1
|
Lingwood C. Is cholesterol both the lock and key to abnormal transmembrane signals in Autism Spectrum Disorder? Lipids Health Dis 2024; 23:114. [PMID: 38643132 PMCID: PMC11032007 DOI: 10.1186/s12944-024-02075-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 03/08/2024] [Indexed: 04/22/2024] Open
Abstract
Disturbances in cholesterol homeostasis have been associated with ASD. Lipid rafts are central in many transmembrane signaling pathways (including mTOR) and changes in raft cholesterol content affect their order function. Cholesterol levels are controlled by several mechanisms, including endoplasmic reticulum associated degradation (ERAD) of the rate limiting HMGCoA reductase. A new approach to increase cholesterol via temporary ERAD blockade using a benign bacterial toxin-derived competitor for the ERAD translocon is suggested.A new lock and key model for cholesterol/lipid raft dependent signaling is proposed in which the rafts provide both the afferent and efferent 'tumblers' across the membrane to allow 'lock and key' receptor transmembrane signals.
Collapse
Affiliation(s)
- Clifford Lingwood
- Division of Molecular Medicine, Research Institute, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada.
- Departments of Biochemistry and Laboratory Medicine & Pathobiology, University of Toronto, Ontario, M5S 1A8, Canada.
| |
Collapse
|
2
|
Luo X, Zhao Y, Cai Y, Chen J, Zhao L, Lan T, Chen Y, Ruan XZ. Dual-monomer solvatochromic probe system (DSPS) for effectively differentiating lipid raft cholesterol and active membrane cholesterol in the inner-leaflet plasma membrane. J Mater Chem B 2024; 12:2547-2558. [PMID: 38358131 DOI: 10.1039/d3tb02857g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2024]
Abstract
Monitoring active membrane cholesterol and lipid raft cholesterol in the inner leaflet of the plasma membrane is significant for understanding the membrane function and cellular physiopathological processes. Limited by existing methods, it is difficult to differentiate active membrane cholesterol and lipid raft cholesterol. A novel dual-monomer solvatochromic probe system (DSPS) that targets two types of cholesterol was developed. Acrylodan-BG/SNAP-D4 composed of SNAP-D4 cholesterol-recognizing monomers and solvatochromic acrylodan-BG-sensing monomers exhibits excellent cholesterol detecting properties in terms of selectivity, accuracy, convenience and economic benefits. Cell imaging revealed that lipid raft cholesterol emitted blue fluorescence, whereas active membrane cholesterol (which partially bobbed in aqueous cytosol) displayed green fluorescence; both the fluorescence emissions increased or decreased in a cholesterol-dependent manner. This system provides a new technology for the determination of two types of cholesterol, which is beneficial for the further study of membrane function, intracellular cholesterol trafficking, and cell signaling.
Collapse
Affiliation(s)
- Xuan Luo
- Centre for Lipid Research & Chongqing Key Laboratory of Metabolism on Lipid and Glucose, Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Institute for Viral Hepatitis, Department of Infectious Diseases, the Second Affiliated Hospital, Chongqing Medical University, 400016, Chongqing, China.
| | - Yunfei Zhao
- Chongqing Key Laboratory for Pharmaceutical Metabolism Research, Chongqing Pharmacodynamic Evaluation Engineering Technology Research Center, College of Pharmacy, Chongqing Medical University, 400016, Chongqing, China
| | - Yang Cai
- Chongqing Key Laboratory for Pharmaceutical Metabolism Research, Chongqing Pharmacodynamic Evaluation Engineering Technology Research Center, College of Pharmacy, Chongqing Medical University, 400016, Chongqing, China
| | - Jun Chen
- Department of Pediatrics, Women and Children' Hospital of Chongging Medical University, 400016, Chongqing, China
| | - Lulu Zhao
- Chongqing Key Laboratory for Pharmaceutical Metabolism Research, Chongqing Pharmacodynamic Evaluation Engineering Technology Research Center, College of Pharmacy, Chongqing Medical University, 400016, Chongqing, China
| | - Tianlan Lan
- Centre for Lipid Research & Chongqing Key Laboratory of Metabolism on Lipid and Glucose, Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Institute for Viral Hepatitis, Department of Infectious Diseases, the Second Affiliated Hospital, Chongqing Medical University, 400016, Chongqing, China.
| | - Yaxi Chen
- Centre for Lipid Research & Chongqing Key Laboratory of Metabolism on Lipid and Glucose, Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Institute for Viral Hepatitis, Department of Infectious Diseases, the Second Affiliated Hospital, Chongqing Medical University, 400016, Chongqing, China.
| | - Xiong Z Ruan
- Centre for Lipid Research & Chongqing Key Laboratory of Metabolism on Lipid and Glucose, Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Institute for Viral Hepatitis, Department of Infectious Diseases, the Second Affiliated Hospital, Chongqing Medical University, 400016, Chongqing, China.
- John Moorhead Research Laboratory, Centre for Nephrology, University College London Medical School, Royal Free Campus, University College London, London NW3 2PF, UK
| |
Collapse
|
3
|
Doktorova M, Levental I, Heberle FA. Seeing the Membrane from Both Sides Now: Lipid Asymmetry and Its Strange Consequences. Cold Spring Harb Perspect Biol 2023; 15:a041393. [PMID: 37604588 PMCID: PMC10691478 DOI: 10.1101/cshperspect.a041393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
Almost all biomembranes are constructed as lipid bilayers and, in almost all of these, the two opposing monolayers (leaflets) have distinct lipid compositions. This lipid asymmetry arises through the concerted action of a suite of energy-dependent enzymes that maintain living bilayers in a far-from-equilibrium steady-state. Recent discoveries reveal that lipid compositional asymmetry imparts biophysical asymmetries and that this dualistic organization may have major consequences for cellular physiology. Importantly, while transbilayer asymmetry appears to be an essential, near-ubiquitous characteristic of biological membranes, it has been challenging to reproduce in reconstituted or synthetic systems. Although recent methodological developments have overcome some critical challenges, it remains difficult to extrapolate results from available models to biological systems. Concurrently, there are few experimental approaches for targeted, controlled manipulation of lipid asymmetry in living cells. Thus, the biophysical and functional consequences of membrane asymmetry remain almost wholly unexplored. This perspective summarizes the current state of knowledge and highlights emerging themes that are beginning to make inroads into the fundamental question of why life tends toward asymmetry in its bilayers.
Collapse
Affiliation(s)
- Milka Doktorova
- Department of Molecular Physiology and Pharmacology, University of Virginia, Center for Membrane and Cell Physiology, Charlottesville, Virginia 22908, USA
| | - Ilya Levental
- Department of Molecular Physiology and Pharmacology, University of Virginia, Center for Membrane and Cell Physiology, Charlottesville, Virginia 22908, USA
| | - Frederick A Heberle
- Department of Chemistry, University of Tennessee Knoxville, Knoxville, Tennessee 37996, USA
| |
Collapse
|
4
|
Zalejski J, Sun J, Sharma A. Unravelling the Mystery inside Cells by Using Single-Molecule Fluorescence Imaging. J Imaging 2023; 9:192. [PMID: 37754956 PMCID: PMC10532472 DOI: 10.3390/jimaging9090192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 09/01/2023] [Accepted: 09/14/2023] [Indexed: 09/28/2023] Open
Abstract
Live-cell imaging is a powerful technique to study the dynamics and mechanics of various biological molecules like proteins, organelles, DNA, and RNA. With the rapid evolution of optical microscopy, our understanding of how these molecules are implicated in the cells' most critical physiological roles deepens. In this review, we focus on how spatiotemporal nanoscale live-cell imaging at the single molecule level allows for profound contributions towards new discoveries in life science. This review will start by summarizing how single-molecule tracking has been used to analyze membrane dynamics, receptor-ligand interactions, protein-protein interactions, inner- and extra-cellular transport, gene expression/transcription, and whole organelle tracking. We then move on to how current authors are trying to improve single-molecule tracking and overcome current limitations by offering new ways of labeling proteins of interest, multi-channel/color detection, improvements in time-lapse imaging, and new methods and programs to analyze the colocalization and movement of targets. We later discuss how single-molecule tracking can be a beneficial tool used for medical diagnosis. Finally, we wrap up with the limitations and future perspectives of single-molecule tracking and total internal reflection microscopy.
Collapse
Affiliation(s)
| | | | - Ashutosh Sharma
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607, USA; (J.Z.); (J.S.)
| |
Collapse
|
5
|
Abstract
The Hedgehog signalling pathway has crucial roles in embryonic tissue patterning, postembryonic tissue regeneration, and cancer, yet aspects of Hedgehog signal transmission and reception have until recently remained unclear. Biochemical and structural studies surprisingly reveal a central role for lipids in Hedgehog signalling. The signal - Hedgehog protein - is modified by cholesterol and palmitate during its biogenesis, thereby necessitating specialized proteins such as the transporter Dispatched and several lipid-binding carriers for cellular export and receptor engagement. Additional lipid transactions mediate response to the Hedgehog signal, including sterol activation of the transducer Smoothened. Access of sterols to Smoothened is regulated by the apparent sterol transporter and Hedgehog receptor Patched, whose activity is blocked by Hedgehog binding. Alongside these lipid-centric mechanisms and their relevance to pharmacological pathway modulation, we discuss emerging roles of Hedgehog pathway activity in stem cells or their cellular niches, with translational implications for regeneration and restoration of injured or diseased tissues.
Collapse
Affiliation(s)
- Yunxiao Zhang
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA
- Howard Hughes Medical Institute and Neuroscience Department, The Scripps Research Institute, La Jolla, CA, USA
| | - Philip A Beachy
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA.
- Department of Urology, Stanford University School of Medicine, Stanford, CA, USA.
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA, USA.
| |
Collapse
|
6
|
Sarmento MJ, Llorente A, Petan T, Khnykin D, Popa I, Nikolac Perkovic M, Konjevod M, Jaganjac M. The expanding organelle lipidomes: current knowledge and challenges. Cell Mol Life Sci 2023; 80:237. [PMID: 37530856 PMCID: PMC10397142 DOI: 10.1007/s00018-023-04889-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 06/13/2023] [Accepted: 07/19/2023] [Indexed: 08/03/2023]
Abstract
Lipids in cell membranes and subcellular compartments play essential roles in numerous cellular processes, such as energy production, cell signaling and inflammation. A specific organelle lipidome is characterized by lipid synthesis and metabolism, intracellular trafficking, and lipid homeostasis in the organelle. Over the years, considerable effort has been directed to the identification of the lipid fingerprints of cellular organelles. However, these fingerprints are not fully characterized due to the large variety and structural complexity of lipids and the great variability in the abundance of different lipid species. The process becomes even more challenging when considering that the lipidome differs in health and disease contexts. This review summarizes the information available on the lipid composition of mammalian cell organelles, particularly the lipidome of the nucleus, mitochondrion, endoplasmic reticulum, Golgi apparatus, plasma membrane and organelles in the endocytic pathway. The lipid compositions of extracellular vesicles and lamellar bodies are also described. In addition, several examples of subcellular lipidome dynamics under physiological and pathological conditions are presented. Finally, challenges in mapping organelle lipidomes are discussed.
Collapse
Affiliation(s)
- Maria J Sarmento
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028, Lisbon, Portugal
| | - Alicia Llorente
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, 0379, Oslo, Norway
- Department for Mechanical, Electronics and Chemical Engineering, Oslo Metropolitan University, 0167, Oslo, Norway
- Faculty of Medicine, Centre for Cancer Cell Reprogramming, University of Oslo, Montebello, 0379, Oslo, Norway
| | - Toni Petan
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Denis Khnykin
- Department of Pathology, Oslo University Hospital, Oslo, Norway
| | - Iuliana Popa
- Pharmacy Department, Bâtiment Henri Moissan, University Paris-Saclay, 17 Avenue des Sciences, 91400, Orsay, France
| | | | - Marcela Konjevod
- Division of Molecular Medicine, Ruder Boskovic Institute, 10000, Zagreb, Croatia
| | - Morana Jaganjac
- Division of Molecular Medicine, Ruder Boskovic Institute, 10000, Zagreb, Croatia.
| |
Collapse
|
7
|
Chiu PL, Orjuela JD, de Groot BL, Aponte-Santamaría C, Walz T. Structure and dynamics of cholesterol-mediated aquaporin-0 arrays and implications for lipid rafts. bioRxiv 2023:2023.05.16.540959. [PMID: 37292626 PMCID: PMC10245776 DOI: 10.1101/2023.05.16.540959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Aquaporin-0 (AQP0) tetramers form square arrays in lens membranes through a yet unknown mechanism, but lens membranes are enriched in sphingomyelin and cholesterol. Here, we determined electron crystallographic structures of AQP0 in sphingomyelin/ cholesterol membranes and performed molecular dynamics (MD) simulations to establish that the observed cholesterol positions represent those seen around an isolated AQP0 tetramer and that the AQP0 tetramer largely defines the location and orientation of most of its associated cholesterol molecules. At a high concentration, cholesterol increases the hydrophobic thickness of the annular lipid shell around AQP0 tetramers, which may thus cluster to mitigate the resulting hydrophobic mismatch. Moreover, neighboring AQP0 tetramers sandwich a cholesterol deep in the center of the membrane. MD simulations show that the association of two AQP0 tetramers is necessary to maintain the deep cholesterol in its position and that the deep cholesterol increases the force required to laterally detach two AQP0 tetramers, not only due to protein-protein contacts but also due to increased lipid-protein complementarity. Since each tetramer interacts with four such 'glue' cholesterols, avidity effects may stabilize larger arrays. The principles proposed to drive AQP0 array formation could also underlie protein clustering in lipid rafts.
Collapse
Affiliation(s)
- Po-Lin Chiu
- Department of Cell Biology, Harvard Medical School, Boston, MA 02467, USA
- Current address: School of Molecular Sciences, Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ 85287, USA
| | - Juan D. Orjuela
- Max Planck Tandem Group in Computational Biophysics, Universidad de los Andes, Bogotá, Colombia
- Biomedical Engineering Department, Universidad de los Andes, Bogotá, Colombia
| | - Bert L. de Groot
- Computational Biomolecular Dynamic Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Camilo Aponte-Santamaría
- Max Planck Tandem Group in Computational Biophysics, Universidad de los Andes, Bogotá, Colombia
- Molecular Biomechanics, Heidelberg Institute for Theoretical Studies, Heidelberg, Germany
| | - Thomas Walz
- Department of Cell Biology, Harvard Medical School, Boston, MA 02467, USA
- Current address: Laboratory of Molecular Electron Microscopy, The Rockefeller University, New York, NY 10065, USA; Biogen, Cambridge, MA 02142, USA
| |
Collapse
|
8
|
Davidović D, Kukulka M, Sarmento MJ, Mikhalyov I, Gretskaya N, Chmelová B, Ricardo JC, Hof M, Cwiklik L, Šachl R. Which Moiety Drives Gangliosides to Form Nanodomains? J Phys Chem Lett 2023:5791-5797. [PMID: 37327454 DOI: 10.1021/acs.jpclett.3c00761] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Gangliosides are important glycosphingolipids involved in a multitude of physiological functions. From a physicochemical standpoint, this is related to their ability to self-organize into nanoscopic domains, even at molar concentrations of one per 1000 lipid molecules. Despite recent experimental and theoretical efforts suggesting that a hydrogen bonding network is crucial for nanodomain stability, the specific ganglioside moiety decisive for the development of these nanodomains has not yet been identified. Here, we combine an experimental technique achieving nanometer resolution (Förster resonance energy transfer analyzed by Monte Carlo simulations) with atomistic molecular dynamic simulations to demonstrate that the sialic acid (Sia) residue(s) at the oligosaccharide headgroup dominates the hydrogen bonding network between gangliosides, driving the formation of nanodomains even in the absence of cholesterol or sphingomyelin. Consequently, the clustering pattern of asialoGM1, a Sia-depleted glycosphingolipid bearing three glyco moieties, is more similar to that of structurally distant sphingomyelin than that of the closely related gangliosides GM1 and GD1a with one and two Sia groups, respectively.
Collapse
Affiliation(s)
- David Davidović
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 2155/3, 182 00 Prague, Czech Republic
- Faculty of Science, Charles University, Hlavova 8, 128 40 Prague, Czech Republic
| | - Mercedes Kukulka
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland
| | - Maria J Sarmento
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisbon, Portugal
| | - Ilya Mikhalyov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Science, Miklukho-Maklaya 16/10, 117997 Moscow, Russia
| | - Natalia Gretskaya
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Science, Miklukho-Maklaya 16/10, 117997 Moscow, Russia
| | - Barbora Chmelová
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 2155/3, 182 00 Prague, Czech Republic
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu, 2027/3, 121 16 Prague, Czech Republic
| | - Joana C Ricardo
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 2155/3, 182 00 Prague, Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 2155/3, 182 00 Prague, Czech Republic
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 2155/3, 182 00 Prague, Czech Republic
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 2155/3, 182 00 Prague, Czech Republic
| |
Collapse
|
9
|
Steck TL, Lange Y. Is reverse cholesterol transport regulated by active cholesterol? J Lipid Res 2023; 64:100385. [PMID: 37169287 PMCID: PMC10279919 DOI: 10.1016/j.jlr.2023.100385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 05/02/2023] [Accepted: 05/05/2023] [Indexed: 05/13/2023] Open
Abstract
This review considers the hypothesis that a small portion of plasma membrane cholesterol regulates reverse cholesterol transport in coordination with overall cellular homeostasis. It appears that almost all of the plasma membrane cholesterol is held in stoichiometric complexes with bilayer phospholipids. The minor fraction of cholesterol that exceeds the complexation capacity of the phospholipids is called active cholesterol. It has an elevated chemical activity and circulates among the organelles. It also moves down its chemical activity gradient to plasma HDL, facilitated by the activity of ABCA1, ABCG1, and SR-BI. ABCA1 initiates this process by perturbing the organization of the plasma membrane bilayer, thereby priming its phospholipids for translocation to apoA-I to form nascent HDL. The active excess sterol and that activated by ABCA1 itself follow the phospholipids to the nascent HDL. ABCG1 similarly rearranges the bilayer and sends additional active cholesterol to nascent HDL, while SR-BI simply facilitates the equilibration of the active sterol between plasma membranes and plasma proteins. Active cholesterol also flows downhill to cytoplasmic membranes where it serves both as a feedback signal to homeostatic ER proteins and as the substrate for the synthesis of mitochondrial 27-hydroxycholesterol (27HC). 27HC binds the LXR and promotes the expression of the aforementioned transport proteins. 27HC-LXR also activates ABCA1 by competitively displacing its inhibitor, unliganded LXR. § Considerable indirect evidence suggests that active cholesterol serves as both a substrate and a feedback signal for reverse cholesterol transport. Direct tests of this novel hypothesis are proposed.
Collapse
Affiliation(s)
- Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, IL, USA.
| |
Collapse
|
10
|
Wang H, Yuan Z, Pavel MA, Jablonski SM, Jablonski J, Hobson R, Valente S, Reddy CB, Hansen SB. The role of high cholesterol in SARS-CoV-2 infectivity. J Biol Chem 2023:104763. [PMID: 37119851 PMCID: PMC10140059 DOI: 10.1016/j.jbc.2023.104763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 04/11/2023] [Accepted: 04/24/2023] [Indexed: 05/01/2023] Open
Abstract
Coronavirus disease 2019 (COVID19) is a respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The virus binds to angiotensinogen converting enzyme 2 (ACE2) which mediates viral entry into mammalian cells. COVID19 is notably severe in elderly and those with underlying chronic conditions. The cause of selective severity is not well understood. Here we show cholesterol and the signaling lipid phosphatidyl-inositol 4,5 bisphosphate (PIP2) regulate viral infectivity through the localization of ACE2's into nanoscopic (<200 nm) lipid clusters. Uptake of cholesterol into cell membranes (a condition common to chronic disease) causes ACE2 to move from PIP2 lipids to endocytic ganglioside (GM1) lipids, where the virus is optimally located for viral entry. In mice, age, and high fat diet increase lung tissue cholesterol by up to 40%. And in smokers with chronic disease, cholesterol is elevated two-fold, a magnitude of change that dramatically increases infectivity of virus in cell culture. We conclude increasing the ACE2 location near endocytic lipids increases viral infectivity and may help explain the selective severity of COVID-19 in aged and diseased populations.
Collapse
Affiliation(s)
- Hao Wang
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL, 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, 33458, USA; Skaggs Graduate School of Chemical and Biological Sciences, The Scripps Research Institute, Jupiter, FL, 33458, USA
| | - Zixuan Yuan
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL, 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, 33458, USA; Skaggs Graduate School of Chemical and Biological Sciences, The Scripps Research Institute, Jupiter, FL, 33458, USA
| | - Mahmud Arif Pavel
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL, 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, 33458, USA
| | | | - Joseph Jablonski
- Department of Immunology and Virology, The Scripps Research Institute, Jupiter, FL, 33458, USA
| | - Robert Hobson
- Bruker Nano Surfaces, Fitchburg, WI, 53711, USA; Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA
| | - Susana Valente
- Department of Immunology and Virology, The Scripps Research Institute, Jupiter, FL, 33458, USA
| | - Chakravarthy B Reddy
- Department of Internal Medicine, University of Utah Health Sciences Center, Salt Lake City, UT, 84112, USA
| | - Scott B Hansen
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL, 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, 33458, USA.
| |
Collapse
|
11
|
Lange Y, Tabei SMA, Steck TL. A basic model for the association of ligands with membrane cholesterol: application to cytolysin binding. J Lipid Res 2023; 64:100344. [PMID: 36791915 PMCID: PMC10119614 DOI: 10.1016/j.jlr.2023.100344] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/19/2023] [Accepted: 02/07/2023] [Indexed: 02/16/2023] Open
Abstract
Almost all the cholesterol in cellular membranes is associated with phospholipids in simple stoichiometric complexes. This limits the binding of sterol ligands such as filipin and Perfringolysin O (PFO) to a small fraction of the total. We offer a simple mathematical model that characterizes this complexity. It posits that the cholesterol accessible to ligands has two forms: active cholesterol, which is that not complexed with phospholipids; and extractable cholesterol, that which ligands can capture competitively from the phospholipid complexes. Simulations based on the model match published data for the association of PFO oligomers with liposomes, plasma membranes and the isolated endoplasmic reticulum. The model shows how the binding of a probe greatly underestimates cholesterol abundance when its affinity for the sterol is so weak that it competes poorly with the membrane phospholipids. Two examples are the under-staining of plasma membranes by filipin and the failure of domain D4 of PFO to label their cytoplasmic leaflets. Conversely, the exaggerated staining of endolysosomes suggests that their cholesterol, being uncomplexed, is readily available. The model is also applicable to the association of cholesterol with intrinsic membrane proteins. For example, it supports the hypothesis that the sharp threshold in the regulation of homeostatic ER proteins by cholesterol derives from the cooperativity of their binding to the sterol weakly held by the phospholipid. § Thus, the model explicates the complexity inherent in the binding of ligands like PFO and filipin to the small accessible fraction of membrane cholesterol.
Collapse
Affiliation(s)
- Yvonne Lange
- 1Department of Pathology, Rush University Medical Center, Chicago, Il 60612, USA.
| | - S M Ali Tabei
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614, USA
| | - Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Il 60637, USA
| |
Collapse
|
12
|
Rosenhouse-Dantsker A, Gazgalis D, Logothetis DE. PI(4,5)P 2 and Cholesterol: Synthesis, Regulation, and Functions. Adv Exp Med Biol 2023; 1422:3-59. [PMID: 36988876 DOI: 10.1007/978-3-031-21547-6_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is the most abundant membrane phosphoinositide and cholesterol is an essential component of the plasma membrane (PM). Both lipids play key roles in a variety of cellular functions including as signaling molecules and major regulators of protein function. This chapter provides an overview of these two important lipids. Starting from a brief description of their structure, synthesis, and regulation, the chapter continues to describe the primary functions and signaling processes in which PI(4,5)P2 and cholesterol are involved. While PI(4,5)P2 and cholesterol can act independently, they often act in concert or affect each other's impact. The chapters in this volume on "Cholesterol and PI(4,5)P2 in Vital Biological Functions: From Coexistence to Crosstalk" focus on the emerging relationship between cholesterol and PI(4,5)P2 in a variety of biological systems and processes. In this chapter, the next section provides examples from the ion channel field demonstrating that PI(4,5)P2 and cholesterol can act via common mechanisms. The chapter ends with a discussion of future directions.
Collapse
Affiliation(s)
| | - Dimitris Gazgalis
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA, USA
| | - Diomedes E Logothetis
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA, USA
| |
Collapse
|
13
|
Jiang M, Chen L, Hong C, Zhang L, Lu L, Zhao W, Ding Y, Zhang T. A novel polyphyllin I-based liposome delivery system sensitizes hepatic carcinoma to doxorubicin via cholesterol modulation. J Drug Deliv Sci Technol 2022; 78:103925. [DOI: 10.1016/j.jddst.2022.103925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
14
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
|
15
|
Bag N, London E, Holowka DA, Baird BA. Transbilayer Coupling of Lipids in Cells Investigated by Imaging Fluorescence Correlation Spectroscopy. J Phys Chem B 2022; 126:2325-2336. [PMID: 35294838 DOI: 10.1021/acs.jpcb.2c00117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Plasma membranes host numerous receptors, sensors, and ion channels involved in cellular signaling. Phase separation within the plasma membrane has emerged as a key biophysical regulator of signaling reactions in multiple physiological and pathological contexts. There is much evidence that plasma membrane composition supports the coexistence of liquid-ordered (Lo) and liquid-disordered (Ld) phases or domains at physiological conditions. However, this phase/domain separation is nanoscopic and transient in live cells. It has been recently proposed that transbilayer coupling between the inner and outer leaflets of the plasma membrane is driven by their asymmetric lipid distribution and by dynamic cytoskeleton-lipid composites that contribute to the formation and transience of Lo/Ld phase separation in live cells. In this Perspective, we highlight new approaches to investigate how transbilayer coupling may influence phase separation. For quantitative evaluation of the impact of these interactions, we introduce an experimental strategy centered around Imaging Fluorescence Correlation Spectroscopy (ImFCS), which measures membrane diffusion with very high precision. To demonstrate this strategy, we choose two well-established model systems for transbilayer interactions: cross-linking by multivalent antigen of immunoglobulin E bound to receptor FcεRI and cross-linking by cholera toxin B of GM1 gangliosides. We discuss emerging methods to systematically perturb membrane lipid composition, particularly exchange of outer leaflet lipids with exogenous lipids using methyl alpha cyclodextrin. These selective perturbations may be quantitatively evaluated with ImFCS and other high-resolution biophysical tools to discover novel principles of lipid-mediated phase separation in live cells in the context of their pathophysiological relevance.
Collapse
Affiliation(s)
- Nirmalya Bag
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11794, United States
| | - David A Holowka
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Barbara A Baird
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| |
Collapse
|
16
|
Skotland T, Sandvig K. Need for more focus on lipid species in studies of biological and model membranes. Prog Lipid Res 2022. [DOI: 10.1016/j.plipres.2022.101160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Accepted: 03/06/2022] [Indexed: 11/23/2022]
|
17
|
Pham H, Singaram I, Sun J, Ralko A, Puckett M, Sharma A, Vrielink A, Cho W. Development of a novel spatiotemporal depletion system for cellular cholesterol. J Lipid Res 2022; 63:100178. [PMID: 35143844 PMCID: PMC8953671 DOI: 10.1016/j.jlr.2022.100178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Revised: 02/03/2022] [Accepted: 02/04/2022] [Indexed: 11/30/2022] Open
Abstract
Cholesterol is an essential component of mammalian cell membranes whose subcellular concentration and function are tightly regulated by de novo biosynthesis, transport, and storage. Although recent reports have suggested diverse functions of cellular cholesterol in different subcellular membranes, systematic investigation of its site-specific roles has been hampered by the lack of a methodology for spatiotemporal manipulation of cellular cholesterol levels. Here, we report the development of a new cholesterol depletion system that allows for spatiotemporal manipulation of intracellular cholesterol levels. This system utilizes a genetically encoded cholesterol oxidase whose intrinsic membrane binding activity is engineered in such a way that its membrane targeting can be controlled in a spatiotemporally specific manner via chemically induced dimerization. In combination with in situ quantitative imaging of cholesterol and signaling activity measurements, this system allows for unambiguous determination of site-specific functions of cholesterol in different membranes, including the plasma membrane and the lysosomal membrane.
Collapse
Affiliation(s)
- Ha Pham
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
| | - Indira Singaram
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
| | - Jiachen Sun
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
| | - Arthur Ralko
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
| | - Madalyn Puckett
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
| | - Ashutosh Sharma
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA
| | - Alice Vrielink
- School of Molecular Sciences, University of Western Australia, Perth, Western Australia, Australia
| | - Wonhwa Cho
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL, USA.
| |
Collapse
|
18
|
Paukner K, Králová Lesná I, Poledne R. Cholesterol in the Cell Membrane-An Emerging Player in Atherogenesis. Int J Mol Sci 2022; 23:533. [PMID: 35008955 PMCID: PMC8745363 DOI: 10.3390/ijms23010533] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 12/30/2021] [Accepted: 12/30/2021] [Indexed: 02/01/2023] Open
Abstract
Membrane cholesterol is essential for cell membrane properties, just as serum cholesterol is important for the transport of molecules between organs. This review focuses on cholesterol transport between lipoproteins and lipid rafts on the surface of macrophages. Recent studies exploring this mechanism and recognition of the central dogma-the key role of macrophages in cardiovascular disease-have led to the notion that this transport mechanism plays a major role in the pathogenesis of atherosclerosis. The exact molecular mechanism of this transport remains unclear. Future research will improve our understanding of the molecular and cellular bases of lipid raft-associated cholesterol transport.
Collapse
Affiliation(s)
- Karel Paukner
- Laboratory for Atherosclerosis Research, Centre for Experimental Medicine, Institute for Clinical and Experimental Medicine, 140 21 Prague, Czech Republic; (I.K.L.); (R.P.)
- Department of Physiology, Faculty of Science, Charles University, 128 44 Prague, Czech Republic
- Faculty of Veterinary Medicine, University of Veterinary Sciences Brno, Small Animal Clinic, 612 00 Brno, Czech Republic
| | - Ivana Králová Lesná
- Laboratory for Atherosclerosis Research, Centre for Experimental Medicine, Institute for Clinical and Experimental Medicine, 140 21 Prague, Czech Republic; (I.K.L.); (R.P.)
- Department of Anesthesia and Intensive Medicine, First Faculty of Medicine, Charles University and University Military Hospital, 128 08 Prague, Czech Republic
| | - Rudolf Poledne
- Laboratory for Atherosclerosis Research, Centre for Experimental Medicine, Institute for Clinical and Experimental Medicine, 140 21 Prague, Czech Republic; (I.K.L.); (R.P.)
| |
Collapse
|
19
|
Abstract
Lipid membrane domains are supramolecular lateral heterogeneities of biological membranes. Of nanoscopic dimensions, they constitute specialized hubs used by the cell as transient signaling platforms for a great variety of biologically important mechanisms. Their property to form and dissolve in the bulk lipid bilayer endow them with the ability to engage in highly dynamic processes, and temporarily recruit subpopulations of membrane proteins in reduced nanometric compartments that can coalesce to form larger mesoscale assemblies. Cholesterol is an essential component of these lipid domains; its unique molecular structure is suitable for interacting intricately with crevices and cavities of transmembrane protein surfaces through its rough β face while "talking" to fatty acid acyl chains of glycerophospholipids and sphingolipids via its smooth α face. Progress in the field of membrane domains has been closely associated with innovative improvements in fluorescence microscopy and new fluorescence sensors. These advances enabled the exploration of the biophysical properties of lipids and their supramolecular platforms. Here I review the rationale behind the use of biosensors over the last few decades and their contributions towards elucidation of the in-plane and transbilayer topography of cholesterol-enriched lipid domains and their molecular constituents. The challenges introduced by super-resolution optical microscopy are discussed, as well as possible scenarios for future developments in the field, including virtual ("no staining") staining.
Collapse
Affiliation(s)
- Francisco J Barrantes
- Biomedical Research Institute (BIOMED), Catholic University of Argentina (UCA)-National Scientific and Technical Research Council (CONICET), Buenos Aires, Argentina.
| |
Collapse
|
20
|
Perez-Salas U, Garg S, Gerelli Y, Porcar L. Deciphering lipid transfer between and within membranes with time-resolved small-angle neutron scattering. Curr Top Membr 2021; 88:359-412. [PMID: 34862031 DOI: 10.1016/bs.ctm.2021.10.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This review focuses on time-resolved neutron scattering, particularly time-resolved small angle neutron scattering (TR-SANS), as a powerful in situ noninvasive technique to investigate intra- and intermembrane transport and distribution of lipids and sterols in lipid membranes. In contrast to using molecular analogues with potentially large chemical tags that can significantly alter transport properties, small angle neutron scattering relies on the relative amounts of the two most abundant isotope forms of hydrogen: protium and deuterium to detect complex membrane architectures and transport processes unambiguously. This review discusses advances in our understanding of the mechanisms that sustain lipid asymmetry in membranes-a key feature of the plasma membrane of cells-as well as the transport of lipids between membranes, which is an essential metabolic process.
Collapse
Affiliation(s)
- Ursula Perez-Salas
- Physics Department, University of Illinois at Chicago, Chicago, IL, United States.
| | - Sumit Garg
- Physics Department, University of Illinois at Chicago, Chicago, IL, United States
| | - Yuri Gerelli
- Department of Life and Environmental Sciences, Universita` Politecnica delle Marche, Ancona, Italy
| | | |
Collapse
|
21
|
Abstract
Membrane protrusions are a critical facet of cell function. Mediating fundamental processes such as cell migration, cell-cell interactions, phagocytosis, as well as assessment and remodeling of the cell environment. Different protrusion types and morphologies can promote different cellular functions and occur downstream of distinct signaling pathways. As such, techniques to quantify and understand the inner workings of protrusion dynamics are critical for a comprehensive understanding of cell biology. In this chapter, we describe approaches to analyze cellular protrusions and correlate physical changes in cell morphology with biochemical signaling processes. We address methods to quantify and characterize protrusion types and velocity, mathematical approaches to predictive models of cytoskeletal changes, and implementation of protein engineering and biosensor design to dissect cell signaling driving protrusive activity. Combining these approaches allows cell biologists to develop a comprehensive understanding of the dynamics of membrane protrusions.
Collapse
Affiliation(s)
- Jordan Fauser
- University of Illinois at Chicago, Department of Cellular and Molecular Pharmacology and Regenerative Medicine, Chicago, IL, United States
| | - Martin Brennan
- University of Illinois at Chicago, Department of Cellular and Molecular Pharmacology and Regenerative Medicine, Chicago, IL, United States
| | - Denis Tsygankov
- Georgia Institute of Technology, Wallace H. Coulter Department of Biomedical Engineering, Atlanta, GA, United States
| | - Andrei V Karginov
- University of Illinois at Chicago, Department of Cellular and Molecular Pharmacology and Regenerative Medicine, Chicago, IL, United States.
| |
Collapse
|
22
|
Kinnebrew M, Luchetti G, Sircar R, Frigui S, Viti LV, Naito T, Beckert F, Saheki Y, Siebold C, Radhakrishnan A, Rohatgi R. Patched 1 reduces the accessibility of cholesterol in the outer leaflet of membranes. eLife 2021; 10:e70504. [PMID: 34698632 PMCID: PMC8654371 DOI: 10.7554/elife.70504] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 10/25/2021] [Indexed: 11/13/2022] Open
Abstract
A long-standing mystery in vertebrate Hedgehog signaling is how Patched 1 (PTCH1), the receptor for Hedgehog ligands, inhibits the activity of Smoothened, the protein that transmits the signal across the membrane. We previously proposed (Kinnebrew et al., 2019) that PTCH1 inhibits Smoothened by depleting accessible cholesterol from the ciliary membrane. Using a new imaging-based assay to directly measure the transport activity of PTCH1, we find that PTCH1 depletes accessible cholesterol from the outer leaflet of the plasma membrane. This transport activity is terminated by binding of Hedgehog ligands to PTCH1 or by dissipation of the transmembrane potassium gradient. These results point to the unexpected model that PTCH1 moves cholesterol from the outer to the inner leaflet of the membrane in exchange for potassium ion export in the opposite direction. Our study provides a plausible solution for how PTCH1 inhibits SMO by changing the organization of cholesterol in membranes and establishes a general framework for studying how proteins change cholesterol accessibility to regulate membrane-dependent processes in cells.
Collapse
Affiliation(s)
- Maia Kinnebrew
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
| | - Giovanni Luchetti
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
- Department of Physiological Chemistry, GenentechSouth San FranciscoUnited States
| | - Ria Sircar
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
| | - Sara Frigui
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
| | - Lucrezia Vittoria Viti
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of OxfordOxfordUnited Kingdom
| | - Tomoki Naito
- Lee Kong Chian School of Medicine, Nanyang Technological UniversitySingaporeSingapore
| | - Francis Beckert
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological UniversitySingaporeSingapore
| | - Christian Siebold
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of OxfordOxfordUnited Kingdom
| | - Arun Radhakrishnan
- Department of Molecular Genetics, University of Texas Southwestern Medical CenterDallasUnited States
| | - Rajat Rohatgi
- Department of Biochemistry and Medicine, Stanford University School of MedicineStanfordUnited States
| |
Collapse
|
23
|
Steck TL, Tabei SMA, Lange Y. A basic model for cell cholesterol homeostasis. Traffic 2021; 22:471-481. [PMID: 34528339 DOI: 10.1111/tra.12816] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 08/26/2021] [Accepted: 09/13/2021] [Indexed: 11/30/2022]
Abstract
Cells manage their cholesterol by negative feedback using a battery of sterol-responsive proteins. How these activities are coordinated so as to specify the abundance and distribution of the sterol is unclear. We present a simple mathematical model that addresses this question. It assumes that almost all of the cholesterol is associated with phospholipids in stoichiometric complexes. A small fraction of the sterol is uncomplexed and thermodynamically active. It equilibrates among the organelles, setting their sterol level according to the affinity of their phospholipids. The activity of the homeostatic proteins in the cytoplasmic membranes is then set by their fractional saturation with uncomplexed cholesterol in competition with the phospholipids. The high-affinity phospholipids in the plasma membrane (PM) are filled to near stoichiometric equivalence, giving it most of the cell sterol. Notably, the affinity of the phospholipids in the endomembranes (EMs) is lower by orders of magnitude than that of the phospholipids in the PM. Thus, the small amount of sterol in the EMs rests far below stoichiometric capacity. Simulations match a variety of experimental data. The model captures the essence of cell cholesterol homeostasis, makes coherent a diverse set of experimental findings, provides a surprising prediction and suggests new experiments.
Collapse
Affiliation(s)
- Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - S M Ali Tabei
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa, USA
| | - Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois, USA
| |
Collapse
|