1
|
The molecular size of the extra-membrane domain influences the diffusion of the GPI-anchored VSG on the trypanosome plasma membrane. Sci Rep 2015; 5:10394. [PMID: 26065579 PMCID: PMC5387117 DOI: 10.1038/srep10394] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 04/13/2015] [Indexed: 12/14/2022] Open
Abstract
A plethora of proteins undergo random and passive diffusion in biological membranes. While the contribution of the membrane-embedded domain to diffusion is well established, the potential impact of the extra-membrane protein part has been largely neglected. Here, we show that the molecular length influences the diffusion coefficient of GPI-anchored proteins: smaller proteins diffuse faster than larger ones. The distinct diffusion properties of differently sized membrane proteins are biologically relevant. The variant surface glycoprotein (VSG) of African trypanosomes, for example, is sized for an effective diffusion-driven randomization on the cell surface, a process that is essential for parasite virulence. We propose that the molecular sizes of proteins dominating the cell surfaces of other eukaryotic pathogens may also be related to diffusion-limited functions.
Collapse
|
2
|
Guigas G, Weiss M. Membrane protein mobility depends on the length of extra-membrane domains and on the protein concentration. SOFT MATTER 2015; 11:33-37. [PMID: 25407767 DOI: 10.1039/c4sm01846j] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Diffusion of membrane proteins is not only determined by the membrane anchor friction but also by the overall concentration of proteins and the length of their extra-membrane domains. We have studied the influence of the latter two cues by mesoscopic simulations. As a result, we have found that the total friction of membrane proteins, γ, increases approximately linearly with the length of the extra-membrane domain, L, whereas a slightly nonlinear dependence on the total protein concentration, ϕ was observed. We provide an educated guess for the functional form of γ(L, ϕ) and the associated diffusion coefficient. This expression not only matches our simulation data but it is also in favorable agreement with previously published experimental data. Our findings indicate that diffusion coefficients of membrane proteins are not solely determined by the friction of membrane anchors but also extra-membrane domains and the crowdedness of the membrane need to be considered to obtain a comprehensive view of protein diffusion on cellular membranes.
Collapse
Affiliation(s)
- Gernot Guigas
- Experimental Physics I, University of Bayreuth, 95440 Bayreuth, Germany.
| | | |
Collapse
|
3
|
Distinct modes of perimembrane TRP channel turnover revealed by TIR-FRAP. Sci Rep 2014; 4:7111. [PMID: 25407951 PMCID: PMC4236744 DOI: 10.1038/srep07111] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 10/31/2014] [Indexed: 01/08/2023] Open
Abstract
Transient Receptor Potential (TRP) channels form a broadly expressed and functionally diverse family of cation channels involved in various (patho)physiological processes. Whereas the mechanisms that control opening of TRP channels have been extensively studied, little is known about the transport processes of TRP channels to and within the plasma membrane. Here we used Total Internal Reflection--Fluorescence Recovery after Photobleaching (TIR-FRAP) to selectively visualize and bleach the fluorescently labeled TRP channels TRPV2 and TRPM4 in close proximity of the glass-plasma membrane interface, allowing detailed analysis of their perimembrane dynamics. We show that recovery of TRPM4 occurs via 200-nm diameter transport vesicles, and demonstrate the full fusion of such vesicles with the plasma membrane. In contrast, TRPV2 recovery proceeded mainly via lateral diffusion from non-bleached areas of the plasma membrane. Analysis of the two-dimensional channel diffusion kinetics yielded 2D diffusion coefficients ranging between 0.1 and 0.3 μm(2)/s, suggesting that these TRP channels move relatively unrestricted within the plasma membrane. These data demonstrate distinct modes of TRP channel turnover at the plasma membrane and illustrate the usefulness of TIR-FRAP to monitor these processes with high resolution.
Collapse
|
4
|
A spatial model for integrin clustering as a result of feedback between integrin activation and integrin binding. Biophys J 2013; 103:1379-89. [PMID: 22995511 DOI: 10.1016/j.bpj.2012.08.021] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 07/19/2012] [Accepted: 08/01/2012] [Indexed: 12/16/2022] Open
Abstract
Integrins are transmembrane adhesion receptors that bind extracellular matrix (ECM) proteins and signal bidirectionally to regulate cell adhesion and migration. In many cell types, integrins cluster at cell-ECM contacts to create the foundation for adhesion complexes that transfer force between the cell and the ECM. Even though the temporal and spatial regulation of these integrin clusters is essential for cell migration, how cells regulate their formation is currently unknown. It has been shown that integrin cluster formation is independent of actin stress fiber formation, but requires active (high-affinity) integrins, phosphoinositol-4,5-bisphosphate (PIP2), talin, and immobile ECM ligand. Based on these observations, we propose a minimal model for initial formation of integrin clusters, facilitated by localized activation and binding of integrins to ECM ligands as a result of biochemical feedback between integrin binding and integrin activation. By employing a diffusion-reaction framework for modeling these reactions, we show how spatial organization of bound integrins into clusters may be achieved by a local source of active integrins, namely protein complexes formed on the cytoplasmic tails of bound integrins. Further, we show how such a mechanism can turn small local increases in the concentration of active talin or active integrin into integrin clusters via positive feedback. Our results suggest that the formation of integrin clusters by the proposed mechanism depends on the relationships between production and diffusion of integrin-activating species, and that changes to the relative rates of these processes may affect the resulting properties of integrin clusters.
Collapse
|
5
|
Proteins on the move: insights gained from fluorescent protein technologies. Nat Rev Mol Cell Biol 2011; 12:656-68. [PMID: 21941275 DOI: 10.1038/nrm3199] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Proteins are always on the move, and this may occur through diffusion or active transport. The realization that the regulation of signal transduction is highly dynamic in space and time has stimulated intense interest in the movement of proteins. Over the past decade, numerous new technologies using fluorescent proteins have been developed, allowing us to observe the spatiotemporal dynamics of proteins in living cells. These technologies have greatly advanced our understanding of protein dynamics, including protein movement and protein interactions.
Collapse
|
6
|
García-Peñarrubia P, Gálvez JJ, Gálvez J. Spatio-temporal dependence of the signaling response in immune-receptor trafficking networks regulated by cell density: a theoretical model. PLoS One 2011; 6:e21786. [PMID: 21789180 PMCID: PMC3136476 DOI: 10.1371/journal.pone.0021786] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Accepted: 06/09/2011] [Indexed: 12/04/2022] Open
Abstract
Cell signaling processes involve receptor trafficking through highly connected networks of interacting components. The binding of surface receptors to their specific ligands is a key factor for the control and triggering of signaling pathways. In most experimental systems, ligand concentration and cell density vary within a wide range of values. Dependence of the signal response on cell density is related with the extracellular volume available per cell. This dependence has previously been studied using non-spatial models which assume that signaling components are well mixed and uniformly distributed in a single compartment. In this paper, a mathematical model that shows the influence exerted by cell density on the spatio-temporal evolution of ligands, cell surface receptors, and intracellular signaling molecules is developed. To this end, partial differential equations were used to model ligand and receptor trafficking dynamics through the different domains of the whole system. This enabled us to analyze several interesting features involved with these systems, namely: a) how the perturbation caused by the signaling response propagates through the system; b) receptor internalization dynamics and how cell density affects the robustness of dose-response curves upon variation of the binding affinity; and c) that enhanced correlations between ligand input and system response are obtained under conditions that result in larger perturbations of the equilibrium . Finally, the results are compared with those obtained by considering that the above components are well mixed in a single compartment.
Collapse
Affiliation(s)
- Pilar García-Peñarrubia
- Department of Biochemistry and Molecular Biology and Immunology, School of Medicine, University of Murcia, Murcia, Spain
| | - Juan J. Gálvez
- Department of Information and Communications Engineering, Computer Science Faculty, University of Murcia, Murcia, Spain
| | - Jesús Gálvez
- Department of Physical Chemistry, Faculty of Chemistry, University of Murcia, Murcia, Spain
- * E-mail:
| |
Collapse
|
7
|
Leshchyns'ka I, Tanaka MM, Schachner M, Sytnyk V. Immobilized pool of NCAM180 in the postsynaptic membrane is homeostatically replenished by the flux of NCAM180 from extrasynaptic regions. J Biol Chem 2011; 286:23397-406. [PMID: 21550975 DOI: 10.1074/jbc.m111.252098] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homeostatic mechanisms maintaining high levels of adhesion molecules in synapses over prolonged periods of time remain incompletely understood. We used fluorescence recovery after photobleaching experiments to analyze the steady state turnover of the immobile pool of green fluorescent protein-labeled NCAM180, the largest postsynaptically accumulating isoform of the neural cell adhesion molecule (NCAM). We show that there is a continuous flux of NCAM180 to the postsynaptic membrane from nonsynaptic regions of dendrites by diffusion. In the postsynaptic membrane, the newly delivered NCAM180 slowly intermixes with the immobilized pool of NCAM180. Preferential immobilization and accumulation of NCAM180 in the postsynaptic membrane is reduced after disruption of the association of NCAM180 with the spectrin cytoskeleton and in the absence of the homophilic interactions of NCAM180 in synapses. Our observations indicate that the homophilic interactions and binding to the cytoskeleton promote immobilization of NCAM180 and its accumulation in the postsynaptic membrane. Flux of NCAM180 from extrasynaptic regions and its slow intermixture with the immobile pool of NCAM180 in the postsynaptic membrane may be important for the continuous homeostatic replenishment of NCAM180 protein at synaptic contacts without compromising the long term synaptic contact stability.
Collapse
Affiliation(s)
- Iryna Leshchyns'ka
- Zentrum für Molekulare Neurobiologie, Universitätskrankenhaus Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
| | | | | | | |
Collapse
|
8
|
Zhao T, Li Y, Dinner AR. How focal adhesion size depends on integrin affinity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1540-1546. [PMID: 19132823 DOI: 10.1021/la8026804] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Understanding how the thermodynamics and kinetics of integrin receptor binding and clustering impact the formation of focal adhesions is important for understanding the mechanisms cells use to sense and respond to physical cues in their environment. Cells on chemically well-defined surfaces were observed to have distributions of focal adhesions shifted toward smaller sizes when presented with higher affinity ligands (Kato, M.; Mrksich, M. Biochemistry 2004, 43, 2699). In this paper, we account for this trend with a simple model in which integrins are treated as particles on a lattice, and their stochastic dynamics are simulated with a kinetic Monte Carlo algorithm. How the trend depends on force-coupled growth, membrane fluctuations, and heterogeneity of receptor-ligand interactions is analyzed. Predictions are made for substrates in which the ligands presented can vary in either space or time, so that the model can be validated experimentally.
Collapse
Affiliation(s)
- Tong Zhao
- Department of Chemistry, Department of Physics, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637
| | | | | |
Collapse
|
9
|
Conchonaud F, Nicolas S, Amoureux MC, Ménager C, Marguet D, Lenne PF, Rougon G, Matarazzo V. Polysialylation increases lateral diffusion of neural cell adhesion molecule in the cell membrane. J Biol Chem 2007; 282:26266-74. [PMID: 17623676 DOI: 10.1074/jbc.m608590200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Polysialic acid (PSA) is a polymer of N-acetylneuraminic acid residues added post-translationally to the membrane-bound neural cell adhesion molecule (NCAM). The large excluded volume created by PSA polymer is thought to facilitate cell migration by decreasing cell adhesion. Here we used live cell imaging (spot fluorescence recovery after photobleaching and fluorescence correlation spectroscopy) combined with biochemical approaches in an attempt to uncover a link between cell motility and the impact of polysialylation on NCAM dynamics. We show that PSA regulates specifically NCAM lateral diffusion and this is dependent on the integrity of the cytoskeleton. However, whereas the glial-derivative neurotrophic factor chemotactic effect is dependent on PSA, the molecular dynamics of PSA-NCAM is not directly affected by glial-derivative neurotrophic factor. These findings reveal a new intrinsic mechanism by which polysialylation regulates NCAM dynamics and thereby a biological function like cell migration.
Collapse
Affiliation(s)
- Fabien Conchonaud
- Institut de Biologie du Développement de Marseille-Luminy and Centre d'Immunologie de Marseille Luminy, MOSAIC Group, Université de la Méditerranée, 13288 Marseille, France
| | | | | | | | | | | | | | | |
Collapse
|
10
|
|
11
|
Thoumine O, Lambert M, Mège RM, Choquet D. Regulation of N-cadherin dynamics at neuronal contacts by ligand binding and cytoskeletal coupling. Mol Biol Cell 2005; 17:862-75. [PMID: 16319177 PMCID: PMC1356595 DOI: 10.1091/mbc.e05-04-0335] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
N-cadherin plays a key role in axonal outgrowth and synaptogenesis, but how neurons initiate and remodel N-cadherin-based adhesions remains unclear. We addressed this issue with a semiartificial system consisting of N-cadherin coated microspheres adhering to cultured neurons transfected for N-cadherin-GFP. Using optical tweezers, we show that growth cones are particularly reactive to N-cadherin coated microspheres, which they capture in a few seconds and drag rearward. Such strong coupling requires an intact connection between N-cadherin receptors and catenins. As they move to the basis of growth cones, microspheres slow down while gradually accumulating N-cadherin-GFP, demonstrating a clear delay between bead coupling to the actin flow and receptor recruitment. Using FRAP and photoactivation, N-cadherin receptors at bead-to-cell contacts were found to continuously recycle, consistently with a model of ligand-receptor reaction not limited by membrane diffusion. The use of N-cadherin-GFP receptors truncated or mutated in specific cytoplasmic regions show that N-cadherin turnover is exquisitely regulated by catenin partners. Turnover rates are considerably lower than those obtained previously in single molecule studies, demonstrating an active regulation of cadherin bond kinetics in intact cells. Finally, spontaneous neuronal contacts enriched in N-cadherin exhibited similar turnover rates, suggesting that such dynamics of N-cadherin may represent an intrinsic mechanism underlying the plasticity of neuronal adhesions.
Collapse
Affiliation(s)
- Olivier Thoumine
- CNRS, UMR 5091, Institut Magendie de Neurosciences, Université Bordeaux 2, 33077 Bordeaux, France.
| | | | | | | |
Collapse
|
12
|
Vilović K, Ilijić E, Glamoclija V, Kolić K, Bocina I, Sapunar D, Saraga-Babić M. Cell death in developing human spinal cord. ACTA ACUST UNITED AC 2005; 211:1-9. [PMID: 16315061 DOI: 10.1007/s00429-005-0044-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/20/2005] [Indexed: 10/25/2022]
Abstract
Cell death in the developing human spinal cord was investigated in 5-12 week human conceptuses using immunohistochemical and TUNEL methods. Expression of pro-apoptotic (Fas-receptor, caspase-3) and anti-apoptotic (bcl-2) markers and marker for internucleosomal fragmentation (TUNEL) were analysed in the cranial and caudal parts of the human spinal cord. In early developmental stages (5-6 weeks) of the cranial spinal cord, bcl-2 positive cells were seen in the ventricular zone and in the roof plate, while in the caudal part they were seen surrounding the central lumen. Subsequently, bcl-2 expression appeared in the basal plates of the grey matter and in the spinal ganglia, and from the seventh week on they also appeared in the intermediate horn of the grey matter. In the fetal period, bcl-2 expression appeared in the dorsal horns of the grey matter (9 weeks) but ceased in the ventricular zone (12 weeks) . In the trunk region, TUNEL-positive cells were found in ventricular and mantle zones along the whole length of the spinal cord. Caspase-3 positive cells and Fas-receptor positive cells appeared only in the grey matter of the cranial segments (head and trunk) of the spinal cord, but they were missing in the caudal parts. Caspase-3 dependant pathway, probably activated by Fas-receptor, seems to operate only in the cranial part of the human spinal cord. In the caudal (sacrococcygeal and tail) parts, cells seem to die by caspase-3 independent pathway. The interplay of pro-apoptotic and anti-apoptotic factors may be associated with cranial spinal cord morphogenesis, adjustment of cells number and selective survival of neurons, while in the caudal regions these factors cause massive cell death associated with regression of the caudal spinal cord.
Collapse
Affiliation(s)
- Katarina Vilović
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, PAK, KB Split, Spincićeva 1, 21000 Split, Croatia.
| | | | | | | | | | | | | |
Collapse
|
13
|
Abstract
Discovery of new genes and proteins directly supporting leukocyte adhesion is waning, whereas there is heightened interest in the cell mechanics and receptor dynamics that lead from transient tethering via selectins to affinity shifts and adhesion strengthening through integrins. New optical tools enable real-time imaging of leukocyte rolling and arrest in parallel plate flow channels (PPFCs), and detection of single-molecule force spectroscopy provides an inner view of the intercellular adhesive contact region. Leukocyte recruitment during acute inflammation is triggered by ligation of G protein-coupled chemotactic receptors (GPCRs) and clustering of selectins. This, in turn, activates beta(2)-integrin (CD18), which facilitates cell capture and arrest in shear flow. This review provides a conceptual model for the molecular events supporting leukocyte recruitment.
Collapse
Affiliation(s)
- Scott I Simon
- Department of Biomedical Engineering, University of California, Davis, CA 95616-5294, USA.
| | | |
Collapse
|
14
|
Kusumi A, Nakada C, Ritchie K, Murase K, Suzuki K, Murakoshi H, Kasai RS, Kondo J, Fujiwara T. Paradigm shift of the plasma membrane concept from the two-dimensional continuum fluid to the partitioned fluid: high-speed single-molecule tracking of membrane molecules. ACTA ACUST UNITED AC 2005; 34:351-78. [PMID: 15869394 DOI: 10.1146/annurev.biophys.34.040204.144637] [Citation(s) in RCA: 807] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Recent advancements in single-molecule tracking methods with nanometer-level precision now allow researchers to observe the movement, recruitment, and activation of single molecules in the plasma membrane in living cells. In particular, on the basis of the observations by high-speed single-particle tracking at a frame rate of 40,000 frames s(1), the partitioning of the fluid plasma membrane into submicron compartments throughout the cell membrane and the hop diffusion of virtually all the molecules have been proposed. This could explain why the diffusion coefficients in the plasma membrane are considerably smaller than those in artificial membranes, and why the diffusion coefficient is reduced upon molecular complex formation (oligomerization-induced trapping). In this review, we first describe the high-speed single-molecule tracking methods, and then we critically review a new model of a partitioned fluid plasma membrane and the involvement of the actin-based membrane-skeleton "fences" and anchored-transmembrane protein "pickets" in the formation of compartment boundaries.
Collapse
Affiliation(s)
- Akihiro Kusumi
- Kusumi Membrane Organizer Project, Exploratory Research for Advanced Technology Organization, Department of Biological Science and Institute for Advanced Research, Nagoya University, Nagoya 464-8602, Japan.
| | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Deverall MA, Gindl E, Sinner EK, Besir H, Ruehe J, Saxton MJ, Naumann CA. Membrane lateral mobility obstructed by polymer-tethered lipids studied at the single molecule level. Biophys J 2004; 88:1875-86. [PMID: 15613633 PMCID: PMC1305241 DOI: 10.1529/biophysj.104.050559] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Obstructed long-range lateral diffusion of phospholipids (TRITC-DHPE) and membrane proteins (bacteriorhodopsin) in a planar polymer-tethered 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer is studied using wide-field single molecule fluorescence microscopy. The obstacles are well-controlled concentrations of hydrophobic lipid-mimicking dioctadecylamine moieties in the polymer-exposed monolayer of the model membrane. Diffusion of both types of tracer molecules is well described by a percolating system with different percolation thresholds for lipids and proteins. Data analysis using a free area model of obstructed lipid diffusion indicates that phospholipids and tethered lipids interact via hard-core repulsion. A comparison to Monte Carlo lattice calculations reveals that tethered lipids act as immobile obstacles, are randomly distributed, and do not self-assemble into large-scale aggregates for low to moderate tethering concentrations. A procedure is presented to identify anomalous subdiffusion from tracking data at a single time lag. From the analysis of the cumulative distribution function of the square displacements, it was found that TRITC-DHPE and W80i show normal diffusion at lower concentrations of tethered lipids and anomalous diffusion at higher ones. This study may help improve our understanding of how lipids and proteins in biomembranes may be obstructed by very small obstacles comprising only one or very few molecules.
Collapse
Affiliation(s)
- M A Deverall
- Department of Chemistry, Indiana University-Purdue University Indianapolis, 402 N. Blackford St., Indianapolis, IN 46202, USA
| | | | | | | | | | | | | |
Collapse
|
16
|
Green CE, Pearson DN, Camphausen RT, Staunton DE, Simon SI. Shear-dependent capping of L-selectin and P-selectin glycoprotein ligand 1 by E-selectin signals activation of high-avidity beta2-integrin on neutrophils. THE JOURNAL OF IMMUNOLOGY 2004; 172:7780-90. [PMID: 15187162 DOI: 10.4049/jimmunol.172.12.7780] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Two adhesive events critical to efficient recruitment of neutrophils at vascular sites of inflammation are up-regulation of endothelial selectins that bind sialyl Lewis(x) ligands and activation of beta(2)-integrins that support neutrophil arrest by binding ICAM-1. We have previously reported that neutrophils rolling on E-selectin are sufficient for signaling cell arrest through beta(2)-integrin binding of ICAM-1 in a process dependent upon ligation of L-selectin and P-selectin glycoprotein ligand 1 (PSGL-1). Unresolved are the spatial and temporal events that occur as E-selectin binds to human neutrophils and dynamically signals the transition from neutrophil rolling to arrest. Here we show that binding of E-selectin to sialyl Lewis(x) on L-selectin and PSGL-1 drives their colocalization into membrane caps at the trailing edge of neutrophils rolling on HUVECs and on an L-cell monolayer coexpressing E-selectin and ICAM-1. Likewise, binding of recombinant E-selectin to PMNs in suspension also elicited coclustering of L-selectin and PSGL-1 that was signaled via mitogen-activated protein kinase. Binding of recombinant E-selectin signaled activation of beta(2)-integrin to high-avidity clusters and elicited efficient neutrophil capture of beta(2)-integrin ligands in shear flow. Inhibition of p38 and p42/44 mitogen-activated protein kinase blocked the cocapping of L-selectin and PSGL-1 and the subsequent clustering of high-affinity beta(2)-integrin. Taken together, the data suggest that E-selectin is unique among selectins in its capacity for clustering sialylated ligands and transducing signals leading to neutrophil arrest in shear flow.
Collapse
Affiliation(s)
- Chad E Green
- Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, CA 95616, USA
| | | | | | | | | |
Collapse
|
17
|
Leikina E, Mittal A, Cho MS, Melikov K, Kozlov MM, Chernomordik LV. Influenza hemagglutinins outside of the contact zone are necessary for fusion pore expansion. J Biol Chem 2004; 279:26526-32. [PMID: 15078874 DOI: 10.1074/jbc.m401883200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Current models for membrane fusion in diverse biological processes are focused on the local action of fusion proteins present in the contact zone where the proteins anchored in one membrane might interact directly with the other membrane. Are the fusion proteins outside of the contact zone just bystanders? Here we assess the role of these "outsider" proteins in influenza virus hemagglutinin-mediated fusion between red blood cells and either hemagglutinin-expressing cells or viral particles. To selectively inhibit or enhance the actions of hemagglutinin outsiders, the antibodies that bind to hemagglutinin and proteases that cleave it were conjugated to polystyrene microspheres too large to enter the contact zone. We also involved hemagglutinin outsiders into interactions with additional red blood cells. We find the hemagglutinin outsiders to be necessary and sufficient for fusion. Interfering with the activity of the hemagglutinin outsiders inhibited fusion. Selective conversion of hemagglutinin outsiders alone into fusion-competent conformation was sufficient to achieve fusion. The discovered functional role of fusion proteins located outside of the contact zone suggests a tempting analogy to mechanisms by which proteins mediate membrane fission from outside of the fission site.
Collapse
Affiliation(s)
- Eugenia Leikina
- Section on Membrane Biology, Laboratory of Cellular and Molecular Biophysics, NICHD, National Institutes of Health, Bethesda, Maryland 20892-1855, USA
| | | | | | | | | | | |
Collapse
|
18
|
Abstract
A framework for quantitative analysis of the mechanisms underlying immunological synapse assembly has been recently developed. This model uses partial differential equations to describe the binding interactions of receptors and ligands, with the constraint that they are embedded in apposed deformable membranes linked to a cytoskeletal complex.
Collapse
Affiliation(s)
- Sung-Joo E Lee
- Biophysics Graduate Group, Dept of Chemistry, University of California, Berkeley, CA, USA
| | | | | | | | | |
Collapse
|
19
|
Qi SY, Groves JT, Chakraborty AK. Synaptic pattern formation during cellular recognition. Proc Natl Acad Sci U S A 2001; 98:6548-53. [PMID: 11371622 PMCID: PMC34390 DOI: 10.1073/pnas.111536798] [Citation(s) in RCA: 285] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2000] [Indexed: 11/18/2022] Open
Abstract
Cell-cell recognition often requires the formation of a highly organized pattern of receptor proteins (a synapse) in the intercellular junction. Recent experiments [e.g., Monks, C. R. F., Freiberg, B. A., Kupfer, H., Sciaky, N. & Kupfer, A. (1998) Nature (London) 395, 82-86; Grakoui, A., Bromley, S. K., Sumen, C., Davis, M. M., Shaw, A. S., Allen, P. M. & Dustin, M. L. (1999) Science 285, 221-227; and Davis, D. M., Chiu, I., Fassett, M., Cohen, G. B., Mandelboim, O. & Strominger, J. L. (1999) Proc. Natl. Acad. Sci. USA 96, 15062-15067] vividly demonstrate a complex evolution of cell shape and spatial receptor-ligand patterns (several microns in size) in the intercellular junction during immunological synapse formation. The current view is that this dynamic rearrangement of proteins into organized supramolecular activation clusters is driven primarily by active cytoskeletal processes [e.g., Dustin, M. L. & Cooper, J. A. (2000) Nat. Immunol. 1, 23-29; and Wulfing, C. & Davis, M. M. (1998) Science 282, 2266-2269]. Here, aided by a quantitative analysis of the relevant physico-chemical processes, we demonstrate that the essential characteristics of synaptic patterns observed in living cells can result from spontaneous self-assembly processes. Active cellular interventions are superimposed on these self-organizing tendencies and may also serve to regulate the spontaneous processes. We find that the protein binding/dissociation characteristics, protein mobilities, and membrane constraints measured in the cellular environment are delicately balanced such that the length and time scales of spontaneously evolving patterns are in near-quantitative agreement with observations for synapse formation between T cells and supported membranes [Grakoui, A., Bromley, S. K., Sumen, C., Davis, M. M., Shaw, A. S., Allen, P. M. & Dustin, M. L. (1999) Science 285, 221-227]. The model we present provides a common way of analyzing immunological synapse formation in disparate systems (e.g., T cell/antigen-presenting cell junctions with different MHC-peptides, natural killer cells, etc.).
Collapse
Affiliation(s)
- S Y Qi
- Departments of Chemical Engineering and Chemistry, Physical Biosciences Division, Materials Science Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA
| | | | | |
Collapse
|
20
|
Varadhachary AS, Edidin M, Hanlon AM, Peter ME, Krammer PH, Salgame P. Phosphatidylinositol 3′-Kinase Blocks CD95 Aggregation and Caspase-8 Cleavage at the Death-Inducing Signaling Complex by Modulating Lateral Diffusion of CD95. THE JOURNAL OF IMMUNOLOGY 2001; 166:6564-9. [PMID: 11359808 DOI: 10.4049/jimmunol.166.11.6564] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Activation of phosphatidylinositol 3'-kinase (PI 3'-K) after ligation of CD3 protects Th2 cells from CD95-mediated apoptosis. Here we show that protection is achieved by inhibition of the formation of CD95 aggregates and consequent activation of caspase-8. Inhibition of aggregate formation is mediated by changes in the actin cytoskeleton, which in turn inhibit lateral diffusion of CD95, reducing its diffusion coefficient, D, 10-fold. After cytochalasin D treatment of stimulated cells, the lateral diffusion of CD95 increases to the value measured on unstimulated cells, and CD95 molecules aggregate to process caspase-8 and mediate apoptosis. Regulation of functional receptor formation by modulating lateral diffusion is a novel mechanism for controlling receptor activity.
Collapse
Affiliation(s)
- A S Varadhachary
- Temple University School of Medicine, 3400 North Broad Street, Philadelphia, PA 19140
| | | | | | | | | | | |
Collapse
|
21
|
Ricard CS, Kobayashi S, Pena JD, Salvador-Silva M, Agapova O, Hernandez MR. Selective expression of neural cell adhesion molecule (NCAM)-180 in optic nerve head astrocytes exposed to elevated hydrostatic pressure in vitro. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 81:62-79. [PMID: 11000479 DOI: 10.1016/s0169-328x(00)00150-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Glaucomatous optic neuropathy is usually associated with elevated intraocular pressure. Optic nerve head astrocytes may respond to intraocular pressure by stimulation of pressure-sensitive mechanoreceptors on the cell surface. Neural cell adhesion molecule (NCAM) a transmembrane protein, mediates cell adhesion and migration. The NCAM 180 isoform increases in astrocytes of glaucomatous optic nerve head. We characterized the relative expression of NCAM isoforms in human optic nerve head astrocytes grown under elevated hydrostatic pressure. Astrocytes cultured from normal human optic nerve heads were exposed to either atmospheric or continuous hydrostatic pressure of 60 mm Hg, and analyzed at 6-48 h. Changes in cell shape, immunoreactivity, and distribution of GFAP, actin and NCAM were observed in pressure-treated cultures. Newly synthesized (35)S-labeled NCAM protein immunoprecipitated from cell lysates was increased 2-fold within 24 h after exposure to elevated pressure compared to control. The increase in NCAM synthesis was primarily due to the NCAM 180 isoform. A significant increase in NCAM 180 mRNA levels was detected by RT-PCR and Northern blots in cultured optic nerve head astrocytes within 6 h after exposure to elevated pressure. NCAM 180 mRNA and protein synthesis decreased after 24 h and returned to control levels by 48 h. Our data indicate that NCAM 180 transcription and synthesis in astrocytes is stimulated by elevated hydrostatic pressure. Because NCAM 180 interacts with the cytoskeleton through an extended cytoplasmic tail, a selective and transient increase in NCAM 180 in optic nerve head astrocytes exposed to elevated pressure may be relevant to the migration and interactions of reactive astrocytes in glaucoma.
Collapse
Affiliation(s)
- C S Ricard
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, 63110, St. Louis, MO, USA
| | | | | | | | | | | |
Collapse
|
22
|
Toomre D, Steyer JA, Keller P, Almers W, Simons K. Fusion of constitutive membrane traffic with the cell surface observed by evanescent wave microscopy. J Cell Biol 2000; 149:33-40. [PMID: 10747085 PMCID: PMC2175107 DOI: 10.1083/jcb.149.1.33] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Monitoring the fusion of constitutive traffic with the plasma membrane has remained largely elusive. Ideally, fusion would be monitored with high spatial and temporal resolution. Recently, total internal reflection (TIR) microscopy was used to study regulated exocytosis of fluorescently labeled chromaffin granules. In this technique, only the bottom cellular surface is illuminated by an exponentially decaying evanescent wave of light. We have used a prism type TIR setup with a penetration depth of approximately 50 nm to monitor constitutive fusion of vesicular stomatitis virus glycoprotein tagged with the yellow fluorescent protein. Fusion of single transport containers (TCs) was clearly observed and gave a distinct analytical signature. TCs approached the membrane, appeared to dock, and later rapidly fuse, releasing a bright fluorescent cloud into the membrane. Observation and analysis provided insight about their dynamics, kinetics, and position before and during fusion. Combining TIR and wide-field microscopy allowed us to follow constitutive cargo from the Golgi complex to the cell surface. Our observations include the following: (1) local restrained movement of TCs near the membrane before fusion; (2) apparent anchoring near the cell surface; (3) heterogeneously sized TCs fused either completely; or (4) occasionally larger tubular-vesicular TCs partially fused at their tips.
Collapse
Affiliation(s)
- Derek Toomre
- Cell Biology/Biophysics Programme, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, D-01307 Dresden, Germany
| | | | - Patrick Keller
- Cell Biology/Biophysics Programme, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, D-01307 Dresden, Germany
| | | | - Kai Simons
- Cell Biology/Biophysics Programme, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, D-01307 Dresden, Germany
| |
Collapse
|
23
|
Kusumi A, Suzuki K, Koyasako K. Mobility and cytoskeletal interactions of cell adhesion receptors. Curr Opin Cell Biol 1999; 11:582-90. [PMID: 10508652 DOI: 10.1016/s0955-0674(99)00020-4] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Clustering of cell adhesion receptors and their interactions with the cytoskeleton are key events in the formation and function of cell adhesion structures. On the free cell surface, cadherin molecules interact with the cytoskeleton/membrane skeleton by being bound or corralled, and such interactions are greatly enhanced by the formation of cadherin oligomers. Corralled cadherin molecules undergo hop diffusion from one compartment to an adjacent one (membrane skeleton fence model), which prompts the initial formation of small adhesion clusters at cell-cell contact sites, but larger-scale assemblies of cadherin and actin filaments might require a further co-ordinated recruitment of these molecules.
Collapse
Affiliation(s)
- A Kusumi
- Department of Biological Science Graduate School of Science Nagoya University Chikusa-ku, 464-8602, Kusumi Membrane Organizer Project ERATO, JST Kumazaki Building, Chiyoda 5-11-33, Nagoya, 460-0012, Japan.
| | | | | |
Collapse
|
24
|
|
25
|
Simson R, Yang B, Moore SE, Doherty P, Walsh FS, Jacobson KA. Structural mosaicism on the submicron scale in the plasma membrane. Biophys J 1998; 74:297-308. [PMID: 9449330 PMCID: PMC1299382 DOI: 10.1016/s0006-3495(98)77787-2] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The lateral mobility of the neural cell adhesion molecule (NCAM) was examined using single particle tracking (SPT). Various isoforms of human NCAM, differing in their ectodomain, their membrane anchorage mode, or the size of their cytoplasmic domain, were expressed in National Institutes of Health 3T3 cells and C2C12 muscle cells. On a 6.6-s time scale, SPT measurements on both transmembrane and glycosylphosphatidylinositol (GPI) anchored isoforms of NCAM expressed in 3T3 cells could be classified into mobile (Brownian diffusion), slow diffusion, corralled diffusion, and immobile subpopulations. On a 90-s time scale, SPT studies in C2C12 cells revealed that 40-60% of transfected NCAM was mobile, whereas a smaller fraction (approximately 10-30%) experienced much slower diffusion. In addition, a fraction of approximately 30% of both transfected GPI and transmembrane isoforms and endogenous NCAM isoforms in C2C12 cells experienced transient confinement for approximately 8 s within regions of approximately 300-nm diameter. Diffusion within both these and the slow diffusion regions was anomalous, consistent with movements through a dense field of obstacles, whereas diffusion outside these regions was normal. Thus the membrane appears as a mosaic containing regions that permit free diffusion as well as regions in which NCAM is transiently confined to small or more extended domains. These results, including a large, freely diffusing fraction, similar confinement of transmembrane and GPI isoforms, a significant slowly diffusing fraction, and relatively large interdomain distances, are at some variance with the membrane skeleton fence model (Kusumi and Sako, 1996). Possible revisions to the model that incorporate these data are discussed.
Collapse
Affiliation(s)
- R Simson
- Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill 27599, USA
| | | | | | | | | | | |
Collapse
|