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Kenkre V, Spendier K. A theory of coalescence of signaling receptor clusters in immune cells. PHYSICA A 2022; 602:127650. [PMID: 35966144 PMCID: PMC9365117 DOI: 10.1016/j.physa.2022.127650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
A theory of coalescence of signal receptor clusters in mast cells is developed in close connection with experiments. It is based on general considerations involving a feedback procedure and a time-dependent capture as part of a reaction-diffusion process. Characteristic features of observations that need to be explained are indicated and it is shown why calculations available in the literature are not satisfactory. While the latter involves static centers at which the reaction part of the phenomenon occurs, by its very nature, coalescence involves dynamically evolving centers. This is so because the process continuously modifies the size of the cluster aggregate which then proceeds to capture more material. We develop a procedure that consists of first solving a static reaction-diffusion problem and then imbuing the center with changing size. The consequence is a dependence of the size of the signal receptor cluster aggregate on time. A preliminary comparison with experiment is shown to reveal a sharp difference between theory and data. The observation indicates that the reaction occurs slowly at first and then picks up rapidly as time proceeds. Parameter modification to fit the observations cannot solve the problem. We use this observation to build into the theory an accumulation rate that is itself dependent on time. A memory representation and its physical basis are explained. The consequence is a theory that can be fit to observations successfully.
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Affiliation(s)
- V.M. Kenkre
- Department of Physics and Astronomy, University of New Mexico, 210 Yale Blvd NE, Albuquerque, 87131, NM, USA
| | - K. Spendier
- Department of Physics and Energy Science and UCCS Center for the Biofrontiers Institute, University of Colorado Colorado Springs, 1420 Austin Bluffs Pkwy, Colorado Springs, 80918, CO, USA
- Corresponding author. (K. Spendier)
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2
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Baird BA. My path in the company of chemistry. PURE APPL CHEM 2022; 94:943-949. [PMID: 36318625 PMCID: PMC9560576 DOI: 10.1515/pac-2021-1205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Experiencing the honor of this international recognition in chemistry, I wonder how this came to be. I reflect on my imperfect but rewarding path to where I am now, and on those who have helped me along the way.
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Affiliation(s)
- Barbara A. Baird
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca NY 14853 , USA
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3
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Lipid-based and protein-based interactions synergize transmembrane signaling stimulated by antigen clustering of IgE receptors. Proc Natl Acad Sci U S A 2021; 118:2026583118. [PMID: 34433665 DOI: 10.1073/pnas.2026583118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Antigen (Ag) crosslinking of immunoglobulin E-receptor (IgE-FcεRI) complexes in mast cells stimulates transmembrane (TM) signaling, requiring phosphorylation of the clustered FcεRI by lipid-anchored Lyn tyrosine kinase. Previous studies showed that this stimulated coupling between Lyn and FcεRI occurs in liquid ordered (Lo)-like nanodomains of the plasma membrane and that Lyn binds directly to cytosolic segments of FcεRI that it initially phosphorylates for amplified activity. Net phosphorylation above a nonfunctional threshold is achieved in the stimulated state but not in the resting state, and current evidence supports the hypothesis that this relies on Ag crosslinking to disrupt a balance between Lyn and tyrosine phosphatase activities. However, the structural interactions that underlie the stimulation process remain poorly defined. This study evaluates the relative contributions and functional importance of different types of interactions leading to suprathreshold phosphorylation of Ag-crosslinked IgE-FcεRI in live rat basophilic leukemia mast cells. Our high-precision diffusion measurements by imaging fluorescence correlation spectroscopy on multiple structural variants of Lyn and other lipid-anchored probes confirm subtle, stimulated stabilization of the Lo-like nanodomains in the membrane inner leaflet and concomitant sharpening of segregation from liquid disordered (Ld)-like regions. With other structural variants, we determine that lipid-based interactions are essential for access by Lyn, leading to phosphorylation of and protein-based binding to clustered FcεRI. By contrast, TM tyrosine phosphatase, PTPα, is excluded from these regions due to its Ld-preference and steric exclusion of TM segments. Overall, we establish a synergy of lipid-based, protein-based, and steric interactions underlying functional TM signaling in mast cells.
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Gupta A, Muralidharan S, Torta F, Wenk MR, Wohland T. Long acyl chain ceramides govern cholesterol and cytoskeleton dependence of membrane outer leaflet dynamics. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183153. [PMID: 31857071 DOI: 10.1016/j.bbamem.2019.183153] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 12/09/2019] [Indexed: 12/20/2022]
Abstract
The spatiotemporal dynamics of the plasma membrane is a consequence of fine-tuned interactions between membrane components. However, the precise identity of molecular factors that maintain this delicate balance, which is lost even in cell membrane derived mimics, remains elusive. Here, we use two cell lines, CHO-K1 and RBL-2H3, which show differences in outer membrane organization, dynamics, and cytoskeleton coupling, to investigate the underlying factors. To our surprise, knock-down of the cytoskeleton-interacting Immunoglobulin E receptor, which is abundant in RBL-2H3 but not in CHO-K1 cells, is not responsible for lipid confinement or cytoskeleton coupling. A subsequent lipidomic analysis of the two cell membranes revealed differences in total membrane ceramide content (C16 to C24). Analysis of the dynamics and organization of ceramide treated live cell membranes by imaging fluorescence correlation spectroscopy demonstrates that C24 and C16 saturated ceramides uniquely alter membrane dynamics by promoting the formation of cholesterol-independent domains and by elevating the inter-leaflet coupling.
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Affiliation(s)
- Anjali Gupta
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, 117557, Singapore
| | - Sneha Muralidharan
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore
| | - Federico Torta
- Department of Biochemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
| | - Markus R Wenk
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore; Department of Biochemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
| | - Thorsten Wohland
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, 117557, Singapore; Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore.
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5
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Drawbond R, Spendier K. TIRF Microscope Image Sequences of Fluorescent IgE-FcεRI Receptor Complexes inside a FcεRI-Centric Synapse in RBL-2H3 Cells. DATA 2019. [PMID: 32704503 DOI: 10.17632/6kvzv95w7r.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023] Open
Abstract
Total internal reflection fluorescence (TIRF) microscope image sequences are commonly used to study receptors in live cells. The dataset presented herein facilitates the study of the IgE-FcεRI receptor signaling complex (IgE-RC) in rat basophilic leukemia (RBL-2H3) cells coming into contact with a supported lipid bilayer with 25 mol% N-dinitrophenyl-aminocaproyl phosphatidylethanolamine, modeling an immunological synapse. TIRF microscopy was used to image IgE-RCs within this FcεRI-centric synapse by loading RBL-2H3 cells with fluorescent anti-dinitrophenyl (anti-DNP) immunoglobulin E (IgE) in suspension for 24 h. Fluorescent anti-DNP IgE (IgE488) concentrations of this suspension increased from 10% to 100% and corresponding non-fluorescent anti-DNP IgE concentrations decreased from 90% to 0%. After the removal of unbound anti-DNP IgE, multiple image sequences were taken for each of these ten conditions. Prior to imaging, anti-DNP IgE-primed RBL-2H3 cells were either kept for a few minutes, for about 30 min, or for about one hour in Hanks buffer. The dataset contains 482 RBL-2H3 model synapse image stacks, dark images to correct for background intensity, and TIRF illumination profile images to correct for non-uniform TIRF illumination. After background subtraction, non-uniform illumination correction, and conversion of pixel units from analog-to-digital units to photo electrons, the average pixel intensity was calculated. The average pixel intensity within FcεRI-centric synapses for all three Hanks buffer conditions increased linearly at a rate of 0.42 ± 0.02 photo electrons per pixel per % IgE488 in suspension. RBL-2H3 cell degranulation was tested by detecting β-hexosaminidase activity. Prolonged RBL-2H3 cell exposure to Hanks buffer inhibited exocytosis in RBL-2H3 cells.
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Affiliation(s)
- Rachel Drawbond
- UCCS Center of the Biofrontiers Institute, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA
- Department of Mathematics, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA
| | - Kathrin Spendier
- Department of Mathematics, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA
- Department of Physics and Energy Science, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA
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Drawbond R, Spendier K. TIRF Microscope Image Sequences of Fluorescent IgE-FcεRI Receptor Complexes inside a FcεRI-Centric Synapse in RBL-2H3 Cells. DATA 2019; 4:111. [PMID: 32704503 PMCID: PMC7377353 DOI: 10.3390/data4030111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Total internal reflection fluorescence (TIRF) microscope image sequences are commonly used to study receptors in live cells. The dataset presented herein facilitates the study of the IgE-FcεRI receptor signaling complex (IgE-RC) in rat basophilic leukemia (RBL-2H3) cells coming into contact with a supported lipid bilayer with 25 mol% N-dinitrophenyl-aminocaproyl phosphatidylethanolamine, modeling an immunological synapse. TIRF microscopy was used to image IgE-RCs within this FcεRI-centric synapse by loading RBL-2H3 cells with fluorescent anti-dinitrophenyl (anti-DNP) immunoglobulin E (IgE) in suspension for 24 h. Fluorescent anti-DNP IgE (IgE488) concentrations of this suspension increased from 10% to 100% and corresponding non-fluorescent anti-DNP IgE concentrations decreased from 90% to 0%. After the removal of unbound anti-DNP IgE, multiple image sequences were taken for each of these ten conditions. Prior to imaging, anti-DNP IgE-primed RBL-2H3 cells were either kept for a few minutes, for about 30 min, or for about one hour in Hanks buffer. The dataset contains 482 RBL-2H3 model synapse image stacks, dark images to correct for background intensity, and TIRF illumination profile images to correct for non-uniform TIRF illumination. After background subtraction, non-uniform illumination correction, and conversion of pixel units from analog-to-digital units to photo electrons, the average pixel intensity was calculated. The average pixel intensity within FcεRI-centric synapses for all three Hanks buffer conditions increased linearly at a rate of 0.42 ± 0.02 photo electrons per pixel per % IgE488 in suspension. RBL-2H3 cell degranulation was tested by detecting β-hexosaminidase activity. Prolonged RBL-2H3 cell exposure to Hanks buffer inhibited exocytosis in RBL-2H3 cells.
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Affiliation(s)
- Rachel Drawbond
- UCCS Center of the Biofrontiers Institute, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA
- Department of Mathematics, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA
| | - Kathrin Spendier
- Department of Mathematics, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA
- Department of Physics and Energy Science, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA
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7
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Abstract
In this paper we construct and analyze a model of cell receptor aggregation. Experiments have shown that receptors in an aggregated state have greatly reduced mobility. We model the effects of this reduced mobility with a density dependent diffusion and study the impact of density dependent diffusion on aggregate formation in a one-dimensional domain. Critical values of receptor diffusivity and receptor activation are found and compared with numerical simulations. We find that the role of density dependant diffusion is quite limited in the formation of aggregate structures. In the case of receptor activation, the analytical results agree very well with the numerical calculations. Finally, we consider our model in higher dimensional domains. In this case our analysis is primarily numerical.
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Kraft ML. Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It. Front Cell Dev Biol 2017; 4:154. [PMID: 28119913 PMCID: PMC5222807 DOI: 10.3389/fcell.2016.00154] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 12/27/2016] [Indexed: 11/13/2022] Open
Abstract
Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with cholesterol or hemagglutinin. The alternate views of plasma membrane organization suggested by these findings are discussed.
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Affiliation(s)
- Mary L Kraft
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana, IL, USA
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Huang S, Lim SY, Gupta A, Bag N, Wohland T. Plasma membrane organization and dynamics is probe and cell line dependent. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:1483-1492. [PMID: 27998689 DOI: 10.1016/j.bbamem.2016.12.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 12/03/2016] [Accepted: 12/08/2016] [Indexed: 01/01/2023]
Abstract
The action and interaction of membrane receptor proteins take place within the plasma membrane. The plasma membrane, however, is not a passive matrix. It rather takes an active role and regulates receptor distribution and function by its composition and the interaction of its lipid components with embedded and surrounding proteins. Furthermore, it is not a homogenous fluid but contains lipid and protein domains of various sizes and characteristic lifetimes which are important in regulating receptor function and signaling. The precise lateral organization of the plasma membrane, the differences between the inner and outer leaflet, and the influence of the cytoskeleton are still debated. Furthermore, there is a lack of comparisons of the organization and dynamics of the plasma membrane of different cell types. Therefore, we used four different specific membrane markers to test the lateral organization, the differences between the inner and outer membrane leaflet, and the influence of the cytoskeleton of up to five different cell lines, including Chinese hamster ovary (CHO-K1), Human cervical carcinoma (HeLa), neuroblastoma (SH-SY5Y), fibroblast (WI-38) and rat basophilic leukemia (RBL-2H3) cells by Imaging Total Internal Reflection (ITIR)-Fluorescence Correlation Spectroscopy (FCS). We measure diffusion in the temperature range of 298-310K to measure the Arrhenius activation energy (EArr) of diffusion and apply the FCS diffusion law to obtain information on the spatial organization of the probe molecules on the various cell membranes. Our results show clear differences of the FCS diffusion law and EArr for the different probes in dependence of their localization. These differences are similar in the outer and inner leaflet of the membrane. However, these values can differ significantly between different cell lines raising the question how molecular plasma membrane events measured in different cell lines can be compared. This article is part of a Special Issue entitled: Interactions between membrane receptors in cellular membranes edited by Kalina Hristova.
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Affiliation(s)
- Shuangru Huang
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore
| | - Shi Ying Lim
- NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore; Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore
| | - Anjali Gupta
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore
| | - Nirmalya Bag
- NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore; Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore
| | - Thorsten Wohland
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore; Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore.
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10
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Madwar C, Gopalakrishnan G, Lennox RB. Interfacing living cells and spherically supported bilayer lipid membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:4704-4712. [PMID: 25826073 DOI: 10.1021/acs.langmuir.5b00862] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Spherically supported bilayer lipid membranes (SS-BLMs) exhibiting co-existing membrane microdomains were created on spherical silica substrates. These 5 μm SiO2-core SS-BLMs are shown to interact dynamically when interfaced with living cells in culture, while keeping the membrane structure and lipid domains on the SS-BLM surface intact. Interactions between the SS-BLMs and cellular components are examined via correlating fluorescently labeled co-existing microdomains on the SS-BLMs, their chemical composition and biophysical properties with the consequent organization of cell membrane lipids, proteins, and other cellular components. This approach is demonstrated in a proof-of-concept experiment involving the dynamic organization of cellular cytoskeleton, monitored as a function of the lipid domains of the SS-BLMs. The compositional versatility of SS-BLMs provides a means to address the relationship between the phenomenon of lipid phase separation and the other contributors to cell membrane lateral heterogeneity.
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Affiliation(s)
- Carolin Madwar
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montréal, Quebec H3A 0B8, Canada
| | - Gopakumar Gopalakrishnan
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montréal, Quebec H3A 0B8, Canada
| | - R Bruce Lennox
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montréal, Quebec H3A 0B8, Canada
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Suzuki R, Scheffel J, Rivera J. New insights on the signaling and function of the high-affinity receptor for IgE. Curr Top Microbiol Immunol 2015; 388:63-90. [PMID: 25553795 DOI: 10.1007/978-3-319-13725-4_4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Clustering of the high-affinity receptor for immunoglobulin E (FcεRI) through the interaction of receptor-bound immunoglobulin E (IgE) antibodies with their cognate antigen is required to couple IgE antibody production to cellular responses and physiological consequences. IgE-induced responses through FcεRI are well known to defend the host against certain infectious agents and to lead to unwanted allergic responses to normally innocuous substances. However, the cellular and/or physiological response of individuals that produce IgE antibodies may be markedly different and such antibodies (even to the same antigenic epitope) can differ in their antigen-binding affinity. How affinity variation in the interaction of FcεRI-bound IgE antibodies with antigen is interpreted into cellular responses and how the local environment may influence these responses is of interest. In this chapter, we focus on recent advances that begin to unravel how FcεRI distinguishes differences in the affinity of IgE-antigen interactions and how such discrimination along with surrounding environmental stimuli can shape the (patho) physiological response.
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Affiliation(s)
- Ryo Suzuki
- Molecular Immunology Section, Laboratory of Molecular Immunogenetics, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
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12
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Abstract
Our long-term efforts to elucidate receptor-mediated signalling in immune cells, particularly transmembrane signalling initiated by FcɛRI, the receptor for IgE in mast cells, led us unavoidably to contemplate the role of the heterogeneous plasma membrane. Our early investigations with fluorescence microscopy revealed co-redistribution of certain lipids and signalling components with antigen-cross-linked IgE-FcɛRI and pointed to participation of ordered membrane domains in the signalling process. With a focus on this function, we have worked along with others to develop diverse and increasingly sophisticated tools to analyse the complexity of membrane structure that facilitates regulation and targeting of signalling events. The present chapter describes how initial membrane interactions of clustered IgE-FcɛRI lead to downstream cellular responses and how biochemical information integrated with nanoscale resolution spectroscopy and imaging is providing mechanistic insights at the level of molecular complexes.
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Affiliation(s)
- David Holowka
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, U.S.A
| | - Barbara Baird
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, U.S.A
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Fteita D, Könönen E, Söderling E, Gürsoy UK. Effect of estradiol on planktonic growth, coaggregation, and biofilm formation of the Prevotella intermedia group bacteria. Anaerobe 2014; 27:7-13. [DOI: 10.1016/j.anaerobe.2014.02.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 01/20/2014] [Accepted: 02/19/2014] [Indexed: 10/25/2022]
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Steinbach G, Pawlak K, Pomozi I, Tóth EA, Molnár A, Matkó J, Garab G. Mapping microscopic order in plant and mammalian cells and tissues: novel differential polarization attachment for new generation confocal microscopes (DP-LSM). Methods Appl Fluoresc 2014; 2:015005. [PMID: 29148454 DOI: 10.1088/2050-6120/2/1/015005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Elucidation of the molecular architecture of complex, highly organized molecular macro-assemblies is an important, basic task for biology. Differential polarization (DP) measurements, such as linear (LD) and circular dichroism (CD) or the anisotropy of the fluorescence emission (r), which can be carried out in a dichrograph or spectrofluorimeter, respectively, carry unique, spatially averaged information about the molecular organization of the sample. For inhomogeneous samples-e.g. cells and tissues-measurements on macroscopic scale are not satisfactory, and in some cases not feasible, thus microscopic techniques must be applied. The microscopic DP-imaging technique, when based on confocal laser scanning microscope (LSM), allows the pixel by pixel mapping of anisotropy of a sample in 2D and 3D. The first DP-LSM configuration, which, in fluorescence mode, allowed confocal imaging of different DP quantities in real-time, without interfering with the 'conventional' imaging, was built on a Zeiss LSM410. It was demonstrated to be capable of determining non-confocally the linear birefringence (LB) or LD of a sample and, confocally, its FDLD (fluorescence detected LD), the degree of polarization (P) and the anisotropy of the fluorescence emission (r), following polarized and non-polarized excitation, respectively (Steinbach et al 2009 Acta Histochem.111 316-25). This DP-LSM configuration, however, cannot simply be adopted to new generation microscopes with considerably more compact structures. As shown here, for an Olympus FV500, we designed an easy-to-install DP attachment to determine LB, LD, FDLD and r, in new-generation confocal microscopes, which, in principle, can be complemented with a P-imaging unit, but specifically to the brand and type of LSM.
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Affiliation(s)
- G Steinbach
- Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary. Biofotonika R&D Ltd, Szeged, Hungary
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Heek T, Nikolaus J, Schwarzer R, Fasting C, Welker P, Licha K, Herrmann A, Haag R. An Amphiphilic Perylene Imido Diester for Selective Cellular Imaging. Bioconjug Chem 2013; 24:153-8. [DOI: 10.1021/bc3005655] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Timm Heek
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Jörg Nikolaus
- Institut für Biologie/Molekulare
Biophysik, Humboldt Universität zu Berlin, Invalidenstraße 42, 10115 Berlin, Germany
| | - Roland Schwarzer
- Institut für Biologie/Molekulare
Biophysik, Humboldt Universität zu Berlin, Invalidenstraße 42, 10115 Berlin, Germany
| | - Carlo Fasting
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
| | - Pia Welker
- mivenion GmbH, Robert-Koch-Platz
4, 10115 Berlin, Germany
| | - Kai Licha
- mivenion GmbH, Robert-Koch-Platz
4, 10115 Berlin, Germany
| | - Andreas Herrmann
- Institut für Biologie/Molekulare
Biophysik, Humboldt Universität zu Berlin, Invalidenstraße 42, 10115 Berlin, Germany
| | - Rainer Haag
- Institut für Chemie und
Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
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16
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Barua D, Goldstein B. A mechanistic model of early FcεRI signaling: lipid rafts and the question of protection from dephosphorylation. PLoS One 2012; 7:e51669. [PMID: 23284735 PMCID: PMC3524258 DOI: 10.1371/journal.pone.0051669] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 10/23/2012] [Indexed: 11/18/2022] Open
Abstract
We present a model of the early events in mast cell signaling mediated by FcεRI where the plasma membrane is composed of many small ordered lipid domains (rafts), surrounded by a non-order region of lipids consisting of the remaining plasma membrane. The model treats the rafts as transient structures that constantly form and breakup, but that maintain a fixed average number per cell. The rafts have a high propensity for harboring Lyn kinase, aggregated, but not unaggregated receptors, and the linker for the activation of T cells (LAT). Phosphatase activity in the rafts is substantially reduced compared to the nonraft region. We use the model to analyze published experiments on the rat basophilic leukemia (RBL)-2H3 cell line that seem to contradict the notion that rafts offer protection. In these experiments IgE was cross-linked with a multivalent antigen and then excess monovalent hapten was added to break-up cross-links. The dephosphorylation of the unaggregated receptor (nonraft associated) and of LAT (raft associated) were then monitored in time and found to decay at similar rates, leading to the conclusion that rafts offer no protection from dephosphorylation. In the model, because the rafts are transient, a protein that is protected while in a raft will be subject to dephosphorylation when the raft breaks up and the protein finds itself in the nonraft region of the membrane. We show that the model is consistent with the receptor and LAT dephosphorylation experiments while still allowing rafts to enhance signaling by providing substantial protection from phosphatases.
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Affiliation(s)
- Dipak Barua
- Theoretical Biology and Biophysics Group, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Byron Goldstein
- Theoretical Biology and Biophysics Group, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
- * E-mail:
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Kusumi A, Fujiwara TK, Morone N, Yoshida KJ, Chadda R, Xie M, Kasai RS, Suzuki KGN. Membrane mechanisms for signal transduction: the coupling of the meso-scale raft domains to membrane-skeleton-induced compartments and dynamic protein complexes. Semin Cell Dev Biol 2012; 23:126-44. [PMID: 22309841 DOI: 10.1016/j.semcdb.2012.01.018] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 01/24/2012] [Indexed: 01/09/2023]
Abstract
Virtually all biological membranes on earth share the basic structure of a two-dimensional liquid. Such universality and peculiarity are comparable to those of the double helical structure of DNA, strongly suggesting the possibility that the fundamental mechanisms for the various functions of the plasma membrane could essentially be understood by a set of simple organizing principles, developed during the course of evolution. As an initial effort toward the development of such understanding, in this review, we present the concept of the cooperative action of the hierarchical three-tiered meso-scale (2-300 nm) domains in the plasma membrane: (1) actin membrane-skeleton-induced compartments (40-300 nm), (2) raft domains (2-20 nm), and (3) dynamic protein complex domains (3-10nm). Special attention is paid to the concept of meso-scale domains, where both thermal fluctuations and weak cooperativity play critical roles, and the coupling of the raft domains to the membrane-skeleton-induced compartments as well as dynamic protein complexes. The three-tiered meso-domain architecture of the plasma membrane provides an excellent perspective for understanding the membrane mechanisms of signal transduction.
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Affiliation(s)
- Akihiro Kusumi
- Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Kyoto 606-8507, Japan.
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18
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Spendier K, Lidke KA, Lidke DS, Thomas JL. Single-particle tracking of immunoglobulin E receptors (FcεRI) in micron-sized clusters and receptor patches. FEBS Lett 2012; 586:416-21. [PMID: 22265688 DOI: 10.1016/j.febslet.2012.01.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 01/04/2012] [Accepted: 01/09/2012] [Indexed: 01/29/2023]
Abstract
When mast cells contact a monovalent antigen-bearing fluid lipid bilayer, IgE-loaded FcεRI receptors aggregate at contact points and trigger degranulation and the release of immune activators. We used two-color total internal reflection fluorescence microscopy and single-particle tracking to show that most fluorescently labeled receptor complexes diffuse freely within these micron-size clusters, with a diffusion coefficient comparable to free receptors in resting cells. At later times, when the small clusters coalesce to form larger patches, receptors diffuse even more rapidly. In all cases, Monte Carlo diffusion simulations ensured that the tracking results were free of bias, and distinguished biological from statistical variation. These results show the diversity in receptor mobility in mast cells, demonstrating at least three distinct states of receptor diffusivity.
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Affiliation(s)
- Kathrin Spendier
- Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131, USA
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19
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Spatio-temporal signaling in mast cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 716:91-106. [PMID: 21713653 DOI: 10.1007/978-1-4419-9533-9_6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
This chapter summarizes the evidence for localized signaling domains in mast cells and basophils, with a particular focus on the high affinity IgE receptor, FcεRI and its crosstalk with other membrane proteins. It is noteworthy that a literature spanning 30 years established the FcεRI as a model receptor for studying activation-induced changes in receptor diffusion and lipid raft association. Now a combination of high resolution microscopy methods, including immunoelectron microscopy and sophisticated fluorescence-based techniques, provide new insight into the nanoscale spatial and temporal aspects of receptor topography on the mast cell plasma membrane. Physical crosslinking of FcεRI with multivalent ligands leads to formation of IgE receptor clusters, termed "signaling patches," that recruit downstream signaling molecules. However, classes of receptors that engage solely withmono valent ligands can also form distinctive signaling patches. The dynamic relationships between receptor diffusion, aggregation state, clustering, signal initiation and signal strength are discussed in the context of these recent findings.
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Abstract
Tracking fluorescent lipids in cellular membranes has been applied for decades to shed light on membrane trafficking, sorting, endocytosis and exocytosis, viral entry, and to understand the functional relevance of membrane heterogeneity, phase separation and lipid rafts. However, fluorescent probes may display different organizing behaviour from their corresponding endogenous lipids. A full characterization of these probes is therefore required for proper interpretation of fluorescence microscopy data in complex membrane systems. Model membrane studies provide essential clues that guide us to design and interpret our experiments, help us to avoid pitfalls and resolve artefacts in complex cellular environments. In the present issue of the Biochemical Journal, Juhasz, Davis and Sharom demonstrate the importance of testing lipid probes systematically in heterogeneous model membranes of specific composition and well-defined thermodynamic properties. The phase-partitioning behaviour of fluorescent probes, alone and/or in combination, cannot simply be assumed, but has to be fully characterized.
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21
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Spendier K, Carroll-Portillo A, Lidke KA, Wilson BS, Timlin JA, Thomas J. Distribution and dynamics of rat basophilic leukemia immunoglobulin E receptors (FcepsilonRI) on planar ligand-presenting surfaces. Biophys J 2010; 99:388-97. [PMID: 20643056 PMCID: PMC2905106 DOI: 10.1016/j.bpj.2010.04.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Revised: 03/22/2010] [Accepted: 04/14/2010] [Indexed: 10/19/2022] Open
Abstract
There is considerable interest in the signaling mechanisms of immunoreceptors, especially when triggered with membrane-bound ligands. We have quantified the spatiotemporal dynamics of the redistribution of immunoglobulin E-loaded receptors (IgE-FcepsilonRI) on rat basophilic leukemia-2H3 mast cells in contact with fluid and gel-phase membranes displaying ligands for immunoglobulin E, using total internal reflection fluorescence microscopy. To clearly separate the kinetics of receptor redistribution from cell spreading, and to precisely define the initial contact time (+/-50 ms), micropipette cell manipulation was used to bring individual cells into contact with surfaces. On ligand-free surfaces, there are micron-scale heterogeneities in fluorescence that likely reflect regions of the cell that are more closely apposed to the substrate. When ligands are present, receptor clusters form with this same size scale. The initial rate of accumulation of receptors into the clusters is consistent with diffusion-limited trapping with D approximately 10(-1) microm2/s. These results support the hypothesis that clusters form by diffusion to cell-surface contact regions. Over longer timescales (>10 s), individual clusters moved with both diffusive and directed motion components. The dynamics of the cluster motion is similar to the dynamics of membrane fluctuations of cells on ligand-free fluid membranes. Thus, the same cellular machinery may be responsible for both processes.
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Affiliation(s)
- Kathrin Spendier
- Consortium of the Americas for Interdisciplinary Science, University of New Mexico, Albuquerque, New Mexico
- Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico
| | | | - Keith A. Lidke
- Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico
| | - Bridget S. Wilson
- Departments of Pathology, University of New Mexico, Albuquerque, New Mexico
| | - Jerilyn A. Timlin
- Biofuels and Biodefense Technologies, Sandia National Laboratories, Albuquerque, New Mexico
| | - James L. Thomas
- Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico
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22
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Lajoie P, Nabi IR. Lipid Rafts, Caveolae, and Their Endocytosis. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 282:135-63. [DOI: 10.1016/s1937-6448(10)82003-9] [Citation(s) in RCA: 266] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
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23
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Fan J, Sammalkorpi M, Haataja M. Influence of nonequilibrium lipid transport, membrane compartmentalization, and membrane proteins on the lateral organization of the plasma membrane. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:011908. [PMID: 20365400 DOI: 10.1103/physreve.81.011908] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 09/16/2009] [Indexed: 05/16/2023]
Abstract
Compositional lipid domains (lipid rafts) in plasma membranes are believed to be important components of many cellular processes. The mechanisms by which cells regulate the sizes, lifetimes, and spatial localization of these domains are rather poorly understood at the moment. We propose a robust mechanism for the formation of finite-sized lipid raft domains in plasma membranes, the competition between phase separation in an immiscible lipid system and active cellular lipid transport processes naturally leads to the formation of such domains. Simulations of a continuum model reveal that the raft size distribution is broad and the average raft size is strongly dependent on the rates of cellular and interlayer lipid transport processes. We demonstrate that spatiotemporal variations in the recycling may enable the cell to localize larger raft aggregates at specific parts along the membrane. Moreover, we show that membrane compartmentalization may further facilitate spatial localization of the raft domains. Finally, we demonstrate that local interactions with immobile membrane proteins can spatially localize the rafts and lead to further clustering.
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Affiliation(s)
- Jun Fan
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
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24
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Korchowiec B, Corvis Y, Viitala T, Feidt C, Guiavarch Y, Corbier C, Rogalska E. Interfacial approach to polyaromatic hydrocarbon toxicity: phosphoglyceride and cholesterol monolayer response to phenantrene, anthracene, pyrene, chrysene, and benzo[a]pyrene. J Phys Chem B 2008; 112:13518-31. [PMID: 18834169 DOI: 10.1021/jp804080h] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Interactions of phenantrene, anthracene, pyrene, chrysene, and benzo[a]pyrene (polyaromatic hydrocarbons) with model phospholipid membranes were probed using the Langmuir technique. The lipid monolayers were prepared using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol, 1,2-dipalmitoyl-sn-glycero-3-phosphoserine, 1,2-myristoyl-sn-glycero-3-phosphoethanolamine, 1,2-dilauroyl-sn-glycero-3-phosphocholine, and cholesterol. Surface pressure and electrical surface potential were measured on mixed phospholipid/PAH monolayers spread on a pure water subphase. The morphology of the mixed monolayers was followed with Brewster angle microscopy. Polarization-modulation infrared reflection-absorption spectroscopy spectra obtained on DPPE/benzo[a]pyrene showed that the latter interacts with the carbonyl groups of the phospholipid. On the other hand, the activity of phospholipase A2 toward DLPC used as a probe to locate benzo[a]pyrene in the monolayers indicates that the polyaromatic hydrocarbons are not accessible to the enzyme. The results obtained show that all PAHs studied affect the properties of the pure lipid, albeit in different ways. The most notable effects, namely, film fluidization and morphology changes, were observed with benzo[a]pyrene. In contrast, the complexity of mixed lipid monolayers makes the effect of PAHs difficult to detect. It can be assumed that the differences observed between PAHs in monolayers correlate with their toxicity.
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Affiliation(s)
- Beata Korchowiec
- Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, ul. Romana Ingardena 3, 30-060 Krakow, Poland
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25
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Pontier SM, Percherancier Y, Galandrin S, Breit A, Galés C, Bouvier M. Cholesterol-dependent separation of the beta2-adrenergic receptor from its partners determines signaling efficacy: insight into nanoscale organization of signal transduction. J Biol Chem 2008; 283:24659-72. [PMID: 18566454 DOI: 10.1074/jbc.m800778200] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Determining the role of lipid raft nanodomains in G protein-coupled receptor signaling remains fraught by the lack of assays directly monitoring rafts in native membranes. We thus combined extensive biochemical and pharmacological approaches to a nanoscale strategy based on bioluminescence resonance energy transfer (BRET) to assess the spatial and functional influence of cholesterol-rich liquid-ordered lipid nanodomains on beta2 adrenergic receptor (beta2AR) signaling. The data revealed that whereas beta2AR did not partition within liquid-ordered lipid phase, a pool of G protein and adenylyl cyclase (AC) were sequestered in these domains. Destabilization of the liquid-ordered phase by cholesterol depletion led to a lateral redistribution of Galphas and AC that favored interactions between the receptor and its signaling partners as assessed by BRET. This resulted in an increased basal and agonist-promoted beta2AR-stimulated cAMP production that was partially dampened as a result of constitutive protein kinase A-dependent phosphorylation and desensitization of the receptor. This restraining influence of nanodomains on beta2AR signaling was further substantiated by showing that liquid-ordered lipid phase stabilization using caveolin overexpression or increasing membrane cholesterol amount led to an inhibition of beta2AR-associated signaling. Given the emerging concept that clustering of receptors and effectors into signaling platforms contributes to the efficacy and selectivity of signal transduction, our results support a model whereby cholesterol-promoted liquid-ordered lipid phase-embedding Gs and AC allows their lateral separation from the receptor, thus restraining the basal activity and controlling responsiveness of beta2AR signaling machinery within larger signaling platforms.
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Affiliation(s)
- Stéphanie M Pontier
- Institut de Recherche en Immunologie et Cancérologie, Département de Biochimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada
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26
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Gullapalli RR, Demirel MC, Butler PJ. Molecular dynamics simulations of DiI-C18(3) in a DPPC lipid bilayer. Phys Chem Chem Phys 2008; 10:3548-60. [PMID: 18548161 DOI: 10.1039/b716979e] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We performed a 40 ns simulation of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI-C18(3)) in a 1,2-dipalmitoyl-sn-glycero-3-phosphatidyl choline (DPPC) bilayer in order to facilitate interpretation of lipid dynamics and membrane structure from fluorescence lifetime, anisotropy, and fluorescence correlations spectroscopy (FCS). Incorporation of DiI of 1.6 to 3.2 mol% induced negligible changes in area per lipid but detectable increases in bilayer thickness, each of which are indicators of membrane structural perturbation. The DiI chromophore angle was 77 +/- 17 degrees with respect to the bilayer normal, consistent with rotational diffusion inferred from polarization studies. The DiI headgroup was located 0.63 nm below the lipid head group-water interface, a novel result in contrast to some popular cartoon representations of DiI but consistent with DiI's increase in quantum yield when incorporated into lipid bilayers. Importantly, the fast component of rotational anisotropy matched published experimental results demonstrating that sufficient free volume exists at the sub-interfacial region to support fast rotations. Simulations with non-charged DiI head groups exhibited DiI flip-flop, demonstrating that the positively-charged chromophore stabilizes the orientation and location of DiI in a single monolayer. DiI induced detectable changes in interfacial properties of water ordering, electrostatic potential, and changes in P-N vector orientation of DPPC lipids. The diffusion coefficient of DiI (9.7 +/- 0.02 x 10(-8) cm2 s(-1)) was similar to the diffusion of DPPC molecules (10.7 +/- 0.04 x 10(-8) cm2 s(-1)), supporting the conclusion that DiI dynamics reflect lipid dynamics. These results provide the first atomistic level insight into DiI dynamics, results essential in elucidating lipid dynamics through single molecule fluorescence studies.
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Affiliation(s)
- Ramachandra R Gullapalli
- Department of Bioengineering, The Pennsylvania State University, 228 Hallowell Building, University Park, PA 16802, USA
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27
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Gombos I, Steinbach G, Pomozi I, Balogh A, Vámosi G, Gansen A, László G, Garab G, Matkó J. Some new faces of membrane microdomains: a complex confocal fluorescence, differential polarization, and FCS imaging study on live immune cells. Cytometry A 2008; 73:220-9. [PMID: 18163467 DOI: 10.1002/cyto.a.20516] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Lipid rafts are cholesterol- and glycosphingolipid-rich plasma membrane microdomains, which control signal transduction, cellular contacts, pathogen recognition, and internalization processes. Their stability/lifetime, heterogeneity remained still controversial, mostly due to the high diversity of raft markers and cellular models. The correspondence of the rafts of living cells to liquid ordered (Lo) domains of model membranes and the effect of modulating rafts on the structural dynamics of their bulk membrane environment are also yet unresolved questions. Spatial overlap of various lipid and protein raft markers on live cells was studied by confocal laser scanning microscopy, while fluorescence polarization of DiIC18(3) and Bodipy-phosphatidylcholine was imaged with differential polarization CLSM (DP-CLSM). Mobility of the diI probe under different conditions was assessed by fluorescence correlation spectroscopic (FCS). GM1 gangliosides highly colocalized with GPI-linked protein markers of rafts and a new anti-cholesterol antibody (AC8) in various immune cells. On the same cells, albeit not fully excluded from rafts, diI colocalized much less with raft markers of both lipid and protein nature, suggesting the Lo membrane regions are not equivalents to lipid rafts. The DP-CLSM technique was capable of imaging probe orientation and heterogeneity of polarization in the plasma membrane of live cells, reflecting differences in lipid order/packing. This property--in accordance with diI mobility assessed by FCS--was sensitive to modulation of rafts either through their lipids or proteins. Our complex imaging analysis demonstrated that two lipid probes--G(M1) and a new anti-cholesterol antibody--equivocally label the membrane rafts on a variety of cell types, while some raft-associated proteins (MHC-II, CD48, CD59, or CD90) do not colocalize with each other. This indicates the compositional heterogeneity of rafts. Usefulness of the DP-CLSM technique in imaging immune cell surface, in terms of lipid order/packing heterogeneities, was also shown together with its sensitivity to monitor biological modulation of lipid rafts.
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Affiliation(s)
- Imre Gombos
- Department of Immunology, Institute of Biology, Eotvos Lorand University, Budapest, Hungary
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28
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The nascent parasitophorous vacuole membrane of Encephalitozoon cuniculi is formed by host cell lipids and contains pores which allow nutrient uptake. EUKARYOTIC CELL 2008; 7:1001-8. [PMID: 18408058 DOI: 10.1128/ec.00004-08] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Microsporidia are obligate intracellular pathogens which enter host cells by the discharge of a hollow tube through which the sporoplasma is extruded into the host cell. Since this invasion mechanism is very different from common entry strategies, the formation of the parasitophorous vacuole (PV) in Encephalitozoon species is likely to be distinct from known principles. We investigated the origin of the nascent Encephalitozoon cuniculi PV membrane with the aid of fluorescent lipid probes. When Bodipy 500/510-C(12)-HPC-labeled spores were used for infection, the emerging PV membrane was unlabeled, suggesting that sporoplasma-derived lipids do not significantly contribute to the formation of the PV membrane. In contrast, when raft and nonraft microdomains of the host cell plasma membrane were selectively labeled with DiIC(16) and Speedy DiO, both tracers were detectable in the nascent PV membrane shortly after infection, indicating that the bulk lipids of the PV membrane are host cell derived. Time-lapse fluorescence microscopy revealed that the formation of the PV membrane is a fast event (<1.3 s), which occurred simultaneously with the extrusion of the sporoplasma. The portion of the discharged tube which is in contact with the host cell was found to be coated with labeled host cell lipids, which might be an indication for a plasma membrane invagination at the contact site. To investigate the presence of pores in the E. cuniculi PV membrane, we microinjected fluorescent dyes of different sizes into infected host cells. A 0.5-kDa dextran as well as 0.8- to 1.1-kDa peptides could rapidly enter the PV, while a 10-kDa dextran was stably excluded from the PV lumen, indicating that the PV membrane possesses pores with an exclusion size of <10 kDa, which should allow metabolite exchange.
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29
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Singh RD, Marks DL, Pagano RE. Using fluorescent sphingolipid analogs to study intracellular lipid trafficking. ACTA ACUST UNITED AC 2008; Chapter 24:Unit 24.1. [PMID: 18228509 DOI: 10.1002/0471143030.cb2401s35] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Sphingolipids (SLs), including glycosphingolipids, are found on the plasma membrane where they play important roles in a wide variety of cell functions, including cell-cell communication, cell growth and differentiation, host-pathogen interactions, and cell-signaling events. This unit illustrates the use of fluorescent SL analogs to identify the mechanisms underlying SL endocytosis and subsequent intracellular trafficking. Techniques used to study SL domain formation at the plasma membrane, endocytic mechanisms and intracellular transport steps are highlighted. The use of biochemical treatments and dominant-negative protein expression to block specific steps in lipid trafficking are also discussed.
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30
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Davey AM, Krise KM, Sheets ED, Heikal AA. Molecular Perspective of Antigen-mediated Mast Cell Signaling. J Biol Chem 2008; 283:7117-27. [DOI: 10.1074/jbc.m708879200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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31
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Sengupta P, Hammond A, Holowka D, Baird B. Structural determinants for partitioning of lipids and proteins between coexisting fluid phases in giant plasma membrane vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:20-32. [PMID: 17936718 DOI: 10.1016/j.bbamem.2007.08.028] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 08/15/2007] [Accepted: 08/20/2007] [Indexed: 12/11/2022]
Abstract
The structural basis for organizational heterogeneity of lipids and proteins underlies fundamental questions about the plasma membrane of eukaryotic cells. A current hypothesis is the participation of liquid ordered (Lo) membrane domains (lipid rafts) in dynamic compartmentalization of membrane function, but it has been difficult to demonstrate the existence of these domains in live cells. Recently, giant plasma membrane vesicles (GPMVs) obtained by chemically induced blebbing of cultured cells were found to phase separate into optically resolvable, coexisting fluid domains containing Lo-like and liquid disordered (Ld)-like phases as identified by fluorescent probes. In the present study, we used these GPMVs to investigate the structural bases for partitioning of selected lipids and proteins between coexisting Lo-like/Ld-like fluid phases in compositionally complex membranes. Our results with lipid probes show that the structure of the polar headgroups, in addition to acyl chain saturation, can significantly affect partitioning. We find that the membrane anchor of proteins and the aggregation state of proteins both significantly influence their distributions between coexisting fluid phases in these biological membranes. Our results demonstrate the value of GPMVs for characterizing the phase preference of proteins and lipid probes in the absence of detergents and other perturbations of membrane structure.
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Affiliation(s)
- Prabuddha Sengupta
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA
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32
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Baumgart T, Hunt G, Farkas ER, Webb WW, Feigenson GW. Fluorescence probe partitioning between Lo/Ld phases in lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2182-94. [PMID: 17588529 PMCID: PMC2702987 DOI: 10.1016/j.bbamem.2007.05.012] [Citation(s) in RCA: 376] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 05/03/2007] [Accepted: 05/11/2007] [Indexed: 01/28/2023]
Abstract
Fluorescence microscopy imaging is an important technique for studying lipid membranes and is increasingly being used for examining lipid bilayer membranes, especially those showing macroscopic coexisting domains. Lipid phase coexistence is a phenomenon of potential biological significance. The identification of lipid membrane heterogeneity by fluorescence microscopy relies on membrane markers with well-defined partitioning behavior. While the partitioning of fluorophores between gel and liquid-disordered phases has been extensively characterized, the same is not true for coexisting liquid phases. We have used fluorescence microscopy imaging to examine a large variety of lipid membrane markers for their liquid phase partitioning in membranes with various lipid compositions. Most fluorescent lipid analogs are found to partition strongly into the liquid-disordered (L(d)) phase. In contrast, some fluorescent polycyclic aromatic hydrocarbons with a flat ring system were found to partition equally, but others partition preferentially into liquid-ordered (L(o)) phases. We have found these fluorescent markers effective for identification of coexisting macroscopic membrane phases in ternary lipid systems composed of phospholipids and cholesterol.
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Affiliation(s)
- Tobias Baumgart
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853
| | - Geoff Hunt
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853
| | - Elaine R. Farkas
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853
| | - Watt W. Webb
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853
- Corresponding Author: Watt W. Webb, 212 Clark Hall, Cornell University, Ithaca, NY, 14853-2501, Phone: (607) 255-3331, Fax: (607) 255-7658, email
| | - Gerald W. Feigenson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853
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33
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Sengupta P, Holowka D, Baird B. Fluorescence resonance energy transfer between lipid probes detects nanoscopic heterogeneity in the plasma membrane of live cells. Biophys J 2007; 92:3564-74. [PMID: 17325019 PMCID: PMC1853158 DOI: 10.1529/biophysj.106.094730] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Fluorescence resonance energy transfer (FRET) between matched carbocyanine lipid analogs in the plasma membrane outer leaflet of RBL mast cells was used to investigate lateral distributions of lipids and to develop a general method for quantitative measurements of lipid heterogeneity in live cell membranes. FRET measured as fluorescence quenching of long-chain donor probes such as DiO-C18 is greater with long-chain, saturated acceptor probes such as DiI-C16 than with unsaturated or shorter-chain acceptors with the same chromophoric headgroup compared at identical concentrations. FRET measurements between these lipid probes in model membranes support the conclusion that differential donor quenching is not caused by nonideal mixing or spectroscopic differences. Sucrose gradient analysis of plasma membrane-labeled, Triton X-100-lysed cells shows that proximity measured by FRET correlates with the extent of lipid probe partitioning into detergent-resistant membranes. FRET between DiO-C16 and DiI-C16 is sensitive to cholesterol depletion and disruption of liquid order (Lo) by short-chain ceramides, and it is enhanced by cross linking of Lo-associated proteins. Consistent results are obtained when homo-FRET is measured by decreased fluorescence anisotropy of DiI-C16. These results support the existence of nanometer-scale Lo/liquid disorder heterogeneity of lipids in the outer leaflet of the plasma membrane in live cells.
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Affiliation(s)
- Prabuddha Sengupta
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA
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34
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Baumgart T, Hammond AT, Sengupta P, Hess ST, Holowka DA, Baird BA, Webb WW. Large-scale fluid/fluid phase separation of proteins and lipids in giant plasma membrane vesicles. Proc Natl Acad Sci U S A 2007; 104:3165-70. [PMID: 17360623 PMCID: PMC1805587 DOI: 10.1073/pnas.0611357104] [Citation(s) in RCA: 606] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The membrane raft hypothesis postulates the existence of lipid bilayer membrane heterogeneities, or domains, supposed to be important for cellular function, including lateral sorting, signaling, and trafficking. Characterization of membrane lipid heterogeneities in live cells has been challenging in part because inhomogeneity has not usually been definable by optical microscopy. Model membrane systems, including giant unilamellar vesicles, allow optical fluorescence discrimination of coexisting lipid phase types, but thus far have focused on coexisting optically resolvable fluid phases in simple lipid mixtures. Here we demonstrate that giant plasma membrane vesicles (GPMVs) or blebs formed from the plasma membranes of cultured mammalian cells can also segregate into micrometer-scale fluid phase domains. Phase segregation temperatures are widely spread, with the vast majority of GPMVs found to form optically resolvable domains only at temperatures below approximately 25 degrees C. At 37 degrees C, these GPMV membranes are almost exclusively optically homogenous. At room temperature, we find diagnostic lipid phase fluorophore partitioning preferences in GPMVs analogous to the partitioning behavior now established in model membrane systems with liquid-ordered and liquid-disordered fluid phase coexistence. We image these GPMVs for direct visual characterization of protein partitioning between coexisting liquid-ordered-like and liquid-disordered-like membrane phases in the absence of detergent perturbation. For example, we find that the transmembrane IgE receptor FcepsilonRI preferentially segregates into liquid-disordered-like phases, and we report the partitioning of additional well known membrane associated proteins. Thus, GPMVs now provide an effective approach to characterize biological membrane heterogeneities.
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Affiliation(s)
| | - Adam T. Hammond
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853; and
| | - Prabuddha Sengupta
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853; and
| | - Samuel T. Hess
- Department of Physics and Astronomy, University of Maine, Orono, ME 04469
| | - David A. Holowka
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853; and
| | - Barbara A. Baird
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853; and
| | - Watt W. Webb
- *School of Applied and Engineering Physics and
- To whom correspondence should be addressed at:
Cornell University, 212 Clark Hall, Ithaca, NY 14853. E-mail:
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35
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Kyoung M, Karunwi K, Sheets ED. A versatile multimode microscope to probe and manipulate nanoparticles and biomolecules. J Microsc 2007; 225:137-46. [PMID: 17359248 DOI: 10.1111/j.1365-2818.2007.01725.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We describe a flexible, multifaceted optical setup that allows quantitative measurement and manipulation of biomolecules and nanoparticles in biomimetic and cellular systems. We have implemented integrated biophotonics techniques (i.e. differential interference contrast, wide-field fluorescence, prism- and objective-based total internal reflection excitation, single particle tracking, fluorescence correlation spectroscopy and dynamic holographic optical trapping) on a single platform. The adaptability of this versatile, custom-designed system allows us to simultaneously monitor cell morphology, while measuring lateral diffusion of biomolecules or controlling their cellular location or interaction partners.
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Affiliation(s)
- M Kyoung
- Department of Chemistry, Pennsylvania State University, University Park PA 16802, USA
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36
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Loura LMS, Prieto M. Fluorescence resonance energy transfer to characterize cholesterol-induced domains. Methods Mol Biol 2007; 400:489-501. [PMID: 17951755 DOI: 10.1007/978-1-59745-519-0_33] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Cholesterol is a major component of mammalian cell membranes. It has remarkable effects on the properties of phospholipids bilayers, and is implicated in the lipid raft model. Depending on the membrane composition, cholesterol-containing bilayers can exist either as single phase or as mixture of coexisting phases. These are organized in domains of variant size determined by composition, but can be smaller than the optical microscopy resolution limit. This chapter describes a methodology based on fluorescence resonance energy transfer, which is sensitive to phase separation and can provide estimates of domain size in these usually hard to characterize systems.
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Affiliation(s)
- Luís M S Loura
- Centro de Química-Física Molecular, Instituto Superior Técnico Lisboa, Portugal
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37
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Abstract
Lipid rafts are liquid-ordered (lo) phase microdomains proposed to exist in biological membranes. Rafts have been widely studied by isolating lo-phase detergent-resistant membranes (DRMs) from cells. Recent findings have shown that DRMs are not the same as preexisting rafts, prompting a major revision of the raft model. Nevertheless, raft-targeting signals identified by DRM analysis are often required for protein function, implicating rafts in a variety of cell processes.
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Affiliation(s)
- Deborah A Brown
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA.
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38
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Gallegos AM, Storey SM, Kier AB, Schroeder F, Ball JM. Structure and cholesterol dynamics of caveolae/raft and nonraft plasma membrane domains. Biochemistry 2006; 45:12100-16. [PMID: 17002310 DOI: 10.1021/bi0602720] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Despite recognition that the plasma membrane (PM) is comprised of lipid raft domains that are key organizing sites of multiple signaling pathways and other cell functions, limited information is available regarding the structure and function in sterol dynamics of these microdomains. To begin to resolve these issues, MDCK membranes were subfractionated by three different techniques to produce (i) detergent-resistant membranes (DRM) and detergent-soluble membranes (DSM), (ii) nondetergent caveolae/rafts (NDCR), and (iii) nondetergent, affinity-purified caveolae/rafts (ACR) and noncaveolae/nonrafts (NR). ACR exhibited the least cross contamination with other PM domains or intracellular membranes, in marked contrast to DRM that contained the highest level of cross contaminants. Spectral properties of dehydroergosterol (DHE), a naturally occurring fluorescent sterol, showed that ACR, NDCR, and NR did not contain crystalline sterol, consistent with the lack of crystalline sterol in PM of intact cells. In contrast, DRM contained significant levels of crystalline sterol. Fluorescence polarization of membrane probes showed that ACR were the least fluid and had the highest transbilayer fluidity gradient, the most liquid ordered phase, and the sterol dynamics most responsive to sterol carrier protein-2 (SCP-2). In contrast, DRM had structural properties similar to those of NR, anomalous (very fast) spontaneous sterol dynamics, and sterol dynamics that were unresponsive to SCP-2. Differences between the structural and functional properties of DRM and those of the nondetergent preparations (ACR and NDCR) were not due to the presence of detergent. A nondetergent, affinity-purified (ACR) lipid domain fraction isolated from MDCK cells for the first time revealed unique structural (noncrystalline sterol, liquid-ordered, high transbilayer fluidity gradient) and functional (cholesterol dynamics) properties of lipid rafts as compared to nonrafts (NR). In summary, this study showed membrane microdomains (rafts/caveolae) isolated by three different methodologies have unique structural, functional, and organizational characteristics.
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Affiliation(s)
- Adalberto M Gallegos
- Department of Pathobiology, Texas A&M University, TVMC, College Station, Texas 77843-4467, USA
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39
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Davey AM, Walvick RP, Liu Y, Heikal AA, Sheets ED. Membrane order and molecular dynamics associated with IgE receptor cross-linking in mast cells. Biophys J 2006; 92:343-55. [PMID: 17040981 PMCID: PMC1697873 DOI: 10.1529/biophysj.106.088815] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cholesterol-rich microdomains (or "lipid rafts") within the plasma membrane have been hypothesized to exist in a liquid-ordered phase and play functionally important roles in cell signaling; however, these microdomains defy detection using conventional imaging. To visualize domains and relate their nanostructure and dynamics to mast cell signaling, we use two-photon (760 nm and 960 nm) fluorescence lifetime imaging microscopy and fluorescence polarization anisotropy imaging, with comparative one-photon anisotropy imaging and single-point lifetime and anisotropy decay measurements. The inherent sensitivity of ultrafast excited-state dynamics and rotational diffusion to the immediate surroundings of a fluorophore allows for real-time monitoring of membrane structure and organization. When the high affinity receptor for IgE (FcepsilonRI) is extensively cross-linked with anti-IgE, molecules associated with cholesterol-rich microdomains (e.g., saturated lipids (the lipid analog diI-C(18) or glycosphingolipids)) and lipid-anchored proteins coredistribute with cross-linked IgE-FcepsilonRI. We find an enhancement in fluorescence lifetime and anisotropy of diI-C(18) and Alexa 488-labeled IgE-FcepsilonRI in the domains where these molecules colocalize. Our results suggest that fluorescence lifetime and, particularly, anisotropy permit us to correlate the recruitment of lipid molecules into more ordered domains that serve as platforms for IgE-mediated signaling.
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Affiliation(s)
- Angel M Davey
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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40
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Abstract
Lipid rafts are membrane microdomains rich in cholesterol and glycosphingolipids that have been implicated in the regulation of intracellular protein trafficking. During exocytosis, a class of proteins termed SNAREs mediate secretory granule-plasma membrane fusion. To investigate the role of lipid rafts in secretory granule exocytosis, we examined the raft association of SNARE proteins and SNARE complexes in rat basophilic leukemia (RBL) mast cells. The SNARE protein SNAP-23 co-localized with a lipid raft marker and was present in detergent-insoluble lipid raft microdomains in RBL cells. By contrast, only small amounts (<20%) of the plasma membrane SNARE syntaxin 4 or the granule-associated SNARE vesicle-associated membrane protein (VAMP)-2 were present in these microdomains. Despite this, essentially all syntaxin 4 and most of VAMP-2 in these rafts were present in SNARE complexes containing SNAP-23, while essentially none of these complexes were present in nonraft membranes. Whereas SNAP-23 is membrane anchored by palmitoylation, the association of the transmembrane protein syntaxin 4 with lipid rafts was because of its binding to SNAP-23. After stimulating mast cells exocytosis, the amount of syntaxin 4 and VAMP-2 present in rafts increased twofold, and these proteins were now present in raft-associated phospho-SNAP-23/syntaxin 4/VAMP-2 complexes, revealing differential association of SNARE fusion complexes during the process of regulated exocytosis.
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Affiliation(s)
- Niti Puri
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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41
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Pucadyil TJ, Chattopadhyay A. Effect of cholesterol on lateral diffusion of fluorescent lipid probes in native hippocampal membranes. Chem Phys Lipids 2006; 143:11-21. [PMID: 16797513 DOI: 10.1016/j.chemphyslip.2006.04.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 04/17/2006] [Accepted: 04/26/2006] [Indexed: 01/11/2023]
Abstract
Cholesterol is an abundant lipid of mammalian membranes and plays a crucial role in membrane organization, dynamics, function and sorting. The role of cholesterol in membrane organization has been a subject of intense investigation that has largely been carried out in model membrane systems. An extension of these studies in natural membranes, more importantly in neuronal membranes, is important to establish a relationship between disease states and changes in membrane physical properties resulting from an alteration in lipid composition. We have monitored the lateral diffusion of lipid probes, DiIC(18)(3) and FAST DiI which are similar in their intrinsic fluorescence properties but differ in their structure, in native and cholesterol-depleted hippocampal membranes using the fluorescence recovery after photobleaching (FRAP) approach. Our results show that the mobility of these probes is in general higher in hippocampal membranes depleted of cholesterol. Interestingly, the increase in mobility of these probes does not linearly correlate with the extent of cholesterol depletion. These results assume significance in the light of recent reports on the requirement of cholesterol to support the function of the G-protein coupled serotonin(1A) receptor present endogenously in hippocampal membranes.
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Affiliation(s)
- Thomas J Pucadyil
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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42
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Sprocati T, Ronchi P, Raimondi A, Francolini M, Borgese N. Dynamic and reversible restructuring of the ER induced by PDMP in cultured cells. J Cell Sci 2006; 119:3249-60. [PMID: 16847050 DOI: 10.1242/jcs.03058] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
In many cells, the endoplasmic reticulum (ER) contains segregated smooth and rough domains, but the mechanism of this segregation is unclear. Here, we used a HeLa cell line, inducibly expressing a GFP fusion protein [GFP-b(5)tail] anchored to the ER membrane, as a tool to investigate factors influencing ER organisation. Induction of GFP-b(5)tail expression caused proliferation of the ER, but its normal branching polygonal meshwork architecture was maintained. Experiments designed to test the effects of drugs that alter ceramide levels revealed that treatment of these cells with Phenyl-2-decanoyl-amino-3-morpholino-1-propanol-hydrocholride (PDMP) generated patches of segregated smooth ER, organised as a random tubular network, which rapidly dispersed after removal of the drug. The effect of PDMP was independent of its activity as sphingolipid synthesis inhibitor, but could be partially reversed by a membrane-permeant Ca(2+) chelator. Although the smooth ER patches maintained connectivity with the remaining ER, they appeared to represent distinct domains differing in protein and lipid composition from the remaining ER. PDMP did not cause detachment of membrane-bound ribosomes, indicating that smooth ER patch generation was due to a reorganisation of pre-existing ribosome-free areas. Our results demonstrate a dynamic relationship between smooth and rough ER and have implications for the mechanisms regulating ER architecture.
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Affiliation(s)
- Teresa Sprocati
- Consiglio Nazionale delle Ricerche Institute of Neuroscience and Department of Medical Pharmacology, via Vanvitelli 32, University of Milano, 20129 Milano, Italy
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43
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Swamy MJ, Ciani L, Ge M, Smith AK, Holowka D, Baird B, Freed JH. Coexisting domains in the plasma membranes of live cells characterized by spin-label ESR spectroscopy. Biophys J 2006; 90:4452-65. [PMID: 16565045 PMCID: PMC1471862 DOI: 10.1529/biophysj.105.070839] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2005] [Accepted: 02/28/2006] [Indexed: 01/08/2023] Open
Abstract
The importance of membrane-based compartmentalization in eukaryotic cell function has become broadly appreciated, and a number of studies indicate that these eukaryotic cell membranes contain coexisting liquid-ordered (L(o)) and liquid-disordered (L(d)) lipid domains. However, the current evidence for such phase separation is indirect, and so far there has been no direct demonstration of differences in the ordering and dynamics for the lipids in these two types of regions or their relative amounts in the plasma membranes of live cells. In this study, we provide direct evidence for the presence of two different types of lipid populations in the plasma membranes of live cells from four different cell lines by electron spin resonance. Analysis of the electron spin resonance spectra recorded over a range of temperatures, from 5 to 37 degrees C, shows that the spin-labeled phospholipids incorporated experience two types of environments, L(o) and L(d), with distinct order parameters and rotational diffusion coefficients but with some differences among the four cell lines. These results suggest that coexistence of lipid domains that differ significantly in their dynamic order in the plasma membrane is a general phenomenon. The L(o) region is found to be a major component in contrast to a model in which small liquid-ordered lipid rafts exist in a 'sea' of disordered lipids. The results on ordering and dynamics for the live cells are also compared with those from model membranes exhibiting coexisting L(o) and L(d) phases.
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Affiliation(s)
- Musti J Swamy
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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44
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Murakoshi M, Gomi T, Iida K, Kumano S, Tsumoto K, Kumagai I, Ikeda K, Kobayashi T, Wada H. Imaging by atomic force microscopy of the plasma membrane of prestin-transfected Chinese hamster ovary cells. J Assoc Res Otolaryngol 2006; 7:267-78. [PMID: 16761115 PMCID: PMC2504612 DOI: 10.1007/s10162-006-0041-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2005] [Accepted: 04/26/2006] [Indexed: 11/27/2022] Open
Abstract
The high sensitivity of mammalian hearing is achieved by amplification of the motion of the cochlear partition. This cochlear amplification is thought to be generated by the elongation and contraction of outer hair cells (OHCs) in response to acoustical stimulation. This motility is made possible by a membrane protein embedded in the lateral membrane of OHCs. Although a fructose transporter, GLUT-5, was initially proposed to be this protein, a later study identified the gene of the motor protein distributed throughout the OHC plasma membrane. This protein has been named "prestin." However, although previous morphological studies by electron microscopy and atomic force microscopy (AFM) found the lateral wall of OHCs to be covered with 10-nm particles, believed to be motor proteins, it is unknown whether such particles consist only of prestin or are a complex of GLUT-5 and prestin molecules. To determine if the 10-nm particles are indeed constituted only of prestin, plasma membranes of prestin-transfected and untransfected Chinese hamster ovary (CHO) cells, which do not express GLUT-5, were observed by AFM. First, the cells attached to a substrate were sonicated so that only the plasma membrane remained on the substrate. The cytoplasmic face of the cell was observed by the tapping mode of the AFM in liquid. As a result, particle-like structures were recognized on the plasma membranes of both the prestin-transfected and untransfected CHO cells. Comparison of the difference in the frequency distribution of these structures between those two cells showed approximately 75% of the particle-like structures with a diameter of 8-12 nm in the prestin-transfected CHO cells to be possibly constituted only by prestin molecules. Our data suggest that the densely packed 10-nm particles observed on the OHC lateral wall are likely to be constituted only of prestin molecules.
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Affiliation(s)
- Michio Murakoshi
- Department of Bioengineering and Robotics, Tohoku University, 6-6-01 Aoba-yama, Sendai, 980-8579 Japan
| | - Takashi Gomi
- Department of Bioengineering and Robotics, Tohoku University, 6-6-01 Aoba-yama, Sendai, 980-8579 Japan
| | - Koji Iida
- Department of Bioengineering and Robotics, Tohoku University, 6-6-01 Aoba-yama, Sendai, 980-8579 Japan
| | - Shun Kumano
- Department of Bioengineering and Robotics, Tohoku University, 6-6-01 Aoba-yama, Sendai, 980-8579 Japan
| | - Kouhei Tsumoto
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8652 Japan
| | - Izumi Kumagai
- Department of Biomolecular Engineering, Tohoku University, 6-6-11 Aoba-yama, Sendai, 980-8579 Japan
| | - Katsuhisa Ikeda
- Department of Otorhinolaryngology, Juntendo University School of Medicine, 2-1-1 Hongo, Tokyo, 113-8421 Japan
| | - Toshimitsu Kobayashi
- Department of Otorhinolaryngology–Head and Neck Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Sendai, 980-8574 Japan
| | - Hiroshi Wada
- Department of Bioengineering and Robotics, Tohoku University, 6-6-01 Aoba-yama, Sendai, 980-8579 Japan
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45
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Wallace EJ, Hooper NM, Olmsted PD. Effect of hydrophobic mismatch on phase behavior of lipid membranes. Biophys J 2006; 90:4104-18. [PMID: 16533859 PMCID: PMC1459530 DOI: 10.1529/biophysj.105.062778] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
We investigate the competing effects of hydrophobic mismatch and chain stretching on the morphology and evolution of domains in lipid membranes via Monte Carlo techniques. We model the membrane as a binary mixture of particles that differ in their preferred lengths, with the shorter particles mimicking unsaturated nonraft lipids and the longer particles mimicking saturated raft lipids. We find that phase separation can be induced upon increasing either the ratio J/kappa of the hydrophobic surface tension J to the compressibility modulus kappa. J/kappa determines the decay length for thickness changes. When this decay length is larger than the system size the membrane remains mixed. Furthermore, increasing the thickness relaxation time can induce transient phase separation.
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Affiliation(s)
- Elizabeth J Wallace
- School of Biochemistry & Microbiology, Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
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46
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Larson DR, Gosse JA, Holowka DA, Baird BA, Webb WW. Temporally resolved interactions between antigen-stimulated IgE receptors and Lyn kinase on living cells. ACTA ACUST UNITED AC 2006; 171:527-36. [PMID: 16275755 PMCID: PMC2171255 DOI: 10.1083/jcb.200503110] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Upon cross-linking by antigen, the high affinity receptor for immunoglobulin E (IgE), FcɛRI, is phosphorylated by the Src family tyrosine kinase Lyn to initiate mast cell signaling, leading to degranulation. Using fluorescence correlation spectroscopy (FCS), we observe stimulation-dependent associations between fluorescently labeled IgE-FcɛRI and Lyn-EGFP on individual cells. We also simultaneously measure temporal variations in the lateral diffusion of these proteins. Antigen-stimulated interactions between these proteins detected subsequent to the initiation of receptor phosphorylation exhibit time-dependent changes, suggesting multiple associations between FcɛRI and Lyn-EGFP. During this period, we also observe a persistent decrease in Lyn-EGFP lateral diffusion that is dependent on Src family kinase activity. These stimulated interactions are not observed between FcɛRI and a chimeric EGFP that contains only the membrane-targeting sequence from Lyn. Our results reveal real-time interactions between Lyn and cross-linked FcɛRI implicated in downstream signaling events. They demonstrate the capacity of FCS cross-correlation analysis to investigate the mechanism of signaling-dependent protein–protein interactions in intact, living cells.
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Affiliation(s)
- Daniel R Larson
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
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47
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Abstract
This commentary presents a series of examples of "impossible experimental problems" that we have encountered over the years in addressing various challenging questions in physiology. We aim to show how stimulating the challenges of physiology can be and demonstrate how our naive invocation of methods from disparate fields of science and engineering has led to delightful resolutions of physiological challenges that were utterly new to this intrepid interdisciplinary researcher.
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Affiliation(s)
- Watt W Webb
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
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48
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Holowka D, Gosse JA, Hammond AT, Han X, Sengupta P, Smith NL, Wagenknecht-Wiesner A, Wu M, Young RM, Baird B. Lipid segregation and IgE receptor signaling: A decade of progress. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1746:252-9. [PMID: 16054713 DOI: 10.1016/j.bbamcr.2005.06.007] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 06/11/2005] [Accepted: 06/15/2005] [Indexed: 11/25/2022]
Abstract
Recent work to characterize the roles of lipid segregation in IgE receptor signaling has revealed a mechanism by which segregation of liquid ordered regions from disordered regions of the plasma membrane results in protection of the Src family kinase Lyn from inactivating dephosphorylation by a transmembrane tyrosine phosphatase. Antigen-mediated crosslinking of IgE receptors drives their association with the liquid ordered regions, commonly called lipid rafts, and this facilitates receptor phosphorylation by active Lyn in the raft environment. Previous work showed that the membrane skeleton coupled to F-actin regulates stimulated receptor phosphorylation and downstream signaling processes, and more recent work implicates cytoskeletal interactions with ordered lipid rafts in this regulation. These and other results provide an emerging view of the complex role of membrane structure in orchestrating signal transduction mediated by immune and other cell surface receptors.
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Affiliation(s)
- David Holowka
- Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, NY 14853-1301, USA
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49
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London E. How principles of domain formation in model membranes may explain ambiguities concerning lipid raft formation in cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1746:203-20. [PMID: 16225940 DOI: 10.1016/j.bbamcr.2005.09.002] [Citation(s) in RCA: 197] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Revised: 09/01/2005] [Accepted: 09/02/2005] [Indexed: 02/07/2023]
Abstract
Sphingolipid and cholesterol-rich liquid ordered lipid domains (lipid rafts) have been studied in both eukaryotic cells and model membranes. However, while the coexistence of ordered and disordered liquid phases can now be easily demonstrated in model membranes, the situation in cell membranes remains ambiguous. Unlike the usual situation in model membranes, under most conditions, cell membranes rich in sphingolipid and cholesterol may have a "granular" organization in which the size of ordered and/or disordered domains is extremely small and domains may be of borderline stability. This review attempts to explain the origin of the divergence between of our understanding of rafts in model membranes and in cells, and how the physical properties of model membranes can help explain many of the ambiguities concerning raft formation and properties in cells. How physical principles of ordered domain formation relate to limitations of detergent insolubility and cholesterol depletion methods used to infer the presence of rafts in cells is also discussed. Possible modifications of these techniques that may increase their reliability are considered. It will be necessary to study model membrane systems more closely approximating cell membranes in order gain a complete understanding of raft properties in cells. Very high concentrations of membrane cholesterol and proteins may explain key physical characteristics of domains in cellular membranes, and are the two of the most obvious factors requiring additional study.
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Affiliation(s)
- Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, S.U.N.Y., Stony Brook, NY 11794-5215, USA.
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50
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Martin SW, Glover BJ, Davies JM. Lipid microdomains--plant membranes get organized. TRENDS IN PLANT SCIENCE 2005; 10:263-5. [PMID: 15949758 DOI: 10.1016/j.tplants.2005.04.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2004] [Revised: 03/17/2005] [Accepted: 04/22/2005] [Indexed: 05/02/2023]
Abstract
The plant plasma membrane is now known to be a more sophisticated structure than was previously thought. Sebastien Mongrand et al. and Georg Borner et al. have isolated specific plasma membrane microdomains ('lipid rafts') that are enriched in sterols and sphingolipids. These rafts contain distinct sets of proteins and might help to explain how plasma membrane proteins are positioned in certain parts of the cell to function in development and signalling.
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Affiliation(s)
- Stephen W Martin
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, UK CB2 3EA
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