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Abstract
Freely suspended liposomes are widely used as model membranes for studying lipid-lipid and protein-lipid interactions. Liposomes prepared by conventional methods have chemically identical bilayer leaflets. By contrast, living cells actively maintain different lipid compositions in the two leaflets of the plasma membrane, resulting in asymmetric membrane properties that are critical for normal cell function. Here, we present a protocol for the preparation of unilamellar asymmetric phospholipid vesicles that better mimic biological membranes. Asymmetry is generated by methyl-β-cyclodextrin-catalyzed exchange of the outer leaflet lipids between vesicle pools of differing lipid composition. Lipid destined for the outer leaflet of the asymmetric vesicles is provided by heavy-donor multilamellar vesicles containing a dense sucrose core. Donor lipid is exchanged into extruded unilamellar acceptor vesicles that lack the sucrose core, facilitating the post-exchange separation of the donor and acceptor pools by centrifugation because of differences in vesicle size and density. We present two complementary assays allowing quantification of each leaflet's lipid composition: the overall lipid composition is determined by gas chromatography-mass spectrometry, whereas the lipid distribution between the two leaflets is determined by NMR, using the lanthanide shift reagent Pr3+. The preparation protocol and the chromatographic assay can be applied to any type of phospholipid bilayer, whereas the NMR assay is specific to lipids with choline-containing headgroups, such as phosphatidylcholine and sphingomyelin. In ~12 h, the protocol can produce a large yield of asymmetric vesicles (up to 20 mg) suitable for a wide range of biophysical studies.
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52
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Effect of sterol structure on ordered membrane domain (raft) stability in symmetric and asymmetric vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:1112-1122. [PMID: 30904407 DOI: 10.1016/j.bbamem.2019.03.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 03/14/2019] [Accepted: 03/15/2019] [Indexed: 12/16/2022]
Abstract
Sterol structure influences liquid ordered domains in membranes, and the dependence of biological functions on sterol structure can help identify processes dependent on ordered domains. In this study we compared the effect of sterol structure on ordered domain formation in symmetric vesicles composed of mixtures of sphingomyelin, 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol, and in asymmetric vesicles in which sphingomyelin was introduced into the outer leaflet of vesicles composed of DOPC and cholesterol. In most cases, sterol behavior was similar in symmetric and asymmetric vesicles, with ordered domains most strongly stabilized by 7-dehydrocholesterol (7DHC) and cholesterol, stabilized to a moderate degree by lanosterol, epicholesterol and desmosterol, and very little if at all by 4-cholesten-3-one. However, in asymmetric vesicles desmosterol stabilized ordered domain almost as well as cholesterol, and to a much greater degree than epicholesterol, so that the ability to support ordered domains decreased in the order 7-DHC > cholesterol > desmosterol > lanosterol > epicholesterol > 4-cholesten-3-one. This contrasts with values for intermediate stabilizing sterols in symmetric vesicles in which the ranking was cholesterol > lanosterol ~ desmosterol ~ epicholesterol or prior studies in which the ranking was cholesterol ~ epicholesterol > lanosterol ~ desmosterol. The reasons for these differences are discussed. Based on these results, we re-evaluated our prior studies in cells and conclude that endocytosis levels and bacterial uptake are even more closely correlated with the ability of sterols to form ordered domains than previously thought, and do not necessarily require that a sterol have a 3β-OH group.
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56
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Tsuchiya M, Hara Y, Okuda M, Itoh K, Nishioka R, Shiomi A, Nagao K, Mori M, Mori Y, Ikenouchi J, Suzuki R, Tanaka M, Ohwada T, Aoki J, Kanagawa M, Toda T, Nagata Y, Matsuda R, Takayama Y, Tominaga M, Umeda M. Cell surface flip-flop of phosphatidylserine is critical for PIEZO1-mediated myotube formation. Nat Commun 2018; 9:2049. [PMID: 29799007 PMCID: PMC5967302 DOI: 10.1038/s41467-018-04436-w] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 04/26/2018] [Indexed: 11/23/2022] Open
Abstract
Myotube formation by fusion of myoblasts and subsequent elongation of the syncytia is essential for skeletal muscle formation. However, molecules that regulate myotube formation remain elusive. Here we identify PIEZO1, a mechanosensitive Ca2+ channel, as a key regulator of myotube formation. During myotube formation, phosphatidylserine, a phospholipid that resides in the inner leaflet of the plasma membrane, is transiently exposed to cell surface and promotes myoblast fusion. We show that cell surface phosphatidylserine inhibits PIEZO1 and that the inward translocation of phosphatidylserine, which is driven by the phospholipid flippase complex of ATP11A and CDC50A, is required for PIEZO1 activation. PIEZO1-mediated Ca2+ influx promotes RhoA/ROCK-mediated actomyosin assemblies at the lateral cortex of myotubes, thus preventing uncontrolled fusion of myotubes and leading to polarized elongation during myotube formation. These results suggest that cell surface flip-flop of phosphatidylserine acts as a molecular switch for PIEZO1 activation that governs proper morphogenesis during myotube formation. Myotube formation by fusion of myoblasts is essential for skeletal muscle formation, but which molecules regulate this process remains elusive. Here authors identify the mechanosensitive PIEZO1 channel as a key element, whose activity is regulated by phosphatidylserine during myotube formation.
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Affiliation(s)
- Masaki Tsuchiya
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - Yuji Hara
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan. .,AMED-PRIME, Japan Agency for Medical Research and Development, Tokyo, 100-0004, Japan.
| | - Masaki Okuda
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - Karin Itoh
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - Ryotaro Nishioka
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - Akifumi Shiomi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - Kohjiro Nagao
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - Masayuki Mori
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - Yasuo Mori
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - Junichi Ikenouchi
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, 819-0395, Japan
| | - Ryo Suzuki
- Institute for Integrated Cell-Material Sciences (WPI iCeMS), Kyoto University, Kyoto, 606-8501, Japan.,Center for Integrative Medicine and Physics, Institute for Advanced Study, Kyoto University, Kyoto, 606-8501, Japan
| | - Motomu Tanaka
- Institute for Integrated Cell-Material Sciences (WPI iCeMS), Kyoto University, Kyoto, 606-8501, Japan.,Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, Heidelberg, 69120, Germany.,Center for Integrative Medicine and Physics, Institute for Advanced Study, Kyoto University, Kyoto, 606-8501, Japan
| | - Tomohiko Ohwada
- Laboratory of Organic and Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 115-0033, Japan
| | - Junken Aoki
- Department of Molecular and Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Miyagi, 980-8578, Japan
| | - Motoi Kanagawa
- Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Hyogo, 650-0017, Japan
| | - Tatsushi Toda
- Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-8655, Japan
| | - Yosuke Nagata
- Department of Life Science, Faculty of Science, Okayama University of Science, Okayama, 700-0005, Japan
| | - Ryoichi Matsuda
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, 153-8902, Japan
| | - Yasunori Takayama
- Division of Cell Signaling, Okazaki Institute for Integrative Bioscience, Aichi, 444-8787, Japan
| | - Makoto Tominaga
- Division of Cell Signaling, Okazaki Institute for Integrative Bioscience, Aichi, 444-8787, Japan
| | - Masato Umeda
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan.
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58
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Bozelli JC, Hou YH, Epand RM. Thermodynamics of Methyl-β-cyclodextrin-Induced Lipid Vesicle Solubilization: Effect of Lipid Headgroup and Backbone. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13882-13891. [PMID: 29120189 DOI: 10.1021/acs.langmuir.7b03447] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The low aqueous solubility of phospholipids makes necessary the use of lipid carriers in studies ranging from lipid traffic and metabolism to the engineering of model membranes bearing lipid transverse asymmetry. One particular lipid carrier that has proven to be particularly useful is methyl-β-cyclodextrin (MβCD). To assess the interaction of MβCD with structurally different phospholipids, the present work reports the results of isothermal titration calorimetry in conjunction with dynamic light scattering measurements. The results showed that the interaction of MβCD with large unilamellar vesicles composed of a single type of lipid led to the solubilization of the lipid vesicle and, consequently, the complexation of MβCD with the lipids. This interaction is dependent on the nature of the lipid headgroup, with a preferable interaction with phosphatidylglycerol in comparison to phosphatidylcholine. It was also possible to show a role played by the phospholipid backbone in this interaction. In many cases, the differences in the transfer energy between one lipid and another in going from a bilayer to a cyclodextrin-bound state can be qualitatively explained by the energy required to extract the lipid from a bilayer. In all cases, the data showed that the solubilization of the vesicles is entropically driven with a large negative ΔCp, suggesting a mechanism dependent on the hydrophobic effect.
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Affiliation(s)
- José Carlos Bozelli
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre , Hamilton, Ontario L8S 4K1 Canada
| | - Yu Heng Hou
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre , Hamilton, Ontario L8S 4K1 Canada
| | - Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre , Hamilton, Ontario L8S 4K1 Canada
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Lipidomics reveals diurnal lipid oscillations in human skeletal muscle persisting in cellular myotubes cultured in vitro. Proc Natl Acad Sci U S A 2017; 114:E8565-E8574. [PMID: 28973848 DOI: 10.1073/pnas.1705821114] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Circadian clocks play an important role in lipid homeostasis, with impact on various metabolic diseases. Due to the central role of skeletal muscle in whole-body metabolism, we aimed at studying muscle lipid profiles in a temporal manner. Moreover, it has not been shown whether lipid oscillations in peripheral tissues are driven by diurnal cycles of rest-activity and food intake or are able to persist in vitro in a cell-autonomous manner. To address this, we investigated lipid profiles over 24 h in human skeletal muscle in vivo and in primary human myotubes cultured in vitro. Glycerolipids, glycerophospholipids, and sphingolipids exhibited diurnal oscillations, suggesting a widespread circadian impact on muscle lipid metabolism. Notably, peak levels of lipid accumulation were in phase coherence with core clock gene expression in vivo and in vitro. The percentage of oscillating lipid metabolites was comparable between muscle tissue and cultured myotubes, and temporal lipid profiles correlated with transcript profiles of genes implicated in their biosynthesis. Lipids enriched in the outer leaflet of the plasma membrane oscillated in a highly coordinated manner in vivo and in vitro. Lipid metabolite oscillations were strongly attenuated upon siRNA-mediated clock disruption in human primary myotubes. Taken together, our data suggest an essential role for endogenous cell-autonomous human skeletal muscle oscillators in regulating lipid metabolism independent of external synchronizers, such as physical activity or food intake.
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60
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Singh A, MacKenzie A, Girnun G, Del Poeta M. Analysis of sphingolipids, sterols, and phospholipids in human pathogenic Cryptococcus strains. J Lipid Res 2017; 58:2017-2036. [PMID: 28811322 DOI: 10.1194/jlr.m078600] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/13/2017] [Indexed: 01/07/2023] Open
Abstract
Cryptococcus species cause invasive infections in humans. Lipids play an important role in the progression of these infections. Independent studies done by our group and others provide some detail about the functions of these lipids in Cryptococcus infections. However, the pathways of biosynthesis and the metabolism of these lipids are not completely understood. To thoroughly understand the physiological role of these Cryptococcus lipids, a proper structure and composition analysis of Cryptococcus lipids is demanded. In this study, a detailed spectroscopic analysis of lipid extracts from Cryptococcus gattii and Cryptococcus grubii strains is presented. Sphingolipid profiling by LC-ESI-MS/MS was used to analyze sphingosine, dihydrosphingosine, sphingosine-1-phosphate, dihydrosphingosine-1-phosphate, ceramide, dihydroceramide, glucosylceramide, phytosphingosine, phytosphingosine-1-phosphate, phytoceramide, α-hydroxy phytoceramide, and inositolphosphorylceramide species. A total of 13 sterol species were identified using GC-MS, where ergosterol is the most abundant species. The 31P-NMR-based phospholipid analysis identified phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidyl-N,N-dimethylethanolamine, phosphatidyl-N-monomethylethanolamine, phosphatidylglycerol, phosphatidic acid, and lysophosphatidylethanolamine. A comparison of lipid profiles among different Cryptococcus strains illustrates a marked change in the metabolic flux of these organisms, especially sphingolipid metabolism. These data improve our understanding of the structure, biosynthesis, and metabolism of common lipid groups of Cryptococcus and should be useful while studying their functional significance and designing therapeutic interventions.
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Affiliation(s)
- Ashutosh Singh
- Department of Molecular Genetics and Microbiology and Stony Brook University, Stony Brook, NY 11794
| | | | - Geoffrey Girnun
- Department of Pathology, Stony Brook School of Medicine, Stony Brook, NY 11794
| | - Maurizio Del Poeta
- Department of Molecular Genetics and Microbiology and Stony Brook University, Stony Brook, NY 11794 .,Veterans Administration Medical Center, Northport, NY 11768.,Division of Infectious Diseases, Stony Brook University, Stony Brook, NY 11794
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