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Yang GS, Wagenknecht-Wiesner A, Yin B, Suresh P, London E, Baird BA, Bag N. Lipid-driven interleaflet coupling of plasma membrane order regulates FcεRI signaling in mast cells. Biophys J 2024; 123:2256-2270. [PMID: 37533258 PMCID: PMC11331041 DOI: 10.1016/j.bpj.2023.07.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 07/28/2023] [Accepted: 07/31/2023] [Indexed: 08/04/2023] Open
Abstract
Interleaflet coupling-the influence of one leaflet on the properties of the opposing leaflet-is a fundamental plasma membrane organizational principle. This coupling is proposed to participate in maintaining steady-state biophysical properties of the plasma membrane, which in turn regulates some transmembrane signaling processes. A prominent example is antigen (Ag) stimulation of signaling by clustering transmembrane receptors for immunoglobulin E (IgE), FcεRI. This transmembrane signaling depends on the stabilization of ordered regions in the inner leaflet for sorting of intracellular signaling components. The resting inner leaflet has a lipid composition that is generally less ordered than the outer leaflet and that does not spontaneously phase separate in model membranes. We propose that interleaflet coupling can mediate ordering and disordering of the inner leaflet, which is poised in resting cells to reorganize upon stimulation. To test this in live cells, we first established a straightforward approach to evaluate induced changes in membrane order by measuring inner leaflet diffusion of lipid probes by imaging fluorescence correlation spectroscopy, by imaging fluorescence correlation spectroscopy (ImFCS), before and after methyl-α-cyclodexrin (mαCD)-catalyzed exchange of outer leaflet lipids (LEX) with exogenous order- or disorder-promoting phospholipids. We examined the functional impact of LEX by monitoring two Ag-stimulated responses: recruitment of cytoplasmic Syk kinase to the inner leaflet and exocytosis of secretory granules (degranulation). Based on the ImFCS data in resting cells, we observed global increase or decrease of inner leaflet order when outer leaflet is exchanged with order- or disorder-promoting lipids, respectively. We find that the degree of both stimulated Syk recruitment and degranulation correlates positively with LEX-mediated changes of inner leaflet order in resting cells. Overall, our results show that resting-state lipid ordering of the outer leaflet influences the ordering of the inner leaflet, likely via interleaflet coupling. This imposed lipid reorganization modulates transmembrane signaling stimulated by Ag clustering of IgE-FcεRI.
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Affiliation(s)
- Gil-Suk Yang
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York
| | | | - Boyu Yin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York
| | - Pavana Suresh
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York
| | - Barbara A Baird
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York
| | - Nirmalya Bag
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York; Department of Chemistry, Indian Institute of Technology, Kharagpur, India.
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2
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Schuck RJ, Ward AE, Sahoo AR, Rybak JA, Pyron RJ, Trybala TN, Simmons TB, Baccile JA, Sgouralis I, Buck M, Lamichhane R, Barrera FN. Cholesterol inhibits assembly and activation of the EphA2 receptor. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.10.598255. [PMID: 38915729 PMCID: PMC11195142 DOI: 10.1101/2024.06.10.598255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
The receptor tyrosine kinase EphA2 drives cancer malignancy by facilitating metastasis. EphA2 can be found in different self-assembly states: as a monomer, dimer, and oligomer. However, our understanding remains limited regarding which EphA2 state is responsible for driving pro-metastatic signaling. To address this limitation, we have developed SiMPull-POP, a single-molecule method for accurate quantification of membrane protein self-assembly. Our experiments revealed that a reduction of plasma membrane cholesterol strongly promoted EphA2 self-assembly. Indeed, low cholesterol caused a similar effect to the EphA2 ligand ephrinA1-Fc. These results indicate that cholesterol inhibits EphA2 assembly. Phosphorylation studies in different cell lines revealed that low cholesterol increased phospho-serine levels, the signature of oncogenic signaling. Investigation of the mechanism that cholesterol uses to inhibit the assembly and activity of EphA2 indicate an in-trans effect, where EphA2 is phosphorylated by protein kinase A downstream of beta-adrenergic receptor activity, which cholesterol also inhibits. Our study not only provides new mechanistic insights on EphA2 oncogenic function, but also suggests that cholesterol acts as a molecular safeguard mechanism that prevents uncontrolled self-assembly and activation of EphA2.
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Affiliation(s)
- Ryan J Schuck
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, USA
| | - Alyssa E Ward
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, USA
| | - Amita R Sahoo
- Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, USA
| | - Jennifer A Rybak
- Genome Science and Technology, University of Tennessee, Knoxville, USA
| | - Robert J Pyron
- Genome Science and Technology, University of Tennessee, Knoxville, USA
| | - Thomas N Trybala
- Department of Chemistry, University of Tennessee, Knoxville, USA
| | - Timothy B Simmons
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, USA
| | - Joshua A Baccile
- Department of Chemistry, University of Tennessee, Knoxville, USA
| | | | - Matthias Buck
- Department of Physiology and Biophysics, Case Western Reserve University, School of Medicine, Cleveland, USA
| | - Rajan Lamichhane
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, USA
| | - Francisco N Barrera
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, USA
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3
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Tripathy A, Priyadarsinee S, Bag N. Evaluation of functional transbilayer coupling in live cells by controlled lipid exchange and imaging fluorescence correlation spectroscopy. Methods Enzymol 2024; 700:1-32. [PMID: 38971596 DOI: 10.1016/bs.mie.2024.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2024]
Abstract
Biophysical coupling between the inner and outer leaflets, known as inter-leaflet or transbilayer coupling, is a fundamental organizational principle in the plasma membranes of live mammalian cells. Lipid-based interactions between the two leaflets are proposed to be a primary mechanism underlying transbilayer coupling. However, there are only a few experimental evidence supporting the existence of such interactions in live cells. This is seemingly due to the lack of experimental strategies to perturb the lipid composition in one leaflet and quantitative techniques to evaluate the biophysical properties of the opposite leaflet. The existing strategies often dependent on immobilization and clustering a component in one of the leaflets and technically demanding biophysical tools to evaluate the effects on the opposing leaflet. In the recent years, the London group developed a simple but elegant method, namely methyl-alpha-cyclodextrin catalyzed lipid exchange (LEX), to efficiently exchange outer leaflet lipids with an exogenous lipid of choice. Here, we adopted this method to perturb outer leaflet lipid composition. The corresponding changes in the inner leaflet is evaluated by comparing the diffusion of lipid probes localized in this leaflet in unperturbed and perturbed conditions. We employed highly multiplexed imaging fluorescence correlation spectroscopy (ImFCS), realized in a commercially available or home-built total internal reflection fluorescence microsocope equipped with a fast and sensitive camera, to determine diffusion coefficient of the lipid probes. Using the combination of LEX and ImFCS, we directly demonstrate lipid-based transbilayer coupling that does not require immobilization of membrane components in live mast cells in resting conditions. Overall, we present a relatively straightforward experimental strategy to evaluate transbilayer coupling quantitively in live cells.
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Affiliation(s)
- Arpita Tripathy
- Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal, India
| | - Sudipti Priyadarsinee
- Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal, India
| | - Nirmalya Bag
- Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal, India.
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4
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Suresh P, London E. MαCD-based plasma membrane outer leaflet lipid exchange in mammalian cells to study insulin receptor activity. Methods Enzymol 2024; 700:485-507. [PMID: 38971611 DOI: 10.1016/bs.mie.2024.03.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2024]
Abstract
Signaling receptors on the plasma membrane, such as insulin receptor, can have their activity modulated to some extent by their surrounding lipids. Studying the contribution of membrane lipid properties such as presence of ordered lipid domains or bilayer thickness on the activity of receptors has been a challenging objective in living cells. Using methyl-alpha cyclodextrin-mediated lipid exchange, we are able to alter the lipids of the outer leaflet plasma membrane of mammalian cells to investigate the effect of the properties of the exchanged lipid upon receptor function in live cells. In this article, we describe the technique of lipid exchange in detail and how it can be applied to better understand lipid-mediated regulation of insulin receptor activity in cells.
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Affiliation(s)
- Pavana Suresh
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States.
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States
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5
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Pabst G, Keller S. Exploring membrane asymmetry and its effects on membrane proteins. Trends Biochem Sci 2024; 49:333-345. [PMID: 38355393 DOI: 10.1016/j.tibs.2024.01.007] [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: 11/06/2023] [Revised: 01/08/2024] [Accepted: 01/19/2024] [Indexed: 02/16/2024]
Abstract
Plasma membranes utilize free energy to maintain highly asymmetric, non-equilibrium distributions of lipids and proteins between their two leaflets. In this review we discuss recent progress in quantitative research enabled by using compositionally controlled asymmetric model membranes. Both experimental and computational studies have shed light on the nuanced mechanisms that govern the structural and dynamic coupling between compositionally distinct bilayer leaflets. This coupling can increase the membrane bending rigidity and induce order - or lipid domains - across the membrane. Furthermore, emerging evidence indicates that integral membrane proteins not only respond to asymmetric lipid distributions but also exhibit intriguing asymmetric properties themselves. We propose strategies to advance experimental research, aiming for a deeper, quantitative understanding of membrane asymmetry, which carries profound implications for cellular physiology.
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Affiliation(s)
- Georg Pabst
- Biophysics, Institute of Molecular Bioscience (IMB), NAWI Graz, University of Graz, Graz 8010, Austria; BioTechMed-Graz, Graz, Austria; Field of Excellence BioHealth, University of Graz, Graz, Austria.
| | - Sandro Keller
- Biophysics, Institute of Molecular Bioscience (IMB), NAWI Graz, University of Graz, Graz 8010, Austria; BioTechMed-Graz, Graz, Austria; Field of Excellence BioHealth, University of Graz, Graz, Austria
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6
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Neuhaus M, Fryklund C, Taylor H, Borreguero-Muñoz A, Kopietz F, Ardalani H, Rogova O, Stirrat L, Bremner SK, Spégel P, Bryant NJ, Gould GW, Stenkula KG. EHD2 regulates plasma membrane integrity and downstream insulin receptor signaling events. Mol Biol Cell 2023; 34:ar124. [PMID: 37703099 PMCID: PMC10846623 DOI: 10.1091/mbc.e23-03-0078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 09/07/2023] [Accepted: 09/08/2023] [Indexed: 09/14/2023] Open
Abstract
Adipocyte dysfunction is a crucial driver of insulin resistance and type 2 diabetes. We identified EH domain-containing protein 2 (EHD2) as one of the most highly upregulated genes at the early stage of adipose-tissue expansion. EHD2 is a dynamin-related ATPase influencing several cellular processes, including membrane recycling, caveolae dynamics, and lipid metabolism. Here, we investigated the role of EHD2 in adipocyte insulin signaling and glucose transport. Using C57BL6/N EHD2 knockout mice under short-term high-fat diet conditions and 3T3-L1 adipocytes we demonstrate that EHD2 deficiency is associated with deterioration of insulin signal transduction and impaired insulin-stimulated GLUT4 translocation. Furthermore, we show that lack of EHD2 is linked with altered plasma membrane lipid and protein composition, reduced insulin receptor expression, and diminished insulin-dependent SNARE protein complex formation. In conclusion, these data highlight the importance of EHD2 for the integrity of the plasma membrane milieu, insulin receptor stability, and downstream insulin receptor signaling events, involved in glucose uptake and ultimately underscore its role in insulin resistance and obesity.
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Affiliation(s)
- Mathis Neuhaus
- Department of Experimental Medical Science, Lund University, 22184 Lund, Sweden
| | - Claes Fryklund
- Department of Experimental Medical Science, Lund University, 22184 Lund, Sweden
| | - Holly Taylor
- Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK
| | | | - Franziska Kopietz
- Department of Experimental Medical Science, Lund University, 22184 Lund, Sweden
| | - Hamidreza Ardalani
- Department of Chemistry, Centre for Analysis and Synthesis, Lund University, 22241 Lund, Sweden
| | - Oksana Rogova
- Department of Chemistry, Centre for Analysis and Synthesis, Lund University, 22241 Lund, Sweden
| | - Laura Stirrat
- Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK
| | - Shaun K. Bremner
- Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK
| | - Peter Spégel
- Department of Chemistry, Centre for Analysis and Synthesis, Lund University, 22241 Lund, Sweden
| | - Nia J. Bryant
- Department of Biology and York Biomedical Research Institute, University of York, York YO10 5DD, UK
| | - Gwyn W. Gould
- Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK
| | - Karin G. Stenkula
- Department of Experimental Medical Science, Lund University, 22184 Lund, Sweden
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7
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Girych M, Kulig W, Enkavi G, Vattulainen I. How Neuromembrane Lipids Modulate Membrane Proteins: Insights from G-Protein-Coupled Receptors (GPCRs) and Receptor Tyrosine Kinases (RTKs). Cold Spring Harb Perspect Biol 2023; 15:a041419. [PMID: 37487628 PMCID: PMC10547395 DOI: 10.1101/cshperspect.a041419] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
Lipids play a diverse and critical role in cellular processes in all tissues. The unique lipid composition of nerve membranes is particularly interesting because it contains, among other things, polyunsaturated lipids, such as docosahexaenoic acid, which the body only gets through the diet. The crucial role of lipids in neurological processes, especially in receptor-mediated cell signaling, is emphasized by the fact that in many neuropathological diseases there are significant deviations in the lipid composition of nerve membranes compared to healthy individuals. The lipid composition of neuromembranes can significantly affect the function of receptors by regulating the physical properties of the membrane or by affecting specific interactions between receptors and lipids. In addition, it is worth noting that the ligand-binding pocket of many receptors is located inside the cell membrane, due to which lipids can even modulate the binding of ligands to their receptors. These mechanisms highlight the importance of lipids in the regulation of membrane receptor activation and function. In this article, we focus on two major protein families: G-protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) and discuss how lipids affect their function in neuronal membranes, elucidating the basic mechanisms underlying neuronal function and dysfunction.
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Affiliation(s)
- Mykhailo Girych
- Department of Physics, University of Helsinki, FI-00014 Helsinki, Finland
| | - Waldemar Kulig
- Department of Physics, University of Helsinki, FI-00014 Helsinki, Finland
| | - Giray Enkavi
- Department of Physics, University of Helsinki, FI-00014 Helsinki, Finland
| | - Ilpo Vattulainen
- Department of Physics, University of Helsinki, FI-00014 Helsinki, Finland
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8
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Xia B, Viswanatha R, Hu Y, Mohr SE, Perrimon N. Pooled genome-wide CRISPR activation screening for rapamycin resistance genes in Drosophila cells. eLife 2023; 12:e85542. [PMID: 37078570 PMCID: PMC10118385 DOI: 10.7554/elife.85542] [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: 12/13/2022] [Accepted: 04/09/2023] [Indexed: 04/21/2023] Open
Abstract
Loss-of-function and gain-of-function genetic perturbations provide valuable insights into gene function. In Drosophila cells, while genome-wide loss-of-function screens have been extensively used to reveal mechanisms of a variety of biological processes, approaches for performing genome-wide gain-of-function screens are still lacking. Here, we describe a pooled CRISPR activation (CRISPRa) screening platform in Drosophila cells and apply this method to both focused and genome-wide screens to identify rapamycin resistance genes. The screens identified three genes as novel rapamycin resistance genes: a member of the SLC16 family of monocarboxylate transporters (CG8468), a member of the lipocalin protein family (CG5399), and a zinc finger C2H2 transcription factor (CG9932). Mechanistically, we demonstrate that CG5399 overexpression activates the RTK-Akt-mTOR signaling pathway and that activation of insulin receptor (InR) by CG5399 requires cholesterol and clathrin-coated pits at the cell membrane. This study establishes a novel platform for functional genetic studies in Drosophila cells.
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Affiliation(s)
- Baolong Xia
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
| | - Raghuvir Viswanatha
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
| | - Yanhui Hu
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
- Drosophila RNAi Screening Center, Harvard Medical SchoolBostonUnited States
| | - Stephanie E Mohr
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
- Drosophila RNAi Screening Center, Harvard Medical SchoolBostonUnited States
| | - Norbert Perrimon
- Department of Genetics, Blavatnik Institute, Harvard Medical SchoolBostonUnited States
- Drosophila RNAi Screening Center, Harvard Medical SchoolBostonUnited States
- Howard Hughes Medical InstituteBostonUnited States
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9
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London E. Ordered Domain (Raft) Formation in Asymmetric Vesicles and Its Induction upon Loss of Lipid Asymmetry in Artificial and Natural Membranes. MEMBRANES 2022; 12:870. [PMID: 36135889 PMCID: PMC9503047 DOI: 10.3390/membranes12090870] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/01/2022] [Accepted: 09/03/2022] [Indexed: 06/16/2023]
Abstract
Lipid asymmetry, the difference in the lipid composition in the inner and outer lipid monolayers (leaflets) of a membrane, is an important feature of eukaryotic plasma membranes. Investigation of the biophysical consequences of lipid asymmetry has been aided by advances in the ability to prepare artificial asymmetric membranes, especially by use of cyclodextrin-catalyzed lipid exchange. This review summarizes recent studies with artificial asymmetric membranes which have identified conditions in which asymmetry can induce or suppress the ability of membranes to form ordered domains (rafts). A consequence of the latter effect is that, under some conditions, a loss of asymmetry can induce ordered domain formation. An analogous study in plasma membrane vesicles has demonstrated that asymmetry can also suppress domain formation in natural membranes. Thus, it is possible that a loss of asymmetry can induce domain formation in vivo.
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Affiliation(s)
- Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
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10
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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] [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.
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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
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11
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Suresh P, London E. Using cyclodextrin-induced lipid substitution to study membrane lipid and ordered membrane domain (raft) function in cells. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183774. [PMID: 34534531 PMCID: PMC9128603 DOI: 10.1016/j.bbamem.2021.183774] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/30/2021] [Accepted: 09/08/2021] [Indexed: 02/03/2023]
Abstract
Methods for efficient cyclodextrin-induced lipid exchange have been developed in our lab. These make it possible to almost completely replace the lipids in the outer leaflet of artificial membranes or the plasma membranes of living cells with exogenous lipids. Lipid replacement/substitution allows detailed studies of how lipid composition and asymmetry influence the structure and function of membrane domains and membrane proteins. In this review, we both summarize progress on cyclodextrin exchange in cells, mainly by the use of methyl-alpha cyclodextrin to exchange phospholipids and sphingolipids, and discuss the issues to consider when carrying out lipid exchange experiments upon cells. Issues that impact interpretation of lipid exchange are also discussed. This includes how overly naïve interpretation of how lipid exchange-induced changes in domain formation can impact protein function.
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12
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Bryan AM, You JK, Li G, Kim J, Singh A, Morstein J, Trauner D, Pereira de Sá N, Normile TG, Farnoud AM, London E, Del Poeta M. Cholesterol and sphingomyelin are critical for Fcγ receptor-mediated phagocytosis of Cryptococcus neoformans by macrophages. J Biol Chem 2021; 297:101411. [PMID: 34793834 PMCID: PMC8661020 DOI: 10.1016/j.jbc.2021.101411] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 11/04/2021] [Accepted: 11/11/2021] [Indexed: 12/21/2022] Open
Abstract
Cryptococcus neoformans is a fungal pathogen that causes life-threatening meningoencephalitis in lymphopenic patients. Pulmonary macrophages comprise the first line of host defense upon inhalation of fungal spores by aiding in clearance but can also potentially serve as a niche for their dissemination. Given that macrophages play a key role in the outcome of a cryptococcal infection, it is crucial to understand factors that mediate phagocytosis of C. neoformans. Since lipid rafts (high-order plasma membrane domains enriched in cholesterol and sphingomyelin [SM]) have been implicated in facilitating phagocytosis, we evaluated whether these ordered domains govern macrophages' ability to phagocytose C. neoformans. We found that cholesterol or SM depletion resulted in significantly deficient immunoglobulin G (IgG)-mediated phagocytosis of fungus. Moreover, repletion of macrophage cells with a raft-promoting sterol (7-dehydrocholesterol) rescued this phagocytic deficiency, whereas a raft-inhibiting sterol (coprostanol) significantly decreased IgG-mediated phagocytosis of C. neoformans. Using a photoswitchable SM (AzoSM), we observed that the raft-promoting conformation (trans-AzoSM) resulted in efficient phagocytosis, whereas the raft-inhibiting conformation (cis-AzoSM) significantly but reversibly blunted phagocytosis. We observed that the effect on phagocytosis may be facilitated by Fcγ receptor (FcγR) function, whereby IgG immune complexes crosslink to FcγRIII, resulting in tyrosine phosphorylation of FcR γ-subunit (FcRγ), an important accessory protein in the FcγR signaling cascade. Correspondingly, cholesterol or SM depletion resulted in decreased FcRγ phosphorylation. Repletion with 7-dehydrocholesterol restored phosphorylation, whereas repletion with coprostanol showed FcRγ phosphorylation comparable to unstimulated cells. Together, these data suggest that lipid rafts are critical for facilitating FcγRIII-mediated phagocytosis of C. neoformans.
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Affiliation(s)
- Arielle M Bryan
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, New York, USA
| | - Jeehyun Karen You
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, New York, USA
| | - Guangtao Li
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA
| | - JiHyun Kim
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA
| | - Ashutosh Singh
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, New York, USA
| | - Johannes Morstein
- Department of Chemistry, New York University, New York, New York, USA
| | - Dirk Trauner
- Department of Chemistry, New York University, New York, New York, USA
| | - Nívea Pereira de Sá
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, New York, USA
| | - Tyler G Normile
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, New York, USA
| | - Amir M Farnoud
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, New York, USA
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA
| | - 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; Veteran Affairs Medical Center, Northport, New York, USA.
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