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Li B, London E. Inner leaflet cationic lipid increases nucleic acid loading independently of outer leaflet lipid charge in asymmetric liposomes. Methods 2023; 219:16-21. [PMID: 37683900 PMCID: PMC10680395 DOI: 10.1016/j.ymeth.2023.08.015] [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: 04/11/2023] [Revised: 07/17/2023] [Accepted: 08/14/2023] [Indexed: 09/10/2023] Open
Abstract
Use of cationic lipid vesicles (liposomes) can yield large amounts of nucleic acid entrapped inside the vesicles and/or bound to the external surface of the vesicles. To show a method to prepare asymmetric lipid vesicles (liposomes) with high amounts of entrapped nucleic acid is possible, symmetric and asymmetric lipid vesicles composed of mixtures of neutral (zwitterionic), anionic, and/or cationic phospholipids were formed in the presence of oligo DNA. For symmetric large unilamellar vesicles nucleic acid association with vesicles was roughly 100 times greater for vesicles with a net cationic charge than for vesicles having a net neutral or anionic net charge. A high degree of association between nucleic acid and lipid was also achieved using asymmetric large unilamellar vesicles with a net cationic charge in their inner leaflet, even when they had an anionic charge in their outer leaflet. In contrast, asymmetric vesicles in which only the outer leaflet had a net cationic charge had only low amounts of vesicle-associated nucleic acid, similar in amount to the amount of nucleic acid associated with asymmetric vesicles with an outer leaflet having a net anionic charge. These results indicate that in asymmetric vesicles with cationic lipid enriched inner leaflets nucleic acid is largely entrapped inside the vesicle lumen rather than bound to their external surface, and that asymmetric vesicles can be used to trap high amounts of nucleic acid even when using a lipid composition in the outer leaflet of a lipid vesicle that does not associate with nucleic acids. Such asymmetrically charged vesicles should have applications in studies of membrane protein-nucleic acid interactions as well as in studies of how membrane charge asymmetry can influence membrane protein structure, orientation, and function.
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Affiliation(s)
- Bingchen Li
- Dept. of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
| | - Erwin London
- Dept. of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA.
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2
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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 2023:S0006-3495(23)00478-2. [PMID: 37533258 DOI: 10.1016/j.bpj.2023.07.027] [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] [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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3
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Li MH, Zhang X, London E, Raleigh DP. Impact of Ca 2+ on membrane catalyzed IAPP amyloid formation and IAPP induced vesicle leakage. Biochim Biophys Acta Biomembr 2023; 1865:184161. [PMID: 37121365 PMCID: PMC10735052 DOI: 10.1016/j.bbamem.2023.184161] [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] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 04/10/2023] [Accepted: 04/24/2023] [Indexed: 05/02/2023]
Abstract
Human islet amyloid polypeptide (hIAPP, also known as amylin) is a 37 amino acid pancreatic polypeptide hormone that plays a role in regulating glucose levels, but forms pancreatic amyloid in type-2 diabetes. The process of amyloid formation by hIAPP contributes to β-cell death in the disease. Multiple mechanisms of hIAPP induced toxicity of β-cells have been proposed including disruption of cellular membranes. However, the nature of hIAPP membrane interactions and the effect of ions and other molecules on hIAPP membrane interactions are not fully understood. Many studies have used model membranes with a high content of anionic lipids, often POPS, however the concentration of anionic lipids in the β-cell plasma membrane is low. Here we study the concentration dependent effect of Ca2+ (0 to 50 mM) on hIAPP membrane interactions using large unilamellar vesicles (LUVs) with anionic lipid content ranging from 0 to 50 mol%. We find that Ca2+ does not effectively inhibit hIAPP amyloid formation and hIAPP induced membrane leakage from binary LUVs with a low percentage of POPS, but has a greater effect on LUVs with a high percentage of POPS. Mg2+ had very similar effects, and the effects of Ca2+ and Mg2+ can be largely rationalized by the neutralization of POPS charge. The implications for hIAPP-membrane interactions are discussed.
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Affiliation(s)
- Ming-Hao Li
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, NY 11794, United States
| | - Xiaoxue Zhang
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, United States
| | - Erwin London
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, NY 11794, United States; Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, United States; Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, United States.
| | - Daniel P Raleigh
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, NY 11794, United States; Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, United States; Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, United States.
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4
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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 (Basel) 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] [What about the content of this article? (0)] [Affiliation(s)] [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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5
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Murata M, Matsumori N, Kinoshita M, London E. Molecular substructure of the liquid-ordered phase formed by sphingomyelin and cholesterol: sphingomyelin clusters forming nano-subdomains are a characteristic feature. Biophys Rev 2022; 14:655-678. [PMID: 35791389 DOI: 10.1007/s12551-022-00967-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 05/26/2022] [Indexed: 11/29/2022] Open
Abstract
As a model of lipid rafts, the liquid-ordered (Lo) phase formed by sphingomyelin (SM) and cholesterol (Cho) in bilayer membranes has long attracted the attention of biophysics researchers. New approaches and methodologies have led to a better understanding of the molecular basis of the Lo domain structure. This review summarizes studies on model membrane systems consisting of SM/unsaturated phospholipid/Cho implying that the Lo phase contains SM-based nanodomains (or nano-subdomains). Some of the Lo phase properties may be attributed to these nanodomains. Several studies suggest that the nanodomains contain clustered SM molecules packed densely to form gel-phase-like subdomains of single-digit nanometer size at physiological temperatures. Cho and unsaturated lipids located in the Lo phase are likely to be concentrated at the boundaries between the subdomains. These subdomains are not readily detected in the Lo phase formed by saturated phosphatidylcholine (PC) molecules, suggesting that they are strongly stabilized by homophilic interactions specific to SM, e.g., between SM amide groups. This model for the Lo phase is supported by experiments using dihydro-SM, which is thought to have stronger homophilic interactions than SM, as well as by studies using the enantiomer of SM having opposite stereochemistry to SM at the 2 and 3 positions and by some molecular dynamics (MD) simulations of lipid bilayers containing Lo-lipids. Nanosized gel subdomains seem to play an important role in controlling membrane organization and function in biological membranes.
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Affiliation(s)
- Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan.,ERATO, Lipid Active Structure Project, Japan Science and Technology Agency, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan
| | - Nobuaki Matsumori
- Department of Chemistry, Faculty of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395 Japan
| | - Masanao Kinoshita
- ERATO, Lipid Active Structure Project, Japan Science and Technology Agency, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan.,Department of Chemistry, Faculty of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395 Japan
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215 USA
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Li MH, Manathunga L, London E, Raleigh DP. Correction to "The Fluorescent Dye 1,6-Diphenyl-1,3,5-hexatriene Binds to Amyloid Fibrils Formed by Human Amylin and Provides a New Probe of Amylin Amyloid Kinetics". Biochemistry 2022; 61:1149-1149. [PMID: 35617707 DOI: 10.1021/acs.biochem.2c00263] [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: 11/30/2022]
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7
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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] [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.
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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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8
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Suresh P, Miller WT, London E. Effect of MαCD-mediated phospholipid exchange on plasma membrane ordered lipid domain stability. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.1866] [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: 11/02/2022] Open
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9
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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. Biochim Biophys Acta Biomembr 2022; 1864:183774. [PMID: 34534531 PMCID: PMC9128603 DOI: 10.1016/j.bbamem.2021.183774] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [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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10
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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] [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: 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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11
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Li MH, Raleigh DP, London E. Preparation of Asymmetric Vesicles with Trapped CsCl Avoids Osmotic Imbalance, Non-Physiological External Solutions, and Minimizes Leakage. Langmuir 2021; 37:11611-11617. [PMID: 34550698 PMCID: PMC9128599 DOI: 10.1021/acs.langmuir.1c01971] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The natural asymmetry of cellular membranes influences their properties. In recent years, methodologies for preparing asymmetric vesicles have been developed that rely on cyclodextrin-catalyzed exchange of lipids between donor lipid multilamellar vesicles and acceptor lipid unilamellar vesicles, and the subsequent separation of the, now asymmetric, acceptor vesicles from the donors. Isolation is often accomplished by preloading acceptor vesicles with a high concentration of sucrose, typically 25% (w/w), and separating from donor and cyclodextrin by sucrose gradient centrifugation. We found that when the asymmetric vesicles prepared using methyl-α-cyclodextrin exchange were dispersed under hypotonic conditions using physiological salt solutions, there was enhanced leakage of an entrapped probe, 6-carboxyfluorescein. Studies with symmetric vesicles showed this was due to osmotic pressure and was specific to hypotonic solutions. Inclusion of cholesterol partly reduced leakage but did not completely eliminate it. To avoid having to use hypotonic conditions or to suspend vesicles at nonphysiological solute concentrations to minimize leakage, a method for preparing asymmetric vesicles using acceptor vesicle-entrapped CsCl at a physiological ion concentration (100 mM) was developed. Asymmetric vesicles prepared with the entrapped CsCl protocol were highly resistant to 6-carboxyfluorescein leakage out of the vesicles.
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Affiliation(s)
- Ming-Hao Li
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794, United States
| | - Daniel P. Raleigh
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794, United States
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, New York 11794, United States
| | - Erwin London
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794, United States
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States
- Department of Biochemistry, Stony Brook University, Stony Brook, New York 11794, United States
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12
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Suresh P, Miller WT, London E. Phospholipid exchange shows insulin receptor activity is supported by both the propensity to form wide bilayers and ordered raft domains. J Biol Chem 2021; 297:101010. [PMID: 34324831 PMCID: PMC8379460 DOI: 10.1016/j.jbc.2021.101010] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 07/21/2021] [Accepted: 07/23/2021] [Indexed: 11/29/2022] Open
Abstract
Insulin receptor (IR) is a membrane tyrosine kinase that mediates the response of cells to insulin. IR activity has been shown to be modulated by changes in plasma membrane lipid composition, but the properties and structural determinants of lipids mediating IR activity are poorly understood. Here, using efficient methyl-alpha-cyclodextrin mediated lipid exchange, we studied the effect of altering plasma membrane outer leaflet phospholipid composition upon the activity of IR in mammalian cells. After substitution of endogenous lipids with lipids having an ability to form liquid ordered (Lo) domains (sphingomyelins) or liquid disordered (Ld) domains (unsaturated phosphatidylcholines (PCs)), we found that the propensity of lipids to form ordered domains is required for high IR activity. Additional substitution experiments using a series of saturated PCs showed that IR activity increased substantially with increasing acyl chain length, which increases both bilayer width and the propensity to form ordered domains. Incorporating purified IR into alkyl maltoside micelles with increasing hydrocarbon lengths also increased IR activity, but more modestly than by increasing lipid acyl chain length in cells. These results suggest that the ability to form Lo domains as well as wide bilayer width contributes to increased IR activity. Inhibition of phosphatases showed that some of the lipid dependence of IR activity upon lipid structure reflected protection from phosphatases by lipids that support Lo domain formation. These results are consistent with a model in which a combination of bilayer width and ordered domain formation modulates IR activity via IR conformation and accessibility to phosphatases.
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Affiliation(s)
- Pavana Suresh
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA
| | - W Todd Miller
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA; Department of Veterans Affairs Medical Center, Northport, New York, USA
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA.
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13
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Li MH, Manathunga L, London E, Raleigh DP. The Fluorescent Dye 1,6-Diphenyl-1,3,5-hexatriene Binds to Amyloid Fibrils Formed by Human Amylin and Provides a New Probe of Amylin Amyloid Kinetics. Biochemistry 2021; 60:1964-1970. [PMID: 34128641 DOI: 10.1021/acs.biochem.1c00328] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fluorescent dye 1,6-diphenyl-1,3,5-hexatriene (DPH) is widely used as a probe of membrane order. We show that DPH also interacts with amyloid fibrils formed by human amylin (h-amylin, also known as islet amyloid polypeptide) in solution, and this results in a 100-fold increase in DPH fluorescence for a sample of 20 μM h-amylin and 0.25 μM DPH. No increase in DPH fluorescence is observed with the non-amyloidogenic rat amylin or with freshly dissolved, nonfibrillar h-amylin. The time course of amyloid formation by amylin was followed by monitoring the fluorescence of added DPH as a function of time and was similar to that monitored by the standard fluorescent probe thioflavin-T. The inclusion of DPH in the buffer did not perturb the time course of amyloid formation under the conditions examined, and the time course was independent of the range of DPH concentrations tested (0.25-5 μM). The maximum final fluorescence intensity is observed at substoichiometric ratios of DPH to amylin. No significant increase in fluorescence was observed during the lag phase of amyloid formation, and the implications for the structure of amylin prefibril oligomers are discussed. h-Amylin contains three aromatic residues. A triple aromatic to leucine mutant forms amyloid, and DPH binds to the resulting fibrils, indicating that interactions with aromatic side chains are not required for DPH-amylin amyloid interactions. DPH may be especially useful for studies of mutant amylins and other polypeptides in which changes in charged residues might complicate interpretation of thioflavin-T fluorescence.
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Affiliation(s)
- Ming-Hao Li
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794, United States
| | - Lakshan Manathunga
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States.,Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, New York 11794, United States
| | - Erwin London
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794, United States.,Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States.,Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11794, United States
| | - Daniel P Raleigh
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794, United States.,Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States.,Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, New York 11794, United States
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14
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Abstract
Studying the interaction of pore-forming toxins, including perfringolysin O (PFO), with lipid is crucial to understanding how they insert into membranes, assemble, and associate with membrane domains. In almost all past studies, symmetric lipid bilayers, i.e., bilayers having the same lipid composition in each monolayer (leaflet), have been used to study this process. However, practical methods to make asymmetric lipid vesicles have now been developed. These involve a cyclodextrin-catalyzed lipid exchange process in which the outer leaflet lipids are switched between two lipid vesicle populations with different lipid compositions. By use of alpha class cyclodextrins, it is practical to include a wide range of sterol concentrations in asymmetric vesicles. In this article, protocols for preparing asymmetric lipid vesicles are described, and to illustrate how they may be applied to studies of pore-forming toxin behavior, we summarize what has been learned about PFO conformation and its lipid interaction in symmetric and in asymmetric artificial lipid vesicles.
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Affiliation(s)
- Shinako Kakuda
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States
| | - Bingchen Li
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States.
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15
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Suresh P, Miller WT, London E. Modulation of Insulin Receptor Activity Upon Plasma Membrane Sterol and Phospholipid Substitutions to Alter Lipid Domain Formation. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.2059] [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: 10/22/2022] Open
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16
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Abstract
We have developed cyclodextrin-catalyzed lipid exchange methods to prepare large unilamellar vesicles (LUVs) with asymmetric charge distributions, i.e., with different net charges on the lipids in the inner and outer leaflets. LUVs contained a mixture of a zwitterionic lipid (phosphatidylcholine), cholesterol, and various cationic lipids (O-ethyl phosphatidylcholine or dioleoyl-3-trimethylammonium propane) or anionic lipids (phosphatidylglycerol, phosphatidylserine, or phosphatidic acid). Symmetric and asymmetric LUVs with a wide variety of lipid combinations were prepared. The asymmetric LUVs contained cationic or anionic outer leaflets and inner leaflets that had either the opposite charge or were uncharged. The behavior of symmetric LUVs prepared with zwitterionic, anionic, or cationic leaflets was compared to those of asymmetric LUVs. Lipid exchange was confirmed by quantitative thin-layer chromatography, and lipid asymmetry by a novel assay measuring binding of a cationic fluorescent probe to the LUV outer leaflet. For both symmetric and asymmetric LUVs, the level of entrapment of the cationic drug doxorubicin was controlled by the charge on the inner leaflet, with the greatest entrapment and slowest leakage in vesicles with an anionic inner leaflet. This shows that it is possible to choose inner leaflet lipids to maximize liposomal loading of charged drugs independently of the identity of outer-leaflet lipids. This implies that it should also be possible to independently vary outer-leaflet lipids to, for example, impart favorable bioavailability and biodistribution properties to lipid vesicles.
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Affiliation(s)
- Bingchen Li
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11794-5215, United States
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11794-5215, United States
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17
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Yano Y, Hanashima S, Tsuchikawa H, Yasuda T, Slotte JP, London E, Murata M. Sphingomyelins and ent-Sphingomyelins Form Homophilic Nano-Subdomains within Liquid Ordered Domains. Biophys J 2020; 119:539-552. [PMID: 32710823 PMCID: PMC7399500 DOI: 10.1016/j.bpj.2020.06.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 06/19/2020] [Accepted: 06/26/2020] [Indexed: 12/29/2022] Open
Abstract
Sphingomyelin (SM), a major component of small domains (or lipid rafts) in mammalian cell membranes, forms a liquid-ordered phase in the presence of cholesterol (Cho). However, the nature of molecular interactions within the ordered SM/Cho phase remains elusive. We previously revealed that stearoyl-SM (SSM) and its enantiomer (ent-SSM) separately form nano-subdomains within the liquid-ordered phase involving homophilic SSM-SSM and ent-SSM-ent-SSM interactions. In this study, the details of the subdomain formation by SSMs at the nanometer range were examined using Förster resonance energy transfer (FRET) measurements in lipid bilayers containing SSM and ent-SSM, dioleoyl-phosphatidylcholine and Cho. Although microscopy detected a stereochemical effect on partition coefficient favoring stereochemically homophilic interactions in the liquid-ordered state, it showed no significant difference in large-scale liquid-ordered domain formation by the two stereoisomers. In contrast to the uniform domains seen microscopy, FRET analysis using fluorescent donor- and acceptor-labeled SSM showed distinct differences in SM and ent-SM colocalization within nanoscale distances. Donor- and acceptor-labeled SSM showed significantly higher FRET efficiency than did donor-labeled SSM and acceptor-labeled ent-SSM in lipid vesicles composed of “racemic” (1:1) mixtures of SSM/ent-SSM with dioleoylphosphatidylcholine and Cho. The difference in FRET efficiency indicated that SSM and ent-SSM assemble to form separate nano-subdomains. The average size of the subdomains decreased as temperature increased, and at physiological temperatures, the subdomains were found to have a single-digit nanometer radius. These results suggest that (even in the absence of ent-SM) SM-SM interactions play a crucial role in forming nano-subdomains within liquid-ordered domains and may be a key feature of lipid microdomains (or rafts) in biological membranes.
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Affiliation(s)
- Yo Yano
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan; ERATO, Lipid Active Structure Project, Japan Science and Technology Agency, Graduate School of Science, Osaka University, Osaka, Japan
| | - Shinya Hanashima
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
| | - Hiroshi Tsuchikawa
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
| | - Tomokazu Yasuda
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York.
| | - Michio Murata
- Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan; ERATO, Lipid Active Structure Project, Japan Science and Technology Agency, Graduate School of Science, Osaka University, Osaka, Japan.
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18
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Suresh P, London E, Miller WT. Modulation of Insulin Receptor Kinase Activity by Lipid Environment. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.1417] [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: 10/25/2022] Open
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19
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Li G, Kakuda S, Li B, Wang Q, London E. Nanodomains Persist to much Higher Temperatures than Large Scale Phase Separation in Giant Plasma Membrane Vesicles and Can Respond Differently to Alterations of Plasma Membrane Lipid Composition. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.1342] [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: 10/25/2022] Open
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20
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Li G, Wang Q, Kakuda S, London E. Nanodomains can persist at physiologic temperature in plasma membrane vesicles and be modulated by altering cell lipids. J Lipid Res 2020; 61:758-766. [PMID: 31964764 DOI: 10.1194/jlr.ra119000565] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [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: 12/03/2019] [Revised: 01/06/2020] [Indexed: 01/04/2023] Open
Abstract
The formation and properties of liquid-ordered (Lo) lipid domains (rafts) in the plasma membrane are still poorly understood. This limits our ability to manipulate ordered lipid domain-dependent biological functions. Giant plasma membrane vesicles (GPMVs) undergo large-scale phase separations into coexisting Lo and liquid-disordered lipid domains. However, large-scale phase separation in GPMVs detected by light microscopy is observed only at low temperatures. Comparing Förster resonance energy transfer-detected versus light microscopy-detected domain formation, we found that nanodomains, domains of nanometer size, persist at temperatures up to 20°C higher than large-scale phases, up to physiologic temperature. The persistence of nanodomains at higher temperatures is consistent with previously reported theoretical calculations. To investigate the sensitivity of nanodomains to lipid composition, GPMVs were prepared from mammalian cells in which sterol, phospholipid, or sphingolipid composition in the plasma membrane outer leaflet had been altered by cyclodextrin-catalyzed lipid exchange. Lipid substitutions that stabilize or destabilize ordered domain formation in artificial lipid vesicles had a similar effect on the thermal stability of nanodomains and large-scale phase separation in GPMVs, with nanodomains persisting at higher temperatures than large-scale phases for a wide range of lipid compositions. This indicates that it is likely that plasma membrane nanodomains can form under physiologic conditions more readily than large-scale phase separation. We also conclude that membrane lipid substitutions carried out in intact cells are able to modulate the propensity of plasma membranes to form ordered domains. This implies lipid substitutions can be used to alter biological processes dependent upon ordered domains.
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Affiliation(s)
- Guangtao Li
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215
| | - Qing Wang
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215
| | - Shinako Kakuda
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215. mailto:
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21
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Li G, Kakuda S, Suresh P, Canals D, Salamone S, London E. Replacing plasma membrane outer leaflet lipids with exogenous lipid without damaging membrane integrity. PLoS One 2019; 14:e0223572. [PMID: 31589646 PMCID: PMC6779269 DOI: 10.1371/journal.pone.0223572] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 09/20/2019] [Indexed: 12/24/2022] Open
Abstract
We recently introduced a MαCD-based method to efficiently replace virtually the entire population of plasma membrane outer leaflet phospholipids and sphingolipids of cultured mammalian cells with exogenous lipids (Li et al, (2016) Proc. Natl. Acad. Sci USA 113:14025–14030). Here, we show if the lipid-to- MαCD ratio is too high or low, cells can round up and develop membrane leakiness. We found that this cell damage can be reversed/prevented if cells are allowed to recover from the exchange step by incubation in complete growth medium. After exchange and transfer to complete growth medium cell growth was similar to that of untreated cells. In some cases, cell damage was also prevented by carrying out exchange at close to room temperature (rather than at 37°C). Exchange with lipids that do (sphingomyelin) or do not (unsaturated phosphatidylcholine) support a high level of membrane order in lipid vesicles had the analogous effect on plasma membrane order, confirming exogenous lipid localization in the plasma membrane. Importantly, changes in lipid composition and plasma membrane properties after exchange and recovery persisted for several hours. Thus, it should be possible to use lipid exchange to investigate the effect of plasma membrane lipid composition upon several aspects of membrane structure and function.
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Affiliation(s)
- Guangtao Li
- Dept. of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States of America
| | - Shinako Kakuda
- Dept. of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States of America
| | - Pavana Suresh
- Dept. of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States of America
| | - Daniel Canals
- Department of Medicine and Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY, United States of America
| | - Silvia Salamone
- Department of Medicine and Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY, United States of America
| | - Erwin London
- Dept. of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States of America
- * E-mail:
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22
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Feitosa A, Assunção C, Yoshida T, Sabbag J, Araujo T, London E. Prolonged status epilepticus as a first symptom of a negative antibody autoimmune disease – A case report. J Neurol Sci 2019. [DOI: 10.1016/j.jns.2019.10.799] [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: 11/26/2022]
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23
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Heerklotz H, London E. Kiss and Run Asymmetric Vesicles to Investigate Coupling. Biophys J 2019; 117:1009-1011. [PMID: 31477242 DOI: 10.1016/j.bpj.2019.07.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 07/29/2019] [Indexed: 10/26/2022] Open
Affiliation(s)
- Heiko Heerklotz
- Institute of Pharmaceutical Sciences, University of Freiburg, Freiburg, Germany; Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada; Signalling Research Centers BIOSS and CIBSS, Freiburg, Germany.
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York.
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24
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Abstract
The lipid bilayer, together with embedded proteins, is the central structure in biomembranes. While artificial lipid bilayers are useful to model natural membranes, they are generally symmetric, with the same membrane lipid composition in each lipid monolayer (leaflet). In contrast, natural membranes are often asymmetric, with different lipids in each leaflet. To prepare asymmetric lipid vesicles, we developed cyclodextrin-catalyzed phospholipid exchange procedures. The basic method is that an excess of vesicles with one set of lipids (the donor vesicles) is mixed with a second set of vesicles (acceptor vesicles) with a different set of lipids. Cyclodextrin is introduced into the external aqueous solution, so that lipids in the outer leaflet of the vesicles bind to it and are shuttled between the vesicles. At equilibrium, the lipids in the outer leaflet of the acceptor vesicles are replaced by those from the donor vesicles. The exchanged acceptor vesicles are then isolated. Asymmetric vesicles are versatile in terms of vesicle sizes and lipid compositions that can be prepared. Measuring asymmetry is often difficult. A variety of assays can be used to measure the extent of asymmetry, but most are specific for one particular membrane lipid type or class, and there are none that can be used in all situations. Studies using asymmetric vesicles have begun to explore how asymmetry influences lipid movement across the bilayer, the formation of ordered lipid domains, coupling between the physical properties in each leaflet, and membrane protein conformation. Lipid domain formation stands out as one of the most important properties in which asymmetry is likely to be crucial. Lipid bilayers can exist in both liquidlike and solid/ordered-like states depending on lipid structure, and in lipid vesicles with a mixture of lipids highly ordered and disordered domains can coexist. However, until very recently, such studies only had been carried out in symmetric artificial membranes. Whether ordered domains (often called lipid rafts) and disordered lipid domains coexist in asymmetric cell membranes remains controversial partly because lipids favoring the formation of an ordered state are largely restricted to the leaflet facing the external environment. Studies using asymmetric vesicles have recently shown that each leaflet can influence the physical behavior of the other, i.e., that the domain forming properties in each leaflet tend to be coupled, with consequences highly dependent upon the details of lipid structure. Future studies investigating the dependence of coupling and properties upon the details of lipid composition should clarify the potential of natural membranes to form lipid domains. In addition, we recently extended the exchange method to living mammalian cells, using exchange to efficiently replace virtually the entire phospholipid and sphingolipid population of the plasma membrane outer leaflet with exogenous lipids without harming cells. This should allow detailed studies of the functional impact of lipid structure, asymmetry, domain organization, and interactions with membrane proteins in living cells.
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Affiliation(s)
- Erwin London
- Department of Biochemistry and Cell Biology and Department of Chemistry Stony Brook University, Stony Brook, New York 11794, United States
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25
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Wang Q, London E. The Influence of Lipid Composition Upon Lipid Domain Formation in the Inner Leaflet of Asymmetric Vesicles Using Spin-Labeled Lipids. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.464] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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26
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Delle Bovi RJ, Kim J, Suresh P, London E, Miller WT. Sterol structure dependence of insulin receptor and insulin-like growth factor 1 receptor activation. Biochim Biophys Acta Biomembr 2019; 1861:819-826. [PMID: 30682326 DOI: 10.1016/j.bbamem.2019.01.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 12/21/2018] [Accepted: 01/21/2019] [Indexed: 01/02/2023]
Abstract
The plasma membrane is a dynamic environment with a complex composition of lipids, proteins, and cholesterol. Areas enriched in cholesterol and sphingolipids are believed to form lipid rafts, domains of highly ordered lipids. The unique physical properties of these domains have been proposed to influence many cellular processes. Here, we demonstrate that the activation of insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF1R) depends critically on the structures of membrane sterols. IR and IGF1R autophosphorylation in vivo was inhibited by cholesterol depletion, and autophosphorylation was restored by the replacement with exogenous cholesterol. We next screened a variety of sterols for effects on IR activation. The ability of sterols to support IR autophosphorylation was strongly correlated to the propensity of the sterols to form ordered domains. IR autophosphorylation was fully restored by the incorporation of ergosterol, dihydrocholesterol, 7-dehydrocholesterol, lathosterol, desmosterol, and allocholesterol, partially restored by epicholesterol, and not restored by lanosterol, coprostanol, and 4-cholesten-3-one. These data support the hypothesis that the ability to form ordered domains is sufficient for a sterol to support ligand-induced activation of IR and IGF1R in intact mammalian cells.
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Affiliation(s)
- Richard J Delle Bovi
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794-8661, United States of America
| | - JiHyun Kim
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, United States of America
| | - Pavana Suresh
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, United States of America
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, United States of America.
| | - W Todd Miller
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794-8661, United States of America; Department of Veterans Affairs Medical Center, Northport, NY 11768, United States of America.
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27
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Abstract
The location of fluorescent groups relative to the lipid bilayer can be evaluated using fluorescence quenchers embedded in the membrane and/or dissolved in aqueous solution. Quenching can be used to define the membrane topography of membrane proteins and individual membrane-embedded hydrophobic helices by combining it with the placement of fluorescent groups, including Trp, at defined sequence positions. This chapter briefly discusses various quenching methods for studies of membrane protein topography, and provides detailed protocols for dual quencher analysis (DQA), a rapid, highly sensitive, and experimentally flexible approach in which the information gained from both a membrane-embedded and aqueous quencher is combined. The advantages of the DQA method include flexibility with regard to the bilayer compositions to which it can be applied, including membranes composed of lipids of varying head group and acyl chain compositions, as well as the ability to identify mixed populations of fluorophores residing at different depths within the bilayer.
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Affiliation(s)
- Gregory A Caputo
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ, USA
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA.
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28
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London E. New Insights into How Cholesterol and Unsaturation Control Lipid Domain Formation. Biophys J 2018; 111:465-466. [PMID: 27508431 DOI: 10.1016/j.bpj.2016.06.037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 06/09/2016] [Indexed: 12/29/2022] Open
Affiliation(s)
- Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York.
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29
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Wang Q, London E. Lipid Structure and Composition Control Consequences of Interleaflet Coupling in Asymmetric Vesicles. Biophys J 2018; 115:664-678. [PMID: 30082033 DOI: 10.1016/j.bpj.2018.07.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 07/05/2018] [Accepted: 07/10/2018] [Indexed: 01/07/2023] Open
Abstract
Using Förster resonance energy transfer, raft/liquid-ordered-domain formation was assessed in asymmetric vesicles containing outer leaflets composed of high-Tm (melting temperature) saturated phosphatidylcholines (diC18:0PC, diC16:0PC, diC15:0PC, or diC14:0PC), low-Tm unsaturated dioleoylphosphatidylcholine (DOPC) and cholesterol, and inner leaflets composed of lipids that by themselves would not form ordered domains (DOPC and cholesterol). Ordered-domain formation in the outer leaflet was compared to that in symmetric vesicles with the same lipid composition as the asymmetric vesicle outer leaflets. The difference between ordered-domain thermal stability in asymmetric and symmetric vesicles was highly dependent on high-Tm PC acyl-chain length. At one extreme, in diC14:0PC-containing asymmetric vesicles, the outer leaflet did not segregate to form ordered domains over the entire experimental temperature range even though ordered domains formed in the symmetric vesicles, indicating the inner leaflet dominated outer-leaflet physical behavior in the asymmetric vesicles. At the other extreme, in diC18:0PC-containing asymmetric vesicles, ordered domains formed over the entire temperature range at which they were present in symmetric vesicles, indicating the inner leaflet did not dominate outer-leaflet physical behavior. DiC15:0PC- and diC16:0PC-containing vesicles exhibited intermediate behaviors. A different set of vesicles was prepared with high-Tm lipid sphingomyelin (SM) in place of saturated phosphatidylcholine, and the % SM was varied. The thermal stability of outer-leaflet ordered domains in asymmetric vesicles was found to decrease more than in symmetric vesicles as SM levels decreased, indicating that the inner leaflet increasingly dominated outer leaflet physical state as SM levels decreased. Overall, inhibition of outer-leaflet ordered-domain formation in asymmetric vesicles by inner-leaflet lipids decreased as the ability of outer-leaflet lipids to form an ordered state by themselves increased, i.e., when outer-leaflet high-Tm lipid content or acyl-chain length increased. This has implications for how ordered-domain formation may be controlled in vivo.
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Affiliation(s)
- Qing Wang
- 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.
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30
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Abstract
Amyloid formation has been implicated in a wide range of human diseases, and the interaction of amyloidogenic proteins with membranes are believed to be important for many of them. In type-2 diabetes, human islet amyloid polypeptide (IAPP) forms amyloids, which contribute to β-cell death and dysfunction in the disease. IAPP-membrane interactions are potential mechanisms of cytotoxicity. In vitro studies have shown that cholesterol significantly modulates the ability of model membranes to induce IAPP amyloid formation and IAPP-mediated membrane damage. It is not known if this is due to the general effects of cholesterol on membranes or because of specific sterol-IAPP interactions. The effects of replacing cholesterol with eight other sterols/steroids on IAPP binding to model membranes, membrane disruption, and membrane-mediated amyloid formation were examined. The primary effect of the sterols/steroids on the IAPP-membrane interactions was found to reflect their effect upon membrane order as judged by fluorescence anisotropy measurements. Specific IAPP-sterol/steroid interactions have smaller effects. The fraction of vesicles that bind IAPP was inversely correlated with the sterols/steroids' effect on membrane order, as was the extent of IAPP-induced membrane leakage and the time to form amyloids. The correlation between the fraction of vesicles binding IAPP and membrane leakage was particularly tight, suggesting the restriction of IAPP to a subset of vesicles is responsible for incomplete leakage.
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31
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Toledo A, Huang Z, Coleman JL, London E, Benach JL. Lipid rafts can form in the inner and outer membranes of Borrelia burgdorferi and have different properties and associated proteins. Mol Microbiol 2018; 108:63-76. [PMID: 29377398 DOI: 10.1111/mmi.13914] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 01/03/2018] [Accepted: 01/21/2018] [Indexed: 01/23/2023]
Abstract
Lipid rafts are microdomains present in the membrane of eukaryotic organisms and bacterial pathogens. They are characterized by having tightly packed lipids and a subset of specific proteins. Lipid rafts are associated with a variety of important biological processes including signaling and lateral sorting of proteins. To determine whether lipid rafts exist in the inner membrane of Borrelia burgdorferi, we separated the inner and outer membranes and analyzed the lipid constituents present in each membrane fraction. We found that both the inner and outer membranes have cholesterol and cholesterol glycolipids. Fluorescence anisotropy and FRET showed that lipids from both membranes can form rafts but have different abilities to do so. The analysis of the biochemically defined proteome of lipid rafts from the inner membrane revealed a diverse set of proteins, different from those associated with the outer membrane, with functions in protein trafficking, chemotaxis and signaling.
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Affiliation(s)
- Alvaro Toledo
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - Zhen Huang
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA
| | - James L Coleman
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA
| | - Jorge L Benach
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
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32
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Park S, Li B, London E. Expanding the Preparation of Asymmetric Lipid Vesicles to Additional Cyclodextrins and Cationic Lipids. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.567] [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: 10/18/2022] Open
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33
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Abstract
Lipid rafts are membrane microdomains that are involved in cellular processes such as protein trafficking and signaling processes, and which play a fundamental role in membrane fluidity and budding. The lipid composition of the membrane and the biochemical characteristics of the lipids found within rafts define the ability of cells to form microdomains and compartmentalize the membrane. In this chapter, we describe the biophysical, biochemical, and molecular approaches used to define and characterize lipid rafts in the Lyme disease agent, Borrelia burgdorferi.
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Affiliation(s)
- Alvaro Toledo
- Department of Entomology, Rutgers University, New Brunswick, NJ, USA.
| | - Zhen Huang
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA
| | - Jorge L Benach
- Department of Molecular Genetics and Microbiology, Stony Brook University, Health Science Center, Level 4, Stony Brook, NY, 11794 8434, USA
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA
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34
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Kim J, Fukuto HS, Brown DA, Bliska JB, London E. Effects of host cell sterol composition upon internalization of Yersinia pseudotuberculosis and clustered β1 integrin. J Biol Chem 2017; 293:1466-1479. [PMID: 29197826 DOI: 10.1074/jbc.m117.811224] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [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: 08/09/2017] [Revised: 11/29/2017] [Indexed: 11/06/2022] Open
Abstract
Yersinia pseudotuberculosis is a foodborne pathogenic bacterium that causes acute gastrointestinal illness, but its mechanisms of infection are incompletely described. We examined how host cell sterol composition affected Y. pseudotuberculosis uptake. To do this, we depleted or substituted cholesterol in human MDA-MB-231 epithelial cells with various alternative sterols. Decreasing host cell cholesterol significantly reduced pathogen internalization. When host cell cholesterol was substituted with various sterols, only desmosterol and 7-dehydrocholesterol supported internalization. This specificity was not due to sterol dependence of bacterial attachment to host cells, which was similar with all sterols studied. Because a key step in Y. pseudotuberculosis internalization is interaction of the bacterial adhesins invasin and YadA with host cell β1 integrin, we compared the sterol dependence of wildtype Y. pseudotuberculosis internalization with that of Δinv, ΔyadA, and ΔinvΔyadA mutant strains. YadA deletion decreased bacterial adherence to host cells, whereas invasin deletion had no effect. Nevertheless, host cell sterol substitution had a similar effect on internalization of these bacterial deletion strains as on the wildtype bacteria. The ΔinvΔyadA double mutant adhered least to cells and so was not significantly internalized. The sterol structure dependence of Y. pseudotuberculosis internalization differed from that of endocytosis, as monitored using antibody-clustered β1 integrin and previous studies on other proteins, which had a more permissive sterol dependence. This study suggests that agents could be designed to interfere with internalization of Yersinia without disturbing endocytosis.
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Affiliation(s)
- JiHyun Kim
- From the Departments of Biochemistry and Cell Biology and
| | - Hana S Fukuto
- Molecular Genetics and Microbiology and.,Center for Infectious Diseases, Stony Brook University, Stony Brook, New York 11794
| | | | - James B Bliska
- Molecular Genetics and Microbiology and.,Center for Infectious Diseases, Stony Brook University, Stony Brook, New York 11794
| | - Erwin London
- From the Departments of Biochemistry and Cell Biology and
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35
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Trampush JW, Yang MLZ, Yu J, Knowles E, Davies G, Liewald DC, Starr JM, Djurovic S, Melle I, Sundet K, Christoforou A, Reinvang I, DeRosse P, Lundervold AJ, Steen VM, Espeseth T, Räikkönen K, Widen E, Palotie A, Eriksson JG, Giegling I, Konte B, Roussos P, Giakoumaki S, Burdick KE, Payton A, Ollier W, Horan M, Chiba-Falek O, Attix DK, Need AC, Cirulli ET, Voineskos AN, Stefanis NC, Avramopoulos D, Hatzimanolis A, Arking DE, Smyrnis N, Bilder RM, Freimer NA, Cannon TD, London E, Poldrack RA, Sabb FW, Congdon E, Conley ED, Scult MA, Dickinson D, Straub RE, Donohoe G, Morris D, Corvin A, Gill M, Hariri AR, Weinberger DR, Pendleton N, Bitsios P, Rujescu D, Lahti J, Le Hellard S, Keller MC, Andreassen OA, Deary IJ, Glahn DC, Malhotra AK, Lencz T. GWAS meta-analysis reveals novel loci and genetic correlates for general cognitive function: a report from the COGENT consortium. Mol Psychiatry 2017; 22:1651-1652. [PMID: 29068436 PMCID: PMC5659072 DOI: 10.1038/mp.2017.197] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This corrects the article DOI: 10.1038/mp.2016.244.
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36
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Raj S, Nazemidashtarjandi S, Kim J, Joffe L, Zhang X, Singh A, Mor V, Desmarini D, Djordjevic J, Raleigh DP, Rodrigues ML, London E, Del Poeta M, Farnoud AM. Changes in glucosylceramide structure affect virulence and membrane biophysical properties of Cryptococcus neoformans. Biochim Biophys Acta Biomembr 2017; 1859:2224-2233. [PMID: 28865794 DOI: 10.1016/j.bbamem.2017.08.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 08/03/2017] [Accepted: 08/27/2017] [Indexed: 11/19/2022]
Abstract
Fungal glucosylceramide (GlcCer) is a plasma membrane sphingolipid in which the sphingosine backbone is unsaturated in carbon position 8 (C8) and methylated in carbon position 9 (C9). Studies in the fungal pathogen, Cryptococcus neoformans, have shown that loss of GlcCer synthase activity results in complete loss of virulence in the mouse model. However, whether the loss of virulence is due to the lack of the enzyme or to the loss of the sphingolipid is not known. In this study, we used genetic engineering to alter the chemical structure of fungal GlcCer and studied its effect on fungal growth and pathogenicity. Here we show that unsaturation in C8 and methylation in C9 is required for virulence in the mouse model without affecting fungal growth in vitro or common virulence factors. However, changes in GlcCer structure led to a dramatic susceptibility to membrane stressors resulting in increased cell membrane permeability and rendering the fungal mutant unable to grow within host macrophages. Biophysical studies using synthetic vesicles containing GlcCer revealed that the saturated and unmethylated sphingolipid formed vesicles with higher lipid order that were more likely to phase separate into ordered domains. Taken together, these studies show for the first time that a specific structure of GlcCer is a major regulator of membrane permeability required for fungal pathogenicity.
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Affiliation(s)
- Shriya Raj
- Department of Mycology, Institut Pasteur, Paris, France
| | | | - Jihyun Kim
- Department of Chemistry and Biochemistry, Stony Brook University, Stony Brook, NY, USA
| | - Luna Joffe
- Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Brazil
| | - Xiaoxue Zhang
- Department of Chemistry and Biochemistry, Stony Brook University, Stony Brook, NY, USA
| | - Ashutosh Singh
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - Visesato Mor
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA
| | - Desmarini Desmarini
- Fungal Pathogenesis Laboratory, Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, Westmead, NSW, Australia
| | - Julianne Djordjevic
- Fungal Pathogenesis Laboratory, Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, Westmead, NSW, Australia; Westmead Clinical School, University of Sydney at Westmead Hospital, Westmead, NSW, Australia; Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney, NSW, Australia
| | - Daniel P Raleigh
- Department of Chemistry and Biochemistry, Stony Brook University, Stony Brook, NY, USA
| | - Marcio L Rodrigues
- Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Brazil; Centro de Desenvolvimento Tecnológico em Saúde (CDTS) da Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, Brazil
| | - Erwin London
- Department of Chemistry and Biochemistry, Stony Brook University, Stony Brook, NY, USA
| | - Maurizio Del Poeta
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA; Veterans Administration Medical Center, Northport, NY, USA; Division of Infectious Diseases, Stony Brook University, Stony Brook, NY, USA.
| | - Amir M Farnoud
- Department of Chemical and Biomolecular Engineering, Ohio University, Athens, OH, USA.
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37
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Kim JH, Singh A, Del Poeta M, Brown DA, London E. The effect of sterol structure upon clathrin-mediated and clathrin-independent endocytosis. J Cell Sci 2017; 130:2682-2695. [PMID: 28655854 DOI: 10.1242/jcs.201731] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [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: 01/18/2017] [Accepted: 06/22/2017] [Indexed: 12/25/2022] Open
Abstract
Ordered lipid domains (rafts) in plasma membranes have been hypothesized to participate in endocytosis based on inhibition of endocytosis by removal or sequestration of cholesterol. To more carefully investigate the role of the sterol in endocytosis, we used a substitution strategy to replace cholesterol with sterols that show various raft-forming abilities and chemical structures. Both clathrin-mediated endocytosis of transferrin and clathrin-independent endocytosis of clustered placental alkaline phosphatase were measured. A subset of sterols reversibly inhibited both clathrin-dependent and clathrin-independent endocytosis. The ability of a sterol to support lipid raft formation was necessary for endocytosis. However, it was not sufficient, because a sterol lacking a 3β-OH group did not support endocytosis even though it had the ability to support ordered domain formation. Double bonds in the sterol rings and an aliphatic tail structure identical to that of cholesterol were neither necessary nor sufficient to support endocytosis. This study shows that substitution using a large number of sterols can define the role of sterol structure in cellular functions. Hypotheses for how sterol structure can similarly alter clathrin-dependent and clathrin-independent endocytosis are discussed.
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Affiliation(s)
- Ji Hyun Kim
- Dept. of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Ashutosh Singh
- Dept. of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Maurizio Del Poeta
- Dept. of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Deborah A Brown
- Dept. of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Erwin London
- Dept. of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA
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38
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Huang Z, Toledo AM, Benach JL, London E. Ordered Membrane Domain-Forming Properties of the Lipids of Borrelia burgdorferi. Biophys J 2017; 111:2666-2675. [PMID: 28002743 DOI: 10.1016/j.bpj.2016.11.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 11/04/2016] [Accepted: 11/16/2016] [Indexed: 11/18/2022] Open
Abstract
Co-existing disordered and ordered (raft) membrane domains exist in Borrelia burgdorferi, the causative agent of Lyme disease. However, although B. burgdorferi contains cholesterol lipids, it lacks sphingolipids-a crucial component of rafts in eukaryotes. To define the principles of ordered lipid domain formation in Borrelia, the domain forming properties of vesicles composed of its three major lipids, acylated cholesteryl galactoside (ACGal), monogalactosyl diacyglycerol (MGalD), and phosphatidylcholine (PC) and/or their mixtures were studied. Anisotropy and fluorescence resonance energy transfer measurements were used to assay membrane order and ordered-domain formation. ACGal had the highest potential to form ordered domains. Interestingly, mixtures of ACGal with B. burgdorferi PC formed ordered domains more readily than mixtures of ACGal with MGalD. This appears to reflect the relatively high level of saturation observed for B. burgdorferi PC, as vesicles containing ACGal and PC, but in which the unsaturated lipid dioleoyl PC was substituted for Borrelia PC, failed to form ordered domains. In addition, the properties of ACGal were compared to those of cholesterol. Depending on what other lipids were present, ordered-domain formation in the presence of ACGal was greater than or equal to that in the presence of cholesterol. Giant unilamellar vesicles formed from ACGal-containing mixtures showed rounded domain shapes similar to those in analogous vesicles containing cholesterol, indicative of liquid-ordered state rather than solid-like gel-state domain formation. Over all, principles of ordered-domain formation in B. burgdorferi appear to be very similar to those in eukaryotes, with saturated PC taking the place of sphingolipids, but with ACGal being the main lipid component inducing ordered-domain formation.
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Affiliation(s)
- Zhen Huang
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York
| | - Alvaro M Toledo
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York
| | - Jorge L Benach
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York.
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39
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Marquardt D, Heberle FA, Miti T, Eicher B, London E, Katsaras J, Pabst G. 1H NMR Shows Slow Phospholipid Flip-Flop in Gel and Fluid Bilayers. Langmuir 2017; 33:3731-3741. [PMID: 28106399 PMCID: PMC5397887 DOI: 10.1021/acs.langmuir.6b04485] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We measured the transbilayer diffusion of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in large unilamellar vesicles, in both the gel (Lβ') and fluid (Lα) phases. The choline resonance of headgroup-protiated DPPC exchanged into the outer leaflet of headgroup-deuterated DPPC-d13 vesicles was monitored using 1H NMR spectroscopy, coupled with the addition of a paramagnetic shift reagent. This allowed us to distinguish between the inner and outer bilayer leaflet of DPPC, to determine the flip-flop rate as a function of temperature. Flip-flop of fluid-phase DPPC exhibited Arrhenius kinetics, from which we determined an activation energy of 122 kJ mol-1. In gel-phase DPPC vesicles, flip-flop was not observed over the course of 250 h. Our findings are in contrast to previous studies of solid-supported bilayers, where the reported DPPC translocation rates are at least several orders of magnitude faster than those in vesicles at corresponding temperatures. We reconcile these differences by proposing a defect-mediated acceleration of lipid translocation in supported bilayers, where long-lived, submicron-sized holes resulting from incomplete surface coverage are the sites of rapid transbilayer movement.
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Affiliation(s)
- Drew Marquardt
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
- E-mail: (D.M.)
| | - Frederick A. Heberle
- The Bredesen
Center and Department of Physics and Astronomy, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Joint Institute for Biological Sciences, Biology and Soft
Matter Division, and Shull Wollan
Center—A Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- E-mail: (F.A.H.)
| | - Tatiana Miti
- Department
of Physics, University of South Florida, Tampa, Florida 33620,United States
| | - Barbara Eicher
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
| | - Erwin London
- Department
of Biochemistry and Cell Biology, Stony Brook, New York 11794, United States
| | - John Katsaras
- The Bredesen
Center and Department of Physics and Astronomy, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Joint Institute for Biological Sciences, Biology and Soft
Matter Division, and Shull Wollan
Center—A Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Georg Pabst
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
- E-mail: (G.P.)
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40
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Trampush JW, Yang MLZ, Yu J, Knowles E, Davies G, Liewald DC, Starr JM, Djurovic S, Melle I, Sundet K, Christoforou A, Reinvang I, DeRosse P, Lundervold AJ, Steen VM, Espeseth T, Räikkönen K, Widen E, Palotie A, Eriksson JG, Giegling I, Konte B, Roussos P, Giakoumaki S, Burdick KE, Payton A, Ollier W, Horan M, Chiba-Falek O, Attix DK, Need AC, Cirulli ET, Voineskos AN, Stefanis NC, Avramopoulos D, Hatzimanolis A, Arking DE, Smyrnis N, Bilder RM, Freimer NA, Cannon TD, London E, Poldrack RA, Sabb FW, Congdon E, Conley ED, Scult MA, Dickinson D, Straub RE, Donohoe G, Morris D, Corvin A, Gill M, Hariri AR, Weinberger DR, Pendleton N, Bitsios P, Rujescu D, Lahti J, Le Hellard S, Keller MC, Andreassen OA, Deary IJ, Glahn DC, Malhotra AK, Lencz T. GWAS meta-analysis reveals novel loci and genetic correlates for general cognitive function: a report from the COGENT consortium. Mol Psychiatry 2017; 22:336-345. [PMID: 28093568 PMCID: PMC5322272 DOI: 10.1038/mp.2016.244] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 10/30/2016] [Accepted: 11/03/2016] [Indexed: 01/12/2023]
Abstract
The complex nature of human cognition has resulted in cognitive genomics lagging behind many other fields in terms of gene discovery using genome-wide association study (GWAS) methods. In an attempt to overcome these barriers, the current study utilized GWAS meta-analysis to examine the association of common genetic variation (~8M single-nucleotide polymorphisms (SNP) with minor allele frequency ⩾1%) to general cognitive function in a sample of 35 298 healthy individuals of European ancestry across 24 cohorts in the Cognitive Genomics Consortium (COGENT). In addition, we utilized individual SNP lookups and polygenic score analyses to identify genetic overlap with other relevant neurobehavioral phenotypes. Our primary GWAS meta-analysis identified two novel SNP loci (top SNPs: rs76114856 in the CENPO gene on chromosome 2 and rs6669072 near LOC105378853 on chromosome 1) associated with cognitive performance at the genome-wide significance level (P<5 × 10-8). Gene-based analysis identified an additional three Bonferroni-corrected significant loci at chromosomes 17q21.31, 17p13.1 and 1p13.3. Altogether, common variation across the genome resulted in a conservatively estimated SNP heritability of 21.5% (s.e.=0.01%) for general cognitive function. Integration with prior GWAS of cognitive performance and educational attainment yielded several additional significant loci. Finally, we found robust polygenic correlations between cognitive performance and educational attainment, several psychiatric disorders, birth length/weight and smoking behavior, as well as a novel genetic association to the personality trait of openness. These data provide new insight into the genetics of neurocognitive function with relevance to understanding the pathophysiology of neuropsychiatric illness.
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Affiliation(s)
- J W Trampush
- Division of Psychiatry Research, Zucker Hillside Hospital, Glen Oaks, NY, USA
| | - M L Z Yang
- Institute of Mental Health, Singapore, Singapore
| | - J Yu
- Division of Psychiatry Research, Zucker Hillside Hospital, Glen Oaks, NY, USA,Center for Psychiatric Neuroscience, Feinstein Institute for Medical Research, Manhasset, NY, USA
| | - E Knowles
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - G Davies
- Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK,Department of Psychology, University of Edinburgh, Edinburgh, UK
| | - D C Liewald
- Department of Psychology, University of Edinburgh, Edinburgh, UK
| | - J M Starr
- Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK,Alzheimer Scotland Dementia Research Centre, University of Edinburgh, Edinburgh, UK
| | - S Djurovic
- Department of Medical Genetics, Oslo University Hospital, University of Bergen, Oslo, Norway,NORMENT, K.G. Jebsen Centre for Psychosis Research, University of Bergen, Bergen, Norway
| | - I Melle
- NORMENT, K.G. Jebsen Centre for Psychosis Research, University of Bergen, Bergen, Norway,Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
| | - K Sundet
- Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway,Department of Psychology, University of Oslo, Oslo, Norway
| | - A Christoforou
- NORMENT, K.G. Jebsen Centre for Psychosis Research, University of Bergen, Bergen, Norway,Dr Einar Martens Research Group for Biological Psychiatry, Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
| | - I Reinvang
- Department of Psychology, University of Oslo, Oslo, Norway
| | - P DeRosse
- Division of Psychiatry Research, Zucker Hillside Hospital, Glen Oaks, NY, USA,Center for Psychiatric Neuroscience, Feinstein Institute for Medical Research, Manhasset, NY, USA
| | - A J Lundervold
- Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway
| | - V M Steen
- NORMENT, K.G. Jebsen Centre for Psychosis Research, University of Bergen, Bergen, Norway,Dr Einar Martens Research Group for Biological Psychiatry, Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
| | - T Espeseth
- Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway,Department of Psychology, University of Oslo, Oslo, Norway
| | - K Räikkönen
- Institute of Behavioural Sciences, University of Helsinki, Helsinki, Finland
| | - E Widen
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland
| | - A Palotie
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland,Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, UK,Department of Medical Genetics, University of Helsinki and University Central Hospital, Helsinki, Finland
| | - J G Eriksson
- National Institute for Health and Welfare, Helsinki, Finland,Department of General Practice and Primary Health Care, University of Helsinki, Helsinki, Finland,Helsinki University Central Hospital, Unit of General Practice, Helsinki, Finland,Folkhälsan Research Centre, Helsinki, Finland
| | - I Giegling
- Department of Psychiatry, Martin Luther University of Halle-Wittenberg, Halle, Germany
| | - B Konte
- Department of Psychiatry, Martin Luther University of Halle-Wittenberg, Halle, Germany
| | - P Roussos
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA,Department of Genetics and Genomic Science and Institute for Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY, USA,Mental Illness Research, Education, and Clinical Center (VISN 3), James J. Peters VA Medical Center, Bronx, NY, USA
| | - S Giakoumaki
- Department of Psychology, University of Crete, Rethymno, Greece
| | - K E Burdick
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA,Mental Illness Research, Education, and Clinical Center (VISN 3), James J. Peters VA Medical Center, Bronx, NY, USA
| | - A Payton
- Manchester Centre for Audiology and Deafness, Manchester Academic Health Science Centre, The University of Manchester, Manchester, UK,Division of Evolution and Genomic Sciences, School of Biological Sciences, The University of Manchester, Manchester, UK
| | - W Ollier
- Centre for Integrated Genomic Medical Research, Institute of Population Health, University of Manchester, Manchester, UK
| | - M Horan
- Manchester Medical School, Institute of Brain, Behaviour, and Mental Health, University of Manchester, Manchester, UK
| | - O Chiba-Falek
- Department of Neurology, Bryan Alzheimer's Disease Research Center, and Center for Genomic and Computational Biology, Duke University Medical Center, Durham, NC, USA
| | - D K Attix
- Department of Neurology, Bryan Alzheimer's Disease Research Center, and Center for Genomic and Computational Biology, Duke University Medical Center, Durham, NC, USA,Division of Medical Psychology, Department of Neurology, Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC, USA
| | - A C Need
- Division of Brain Sciences, Department of Medicine, Imperial College, London, UK
| | - E T Cirulli
- Center for Applied Genomics and Precision Medicine, Duke University School of Medicine, Durham, NC, USA
| | - A N Voineskos
- Campbell Family Mental Health Institute, Centre for Addiction and Mental Health, University of Toronto, Toronto, ON, Canada
| | - N C Stefanis
- Department of Psychiatry, University of Athens School of Medicine, Eginition Hospital, Athens, Greece,University Mental Health Research Institute, Athens, Greece,Neurobiology Research Institute, Theodor Theohari Cozzika Foundation, Athens, Greece
| | - D Avramopoulos
- Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD, USA,Department of Psychiatry and McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - A Hatzimanolis
- Department of Psychiatry, University of Athens School of Medicine, Eginition Hospital, Athens, Greece,University Mental Health Research Institute, Athens, Greece,Neurobiology Research Institute, Theodor Theohari Cozzika Foundation, Athens, Greece
| | - D E Arking
- Department of Psychiatry and McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - N Smyrnis
- Department of Psychiatry, University of Athens School of Medicine, Eginition Hospital, Athens, Greece,University Mental Health Research Institute, Athens, Greece
| | - R M Bilder
- UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA
| | - N A Freimer
- UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA
| | - T D Cannon
- Department of Psychology, Yale University, New Haven, CT, USA
| | - E London
- UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA
| | - R A Poldrack
- Department of Psychology, Stanford University, Palo Alto, CA, USA
| | - F W Sabb
- Robert and Beverly Lewis Center for Neuroimaging, University of Oregon, Eugene, OR, USA
| | - E Congdon
- UCLA Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA, USA
| | | | - M A Scult
- Department of Psychology & Neuroscience, Laboratory of NeuroGenetics, Duke University, Durham, NC, USA
| | - D Dickinson
- Clinical and Translational Neuroscience Branch, Intramural Research Program, National Institute of Mental Health, National Institute of Health, Bethesda, MD, USA
| | - R E Straub
- Lieber Institute for Brain Development, Johns Hopkins University Medical Campus, Baltimore, MD, USA
| | - G Donohoe
- Department of Psychology, National University of Ireland, Galway, Ireland
| | - D Morris
- Department of Psychiatry, Neuropsychiatric Genetics Research Group, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
| | - A Corvin
- Department of Psychiatry, Neuropsychiatric Genetics Research Group, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
| | - M Gill
- Department of Psychiatry, Neuropsychiatric Genetics Research Group, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
| | - A R Hariri
- Department of Psychology & Neuroscience, Laboratory of NeuroGenetics, Duke University, Durham, NC, USA
| | - D R Weinberger
- Lieber Institute for Brain Development, Johns Hopkins University Medical Campus, Baltimore, MD, USA
| | - N Pendleton
- Centre for Integrated Genomic Medical Research, Institute of Population Health, University of Manchester, Manchester, UK,Manchester Medical School, Institute of Brain, Behaviour, and Mental Health, University of Manchester, Manchester, UK
| | - P Bitsios
- Department of Psychiatry and Behavioral Sciences, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - D Rujescu
- Department of Psychiatry, Martin Luther University of Halle-Wittenberg, Halle, Germany
| | - J Lahti
- Institute of Behavioural Sciences, University of Helsinki, Helsinki, Finland,Helsinki Collegium for Advanced Studies, University of Helsinki, Helsinki, Finland
| | - S Le Hellard
- NORMENT, K.G. Jebsen Centre for Psychosis Research, University of Bergen, Bergen, Norway,Dr Einar Martens Research Group for Biological Psychiatry, Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
| | - M C Keller
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO, USA
| | - O A Andreassen
- NORMENT, K.G. Jebsen Centre for Psychosis Research, University of Bergen, Bergen, Norway,Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway,Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - I J Deary
- Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK,Department of Psychology, University of Edinburgh, Edinburgh, UK
| | - D C Glahn
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - A K Malhotra
- Division of Psychiatry Research, Zucker Hillside Hospital, Glen Oaks, NY, USA,Center for Psychiatric Neuroscience, Feinstein Institute for Medical Research, Manhasset, NY, USA,Department of Psychiatry, Hofstra Northwell School of Medicine, Hempstead, NY, USA
| | - T Lencz
- Division of Psychiatry Research, Zucker Hillside Hospital, Glen Oaks, NY, USA,Center for Psychiatric Neuroscience, Feinstein Institute for Medical Research, Manhasset, NY, USA,Department of Psychiatry, Hofstra Northwell School of Medicine, Hempstead, NY, USA,Division of Psychiatry Research, Zucker Hillside Hospital, 75-59 263rd Street, Glen Oaks, NY 11004, USA. E-mail:
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41
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Abstract
Amyloid formation by islet amyloid polypeptide (IAPP) contributes to β-cell dysfunction in type 2 diabetes. Perturbation of the β-cell membrane may contribute to IAPP-induced toxicity. We examine the effects of lipid composition, salt, and buffer on IAPP amyloid formation and on the ability of IAPP to induce leakage of model membranes. Even low levels of anionic lipids promote amyloid formation and membrane permeabilization. Increasing the percentage of the anionic lipids, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS) or 1,2-dioleoyl-sn-glycero-3-phospho(1'-rac-glycerol), enhances the rate of amyloid formation and increases the level of membrane permeabilization. The choice of zwitterionic lipid has no noticeable effect on membrane-catalyzed amyloid formation but in most cases affects leakage, which tends to decrease in the following order: 1,2-dioleoyl-sn-glycero-3-phosphocholine > 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine > sphingomyelin. Uncharged lipids that increase the level of membrane order weaken the ability of IAPP to induce leakage. Leakage is due predominately to pore formation rather than complete disruption of the vesicles under the conditions used in these studies. Cholesterol at or below physiological levels significantly reduces the rate of vesicle-catalyzed IAPP amyloid formation and decreases the susceptibility to IAPP-induced leakage. The effects of cholesterol on amyloid formation are masked by 25 mol % POPS. Overall, there is a strong inverse correlation between the time to form amyloid and the extent of vesicle leakage. NaCl reduces the rate of membrane-catalyzed amyloid formation by anionic vesicles, but accelerates amyloid formation in solution. The implications for IAPP membrane interactions are discussed, as is the possibility that the loss of phosphatidylserine asymmetry enhances IAPP amyloid formation and membrane damage in vivo via a positive feedback loop.
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Affiliation(s)
- Xiaoxue Zhang
- Department of Chemistry, Stony Brook University , Stony Brook, New York 11794-3400, United States
| | - Johnna R St Clair
- Department of Biochemistry and Cell Biology, Stony Brook University , Stony Brook, New York 11794-5215, United States
| | - Erwin London
- Department of Chemistry, Stony Brook University , Stony Brook, New York 11794-3400, United States.,Department of Biochemistry and Cell Biology, Stony Brook University , Stony Brook, New York 11794-5215, United States
| | - Daniel P Raleigh
- Department of Chemistry, Stony Brook University , Stony Brook, New York 11794-3400, United States.,Graduate Program in Biochemistry and Structural Biology, Stony Brook University , Stony Brook, New York 11794-5215, United States
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42
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St. Clair JR, Wang Q, Li G, London E. Preparation and Physical Properties of Asymmetric Model Membrane Vesicles. Springer Series in Biophysics 2017. [DOI: 10.1007/978-981-10-6244-5_1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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43
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Abstract
Hydrophilic segments attached to transmembrane helices often cross membranes. In an increasing number of cases, it has become apparent that this occurs in a biologically relevant post-translational event. In this study, we investigate whether juxta-membrane (JM) hydrophilic sequences attached to hydrophobic helices are able to rapidly cross lipid bilayers via their ability or inability to block hydrophobic helix interconversion between a transmembrane (TM) and non-TM membrane-associated state. Interconversion was triggered by changing the protonation state of an Asp residue in the hydrophobic core of the peptides, and peptide configuration was monitored by the fluorescence of a Trp residue at the center of the hydrophobic sequence. In POPC vesicles, conversion of the TM to non-TM state at high pH and the non-TM to TM state at low pH was rapid (seconds or less) for KK, KKNN, and the KKNNNNNN flanking sequences on both N- and C-termini and the KLFAGHQ sequence that flanks the spontaneously TM-inserting 3A protein of polio virus. In vesicles composed of 6:4 (mol/mol) POPC/cholesterol, interconversion was still rapid, with the exception of the peptide flanked by KKNNNNNN sequences, for which the half time of interconversion slowed to minutes. This behavior suggests that, at least in membranes with low levels of cholesterol, movement of hydrophilic JM segments (and analogous hydrophobic loops in multipass TM proteins) across membranes may be more facile than previously thought. This may have important biological implications.
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Affiliation(s)
- Jamie LeBarron
- Stony Brook University Stony Brook, New York 11794-5215, United States
| | - Erwin London
- Stony Brook University Stony Brook, New York 11794-5215, United States
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44
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Heberle FA, Marquardt D, Doktorova M, Geier B, Standaert RF, Heftberger P, Kollmitzer B, Nickels JD, Dick R, Feigenson GW, Katsaras J, London E, Pabst G. Subnanometer Structure of an Asymmetric Model Membrane: Interleaflet Coupling Influences Domain Properties. Langmuir 2016; 32:5195-200. [PMID: 27128636 PMCID: PMC4910133 DOI: 10.1021/acs.langmuir.5b04562] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Cell membranes possess a complex three-dimensional architecture, including nonrandom lipid lateral organization within the plane of a bilayer leaflet, and compositional asymmetry between the two leaflets. As a result, delineating the membrane structure-function relationship has been a highly challenging task. Even in simplified model systems, the interactions between bilayer leaflets are poorly understood, due in part to the difficulty of preparing asymmetric model membranes that are free from the effects of residual organic solvent or osmotic stress. To address these problems, we have modified a technique for preparing asymmetric large unilamellar vesicles (aLUVs) via cyclodextrin-mediated lipid exchange in order to produce tensionless, solvent-free aLUVs suitable for a range of biophysical studies. Leaflet composition and structure were characterized using isotopic labeling strategies, which allowed us to avoid the use of bulky labels. NMR and gas chromatography provided precise quantification of the extent of lipid exchange and bilayer asymmetry, while small-angle neutron scattering (SANS) was used to resolve bilayer structural features with subnanometer resolution. Isotopically asymmetric POPC vesicles were found to have the same bilayer thickness and area per lipid as symmetric POPC vesicles, demonstrating that the modified exchange protocol preserves native bilayer structure. Partial exchange of DPPC into the outer leaflet of POPC vesicles produced chemically asymmetric vesicles with a gel/fluid phase-separated outer leaflet and a uniform, POPC-rich inner leaflet. SANS was able to separately resolve the thicknesses and areas per lipid of coexisting domains, revealing reduced lipid packing density of the outer leaflet DPPC-rich phase compared to typical gel phases. Our finding that a disordered inner leaflet can partially fluidize ordered outer leaflet domains indicates some degree of interleaflet coupling, and invites speculation on a role for bilayer asymmetry in modulating membrane lateral organization.
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Affiliation(s)
- Frederick A. Heberle
- Biology and Soft Matter Division, Joint Institute for
Neutron Sciences, and Biosciences Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee 37831, United States
- E-mail:
| | - Drew Marquardt
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
- E-mail:
| | - Milka Doktorova
- Tri-Institutional
PhD Program in Computational Biology and Medicine, Weill Cornell Medical College, New York, New York 10065, United States
- Department
of Molecular Biology and Genetics, Cornell
University, Ithaca, New York 14853, United
States
| | - Barbara Geier
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
| | - Robert F. Standaert
- Biology and Soft Matter Division, Joint Institute for
Neutron Sciences, and Biosciences Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Biochemistry and Cellular
& Molecular Biology, and Department of
Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Peter Heftberger
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
| | - Benjamin Kollmitzer
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
| | - Jonathan D. Nickels
- Biology and Soft Matter Division, Joint Institute for
Neutron Sciences, and Biosciences Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Robert
A. Dick
- Department
of Molecular Biology and Genetics, Cornell
University, Ithaca, New York 14853, United
States
| | - Gerald W. Feigenson
- Department
of Molecular Biology and Genetics, Cornell
University, Ithaca, New York 14853, United
States
| | - John Katsaras
- Biology and Soft Matter Division, Joint Institute for
Neutron Sciences, and Biosciences Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Biochemistry and Cellular
& Molecular Biology, and Department of
Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Erwin London
- Department
of Biochemistry and Cell Biology, Stony
Brook University, Stony Brook, New York 11794, United States
| | - Georg Pabst
- Institute
of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria
- BioTechMed-Graz, Graz 8010, Austria
- E-mail:
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45
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LeBarron J, London E. Effect of lipid composition and amino acid sequence upon transmembrane peptide-accelerated lipid transleaflet diffusion (flip-flop). Biochim Biophys Acta 2016; 1858:1812-20. [PMID: 27131444 DOI: 10.1016/j.bbamem.2016.04.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 03/21/2016] [Accepted: 04/21/2016] [Indexed: 12/15/2022]
Abstract
We examined how hydrophobic peptide-accelerated transleaflet lipid movement (flip-flop) was affected by peptide sequence and vesicle composition and properties. A peptide with a completely hydrophobic sequence had little if any effect upon flip-flop. While peptides with a somewhat less hydrophobic sequence accelerated flip-flop, the half-time remained slow (hours) with substantial (0.5mol%) peptide in the membranes. It appears that peptide-accelerated lipid flip-flop involves a rare event that may reflect a rare state of the peptide or lipid bilayer. There was no simple relationship between peptide overall hydrophobicity and flip-flop. In addition, flip-flop was not closely linked to whether the peptides were in a transmembrane or non-transmembrane (interfacial) inserted state. Flip-flop was also not associated with peptide-induced pore formation. We found that peptide-accelerated flip-flop is initially faster in small (highly curved) unilamellar vesicles relative to that in large unilamellar vesicles. Peptide-accelerated flip-flop was also affected by lipid composition, being slowed in vesicles with thick bilayers or those containing 30% cholesterol. Interestingly, these factors also slow spontaneous lipid flip-flop in the absence of peptide. Combined with previous studies, the results are most consistent with acceleration of lipid flip-flop by peptide-induced thinning of bilayer width.
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Affiliation(s)
- Jamie LeBarron
- Dept. of Biochemistry and Cell Biology, Stony Brook, NY 11794-5215, United States
| | - Erwin London
- Dept. of Biochemistry and Cell Biology, Stony Brook, NY 11794-5215, United States
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46
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Haltiwanger RS, Yu H, Takeuchi M, LeBarron J, Kantharia J, London E, Bakker H, Li H, Takeuchi H. Regulation of Notch signaling by
O
‐glucosylation: Notch‐modifying xylosyltransferase‐substrate complexes support an S
N
i‐like retaining mechanism. FASEB J 2016. [DOI: 10.1096/fasebj.30.1_supplement.624.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Megumi Takeuchi
- Biochemistry and Molecular BiologyUniversity of GeorgiaAthensGA
| | | | | | | | | | - Huilin Li
- Brookhaven National LaboratoryUptonNY
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47
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Abstract
Sterols are important components of eukaryotic membranes, but rare in bacteria. Some bacteria obtain sterols from their host or environment. In some cases, these sterols form membrane domains analogous the lipid rafts proposed to exist in eukaryotic membranes. This review describes the properties and roles of sterols in Borrelia and Helicobacter.
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Affiliation(s)
- Zhen Huang
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, 11794-5215 USA
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, 11794-5215 USA.
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48
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St Clair J, Wang Q, London E. Improved Methods for Preparing Asymmetric Vesicles using Methyl-Alpha-Cyclodextrin. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.520] [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: 10/22/2022] Open
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49
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Hyun Kim J, Singh A, Del Poeta M, Brown D, London E. Effects of Sterol Structure and Sterol Ability to form Ordered Membrane Domains upon Cellular Endocytosis. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.3176] [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: 10/22/2022] Open
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50
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London E, Brown DA, Huang Z, Kim J, Li G, St Clair J, Wang Q. Lipid Structure and Control of Membrane Ordered Domain Formation And Size by Lipid Composition and Asymmetry in Vitro and in Vivo. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1843] [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: 11/28/2022] Open
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