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Wilson KJ, Nguyen HQ, Gervay-Hague J, Keller SL. Sterol-lipids enable large-scale, liquid-liquid phase separation in membranes of only 2 components. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.02.578692. [PMID: 38370758 PMCID: PMC10871287 DOI: 10.1101/2024.02.02.578692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Despite longstanding excitement and progress toward understanding liquid-liquid phase separation in natural and artificial membranes, fundamental questions have persisted about which molecules are required for this phenomenon. Except in extraordinary circumstances, the smallest number of components that has produced large-scale, liquid-liquid phase separation in bilayers has stubbornly remained at three: a sterol, a phospholipid with ordered chains, and a phospholipid with disordered chains. This requirement of three components is puzzling for two reasons: (1) the Gibbs Phase Rule states that only two components are necessary, and (2) only two components are required for liquid-liquid phase separation in lipid monolayers, which resemble half of a bilayer. Inspired by reports that sterols interact closely with lipids with ordered chains, we tested whether phase separation would occur in bilayers in which a sterol and lipid were replaced by a single, joined sterol-lipid. By evaluating a panel of sterol-lipids, we discovered a minimal bilayer of only two components (PChemsPC and diPhyPC) that demixes into micron-scale, liquid phases. In this system, the sterol-lipid behaves as a 3:1 ratio of cholesterol to phospholipid. Our system gives the computation and theory community a two-component membrane that maps directly onto simplified theories and that can be used to validate simulation force fields. It suggests a new role for sterol-lipids in nature, and it gives experimental communities a membrane in which tie-lines (and, therefore, the lipid composition of each phase) are easily determined and will be consistent across multiple laboratories. Significance Statement A wide diversity of bilayer membranes, from those with hundreds of lipids (e.g., vacuoles of living yeast cells) to those with very few (e.g., artificial vesicles) phase separate into micron-scale liquid domains. The number of components required for liquid-liquid phase separation has been perplexing: only two should be necessary, but more are required except in extraordinary circumstances. What minimal set of molecular characteristics leads to liquid-liquid phase separation in bilayer membranes? This question inspired us to search for single, joined "sterol-lipid" molecules to replace both a sterol and a phospholipid in membranes undergoing liquid-liquid phase separation. By producing phase-separating membranes with only two components, we mitigate experimental challenges in determining tie-lines and in maintaining constant chemical potentials of lipids.
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Stolarek P, Bernat P, Różalski A. Adjustment in the Composition and Organization of Proteus mirabilis Lipids during the Swarming Process. Int J Mol Sci 2023; 24:16461. [PMID: 38003652 PMCID: PMC10671106 DOI: 10.3390/ijms242216461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 11/07/2023] [Accepted: 11/15/2023] [Indexed: 11/26/2023] Open
Abstract
Proteus mirabilis, an opportunistic pathogen of the urinary tract, is known for its dimorphism and mobility. A connection of lipid alterations, induced by the rods elongation process, with enhanced pathogenicity of long-form morphotype for the development of urinary tract infections, seems highly probable. Therefore, research on the adjustment in the composition and organization of P. mirabilis lipids forming elongated rods was undertaken. The analyses performed using the ultra-high performance liquid chromatography with tandem mass spectrometry showed that drastic modifications in the morphology of P. mirabilis rods that occur during the swarming process are directly related to deprivation of the long-form cells of PE 33:1 and PG 31:2 and their enrichment with PE 32:1, PE 34:1, PE 34:2, PG 30:2, PG 32:1, and PG 34:1. The analyses conducted by the gas chromatography-mass spectrometry showed negligible effects of the swarming process on fatty acids synthesis. However, the constant proportions between unsaturated and saturated fatty acids confirmed that phenotypic modifications in the P. mirabilis rods induced by motility were independent of the saturation of the phospholipid tails. The method of the Förster resonance energy transfer revealed the influence of the swarming process on the melting of ordered lipid rafts present in the short-form rods, corresponding to the homogeneity of lipid bilayers in the long-form rods of P. mirabilis. Confocal microscope photographs visualized strong Rhod-PE fluorescence of the whole area of swarmer cells, in contrast to weak membrane fluorescence of non-swarmer cells. It suggested an increased permeability of the P. mirabilis bilayers in long-form rods morphologically adapted to the swarming process. These studies clearly demonstrate that swarming motility regulates the lipid composition and organization in P. mirabilis rods.
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Affiliation(s)
- Paulina Stolarek
- Department of Biology of Bacteria, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12/16, 90-237 Lodz, Poland;
| | - Przemysław Bernat
- Department of Industrial Microbiology and Biotechnology, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12/16, 90-237 Lodz, Poland;
| | - Antoni Różalski
- Department of Biology of Bacteria, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12/16, 90-237 Lodz, Poland;
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Meers PR. Membrane Organization Strategies in Vesicular Antibiotic Delivery. J Membr Biol 2022; 255:523-535. [PMID: 35018488 DOI: 10.1007/s00232-021-00210-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 12/06/2021] [Indexed: 01/08/2023]
Abstract
Small molecule antibiotics are often derived from microorganisms that thrive in competitive environments. Their importance as therapeutics for infectious disease in humans has been established over many years. It has now become clear that antibiotic-producing organisms use packaging and delivery in the form of vesicles in many cases. A similar strategy has evolved in recent decades in the pharmaceutical industry for formulation of antibiotic therapies. The top-down approach that has evolved over millions of years in various micro-organisms has generated complex, efficient delivery systems that we are just now beginning to understand. The bottom-up formulation approach involves simple, safe compositions, which are being continually enhanced by trying to add features of which the natural systems inform us. A comparison is made here of these paradigms. Despite the differences, there are a number of common features in the basic physical and biological requirements that must be satisfied. In this review, illustration and comparison of some of these requirements is given, demonstrating the ongoing challenges in this area of research.
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Affiliation(s)
- Paul R Meers
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ, USA.
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Structure, metabolism and biological functions of steryl glycosides in mammals. Biochem J 2021; 477:4243-4261. [PMID: 33186452 PMCID: PMC7666875 DOI: 10.1042/bcj20200532] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/09/2020] [Accepted: 10/21/2020] [Indexed: 12/20/2022]
Abstract
Steryl glycosides (SGs) are sterols glycosylated at their 3β-hydroxy group. They are widely distributed in plants, algae, and fungi, but are relatively rare in bacteria and animals. Glycosylation of sterols, resulting in important components of the cell membrane SGs, alters their biophysical properties and confers resistance against stress by freezing or heat shock to cells. Besides, many biological functions in animals have been suggested from the observations of SG administration. Recently, cholesteryl glucosides synthesized via the transglycosidation by glucocerebrosidases (GBAs) were found in the central nervous system of animals. Identification of patients with congenital mutations in GBA genes or availability of respective animal models will enable investigation of the function of such endogenously synthesized cholesteryl glycosides by genetic approaches. In addition, mechanisms of the host immune responses against pathogenic bacterial SGs have partially been resolved. This review is focused on the biological functions of SGs in mammals taking into consideration their therapeutic applications in the future.
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Abstract
Lyme disease (Lyme borreliosis) is a tick-borne, zoonosis of adults and children caused by genospecies of the Borrelia burgdorferi sensu lato complex. The ailment, widespread throughout the Northern Hemisphere, continues to increase globally due to multiple environmental factors, coupled with increased incursion of humans into habitats that harbor the spirochete. B. burgdorferi sensu lato is transmitted by ticks from the Ixodes ricinus complex. In North America, B. burgdorferi causes nearly all infections; in Europe, B. afzelii and B. garinii are most associated with human disease. The spirochete's unusual fragmented genome encodes a plethora of differentially expressed outer surface lipoproteins that play a seminal role in the bacterium's ability to sustain itself within its enzootic cycle and cause disease when transmitted to its incidental human host. Tissue damage and symptomatology (i.e., clinical manifestations) result from the inflammatory response elicited by the bacterium and its constituents. The deposition of spirochetes into human dermal tissue generates a local inflammatory response that manifests as erythema migrans (EM), the hallmark skin lesion. If treated appropriately and early, the prognosis is excellent. However, in untreated patients, the disease may present with a wide range of clinical manifestations, most commonly involving the central nervous system, joints, or heart. A small percentage (~10%) of patients may go on to develop a poorly defined fibromyalgia-like illness, post-treatment Lyme disease (PTLD) unresponsive to prolonged antimicrobial therapy. Below we integrate current knowledge regarding the ecologic, epidemiologic, microbiologic, and immunologic facets of Lyme disease into a conceptual framework that sheds light on the disorder that healthcare providers encounter.
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Affiliation(s)
- Justin D. Radolf
- Department of Medicine, UConn Health, Farmington, CT 06030, USA
- Department of Pediatrics, UConn Health, Farmington, CT 06030, USA
- Departments of Genetics and Genome Sciences, UConn Health, Farmington, CT 06030, USA
- Departments of Molecular Biology and Biophysics, UConn Health, Farmington, CT 06030, USA
- Department of Immunology, UConn Health, Farmington, CT 06030, USA
| | - Klemen Strle
- Division of Infectious Diseases, Wadsworth Center, NY Department of Health, Albany NY, 12208, USA
| | - Jacob E. Lemieux
- Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Franc Strle
- Department of Infectious Diseases, University Medical Center Ljubljana, Ljubljana, Slovenia
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Tsai YT, Moore W, Kim H, Budin I. Bringing rafts to life: Lessons learned from lipid organization across diverse biological membranes. Chem Phys Lipids 2020; 233:104984. [PMID: 33203526 DOI: 10.1016/j.chemphyslip.2020.104984] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 09/13/2020] [Accepted: 09/28/2020] [Indexed: 10/23/2022]
Abstract
The ability of lipids to drive lateral organization is a remarkable feature of membranes and has been hypothesized to underlie the architecture of cells. Models for lipid rafts and related domains were originally based on the mammalian plasma membrane, but the nature of heterogeneity in this system is still not fully resolved. However, the concept of lipid-driven organization has been highly influential across biology, and has led to discoveries in organisms that feature a diversity of lipid chemistries and physiological needs. Here we review several emerging and instructive cases of membrane organization in non-mammalian systems. In bacteria, several types of membrane domains that act in metabolism and signaling have been elucidated. These widen our view of what constitutes a raft, but also introduce new questions about the relationship between organization and function. In yeast, observable membrane organization is found in both the plasma membrane and the vacuole. The latter serves as the best example of classic membrane phase partitioning in a living system to date, suggesting that internal organelles are important membranes to investigate across eukaryotes. Finally, we highlight plants as powerful model systems for complex membrane interactions in multicellular organisms. Plant membranes are organized by unique glycosphingolipids, supporting the importance of carbohydrate interactions in organizing lateral domains. These examples demonstrate that membrane organization is a potentially universal phenonenon in biology and argue for the continued broadening of lipid physical chemistry research into a wide range of systems.
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Affiliation(s)
- Yi-Ting Tsai
- Department of Chemistry & Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, United States
| | - William Moore
- Department of Chemistry & Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, United States
| | - Hyesoo Kim
- Department of Chemistry & Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, United States
| | - Itay Budin
- Department of Chemistry & Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, United States.
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Structural and Functional Analysis of BBA03, Borrelia burgdorferi Competitive Advantage Promoting Outer Surface Lipoprotein. Pathogens 2020; 9:pathogens9100826. [PMID: 33050189 PMCID: PMC7650648 DOI: 10.3390/pathogens9100826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 09/30/2020] [Accepted: 10/07/2020] [Indexed: 11/17/2022] Open
Abstract
BBA03 is a Borrelia burgdorferi outer surface lipoprotein encoded on one of the most conserved plasmids in Borrelia genome, linear plasmid 54 (lp54). Although many of its genes have been identified as contributing or essential for spirochete fitness in vivo, the majority of the proteins encoded on this plasmid have no known function and lack homologs in other organisms. In this paper, we report the solution NMR structure of the B. burgdorferi outer surface lipoprotein BBA03, which is known to provide a competitive advantage to the bacteria during the transmission from tick vector to mammalian host. BBA03 shows structural homology to other outer surface lipoproteins reflecting their genetic and evolutionary relatedness. Analysis of the structure reveals a pore in BBA03, which could potentially bind lipids.
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Helicobacter pylori lipids can form ordered membrane domains (rafts). BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183050. [PMID: 31449801 DOI: 10.1016/j.bbamem.2019.183050] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 08/09/2019] [Accepted: 08/21/2019] [Indexed: 02/07/2023]
Abstract
Ordered lipid domains (rafts) are generally considered to be features of eukaryotic cells, but ordered lipid domains formed by cholesterol lipids have been identified in bacteria from the genus Borrelia, and similar cholesterol lipids exist in the bacterium Helicobacter pylori. To determine whether H. pylori lipids could form ordered membrane domains, we investigated domain formation in aqueous dispersions of H. pylori whole lipid extracts, individual H. pylori lipids, or defined mixtures of H. pylori lipids and other membrane-forming lipids. DPH (1,6-diphenyl-1,3,5-hexatriene) anisotropy measurements were used to assay membrane order and FRET (Förster resonance energy transfer) was used to detect the presence of co-existing ordered and disordered domains. We found that H. pylori membrane lipid extracts spontaneously formed lipid domains. Domain formation was more stable when lipids were extracted from H. pylori cells grown in the presence of cholesterol. Certain isolated H. pylori lipids (by themselves or when mixed with other lipids) also had the ability to form ordered domains. To be specific, H. pylori cholesteryl-6-O-tetradecanoyl-α-D-glucopyranoside (CAG) and cholesterol-6-O-phosphatidyl-α-D-glucopyranoside (CPG) had the ability to form and/or stabilize ordered domain formation, while H. pylori phosphatidylethanolamine did not, behaving similarly to unsaturated phosphatidylethanolamines. We conclude that specific H. pylori cholesterol lipids have a marked ability to form ordered lipid domains.
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Siavashi R, Phaterpekar T, Leung SSW, Alonso A, Goñi FM, Thewalt JL. Lamellar Phases Composed of Phospholipid, Cholesterol, and Ceramide, as Studied by 2H NMR. Biophys J 2019; 117:296-306. [PMID: 31279446 PMCID: PMC6702149 DOI: 10.1016/j.bpj.2019.05.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 04/23/2019] [Accepted: 05/07/2019] [Indexed: 11/28/2022] Open
Abstract
Sphingolipids constitute a significant fraction of cellular plasma membrane lipid content. Among sphingolipids, ceramide levels are usually very low. However, in some cell processes like apoptosis, cell membrane ceramide levels increase markedly because of the activation of enzymes like acid sphingomyelinase. This increase can change the physical state of the membrane by promoting molecular order and inducing solid-ordered (So) phase domains. This effect has been observed in a previous 2H NMR study on membranes consisting of palmitoyl sphingomyelin (PSM) and palmitoyl ceramide (PCer). Cholesterol (Chol), too, is present at high concentrations in mammalian plasma membranes and has a favorable interaction with sphingomyelin (SM), together forming domains in the liquid-ordered phase in model membranes. There are reports that Chol is able to displace ceramide (Cer) in SM bilayers and abolish the So phase domains formed by SM:Cer. This ability of Chol appears to be concentration dependent; in membranes with low Chol and high Cer contents, So phase domains rich in Cer coexist with the continuous fluid phase of the membrane. Here, we studied the effect of increasing PCer concentration in PSM:Chol bilayers, using 2H NMR. Chol:PCer mole ratios were 3:1, 3:2, and 3:3, at a fixed 7:3 phospholipid:cholesterol mol ratio. Both PSM and PCer were monitored in separate samples for changes in their physical state by introducing a perdeuterated palmitoyl chain in either molecule. Moreover, the effect of replacing PSM with DPPC was investigated to test the impact on membrane phase behavior of replacing the sphingosine with a palmitoylated glycerol backbone. We found that PCer can increase acyl chain order in both PSM:Chol and DPPC:Chol bilayers. Especially in bilayers with Chol:PCer 1:1 molar ratios, PCer induces highly stable So phase domains in both PSM and DPPC bilayers near 37°C. However, PCer has a more pronounced ordering effect on PSM compared to DPPC bilayers.
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Affiliation(s)
- Reza Siavashi
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Tejas Phaterpekar
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Sherry S W Leung
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Alicia Alonso
- Instituto Biofisika, University of the Basque Country/Spanish National Research Council (CSIC), Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country, Leioa, Spain
| | - Félix M Goñi
- Instituto Biofisika, University of the Basque Country/Spanish National Research Council (CSIC), Leioa, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country, Leioa, Spain
| | - Jenifer L Thewalt
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada; Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
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Claude-Henri C, Binot C, Sadoc JF. The involvement of liquid crystals in multichannel implanted neurostimulators, hearing and ENT infections, and cancer. Acta Otolaryngol 2019; 139:316-332. [PMID: 31035839 DOI: 10.1080/00016489.2018.1554265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Liquid crystals (LCs) consist of assemblies of molecules, between one and tens of nanometers, grouped in identifiable cohorts according to orientation and structure, which is often lamellar with varying chirality. The term liquid phase (Lo phase) designates certain such mesophases. This variety in geometry corresponds to a variety of functions. Some molecules, both organic and inorganic, used in applied engineering, and association with LCs confer new properties. Applying these aspects of LCs in manufacturing implantable material is a growing technology, especially in the interfaces of differentiated multichannel electro-neurostimulation. We highlight the involvement of LCs in the head and neck region, and the role mesophases play in outer hair cell electromotility (mechanotransduction). We summarize implications of LCs this for multichannel electroneurostimulation implant engineering, and highlight their role importance of LCs in early oncogenic process, HPV, and latency in (Epstein-Barr) and other pathogens. Our approach should help give rise to new therapeutic perspectives. Focusing on upstream nanometric phenomena needs to take on board classic determinism, quantum probability, and statistical complexity.
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Kimble-Hill AC, Petrache HI, Seifert S, Firestone MA. Reorganization of Ternary Lipid Mixtures of Nonphosphorylated Phosphatidylinositol Interacting with Angiomotin. J Phys Chem B 2018; 122:8404-8415. [PMID: 29877706 PMCID: PMC6351316 DOI: 10.1021/acs.jpcb.7b12641] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Phosphatidylinositol (PI) lipids are necessary for many cellular signaling pathways of membrane associated proteins, such as angiomotin (Amot). The Amot family regulates cellular polarity, growth, and migration. Given the low concentration of PI lipids in these membranes, it is likely that such protein-membrane interactions are stabilized by lipid domains or small lipid clusters. By small-angle X-ray scattering, we show that nonphosphorylated PI lipids induce lipid demixing in ternary mixtures of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), likely because of preferential interactions between the head groups of PE and PI. These results were obtained in the presence of buffer containing tris(hydroxymethyl)aminomethane, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, NaCl, ethylenediaminetetraacetic acid, dithiothreitol, and benzamidine at pH 8.0 that in previous work showed an ability to cause PC to phase separate but are necessary to stabilize Amot for in vitro experimentation. Collectively, this provided a framework for determining the effect of Amot on lipid organization. Using fluorescence spectroscopy, we were able to show that the association of Amot with this lipid platform causes significant reorganization of the lipid into a more homogenous structure. This reorganization mechanism could be the basis for Amot membrane association and fusogenic activity previously described in the literature and should be taken into consideration in future protein-membrane interaction studies.
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Affiliation(s)
- Ann C. Kimble-Hill
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, MS 4053, 635 Barnhill Dr., Indianapolis, Indiana 46202, United States
| | - Horia I. Petrache
- Department of Physics, Indiana University Purdue University Indianapolis, LD 154, 402 N. Blackford Street, Indianapolis, Indiana 46202, United States
| | - Soenke Seifert
- X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Millicent A. Firestone
- Center for Integrated Nanotechnologies, Los Alamos National Laboratory, MPA-CINT, MS K771, Los Alamos, New Mexico 87545, United States
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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] [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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