH, Saheki Y. Regulation of Plasma Membrane Sterol Homeostasis by Nonvesicular Lipid Transport. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2021; 4:25152564211042451. [PMID: 37366378 PMCID: PMC10259818 DOI: 10.1177/25152564211042451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
Sterol contributes to the structural integrity of cellular membranes and plays an important role in the regulation of cell signaling in eukaryotes. It is either produced in the endoplasmic reticulum or taken up from the extracellular environment. In most eukaryotic cells, however, the majority of sterol is enriched in the plasma membrane. Thus, the transport of sterol between the plasma membrane and other organelles, including the endoplasmic reticulum, is crucial for maintaining sterol homeostasis. While vesicular transport that relies on membrane budding and fusion reactions plays an important role in bulk sterol transport, this mode of transport is slow and non-selective. Growing evidence suggests a critical role of nonvesicular transport mediated by evolutionarily conserved families of lipid transfer proteins in more rapid and selective delivery of sterol. Some lipid transfer proteins act primarily at the sites of contacts formed between the endoplasmic reticulum and other organelles or the plasma membrane without membrane fusion. In this review, we describe the similarities and differences of sterol biosynthesis and uptake in mammals and yeast and discuss the role of their lipid transfer proteins in maintaining plasma membrane sterol homeostasis.
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Affiliation(s)
- Dylan Hong Zheng Koh
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore
- Institute of Resource Development and
Analysis, Kumamoto University, Kumamoto 860-0811, Japan
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26
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Zhu XM, Li L, Cai YY, Wu XY, Shi HB, Liang S, Qu YM, Naqvi NI, Del Poeta M, Dong B, Lin FC, Liu XH. A VASt-domain protein regulates autophagy, membrane tension, and sterol homeostasis in rice blast fungus. Autophagy 2020; 17:2939-2961. [PMID: 33176558 DOI: 10.1080/15548627.2020.1848129] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Sterols are a class of lipids critical for fundamental biological processes and membrane dynamics. These molecules are synthesized in the endoplasmic reticulum (ER) and are transported bi-directionally between the ER and plasma membrane (PM). However, the trafficking mechanism of sterols and their relationship with macroautophagy/autophagy are still poorly understood in the rice blast fungus Magnaporthe oryzae. Here, we identified the VAD1 Analog of StAR-related lipid transfer (VASt) domain-containing protein MoVast1 via co-immunoprecipitation in M. oryzae. Loss of MoVAST1 resulted in conidial defects, impaired appressorium development, and reduced pathogenicity. The MoTor (target of rapamycin in M. oryzae) activity is inhibited because MoVast1 deletion leads to high levels of sterol accumulation in the PM. Site-directed mutagenesis showed that the 902 T site is essential for localization and function of MoVast1. Through filipin or Flipper-TR staining, autophagic flux detection, MoAtg8 lipidation, and drug sensitivity assays, we uncovered that MoVast1 acts as a novel autophagy inhibition factor that monitors tension in the PM by regulating the sterol content, which in turn modulates the activity of MoTor. Lipidomics and transcriptomics analyses further confirmed that MoVast1 is an important regulator of lipid metabolism and the autophagy pathway. Our results revealed and characterized a novel sterol transfer protein important for M. oryzae pathogenicity.Abbreviations: AmB: amphotericin B; ATMT: Agrobacterium tumefaciens-mediated transformation; CM: complete medium; dpi: days post-inoculation; ER: endoplasmic reticulum; Flipper-TR: fluorescent lipid tension reporter; GO: Gene ontology; hpi: hours post-inoculation; IH: invasive hyphae; KEGG: kyoto encyclopedia of genes and genomes; MoTor: target of rapamycin in Magnaporthe oryzae; PalmC: palmitoylcarnitine; PM: plasma membrane; SD-N: synthetic defined medium without amino acids and ammonium sulfate; TOR: target of rapamycin; VASt: VAD1 Analog of StAR-related lipid transfer; YFP, yellow fluorescent protein.
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Affiliation(s)
- Xue-Ming Zhu
- St Ate Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University, Hangzhou, China.,State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Lin Li
- St Ate Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Ying-Ying Cai
- St Ate Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Xi-Yu Wu
- St Ate Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Huan-Bin Shi
- St Ate Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Shuang Liang
- St Ate Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Ying-Min Qu
- St Ate Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Naweed I Naqvi
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore
| | - Maurizio Del Poeta
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, New York, USA.,Division of Infectious Diseases, Stony Brook University, Stony Brook, New York, USA.,Veterans Affairs Medical Center, Northport, New York, USA
| | - Bo Dong
- Markey Cancer Center, University of Kentucky, College of Medicine, Lexington, KY, USA
| | - Fu-Cheng Lin
- St Ate Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University, Hangzhou, China.,State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Xiao-Hong Liu
- St Ate Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Institute of Biotechnology, Zhejiang University, Hangzhou, China
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27
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Topolska M, Roelants FM, Si EP, Thorner J. TORC2-Dependent Ypk1-Mediated Phosphorylation of Lam2/Ltc4 Disrupts Its Association with the β-Propeller Protein Laf1 at Endoplasmic Reticulum-Plasma Membrane Contact Sites in the Yeast Saccharomyces cerevisiae. Biomolecules 2020; 10:biom10121598. [PMID: 33255682 PMCID: PMC7760575 DOI: 10.3390/biom10121598] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 11/23/2020] [Accepted: 11/23/2020] [Indexed: 12/11/2022] Open
Abstract
Membrane-tethered sterol-binding Lam/Ltc proteins localize at junctions between the endoplasmic reticulum (ER) membrane and other organelles. Two of the six family members-Lam2/Ltc4 (initially Ysp2) and paralog Lam4/Ltc3-localize to ER-plasma membrane (PM) contact sites (CSs) and mediate retrograde ergosterol transport from the PM to the ER. Our prior work demonstrated that Lam2 and Lam4 are substrates of TORC2-regulated protein kinase Ypk1, that Ypk1-mediated phosphorylation inhibits their function in retrograde sterol transport, and that PM sterol retention bolsters cell survival under stressful conditions. At ER-PM CSs, Lam2 and Lam4 associate with Laf1/Ymr102c and Dgr2/Ykl121w (paralogous WD40 repeat-containing proteins) that reportedly bind sterol. Using fluorescent tags, we found that Lam2 and Lam4 remain at ER-PM CSs when Laf1 and Dgr2 are absent, whereas neither Laf1 nor Dgr2 remain at ER-PM CSs when Lam2 and Lam4 are absent. Loss of Laf1 (but not Dgr2) impedes retrograde ergosterol transport, and a laf1∆ mutation does not exacerbate the transport defect of lam2∆ lam4∆ cells, indicating a shared function. Lam2 and Lam4 bind Laf1 and Dgr2 in vitro in a pull-down assay, and the PH domain in Lam2 hinders its interaction with Laf1. Lam2 phosphorylated by Ypk1, and Lam2 with phosphomimetic (Glu) replacements at its Ypk1 sites, exhibited a marked reduction in Laf1 binding. Thus, phosphorylation prevents Lam2 interaction with Laf1 at ER-PM CSs, providing a mechanism by which Ypk1 action inhibits retrograde sterol transport.
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Affiliation(s)
- Magdalena Topolska
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; (M.T.); (F.M.R.); (E.P.S.)
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5000 Odense, Denmark
| | - Françoise M. Roelants
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; (M.T.); (F.M.R.); (E.P.S.)
| | - Edward P. Si
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; (M.T.); (F.M.R.); (E.P.S.)
- Eastern Virginia Medical School, P.O. Box 1980, Norfolk, VA 23501-1980, USA
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; (M.T.); (F.M.R.); (E.P.S.)
- Correspondence: ; Tel.: +1-510-642-2558; Fax: +1-510-642-6420
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28
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Kreimendahl S, Rassow J. The Mitochondrial Outer Membrane Protein Tom70-Mediator in Protein Traffic, Membrane Contact Sites and Innate Immunity. Int J Mol Sci 2020; 21:E7262. [PMID: 33019591 PMCID: PMC7583919 DOI: 10.3390/ijms21197262] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 09/25/2020] [Accepted: 09/28/2020] [Indexed: 02/08/2023] Open
Abstract
Tom70 is a versatile adaptor protein of 70 kDa anchored in the outer membrane of mitochondria in metazoa, fungi and amoeba. The tertiary structure was resolved for the Tom70 of yeast, showing 26 α-helices, most of them participating in the formation of 11 tetratricopeptide repeat (TPR) motifs. Tom70 serves as a docking site for cytosolic chaperone proteins and co-chaperones and is thereby involved in the uptake of newly synthesized chaperone-bound proteins in mitochondrial biogenesis. In yeast, Tom70 additionally mediates ER-mitochondria contacts via binding to sterol transporter Lam6/Ltc1. In mammalian cells, TOM70 promotes endoplasmic reticulum (ER) to mitochondria Ca2+ transfer by association with the inositol-1,4,5-triphosphate receptor type 3 (IP3R3). TOM70 is specifically targeted by the Bcl-2-related protein MCL-1 that acts as an anti-apoptotic protein in macrophages infected by intracellular pathogens, but also in many cancer cells. By participating in the recruitment of PINK1 and the E3 ubiquitin ligase Parkin, TOM70 can be implicated in the development of Parkinson's disease. TOM70 acts as receptor of the mitochondrial antiviral-signaling protein (MAVS) and thereby participates in the corresponding system of innate immunity against viral infections. The protein encoded by Orf9b in the genome of SARS-CoV-2 binds to TOM70, probably compromising the synthesis of type I interferons.
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Affiliation(s)
| | - Joachim Rassow
- Institute for Biochemistry and Pathobiochemistry, Ruhr-University Bochum, 44801 Bochum, Germany;
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29
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Garten M, Beck JR, Roth R, Tenkova-Heuser T, Heuser J, Istvan ES, Bleck CKE, Goldberg DE, Zimmerberg J. Contacting domains segregate a lipid transporter from a solute transporter in the malarial host-parasite interface. Nat Commun 2020; 11:3825. [PMID: 32732874 PMCID: PMC7393353 DOI: 10.1038/s41467-020-17506-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 06/30/2020] [Indexed: 12/18/2022] Open
Abstract
The malaria parasite interfaces with its host erythrocyte (RBC) using a unique organelle, the parasitophorous vacuole (PV). The mechanism(s) are obscure by which its limiting membrane, the parasitophorous vacuolar membrane (PVM), collaborates with the parasite plasma membrane (PPM) to support the transport of proteins, lipids, nutrients, and metabolites between the cytoplasm of the parasite and the cytoplasm of the RBC. Here, we demonstrate that the PV has structure characterized by micrometer-sized regions of especially close apposition between the PVM and the PPM. To determine if these contact sites are involved in any sort of transport, we localize the PVM nutrient-permeable and protein export channel EXP2, as well as the PPM lipid transporter PfNCR1. We find that EXP2 is excluded from, but PfNCR1 is included within these regions of close apposition. We conclude that the host-parasite interface is structured to segregate those transporters of hydrophilic and hydrophobic substrates.
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Affiliation(s)
- Matthias Garten
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Josh R Beck
- Department of Biomedical Sciences, Iowa State University, Ames, IA, 50011, USA
| | - Robyn Roth
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Tatyana Tenkova-Heuser
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - John Heuser
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Eva S Istvan
- Departments of Medicine and Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Christopher K E Bleck
- Electron Microscopy Core Facility, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Daniel E Goldberg
- Departments of Medicine and Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
| | - Joshua Zimmerberg
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA.
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30
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Zaman MF, Nenadic A, Radojičić A, Rosado A, Beh CT. Sticking With It: ER-PM Membrane Contact Sites as a Coordinating Nexus for Regulating Lipids and Proteins at the Cell Cortex. Front Cell Dev Biol 2020; 8:675. [PMID: 32793605 PMCID: PMC7387695 DOI: 10.3389/fcell.2020.00675] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 07/03/2020] [Indexed: 12/31/2022] Open
Abstract
Membrane contact sites between the cortical endoplasmic reticulum (ER) and the plasma membrane (PM) provide a direct conduit for small molecule transfer and signaling between the two largest membranes of the cell. Contact is established through ER integral membrane proteins that physically tether the two membranes together, though the general mechanism is remarkably non-specific given the diversity of different tethering proteins. Primary tethers including VAMP-associated proteins (VAPs), Anoctamin/TMEM16/Ist2p homologs, and extended synaptotagmins (E-Syts), are largely conserved in most eukaryotes and are both necessary and sufficient for establishing ER-PM association. In addition, other species-specific ER-PM tether proteins impart unique functional attributes to both membranes at the cell cortex. This review distils recent functional and structural findings about conserved and species-specific tethers that form ER-PM contact sites, with an emphasis on their roles in the coordinate regulation of lipid metabolism, cellular structure, and responses to membrane stress.
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Affiliation(s)
- Mohammad F Zaman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Aleksa Nenadic
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Ana Radojičić
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,Department of Botany, University of British Columbia, Vancouver, BC, Canada
| | - Abel Rosado
- Department of Botany, University of British Columbia, Vancouver, BC, Canada
| | - Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,The Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, BC, Canada
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31
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Athanasopoulos A, André B, Sophianopoulou V, Gournas C. Fungal plasma membrane domains. FEMS Microbiol Rev 2020; 43:642-673. [PMID: 31504467 DOI: 10.1093/femsre/fuz022] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/25/2019] [Indexed: 12/11/2022] Open
Abstract
The plasma membrane (PM) performs a plethora of physiological processes, the coordination of which requires spatial and temporal organization into specialized domains of different sizes, stability, protein/lipid composition and overall architecture. Compartmentalization of the PM has been particularly well studied in the yeast Saccharomyces cerevisiae, where five non-overlapping domains have been described: The Membrane Compartments containing the arginine permease Can1 (MCC), the H+-ATPase Pma1 (MCP), the TORC2 kinase (MCT), the sterol transporters Ltc3/4 (MCL), and the cell wall stress mechanosensor Wsc1 (MCW). Additional cortical foci at the fungal PM are the sites where clathrin-dependent endocytosis occurs, the sites where the external pH sensing complex PAL/Rim localizes, and sterol-rich domains found in apically grown regions of fungal membranes. In this review, we summarize knowledge from several fungal species regarding the organization of the lateral PM segregation. We discuss the mechanisms of formation of these domains, and the mechanisms of partitioning of proteins there. Finally, we discuss the physiological roles of the best-known membrane compartments, including the regulation of membrane and cell wall homeostasis, apical growth of fungal cells and the newly emerging role of MCCs as starvation-protective membrane domains.
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Affiliation(s)
- Alexandros Athanasopoulos
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
| | - Bruno André
- Molecular Physiology of the Cell laboratory, Université Libre de Bruxelles (ULB), Institut de Biologie et de Médecine Moléculaires, rue des Pr Jeener et Brachet 12, 6041, Gosselies, Belgium
| | - Vicky Sophianopoulou
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
| | - Christos Gournas
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
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32
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Marek M, Vincenzetti V, Martin SG. Sterol biosensor reveals LAM-family Ltc1-dependent sterol flow to endosomes upon Arp2/3 inhibition. J Cell Biol 2020; 219:e202001147. [PMID: 32320462 PMCID: PMC7265315 DOI: 10.1083/jcb.202001147] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 03/03/2020] [Accepted: 03/04/2020] [Indexed: 01/01/2023] Open
Abstract
Sterols are crucial components of biological membranes, which are synthetized in the ER and accumulate in the plasma membrane (PM). Here, by applying a genetically encoded sterol biosensor (D4H), we visualize a sterol flow between PM and endosomes in the fission yeast Schizosaccharomyces pombe. Using time-lapse and correlative light-electron microscopy, we found that inhibition of Arp2/3-dependent F-actin assembly promotes the reversible relocalization of D4H from the PM to internal sterol-rich compartments (STRIC) labeled by synaptobrevin Syb1. Retrograde sterol internalization to STRIC is independent of endocytosis or an intact Golgi, but depends on Ltc1, a LAM/StARkin-family protein localized to ER-PM contact sites. The PM in ltc1Δ cells over-accumulates sterols and upon Arp2/3 inhibition forms extended ER-interacting invaginations, indicating that sterol transfer contributes to PM size homeostasis. Anterograde sterol movement from STRIC is independent of canonical vesicular trafficking but requires Arp2/3, suggesting a novel role for this complex. Thus, transfer routes orthogonal to vesicular trafficking govern the flow of sterols in the cell.
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Affiliation(s)
| | | | - Sophie G. Martin
- Department of Fundamental Microbiology, University of Lausanne, Switzerland
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33
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Balla T, Kim YJ, Alvarez-Prats A, Pemberton J. Lipid Dynamics at Contact Sites Between the Endoplasmic Reticulum and Other Organelles. Annu Rev Cell Dev Biol 2020; 35:85-109. [PMID: 31590585 DOI: 10.1146/annurev-cellbio-100818-125251] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Phospholipids are synthesized primarily within the endoplasmic reticulum and are subsequently distributed to various subcellular membranes to maintain the unique lipid composition of specific organelles. As a result, in most cases, the steady-state localization of membrane phospholipids does not match their site of synthesis. This raises the question of how diverse lipid species reach their final membrane destinations and what molecular processes provide the energy to maintain the lipid gradients that exist between various membrane compartments. Recent studies have highlighted the role of inositol phospholipids in the nonvesicular transport of lipids at membrane contact sites. This review attempts to summarize our current understanding of these complex lipid dynamics and highlights their implications for defining future research directions.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Yeun Ju Kim
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Alejandro Alvarez-Prats
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Joshua Pemberton
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA;
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34
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Mycobacterium smegmatis MSMEG_0129 is a nutrition-associated regulator that interacts with CarD and ClpP2. Int J Biochem Cell Biol 2020; 124:105763. [PMID: 32389745 DOI: 10.1016/j.biocel.2020.105763] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 04/14/2020] [Accepted: 04/29/2020] [Indexed: 12/16/2022]
Abstract
Mycobacterium smegmatis MSMEG_0129 and Rv0164, its homologue in Mycobacterium tuberculosis, are single START-domain proteins essential for bacterial growth and survival, but their biochemical activities and biological roles remain undetermined. Here, we probed the possible functions of MSMEG_0129 and its underlying mechanisms by determining its cellular location, searching for its interaction partners and monitoring its transcription profile. MSMEG_0129, and Rv0164 by extension, were found to be cytosolic proteins rather than secreted components as previously understood. Increases in MSMEG_0129 expression at physiological levels accelerated bacterial growth in a proportional manner, but additional growth acceleration was not observed when MSMEG_0129 was overexpressed up to 20 fold. MSMEG_0129 is a short-lived protein, unstable at both the mRNA and protein levels. Co-IP and GST pull-down assays showed that MSMEG_0129 interacts with the ClpP2 protease and a global transcription factor, CarD, their expression being correlated with that of MSMEG_0129. Nutrient deficiency led to the downregulation of MSMEG_0129 but upregulation of CarD. However, in the context of constitutive MSMEG_0129 overexpression under nutrient-rich or starvation conditions, the mRNA level of CarD was reduced 3 fold. Conversely, expression of ClpP2 decreased with MSMEG_0129 downregulation under starvation conditions, but increased 4-8 fold when MSMEG_0129 was overexpressed. Our data suggest that MSMEG_0129, and Rv0164 by analogy, are likely to be nutrition sensing factors that regulate mycobacterial growth and may be involved in signal transfer under nutrient deficiency, possibly via physical and regulatory interactions with CarD and ClpP2.
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35
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Moesgaard L, Reinholdt P, Wüstner D, Kongsted J. Modeling the Sterol-Binding Domain of Aster-A Provides Insight into Its Multiligand Specificity. J Chem Inf Model 2020; 60:2268-2281. [PMID: 32233488 DOI: 10.1021/acs.jcim.0c00086] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Intracellular transport of cholesterol and related sterols relies to a large degree on nonvesicular mechanisms, which are only partly understood at the molecular level. Aster proteins belonging to the Lam family of sterol transfer proteins have recently been identified as important catalysts of nonvesicular sterol exchange between the plasma membrane (PM) and endoplasmic reticulum (ER). Here, we used a range of computational tools to study the molecular mechanisms underlying sterol binding as well as multisterol ligand specificity of Aster-A. Our study focused primarily on gaining atomistic insight into the bound ligand-protein complex and was, on this basis, performed in the absence of any membrane. Molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) calculations provide a rationale for the experimentally found ranking of binding affinities of various sterols to Aster-A. In particular, the polarity of the sterols and the length of their alkyl chain could be identified as being critical determinants of ligand affinity. A Gibbs free energy decomposition identified a charged residue, Glu444, at the base of the binding pose as an important control point for sterol binding. Removing its net charge via protonation was found to cause significant changes to the environment surrounding this residue. In addition, the protonation of Glu444 was found to be paralleled by a large redistribution of molecular flexibility in the Aster domain. This finding was supplemented by multiple branched adaptive steered molecular dynamics (MB-ASMD) simulations by which we defined a possible molecular path for sterol release and demonstrated the importance of Glu444 in this process.
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Affiliation(s)
- Laust Moesgaard
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Peter Reinholdt
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
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36
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Meng Y, Heybrock S, Neculai D, Saftig P. Cholesterol Handling in Lysosomes and Beyond. Trends Cell Biol 2020; 30:452-466. [PMID: 32413315 DOI: 10.1016/j.tcb.2020.02.007] [Citation(s) in RCA: 81] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 02/14/2020] [Accepted: 02/21/2020] [Indexed: 01/06/2023]
Abstract
Lysosomes are of major importance for the regulation of cellular cholesterol homeostasis. Food-derived cholesterol and cholesterol esters contained within lipoproteins are delivered to lysosomes by endocytosis. From the lysosomal lumen, cholesterol is transported to the inner surface of the lysosomal membrane through the glycocalyx; this shuttling requires Niemann-Pick C (NPC) 1 and NPC2 proteins. The lysosomal membrane proteins lysosomal-associated membrane protein (LAMP)-2 and lysosomal integral membrane protein (LIMP)-2/SCARB2 also bind cholesterol. LAMP-2 may serve as a cholesterol reservoir, whereas LIMP-2, like NPC1, is able to transport cholesterol through a transglycocalyx tunnel. Contact sites and fusion events between lysosomes and other organelles mediate the distribution of cholesterol. Lysosomal cholesterol content is sensed thereby regulating mammalian target of rapamycin complex (mTORC)-dependent signaling. This review summarizes our understanding of the major steps in cholesterol handling from the moment it enters the lysosome until it leaves this compartment.
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Affiliation(s)
- Ying Meng
- Department of Cell Biology, School of Basic Medical Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Saskia Heybrock
- Biochemisches Institut, Christian-Albrechts-Universität Kiel, Kiel, Germany
| | - Dante Neculai
- Department of Cell Biology, School of Basic Medical Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Paul Saftig
- Biochemisches Institut, Christian-Albrechts-Universität Kiel, Kiel, Germany.
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37
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Inter-organelle lipid transfer: a channel model for Vps13 and chorein-N motif proteins. Curr Opin Cell Biol 2020; 65:66-71. [PMID: 32213462 DOI: 10.1016/j.ceb.2020.02.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/10/2020] [Accepted: 02/15/2020] [Indexed: 12/11/2022]
Abstract
Membrane contact sites, where two organelles are in close proximity, are critical regulators of cellular membrane homeostasis, with roles in signaling, lipid metabolism, and ion dynamics. A growing catalog of specialized lipid transfer proteins carry out lipid exchange at these sites. Currently characterized eukaryotic lipid transport proteins are shuttles that typically extract a single lipid from the membrane of the donor organelle, solubilize it during transport through the cytosol, and deposit it in the acceptor organelle membrane. Here, we highlight the recently identified chorein_N family of lipid transporters, including the Vps13 proteins and the autophagy protein Atg2. These are elongated proteins that, distinct from previously characterized transport proteins, bind tens of lipids at once. They feature an extended channel, most likely lined with hydrophobic residues. We discuss the possibility that they are not shuttles but instead are bridges between membranes, with lipids traversing the cytosol via the hydrophobic channel.
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38
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Clark BJ. The START-domain proteins in intracellular lipid transport and beyond. Mol Cell Endocrinol 2020; 504:110704. [PMID: 31927098 DOI: 10.1016/j.mce.2020.110704] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 01/08/2020] [Accepted: 01/08/2020] [Indexed: 12/17/2022]
Abstract
The Steroidogenic Acute Regulatory Protein-related Lipid Transfer (START) domain is a ~210 amino acid sequence that folds into an α/β helix-grip structure forming a hydrophobic pocket for lipid binding. The helix-grip fold structure defines a large superfamily of proteins, and this review focuses on the mammalian START domain family members that include single START domain proteins with identified ligands, and larger multi-domain proteins that may have novel roles in metabolism. Much of our understanding of the mammalian START domain proteins in lipid transport and changes in metabolism has advanced through studies using knockout mouse models, although for some of these proteins the identity and/or physiological role of ligand binding remains unknown. The findings that helped define START domain lipid-binding specificity, lipid transport, and changes in metabolism are presented to highlight that fundamental questions remain regarding the biological function(s) for START domain-containing proteins.
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Affiliation(s)
- Barbara J Clark
- Department of Biochemistry & Molecular Genetics, University of Louisville School of Medicine, Louisville, KY, 40292, USA.
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39
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Sokolov SS, Vorobeva MA, Smirnova AI, Smirnova EA, Trushina NI, Galkina KV, Severin FF, Knorre DA. LAM Genes Contribute to Environmental Stress Tolerance but Sensibilize Yeast Cells to Azoles. Front Microbiol 2020; 11:38. [PMID: 32047490 PMCID: PMC6997477 DOI: 10.3389/fmicb.2020.00038] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 01/09/2020] [Indexed: 11/25/2022] Open
Abstract
Lam proteins transport sterols between the membranes of different cellular compartments. In Saccharomyces cerevisiae, the LAM gene family consists of three pairs of paralogs. Because the function of paralogous genes can be redundant, the phenotypes of only a small number of LAM gene deletions have been reported; thus, the role of these genes in yeast physiology is still unclear. Here, we surveyed the phenotypes of double and quadruple deletants of paralogous LAM2(YSP2)/LAM4 and LAM1(YSP1)/LAM3(SIP3) genes that encode proteins localized in the junctions of the plasma membrane and endoplasmic reticulum. The quadruple deletant showed increased sterol content and a strong decrease in ethanol, heat shock and high osmolarity resistance. Surprisingly, the quadruple deletant and LAM2/LAM4 double deletion strain showed increased tolerance to the azole antifungals clotrimazole and miconazole. This effect was not associated with an increased rate of ABC-transporter substrate efflux. Possibly, increased sterol pool in the LAM deletion strains postpones the effect of azoles on cell growth. Alternatively, LAM deletions might alleviate the toxic effect of sterols as Lam proteins can transport toxic sterol biosynthesis intermediates into membrane compartments that are sensitive to these compounds. Our findings reveal novel biological roles of LAM genes in stress tolerance and suggest that mutations in these genes may confer upregulation of a mechanism that provides resistance to azole antifungals in pathogenic fungi.
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Affiliation(s)
- Svyatoslav S Sokolov
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Margarita A Vorobeva
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia
| | - Alexandra I Smirnova
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia
| | - Ekaterina A Smirnova
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Nataliya I Trushina
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Department of Neurobiology, University of Osnabrück, Osnabrück, Germany
| | - Kseniia V Galkina
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia
| | - Fedor F Severin
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Dmitry A Knorre
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Institute of Molecular Medicine, Sechenov First Moscow State Medical University, Moscow, Russia
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40
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Chauhan N, Sere YY, Sokol AM, Graumann J, Menon AK. A PhotoClick cholesterol‐based quantitative proteomics screen for cytoplasmic sterol‐binding proteins in
Saccharomyces cerevisiae. Yeast 2020; 37:15-25. [DOI: 10.1002/yea.3448] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 10/30/2019] [Accepted: 11/15/2019] [Indexed: 02/02/2023] Open
Affiliation(s)
- Neha Chauhan
- Department of Biochemistry Weill Cornell Medical College 1300 York Ave. New York NY 10065 USA
| | - Yves Y. Sere
- Department of Biochemistry Weill Cornell Medical College 1300 York Ave. New York NY 10065 USA
| | - Anna M. Sokol
- Biomolecular Mass Spectrometry Max Planck Institute for Heart and Lung Research, W.G. Kerckhoff Institute Ludwigstr. 43 Bad Nauheim Germany
- Biomolecular Mass Spectrometry German Centre for Cardiovascular Research (DZHK), Rhine‐Main site Bad Nauheim Germany
| | - Johannes Graumann
- Biomolecular Mass Spectrometry Max Planck Institute for Heart and Lung Research, W.G. Kerckhoff Institute Ludwigstr. 43 Bad Nauheim Germany
- Biomolecular Mass Spectrometry German Centre for Cardiovascular Research (DZHK), Rhine‐Main site Bad Nauheim Germany
| | - Anant K. Menon
- Department of Biochemistry Weill Cornell Medical College 1300 York Ave. New York NY 10065 USA
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41
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Khelashvili G, Chauhan N, Pandey K, Eliezer D, Menon AK. Exchange of water for sterol underlies sterol egress from a StARkin domain. eLife 2019; 8:53444. [PMID: 31799930 PMCID: PMC6940019 DOI: 10.7554/elife.53444] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 11/29/2019] [Indexed: 12/18/2022] Open
Abstract
Previously we identified Lam/GramD1 proteins, a family of endoplasmic reticulum membrane proteins with sterol-binding StARkin domains that are implicated in intracellular sterol homeostasis. Here, we show how these proteins exchange sterol molecules with membranes. An aperture at one end of the StARkin domain enables sterol to enter/exit the binding pocket. Strikingly, the wall of the pocket is longitudinally fractured, exposing bound sterol to solvent. Large-scale atomistic molecular dynamics simulations reveal that sterol egress involves widening of the fracture, penetration of water into the cavity, and consequent destabilization of the bound sterol. The simulations identify polar residues along the fracture that are important for sterol release. Their replacement with alanine affects the ability of the StARkin domain to bind sterol, catalyze inter-vesicular sterol exchange and alleviate the nystatin-sensitivity of lam2Δ yeast cells. These data suggest an unprecedented, water-controlled mechanism of sterol discharge from a StARkin domain.
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Affiliation(s)
- George Khelashvili
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, United States.,Institute for Computational Biomedicine, Weill Cornell Medical College, New York, United States
| | - Neha Chauhan
- Department of Biochemistry, Weill Cornell Medical College, New York, United States
| | - Kalpana Pandey
- Department of Biochemistry, Weill Cornell Medical College, New York, United States
| | - David Eliezer
- Department of Biochemistry, Weill Cornell Medical College, New York, United States
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, United States
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42
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Naito T, Ercan B, Krshnan L, Triebl A, Koh DHZ, Wei FY, Tomizawa K, Torta FT, Wenk MR, Saheki Y. Movement of accessible plasma membrane cholesterol by the GRAMD1 lipid transfer protein complex. eLife 2019; 8:51401. [PMID: 31724953 PMCID: PMC6905856 DOI: 10.7554/elife.51401] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 11/13/2019] [Indexed: 12/18/2022] Open
Abstract
Cholesterol is a major structural component of the plasma membrane (PM). The majority of PM cholesterol forms complexes with other PM lipids, making it inaccessible for intracellular transport. Transition of PM cholesterol between accessible and inaccessible pools maintains cellular homeostasis, but how cells monitor the accessibility of PM cholesterol remains unclear. We show that endoplasmic reticulum (ER)-anchored lipid transfer proteins, the GRAMD1s, sense and transport accessible PM cholesterol to the ER. GRAMD1s bind to one another and populate ER-PM contacts by sensing a transient expansion of the accessible pool of PM cholesterol via their GRAM domains. They then facilitate the transport of this cholesterol via their StART-like domains. Cells that lack all three GRAMD1s exhibit striking expansion of the accessible pool of PM cholesterol as a result of less efficient PM to ER transport of accessible cholesterol. Thus, GRAMD1s facilitate the movement of accessible PM cholesterol to the ER in order to counteract an acute increase of PM cholesterol, thereby activating non-vesicular cholesterol transport. The human body contains trillions of cells. At the outer edge of each cell is the plasma membrane, which protects the cell from the external environment. This membrane is mostly made of fatty molecules known as lipids and about half of these lipids are specifically cholesterol. Human cells can either take up cholesterol that were obtained via the diet or produce it within a compartment of the cell called the endoplasmic reticulum. Cells need to monitor the cholesterol levels in both the endoplasmic reticulum and the plasma membrane in order to regulate the uptake or production of this lipid. For example, if there is too much of cholesterol in the plasma membrane, then the cell transports some to the endoplasmic reticulum to tell it to shut down cholesterol production. However, how these different areas of the cell communicate with each other, and transport cholesterol, has remained unclear. Naito et al. set out to look for key regulators of cholesterol transport and identified a group of endoplasmic reticulum proteins called GRAMD1 proteins. Cholesterol in the plasma membrane is either accessible or inaccessible, meaning it either can or cannot be moved back into the cell. The GRAMD1 proteins sense accessible cholesterol, and experiments with human cells grown in the laboratory showed that, specifically, the GRAMD1 proteins work together in a complex to sense accessible cholesterol at or near the plasma membrane. One particular part of the protein senses when the amount of accessible cholesterol reaches a certain level at the plasma membrane; when this threshold is reached, the complex flips a switch to start the transport of cholesterol to the endoplasmic reticulum and tell it to shut down cholesterol production. This coupling of sensing and transporting lipids by one protein complex also helps maintain the right ratio of accessible and inaccessible cholesterol in the plasma membrane to prevent cells from activating unwanted cell-signaling events. Getting rid of the GRAMD1 proteins in cells, or removing sensing part of these proteins, leads to inefficient transport of cholesterol. A better understanding of how GRAMD1 proteins sense the accessibility of cholesterol could potentially help identify new approaches to control cholesterol transport inside cells. This may in turn eventually lead to new treatments that counteract the defects in cholesterol metabolism seen in some forms of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease.
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Affiliation(s)
- Tomoki Naito
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Bilge Ercan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Logesvaran Krshnan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Alexander Triebl
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Dylan Hong Zheng Koh
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Fan-Yan Wei
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Federico Tesio Torta
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Markus R Wenk
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.,Institute of Resource Development and Analysis, Kumamoto University, Kumamoto, Japan
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43
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Tan L, Tong J, Chun C, Im YJ. Structural analysis of human sterol transfer protein STARD4. Biochem Biophys Res Commun 2019; 520:466-472. [PMID: 31607485 DOI: 10.1016/j.bbrc.2019.10.054] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Accepted: 10/04/2019] [Indexed: 10/25/2022]
Abstract
The steroidogenic acute regulatory protein (StAR)-related lipid transfer domain-4 (STARD4) is a sterol-binding protein that is involved in cholesterol homeostasis by intracellular sterol transport. In this work, we determined the crystal structures of human STARD4 and its Ω1-loop mutant in apo forms at 1.95 and 1.7 Å resolutions, respectively. The structure of human STARD4 displays a conserved α-helix/β-grip fold containing a deep hydrophobic pocket. The Ω1-loop which serves as a lid for the hydrophobic pocket has a closed conformation. The shape of the sterol-binding cavity in the closed form is not complementary to accommodate cholesterol, suggesting that a conformational change of the Ω1-loop is essential for sterol binding. The human STARD4 displayed sterol transfer activity between liposomes, and the mutations in the Ω1-loop and the hydrophobic wall abolished the transfer activity. This study confirms the structural conservation of the STARD4 subfamily proteins and the flexibility of the Ω1-loop and helix α4 required for sterol transport.
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Affiliation(s)
- Lingchen Tan
- College of Pharmacy, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju, 61186, South Korea
| | - Junsen Tong
- College of Pharmacy, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju, 61186, South Korea
| | - ChangJu Chun
- College of Pharmacy, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju, 61186, South Korea.
| | - Young Jun Im
- College of Pharmacy, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju, 61186, South Korea.
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44
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Abstract
Cholesterol homeostasis is of central importance for life. Therefore, cells have developed a divergent set of pathways to meet their cholesterol needs. In this review, we focus on the direct transfer of cholesterol from lipoprotein particles to the cell membrane. More molecular details on the transfer of lipoprotein-derived lipids were gained by recent studies using phospholipid bilayers. While amphiphilic lipids are transferred right after contact of the lipoprotein particle with the membrane, the transfer of core lipids is restricted. Amphiphilic lipid transfer gains special importance in genetic diseases impairing lipoprotein metabolism like familial hypercholesterolemia. Taken together, these data indicate that there is a constant exchange of amphiphilic lipids between lipoprotein particles and the cell membrane.
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45
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NPC1 regulates ER contacts with endocytic organelles to mediate cholesterol egress. Nat Commun 2019; 10:4276. [PMID: 31537798 PMCID: PMC6753064 DOI: 10.1038/s41467-019-12152-2] [Citation(s) in RCA: 159] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 08/19/2019] [Indexed: 12/19/2022] Open
Abstract
Transport of dietary cholesterol from endocytic organelles to the endoplasmic reticulum (ER) is essential for cholesterol homoeostasis, but the mechanism and regulation of this transport remains poorly defined. Membrane contact sites (MCS), microdomains of close membrane apposition, are gaining attention as important platforms for non-vesicular, inter-organellar communication. Here we investigate the impact of ER-endocytic organelle MCS on cholesterol transport. We report a role for Niemann-Pick type C protein 1 (NPC1) in tethering ER-endocytic organelle MCS where it interacts with the ER-localised sterol transport protein Gramd1b to regulate cholesterol egress. We show that artificially tethering MCS rescues the cholesterol accumulation that characterises NPC1-deficient cells, consistent with direct lysosome to ER cholesterol transport across MCS. Finally, we identify an expanded population of lysosome-mitochondria MCS in cells depleted of NPC1 or Gramd1b that is dependent on the late endosomal sterol-binding protein STARD3, likely underlying the mitochondrial cholesterol accumulation in NPC1-deficient cells. Though endocytosed dietary cholesterol is transferred to the endoplasmic reticulum (ER), how this is regulated is unclear. Here, the authors report a role for Niemann-Pick Type C Protein 1 (NPC1) in tethering endocytic organelles to the ER, which may contribute to interorganelle cholesterol transport.
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46
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Steady state analysis of influx and transbilayer distribution of ergosterol in the yeast plasma membrane. Theor Biol Med Model 2019; 16:13. [PMID: 31412941 PMCID: PMC6694696 DOI: 10.1186/s12976-019-0108-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 07/15/2019] [Indexed: 01/05/2023] Open
Abstract
Background The transbilayer sterol distribution between both plasma membrane (PM) leaflets has long been debated. Recent studies in mammalian cells and in yeast show that the majority of sterol resides in the inner PM leaflet. Since sterol flip-flop in model membranes is rapid and energy-independent, a mechanistic understanding for net enrichment of sterol in one leaflet is lacking. Import of ergosterol in yeast can take place via the ABC transporters Aus1/Pdr11 under anaerobic growth conditions, eventually followed by rapid non-vesicular sterol transport to the endoplasmic reticulum (ER). Little is known about how these transport steps are dynamically coordinated. Methods Here, a kinetic steady state model is presented which considers sterol import via Aus1/Pdr11, sterol flip-flop across the PM, bi-molecular complex formation and intracellular sterol release followed by eventual transport to and esterification of sterol in the ER. The steady state flux is calculated, and a thermodynamic analysis of feasibility is presented. Results It is shown that the steady state sterol flux across the PM can be entirely controlled by irreversible sterol import via Aus1/Pdr11. The transbilayer sterol flux at steady state is a non-linear function of the chemical potential difference of sterol between both leaflets. Non-vesicular release of sterol on the cytoplasmic side of the PM lowers the attainable sterol enrichment in the inner leaflet. Including complex formation of sterol with phospholipids or proteins can explain several puzzling experimental observations; 1) rapid sterol flip-flop across the PM despite net sterol enrichment in one leaflet, 2) a pronounced steady state sterol gradient between PM and ER despite fast non-vesicular sterol exchange between both compartments and 3) a non-linear dependence of ER sterol on ergosterol abundance in the PM. Conclusions A steady state model is presented that can account for the observed sterol asymmetry in the yeast PM, the strong sterol gradient between PM and ER and threshold-like expansion of ER sterol for increasing sterol influx into the PM. The model also provides new insight into selective uptake of cholesterol and its homeostasis in mammalian cells, and it provides testable predictions for future experiments.
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47
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And three’s a party: lysosomes, lipid droplets, and the ER in lipid trafficking and cell homeostasis. Curr Opin Cell Biol 2019; 59:40-49. [DOI: 10.1016/j.ceb.2019.02.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 02/12/2019] [Accepted: 02/26/2019] [Indexed: 01/22/2023]
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48
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Nishimura T, Stefan CJ. Specialized ER membrane domains for lipid metabolism and transport. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158492. [PMID: 31349025 DOI: 10.1016/j.bbalip.2019.07.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 07/02/2019] [Accepted: 07/03/2019] [Indexed: 11/15/2022]
Abstract
The endoplasmic reticulum (ER) is a highly organized organelle that performs vital functions including de novo membrane lipid synthesis and transport. Accordingly, numerous lipid biosynthesis enzymes are localized in the ER membrane. However, it is now evident that lipid metabolism is sub-compartmentalized within the ER and that lipid biosynthetic enzymes engage with lipid transfer proteins (LTPs) to rapidly shuttle newly synthesized lipids from the ER to other organelles. As such, intimate relationships between lipid metabolism and lipid transfer pathways exist within the ER network. Notably, certain LTPs enhance the activities of lipid metabolizing enzymes; likewise, lipid metabolism can ensure the specificity of LTP transfer/exchange reactions. Yet, our understanding of these mutual relationships is still emerging. Here, we highlight past and recent key findings on specialized ER membrane domains involved in efficient lipid metabolism and transport and consider unresolved issues in the field.
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Affiliation(s)
- Taki Nishimura
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK.
| | - Christopher J Stefan
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK.
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49
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Laraia L, Friese A, Corkery DP, Konstantinidis G, Erwin N, Hofer W, Karatas H, Klewer L, Brockmeyer A, Metz M, Schölermann B, Dwivedi M, Li L, Rios-Munoz P, Köhn M, Winter R, Vetter IR, Ziegler S, Janning P, Wu YW, Waldmann H. The cholesterol transfer protein GRAMD1A regulates autophagosome biogenesis. Nat Chem Biol 2019; 15:710-720. [PMID: 31222192 DOI: 10.1038/s41589-019-0307-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 05/10/2019] [Indexed: 12/14/2022]
Abstract
Autophagy mediates the degradation of damaged proteins, organelles and pathogens, and plays a key role in health and disease. Thus, the identification of new mechanisms involved in the regulation of autophagy is of major interest. In particular, little is known about the role of lipids and lipid-binding proteins in the early steps of autophagosome biogenesis. Using target-agnostic, high-content, image-based identification of indicative phenotypic changes induced by small molecules, we have identified autogramins as a new class of autophagy inhibitor. Autogramins selectively target the recently discovered cholesterol transfer protein GRAM domain-containing protein 1A (GRAMD1A, which had not previously been implicated in autophagy), and directly compete with cholesterol binding to the GRAMD1A StART domain. GRAMD1A accumulates at sites of autophagosome initiation, affects cholesterol distribution in response to starvation and is required for autophagosome biogenesis. These findings identify a new biological function of GRAMD1A and a new role for cholesterol in autophagy.
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Affiliation(s)
- Luca Laraia
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.,Department of Chemistry, Technical University of Denmark, Lyngby, Denmark
| | - Alexandra Friese
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Dale P Corkery
- Chemical Genomics Centre of the Max Planck Society, Dortmund, Germany.,Department of Chemistry, Umeå University, Umeå, Sweden
| | - Georgios Konstantinidis
- Chemical Genomics Centre of the Max Planck Society, Dortmund, Germany.,Department of Chemistry, Umeå University, Umeå, Sweden
| | - Nelli Erwin
- Faculty of Chemistry and Chemical Biology, Technical University Dortmund, Dortmund, Germany
| | - Walter Hofer
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Hacer Karatas
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Laura Klewer
- Chemical Genomics Centre of the Max Planck Society, Dortmund, Germany
| | - Andreas Brockmeyer
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Malte Metz
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Beate Schölermann
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Mridula Dwivedi
- Faculty of Chemistry and Chemical Biology, Technical University Dortmund, Dortmund, Germany
| | - Lei Li
- Faculty of Chemistry and Chemical Biology, Technical University Dortmund, Dortmund, Germany
| | - Pablo Rios-Munoz
- Centre for Biological Signalling Studies (BIOSS), University of Freiburg, Freiburg, Germany.,Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Maja Köhn
- Centre for Biological Signalling Studies (BIOSS), University of Freiburg, Freiburg, Germany.,Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Roland Winter
- Faculty of Chemistry and Chemical Biology, Technical University Dortmund, Dortmund, Germany
| | - Ingrid R Vetter
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Slava Ziegler
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Petra Janning
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Yao-Wen Wu
- Chemical Genomics Centre of the Max Planck Society, Dortmund, Germany. .,Department of Chemistry, Umeå University, Umeå, Sweden.
| | - Herbert Waldmann
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany. .,Faculty of Chemistry and Chemical Biology, Technical University Dortmund, Dortmund, Germany.
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Grefhorst A, Verkade HJ, Groen AK. The TICE Pathway: Mechanisms and Lipid-Lowering Therapies. Methodist Debakey Cardiovasc J 2019; 15:70-76. [PMID: 31049152 DOI: 10.14797/mdcj-15-1-70] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Besides the well-known hepatobiliary pathway of cholesterol excretion into the feces, transintestinal cholesterol excretion (TICE) is a second major pathway through which cholesterol is disposed from the body. In the process of TICE, cholesterol is taken up from lipoprotein particles at the basolateral side of the enterocyte and translocates towards the apical side of the enterocyte. At the apical side, the ATP-binding cassette transporters G5 and G8 form a heterodimer that transports cholesterol into the intestinal lumen. A substantial amount of the secreted cholesterol is likely reabsorbed by the cholesterol influx transporter Niemann-Pick C1-Like 1 (NPC1L1) since recent data indicate that inhibition of NPC1L1 increases the efficacy of TICE for disposal of cholesterol via the feces. The pathways and proteins involved in intracellular cholesterol trafficking in the enterocyte have not yet been identified. Therefore, in addition to discussing known mediators of TICE, this review will also examine potential candidates involved in cholesterol translocation in the enterocyte. Both the cholesterol reuptake and efflux pathways can be influenced by pharmaceutical means; thus, the TICE pathway is a very attractive target to increase cholesterol excretion from the body and prevent or mitigate atherosclerotic cardiovascular disease.
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Affiliation(s)
- Aldo Grefhorst
- AMSTERDAM UNIVERSITY MEDICAL CENTERS, AMSTERDAM, THE NETHERLANDS
| | - Henkjan J Verkade
- UNIVERSITY MEDICAL CENTER GRONINGEN, UNIVERSITY OF GRONINGEN, GRONINGEN, THE NETHERLANDS
| | - Albert K Groen
- AMSTERDAM UNIVERSITY MEDICAL CENTERS, AMSTERDAM, THE NETHERLANDS.,UNIVERSITY MEDICAL CENTER GRONINGEN, UNIVERSITY OF GRONINGEN, GRONINGEN, THE NETHERLANDS
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