101
|
Clark AG, Paluch E. Mechanics and regulation of cell shape during the cell cycle. Results Probl Cell Differ 2011; 53:31-73. [PMID: 21630140 DOI: 10.1007/978-3-642-19065-0_3] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Many cell types undergo dramatic changes in shape throughout the cell cycle. For individual cells, a tight control of cell shape is crucial during cell division, but also in interphase, for example during cell migration. Moreover, cell cycle-related cell shape changes have been shown to be important for tissue morphogenesis in a number of developmental contexts. Cell shape is the physical result of cellular mechanical properties and of the forces exerted on the cell. An understanding of the causes and repercussions of cell shape changes thus requires knowledge of both the molecular regulation of cellular mechanics and how specific changes in cell mechanics in turn effect global shape changes. In this chapter, we provide an overview of the current knowledge on the control of cell morphology, both in terms of general cell mechanics and specifically during the cell cycle.
Collapse
Affiliation(s)
- Andrew G Clark
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
| | | |
Collapse
|
102
|
Abstract
Cortical forces drive a variety of cell shape changes and cell movements during tissue morphogenesis. While the molecular components underlying these forces have been largely identified, how they assemble and spatially and temporally organize at cell surfaces to promote cell shape changes in developing tissues are open questions. We present here different key aspects of cortical forces: their physical nature, some rules governing their emergence, and how their deployment at cell surfaces drives important morphogenetic movements in epithelia. We review a wide range of literature combining genetic/molecular, biophysical and modeling approaches, which explore essential features of cortical force generation and transmission in tissues.
Collapse
Affiliation(s)
- Matteo Rauzi
- IBDML, UMR6216 CNRS-Université de Méditerraneé, Campus de Luminy, Case 907, 13288 Marseille Cedex 09, France
| | | |
Collapse
|
103
|
Abstract
Biochemical patterning and morphogenetic movements coordinate the design of embryonic development. The molecular processes that pattern and closely control morphogenetic movements are today becoming well understood. Recent experimental evidence demonstrates that mechanical cues generated by morphogenesis activate mechanotransduction pathways, which in turn regulate cytoskeleton remodeling, cell proliferation, tissue differentiation. From Drosophila oocytes and embryos to Xenopus and mouse embryos and Arabidopsis meristem, here we review the developmental processes known to be activated in vivo by the mechanical strains associated to embryonic multicellular tissue morphogenesis. We describe the genetic, mechanical, and magnetic tools that have allowed the testing of mechanical induction in development by a step-by-step uncoupling of genetic inputs from mechanical inputs in embryogenesis. We discuss the known underlying molecular mechanisms involved in such mechanotransduction processes, including the Armadillo/β-catenin activation of Twist and the Fog-dependent stabilization of Myosin-II. These mechanotransduction processes are associated with a variety of physiological functions, such as mid-gut differentiation, mesoderm invagination and skeletal joint differentiation in embryogenesis, cell migration and internal pressure regulation during oogenesis, and meristem morphogenesis. We describe how the conservation of associated mechanosensitive pathways in embryonic and adult tissues opens new perspectives on mechanical involvement, potentially in evolution, and in cancer progression.
Collapse
Affiliation(s)
- Emmanuel Farge
- Mechanics and Genetics of Embryonic and Tumoral Development Group, UMR168 CNRS, Institut Curie, Paris, France
| |
Collapse
|
104
|
Kinetic analysis of the interaction between poly(amidoamine) dendrimers and model lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:209-18. [DOI: 10.1016/j.bbamem.2010.08.017] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 08/11/2010] [Accepted: 08/24/2010] [Indexed: 01/11/2023]
|
105
|
Liu L, Shi H, Chen X, Wang Z. Regulation of EGF-Stimulated EGF Receptor Endocytosis During M Phase. Traffic 2010; 12:201-17. [DOI: 10.1111/j.1600-0854.2010.01141.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
106
|
Chetrit D, Barzilay L, Horn G, Bielik T, Smorodinsky NI, Ehrlich M. Negative regulation of the endocytic adaptor disabled-2 (Dab2) in mitosis. J Biol Chem 2010; 286:5392-403. [PMID: 21097498 DOI: 10.1074/jbc.m110.161851] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mitotic cells undergo extensive changes in shape and size through the altered regulation and function of their membrane trafficking machinery. Disabled 2 (Dab2), a multidomain cargo-specific endocytic adaptor and a mediator of signal transduction, is a potential integrator of trafficking and signaling. Dab2 binds effectors of signaling and trafficking that localize to different intracellular compartments. Thus, differential localization is a putative regulatory mechanism of Dab2 function. Furthermore, Dab2 is phosphorylated in mitosis and is thus regulated in the cell cycle. However, a detailed description of the intracellular localization of Dab2 in the different phases of mitosis and an understanding of the functional consequences of its phosphorylation are lacking. Here, we show that Dab2 is progressively displaced from the membrane in mitosis. This phenomenon is paralleled by a loss of co-localization with clathrin. Both phenomena culminate in metaphase/anaphase and undergo partial recovery in cytokinesis. Treatment with 2-methoxyestradiol, which arrests cells at the spindle assembly checkpoint, induces the same effects observed in metaphase cells. Moreover, 2-methoxyestradiol also induced Dab2 phosphorylation and reduced Dab2/clathrin interactions, endocytic vesicle motility, clathrin exchange dynamics, and the internalization of a receptor endowed with an NPXY endocytic signal. Serine/threonine to alanine mutations, of residues localized to the central region of Dab2, attenuated its phosphorylation, reduced its membrane displacement, and maintained its endocytic abilities in mitosis. We propose that the negative regulation of Dab2 is part of an accommodation of the cell to the altered physicochemical conditions prevalent in mitosis, aimed at allowing endocytic activity throughout the cell cycle.
Collapse
Affiliation(s)
- David Chetrit
- Department of Cell Research and Immunology, George S Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | | | | | | | | | | |
Collapse
|
107
|
Tollis S, Dart AE, Tzircotis G, Endres RG. The zipper mechanism in phagocytosis: energetic requirements and variability in phagocytic cup shape. BMC SYSTEMS BIOLOGY 2010; 4:149. [PMID: 21059234 PMCID: PMC2991294 DOI: 10.1186/1752-0509-4-149] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Accepted: 11/08/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND Phagocytosis is the fundamental cellular process by which eukaryotic cells bind and engulf particles by their cell membrane. Particle engulfment involves particle recognition by cell-surface receptors, signaling and remodeling of the actin cytoskeleton to guide the membrane around the particle in a zipper-like fashion. Despite the signaling complexity, phagocytosis also depends strongly on biophysical parameters, such as particle shape, and the need for actin-driven force generation remains poorly understood. RESULTS Here, we propose a novel, three-dimensional and stochastic biophysical model of phagocytosis, and study the engulfment of particles of various sizes and shapes, including spiral and rod-shaped particles reminiscent of bacteria. Highly curved shapes are not taken up, in line with recent experimental results. Furthermore, we surprisingly find that even without actin-driven force generation, engulfment proceeds in a large regime of parameter values, albeit more slowly and with highly variable phagocytic cups. We experimentally confirm these predictions using fibroblasts, transfected with immunoreceptor FcγRIIa for engulfment of immunoglobulin G-opsonized particles. Specifically, we compare the wild-type receptor with a mutant receptor, unable to signal to the actin cytoskeleton. Based on the reconstruction of phagocytic cups from imaging data, we indeed show that cells are able to engulf small particles even without support from biological actin-driven processes. CONCLUSIONS This suggests that biochemical pathways render the evolutionary ancient process of phagocytic highly robust, allowing cells to engulf even very large particles. The particle-shape dependence of phagocytosis makes a systematic investigation of host-pathogen interactions and an efficient design of a vehicle for drug delivery possible.
Collapse
Affiliation(s)
- Sylvain Tollis
- Division of Molecular Biosciences, South Kensington Campus, Imperial College London, SW72AZ London, UK
| | | | | | | |
Collapse
|
108
|
Oeckler RA, Lee WY, Park MG, Kofler O, Rasmussen DL, Lee HB, Belete H, Walters BJ, Stroetz RW, Hubmayr RD. Determinants of plasma membrane wounding by deforming stress. Am J Physiol Lung Cell Mol Physiol 2010; 299:L826-33. [PMID: 20889673 DOI: 10.1152/ajplung.00217.2010] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Once excess liquid gains access to air spaces of an injured lung, the act of breathing creates and destroys foam and thereby contributes to the wounding of epithelial cells by interfacial stress. Since cells are not elastic continua, but rather complex network structures composed of solid as well as liquid elements, we hypothesize that plasma membrane (PM) wounding is preceded by a phase separation, which results in blebbing. We postulate that interventions such as a hypertonic treatment increase adhesive PM-cytoskeletal (CSK) interactions, thereby preventing blebbing as well as PM wounds. We formed PM tethers in alveolar epithelial cells and fibroblasts and measured their retractive force as readout of PM-CSK adhesive interactions using optical tweezers. A 50-mOsm increase in media osmolarity consistently increased the tether retractive force in epithelial cells but lowered it in fibroblasts. The osmo-response was abolished by pretreatment with latrunculin, cytochalasin D, and calcium chelation. Epithelial cells and fibroblasts were exposed to interfacial stress in a microchannel, and the fraction of wounded cells were measured. Interventions that increased PM-CSK adhesive interactions prevented blebbing and were cytoprotective regardless of cell type. Finally, we exposed ex vivo perfused rat lungs to injurious mechanical ventilation and showed that hypertonic conditioning reduced the number of wounded subpleural alveolus resident cells to baseline levels. Our observations support the hypothesis that PM-CSK adhesive interactions are important determinants of the cellular response to deforming stress and pave the way for preclinical efficacy trials of hypertonic treatment in experimental models of acute lung injury.
Collapse
|
109
|
Villa-Diaz LG, Garcia-Perez JL, Krebsbach PH. Enhanced transfection efficiency of human embryonic stem cells by the incorporation of DNA liposomes in extracellular matrix. Stem Cells Dev 2010; 19:1949-57. [PMID: 20367256 DOI: 10.1089/scd.2009.0505] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Because human embryonic stem (hES) cells can differentiate into virtually any cell type in the human body, these cells hold promise for regenerative medicine. The genetic manipulation of hES cells will enhance our understanding of genes involved in early development and will accelerate their potential use and application for regenerative medicine. The objective of this study was to increase the transfection efficiency of plasmid DNA into hES cells by modifying a standard reverse transfection (RT) protocol of lipofection. We hypothesized that immobilization of plasmid DNA in extracellular matrix would be a more efficient method for plasmid transfer due to the affinity of hES cells for substrates such as Matrigel and to the prolonged exposure of cells to plasmid DNA. Our results demonstrate that this modification doubled the transfection efficiency of hES cells and the generation of clonal cell lines containing a piece of foreign DNA stably inserted in their genomes compared to results obtained with standard forward transfection. In addition, treatment with dimethyl sulfoxide further increased the transfection efficiency of hES cells. In conclusion, modifications to the RT protocol of lipofection result in a significant and robust increase in the transfection efficiency of hES cells.
Collapse
Affiliation(s)
- Luis G Villa-Diaz
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan 48109-1078, USA
| | | | | |
Collapse
|
110
|
Rauch C, Pluen A, Foster N, Loughna P, Mobasheri A, Lagadic-Gossmann D, Counillon L. On some aspects of the thermodynamic of membrane recycling mediated by fluid phase endocytosis: evaluation of published data and perspectives. Cell Biochem Biophys 2010; 56:73-90. [PMID: 20013072 DOI: 10.1007/s12013-009-9072-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The theoretical and experimental description of fluid phase endocytosis (FPE) requires an asymmetry in phospholipid number between the two leaflets of the cell membrane, which provides the biomechanical torque needed to generate membrane budding. Although the motor force behind FPE is defined, its kinetic has yet to be determined. Based on a body of evidences suggesting that the mean surface tension is unlikely to be involved in endocytosis we decided to determine whether the cytosolic hydrostatic pressure could be involved, by considering a constant energy exchanged between the cytosol and the cell membrane. The theory is compared to existing experimental data obtained from FPE kinetic studies in living cells where altered phospholipid asymmetry or changes in the extracellular osmotic pressure have been investigated. The model demonstrates that FPE is dependent on the influx and efflux of vesicular volumes (i.e. vesicular volumes recycling) rather than the membrane tension of cells. We conclude that: (i) a relationship exists between membrane lipid number asymmetry and resting cytosolic pressure and (ii) the validity of Laplace's law is limited to cells incubated in a definite hypotonic regime. Finally, we discuss how the model could help clarifying elusive observations obtained from different fields and including: (a) the non-canonical shuttling of aquaporin in cells, (b) the relationship between high blood pressure and inflammation and (c) the mechanosensitivity of the sodium/proton exchanger.
Collapse
Affiliation(s)
- Cyril Rauch
- School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, UK.
| | | | | | | | | | | | | |
Collapse
|
111
|
Wickramasinghe RD, Ko Ferrigno P, Roghi C. Peptide aptamers as new tools to modulate clathrin-mediated internalisation--inhibition of MT1-MMP internalisation. BMC Cell Biol 2010; 11:58. [PMID: 20653933 PMCID: PMC2919464 DOI: 10.1186/1471-2121-11-58] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Accepted: 07/23/2010] [Indexed: 12/23/2022] Open
Abstract
Background Peptide aptamers are combinatorial protein reagents that bind to targets with a high specificity and a strong affinity thus providing a molecular tool kit for modulating the function of their targets in vivo. Results Here we report the isolation of a peptide aptamer named swiggle that interacts with the very short (21 amino acid long) intracellular domain of membrane type 1-metalloproteinase (MT1-MMP), a key cell surface protease involved in numerous and crucial physiological and pathological cellular events. Expression of swiggle in mammalian cells was found to increase the cell surface expression of MT1-MMP by impairing its internalisation. Swiggle interacts with the LLY573 internalisation motif of MT1-MMP intracellular domain, thus disrupting the interaction with the μ2 subunit of the AP-2 internalisation complex required for endocytosis of the protease. Interestingly, swiggle-mediated inhibition of MT1-MMP clathrin-mediated internalisation was also found to promote MT1-MMP-mediated cell migration. Conclusions Taken together, our results provide further evidence that peptide aptamers can be used to dissect molecular events mediated by individual protein domains, in contrast to the pleiotropic effects of RNA interference techniques.
Collapse
Affiliation(s)
- Rochana D Wickramasinghe
- Department of Oncology, Cambridge Research Centre, University of Cambridge, Cambridge CB2 0RE, UK
| | | | | |
Collapse
|
112
|
Schiel JA, Prekeris R. Making the final cut - mechanisms mediating the abscission step of cytokinesis. ScientificWorldJournal 2010; 10:1424-34. [PMID: 20661535 PMCID: PMC4365978 DOI: 10.1100/tsw.2010.129] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Cytokinesis is the final stage of mitotic cell division that results in a physical separation of two daughter cells. Cytokinesis begins in the early stages of anaphase after the positioning of the cleavage plane and after the chromosomes segregate. This involves the recruitment and assembly of an actomyosin contractile ring, which constricts the plasma membrane and compacts midzone microtubules to form an electron-dense region, termed the midbody, located within an intracellular bridge. The resolution of this intracellular bridge, known as abscission, is the last step in cytokinesis that separates the two daughter cells. While much research has been done to delineate the mechanisms mediating actomyosin ring formation and contraction, the machinery that is responsible for abscission remains largely unclear. Recent work from several laboratories has demonstrated that dramatic changes occur in cytoskeleton and endosome dynamics, and are a prerequisite for abscission. However, the mechanistic details that regulate the final plasma membrane fusion during abscission are only beginning to emerge and are the subject of considerable controversy. Here we review recent studies within this field and discuss the proposed models of cell abscission.
Collapse
Affiliation(s)
- John A Schiel
- Department of Cell and Developmental Biology, School of Medicine, University of Colorado, Aurora, USA
| | | |
Collapse
|
113
|
Ou-Yang HD, Wei MT. Complex fluids: probing mechanical properties of biological systems with optical tweezers. Annu Rev Phys Chem 2010; 61:421-40. [PMID: 20055681 DOI: 10.1146/annurev.physchem.012809.103454] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The mechanical properties of cells are crucial for cell sensing and reaction to mechanical environments. This review describes the basic principles of optical tweezers and their use as force sensors for studying the mechanical properties of biological systems. It covers experiments of four groups of biological systems arranged by increasing complexity: (a) packaging DNA into viral capsids by bacteriophage portal motors and the dynamical stiffness of DNA upon protein binding, (b) actin-coated giant vesicles and the myosin-II embedded actin polymer network, (c) suspension cells, and (d) adhesion cells. These examples demonstrate how optical tweezers have been used to improve the understanding of the mechanical properties of biological systems at subcellular and molecular levels.
Collapse
Affiliation(s)
- H Daniel Ou-Yang
- Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
| | | |
Collapse
|
114
|
Soh S, Byrska M, Kandere-Grzybowska K, Grzybowski BA. Reaction-diffusion systems in intracellular molecular transport and control. Angew Chem Int Ed Engl 2010; 49:4170-98. [PMID: 20518023 PMCID: PMC3697936 DOI: 10.1002/anie.200905513] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Chemical reactions make cells work only if the participating chemicals are delivered to desired locations in a timely and precise fashion. Most research to date has focused on active-transport mechanisms, although passive diffusion is often equally rapid and energetically less costly. Capitalizing on these advantages, cells have developed sophisticated reaction-diffusion (RD) systems that control a wide range of cellular functions-from chemotaxis and cell division, through signaling cascades and oscillations, to cell motility. These apparently diverse systems share many common features and are "wired" according to "generic" motifs such as nonlinear kinetics, autocatalysis, and feedback loops. Understanding the operation of these complex (bio)chemical systems requires the analysis of pertinent transport-kinetic equations or, at least on a qualitative level, of the characteristic times of the constituent subprocesses. Therefore, in reviewing the manifestations of cellular RD, we also describe basic theory of reaction-diffusion phenomena.
Collapse
Affiliation(s)
- Siowling Soh
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208
| | - Marta Byrska
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208
| | - Kristiana Kandere-Grzybowska
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208
| | - Bartosz A. Grzybowski
- Department of Chemistry, Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, Homepage: http://www.dysa.northwestern.edu
| |
Collapse
|
115
|
Soh S, Byrska M, Kandere-Grzybowska K, Grzybowski B. Reaktions-Diffusions-Systeme für intrazellulären Transport und Kontrolle. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200905513] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
116
|
Evstifeeva AY, Kremnyov SV, Beloussov LV. Changes in topology and geometry of the embryonic epithelium of Xenopus during relaxation of mechanical tension. Russ J Dev Biol 2010. [DOI: 10.1134/s1062360410030033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
117
|
Lenz M, Morlot S, Roux A. Mechanical requirements for membrane fission: common facts from various examples. FEBS Lett 2009; 583:3839-46. [PMID: 19903475 DOI: 10.1016/j.febslet.2009.11.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 11/03/2009] [Accepted: 11/05/2009] [Indexed: 12/11/2022]
Abstract
Membrane fission is the last step of membrane carrier formation. As fusion, it is a very common process in eukaryotic cells, and participates in the integrity and specificity of organelles. Although many proteins have been isolated to participate in the various membrane fission reactions, we are far from understanding how membrane fission is mechanically triggered. Here we aim at reviewing the well-described examples of dynamin and lipid phase separation, and try to extract the essential requirements for fission. Then, we survey the recent knowledge obtained on other fission reactions, analyzing the similarities and differences with previous examples.
Collapse
Affiliation(s)
- Martin Lenz
- Institut Curie, Centre de Recherche, CNRS, UMR 168, Physico-Chimie Curie, Université Pierre et Marie Curie/Paris 6, F-75248 Paris, France
| | | | | |
Collapse
|
118
|
Liu AP, Loerke D, Schmid SL, Danuser G. Global and local regulation of clathrin-coated pit dynamics detected on patterned substrates. Biophys J 2009; 97:1038-47. [PMID: 19686651 DOI: 10.1016/j.bpj.2009.06.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 06/02/2009] [Accepted: 06/03/2009] [Indexed: 02/02/2023] Open
Abstract
Live-cell imaging of individual clathrin-coated pit (CCP) dynamics has revealed a broad variation in their internalization kinetics, but the functional significance and mechanistic underpinnings of this heterogeneity remain unknown. One contributing factor may be the spatial variations in the underlying actin cortex. To test this, we cultured cells on fibronectin (Fn) micropatterned substrates to vary the cortical actin mechanics in a defined manner. Under these conditions, stress fibers became organized to bridge adhesive islands, creating spatial heterogeneity in the cortical actin architecture. CCP lifetimes within the Fn-coated islands were selectively prolonged. This differential effect was not due to adherence to Fn-coated surfaces, and was not observed in cells grown on patterned surfaces that did not induce organized stress fiber assembly. Pharmacological agents that lower cortical tension selectively lowered CCP lifetimes within Fn islands, thus abolishing the spatial heterogeneity in the CCP dynamics. Although we cannot rule out the possibility that other factors might locally affect CCP dynamics at Fn islands, our data suggest that localized modulation in cortical tension may spatially regulate clathrin-mediated endocytosis.
Collapse
Affiliation(s)
- Allen P Liu
- Department of Cell Biology, Scripps Research Institute, La Jolla, California, USA
| | | | | | | |
Collapse
|
119
|
Jing J, Prekeris R. Polarized endocytic transport: the roles of Rab11 and Rab11-FIPs in regulating cell polarity. Histol Histopathol 2009; 24:1171-80. [PMID: 19609864 DOI: 10.14670/hh-24.1171] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Endocytic transport plays a vital role in the establishment and maintenance of cell polarity. Many studies have demonstrated that endosome-dependent protein targeting is required for polarization of epithelial cells and neurons. Endocytic transport regulates several highly polarized cellular events, such as cell motility and division. Rab11 GTPase has been shown to be a master regulator of protein transport via recycling endosomes, and many recent studies have focused on the molecular machinery that mediates Rab11-dependent endocytic protein transport in polarized cells. This mini-review describes the recent advances in identifying and characterizing the role of Rab11 and its effector proteins that play important roles in polarized endocytic sorting and transport.
Collapse
Affiliation(s)
- Jian Jing
- Department of Cell and Developmental Biology, School of Medicine, University of Colorado Denver, Aurora, COA 80045 USA
| | | |
Collapse
|
120
|
Pouille PA, Ahmadi P, Brunet AC, Farge E. Mechanical signals trigger Myosin II redistribution and mesoderm invagination in Drosophila embryos. Sci Signal 2009; 2:ra16. [PMID: 19366994 DOI: 10.1126/scisignal.2000098] [Citation(s) in RCA: 185] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
During Drosophila gastrulation, two waves of constriction occur in the apical ventral cells, leading to mesoderm invagination. The first constriction wave is a stochastic process mediated by the constriction of 40% of randomly positioned mesodermal cells and is controlled by the transcription factor Snail. The second constriction wave immediately follows and involves the other 60% of the mesodermal cells. The second wave is controlled by the transcription factor Twist and requires the secreted protein Fog. Complete mesoderm invagination requires redistribution of the motor protein Myosin II to the apical side of the constricting cells. We show that apical redistribution of Myosin II and mesoderm invagination, both of which are impaired in snail homozygous mutants that are defective in both constriction waves, are rescued by local mechanical deformation of the mesoderm with a micromanipulated needle. Mechanical deformation appears to promote Fog-dependent signaling by inhibiting Fog endocytosis. We propose that the mechanical tissue deformation that occurs during the Snail-dependent stochastic phase is necessary for the Fog-dependent signaling that mediates the second collective constriction wave.
Collapse
|
121
|
Yamazaki T, Kawamura Y, Uemura M. Extracellular freezing-induced mechanical stress and surface area regulation on the plasma membrane in cold-acclimated plant cells. PLANT SIGNALING & BEHAVIOR 2009; 4:231-3. [PMID: 19721759 PMCID: PMC2652538 DOI: 10.4161/psb.4.3.7911] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Accepted: 01/22/2009] [Indexed: 05/20/2023]
Abstract
Freezing tolerance is an important feature for plant survival during winter. In plants, extracellular freezing occurs at subzero temperatures, resulting in dehydration and mechanical stresses upon the plasma membrane. However, many plants can acquire enhanced freezing tolerance by exposure to non-freezing temperatures, which is referred to as cold acclimation. The plasma membrane is the primary site of freezing injury. During cold acclimation, the lipid composition in the plasma membrane changes, which may protect the plasma membrane from injuries caused by freeze-induced dehydration stress (e.g., phase transition). Recently, we have examined the behavior of the plasma membrane during the freezing process using protoplasts isolated from cold-acclimated Arabidopsis leaves. The observations indicate that the cryobehavior of the plasma membrane after cold acclimation may act to resist the mechanical stress caused by freezing.
Collapse
Affiliation(s)
| | - Yukio Kawamura
- The Iwate University 21 Century COE Program; Morioka, Iwate, Japan
| | - Matsuo Uemura
- The Iwate University 21 Century COE Program; Morioka, Iwate, Japan
- Cryobiofrontier Research Center; Faculty of Agriculture; Iwate University; Morioka, Iwate, Japan
| |
Collapse
|
122
|
Mechanisms regulating targeting of recycling endosomes to the cleavage furrow during cytokinesis. Biochem Soc Trans 2008; 36:391-4. [PMID: 18481966 DOI: 10.1042/bst0360391] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Recently, recycling endosomes have emerged as a key components required for the successful completion of cytokinesis. Furthermore, FIP3 (family of Rab11-interacting protein 3), a Rab11 GTPase-binding protein, has been implicated in targeting the recycling endosomes to the midbody of dividing cells. Previously, we have shown that FIP3/Rab11-containing endosomes associate with centrosomes until anaphase, at which time they translocate to the cleavage furrow. At telophase, FIP3/Rab11-containing endosomes move from the furrow into the midbody, and this step is required for abscission. While several other proteins were implicated in regulating FIP3 targeting to the cleavage furrow, the mechanisms regulating the dynamics of FIP3-containing endosomes during mitosis have not been defined. To identify the factors regulating FIP3 targeting to the furrow, we used a combination of siRNA (small interfering RNA) screens and proteomic analysis to identify Cyk-4/MgcRacGAP (GTPase-activating protein) and kinesin I as FIP3-binding proteins. Furthermore, kinesin I mediates the transport of FIP3-containing endosomes to the cleavage furrow. Once in the furrow, FIP3 binds to Cyk-4 as part of centralspindlin complex and accumulates at the midbody. Finally, we demonstrated that ECT2 regulates FIP3 association with the centralspindlin complex. Thus we propose that kinesin I, in concert with centralspindlin complex, plays a role in temporal and spatial regulation of endosome transport to the cleavage furrow during cytokinesis.
Collapse
|
123
|
Moisescu MG, Leveque P, Bertrand JR, Kovacs E, Mir LM. Microscopic observation of living cells during their exposure to modulated electromagnetic fields. Bioelectrochemistry 2008; 74:9-15. [DOI: 10.1016/j.bioelechem.2007.11.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 07/20/2007] [Accepted: 11/06/2007] [Indexed: 12/16/2022]
|
124
|
Abstract
Throughout normal development, and in aberrant conditions such as cancer, cells divide by a process called cytokinesis. Most textbooks suggest that animal cells execute cytokinesis using an actomyosin-containing contractile ring, whereas plant cells generate a new cell wall by the assembly of a novel membrane compartment using vesicle-trafficking machinery in an apparently distinct manner. Recent studies have shown that cytokinesis in animal and plant cells may not be as distinct as these models imply - both have an absolute requirement for vesicle traffic. Moreover, some of the key molecular components of cytokinesis have been identified, many of which are proteins that function to control membrane traffic. Here, we review recent advances in this area.
Collapse
Affiliation(s)
- Rytis Prekeris
- Department of Cellular and Developmental Biology, School of Medicine, University of Colorado Health Sciences Center, 12801 E. 17th Avenue, Aurora, CO 80045, USA
| | - Gwyn W. Gould
- Henry Wellcome Laboratory of Cell Biology, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| |
Collapse
|
125
|
Chapter 17 Application of Laser Tweezers to Studies of Membrane–Cytoskeleton Adhesion. Methods Cell Biol 2008; 89:451-66. [DOI: 10.1016/s0091-679x(08)00617-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
|
126
|
Pawlowski PH. Mechanokinetic model of cell membrane: theoretical analysis of plasmalemma homeostasis, growth and division. J Theor Biol 2007; 249:67-76. [PMID: 17716691 DOI: 10.1016/j.jtbi.2007.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2007] [Revised: 07/04/2007] [Accepted: 07/06/2007] [Indexed: 11/27/2022]
Abstract
A theoretical model dealing with endocytosis, exocytosis and caveolae invagination, describing plasmalemma homeostasis during cell growth and division, is proposed. It considers transmembrane pressure, membrane tension and mechanosensitivity of membrane processes. Membrane hydraulic conductivity and the flux of transmembrane nonvesicular transport are taken into account. The developed mathematical analysis operates with a formulated set of constitutive equations describing the mechanical state and kinetics of changes in an open dynamic membrane system. The standard version of a model with adjusted parameters was implemented, and predictions including a discussion on the effect of possible parameter modifications were presented. Computer simulations indicate big changes in the magnitude of membrane tension and elasticity, and in the number of membrane buddings in young cells and during mitosis. They also show the extent of cell growth inhibition resulting from a decrease in transmembrane transport or an increase in the exerted difference in osmotic pressure. Moreover, the simulations reveal that exocytosis regulated during mitosis may not be as important for cell growth, as sometimes presumed. Finally, practical application and possible extension of the model are discussed.
Collapse
Affiliation(s)
- Piotr H Pawlowski
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warszawa, Poland.
| |
Collapse
|
127
|
Abstract
We present a physical mechanism to describe initiation of the contractile ring during cell division. The model couples the membrane curvature with the contractile forces produced by protein clusters attached to the membrane. These protein clusters are mobile on the membrane and possess either an isotropic or an anisotropic spontaneous curvature. Our results show that under these conditions the contraction force gives rise to an instability that corresponds in a closed cellular system to the initiation of the contractile ring. We find a quantization of this process at distinct length-scales, which we compare to available data for different types of eukaryote cells.
Collapse
|
128
|
Riddle KW, Kong HJ, Leach JK, Fischbach C, Cheung C, Anseth KS, Mooney DJ. Modifying the proliferative state of target cells to control DNA expression and identifying cell types transfected in vivo. Mol Ther 2007; 15:361-8. [PMID: 17235315 DOI: 10.1038/sj.mt.6300017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Although the majority of current gene transfer techniques have focused on increasing the ability of the DNA to enter the cell, it is possible that changing the proliferative and migratory state of cells will influence the cells ability to take up and express plasmid DNA. This study was designed to test the hypothesis that growth factors (basic fibroblast growth factor (bFGF) and hepatocyte growth factor/scatter factor (HGF/SF)) used to alter the proliferative and migratory state of cells can alter plasmid DNA uptake and expression. In vitro studies indicate that enhancing cell proliferation with growth factor exposure enhances plasmid DNA uptake and expression. Furthermore, dual localized delivery of bFGF and plasmid DNA in vivo increases the expression, 3-6 times over control, as compared to plasmid delivery alone. Dual delivery of a factor promoting cell proliferation and a plasmid led to a further increase in the expression of the plasmid encoding bone morphogenetic protein-2 in a rat cranial defect by specific cell populations. The results of these studies suggest that increasing the proliferative state of target cell populations can enhance non-viral gene transfer.
Collapse
Affiliation(s)
- Kathryn W Riddle
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | | | | | | | | | | | | |
Collapse
|
129
|
Girard PP, Cavalcanti-Adam EA, Kemkemer R, Spatz JP. Cellular chemomechanics at interfaces: sensing, integration and response. SOFT MATTER 2007; 3:307-326. [PMID: 32900147 DOI: 10.1039/b614008d] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Living cells are complex entities whose remarkable, emergent capacity to sense, integrate, and respond to environmental cues relies on an intricate series of interactions among the cell's macromolecular components. Defects in mechanosensing, transduction,or responses underlie many diseases such as cancers, immune disorders, cardiac hypertrophy, genetic malformations, and neuropathies. Here, we highlight micro- and nanotechnology-based tools that have been used to study how chemical and mechanical cues modulate the responses of single cells in contact with the extracellular environment. Understanding the physical aspects of these complex processes at the micro- and nanometer scale could produce profound and fundamental new insights into how the processes of cell migration, metastasis, immune function and other areas which are regulated by mechanical forces.
Collapse
Affiliation(s)
- Philippe P Girard
- Max-Planck-Institute for Metals Research, Dept. New Materials and Biosystems, Heisenbergstr. 3, D-70569 Stuttgart, Germany and University of Heidelberg, Dept. Biophysical Chemistry, INF 253, D-69120 Heidelberg, Germany.
| | - Elisabetta A Cavalcanti-Adam
- Max-Planck-Institute for Metals Research, Dept. New Materials and Biosystems, Heisenbergstr. 3, D-70569 Stuttgart, Germany and University of Heidelberg, Dept. Biophysical Chemistry, INF 253, D-69120 Heidelberg, Germany.
| | - Ralf Kemkemer
- Max-Planck-Institute for Metals Research, Dept. New Materials and Biosystems, Heisenbergstr. 3, D-70569 Stuttgart, Germany and University of Heidelberg, Dept. Biophysical Chemistry, INF 253, D-69120 Heidelberg, Germany.
| | - Joachim P Spatz
- Max-Planck-Institute for Metals Research, Dept. New Materials and Biosystems, Heisenbergstr. 3, D-70569 Stuttgart, Germany and University of Heidelberg, Dept. Biophysical Chemistry, INF 253, D-69120 Heidelberg, Germany.
| |
Collapse
|
130
|
Rauch C, Pluen A. Multi drug resistance-dependent “vacuum cleaner” functionality potentially driven by the interactions between endocytosis, drug size and Pgp-like transporters surface density. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2007; 36:121-31. [PMID: 17211622 DOI: 10.1007/s00249-006-0113-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Revised: 08/31/2006] [Accepted: 10/31/2006] [Indexed: 10/23/2022]
Abstract
In cells, multi drug resistance (MDR) is associated with Pgp-like transporters expression extruding drugs from cellular membranes. MDR is efficiently generated with a relatively small fraction of membrane transporters. As the insertion of drugs into cellular membranes is widespread, there are no reasons why a drug should incorporate the membrane in the vicinity of a transporter. As a result a further elusive hypothesis is usually invoked: these transporters act like "vacuum cleaners" of drugs embedded in the membrane. Nonetheless, how these transporters attract drugs remains obscure. To clarify the "vacuum cleaner" notion, we suggest that during its residency time in cellular membranes, the lateral movement of drugs from their point of insertion to transporters is governed by Brownian's diffusion, which allows the drugs/transporters interaction. Taking into account the functionality of Pgp-like transporters, namely the extrusion of drugs from the plasma membrane inner leaflet, we characterize how the state of drug resistance is triggered involving: membrane endocytosis, drug physico-chemical properties and the surface density of Pgp-like transporters. In addition, the theory developed provides for the first time a theoretical proof of Lipinski's second rule with regard to drugs' size (or MW) selectivity on their permeation across cellular membranes.
Collapse
Affiliation(s)
- Cyril Rauch
- School of Veterinary Medicine and Science, Sutton Bonington Campus, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD, UK.
| | | |
Collapse
|
131
|
|
132
|
Mangoura D, Sun Y, Li C, Singh D, Gutmann DH, Flores A, Ahmed M, Vallianatos G. Phosphorylation of neurofibromin by PKC is a possible molecular switch in EGF receptor signaling in neural cells. Oncogene 2006; 25:735-45. [PMID: 16314845 DOI: 10.1038/sj.onc.1209113] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Children with neurofibromatosis (NF1) typically develop central nervous system (CNS) abnormalities, including aberrant proliferation of astrocytes and formation of benign astrocytomas. The NF1 gene encodes neurofibromin, a Ras-GAP, highly expressed in developing neural cells; the mechanism of regulation of neurofibromin as a Ras-GAP, remains however unknown. We now show that, in response to EGF, neurofibromin is in vivo phosphorylated on serine residues by PKC-alpha, in human, rat, and avian CNS cells and cell lines. EGF-induced PKC phosphorylation was prominent in the cysteine/serine-rich domain (CSRD) of neurofibromin, which lies in the N-terminus and upstream of the Ras-GAP domain (GRD), and this modification significantly increased the association of neurofibromin with actin in co-immunoprecipitations. In addition, we show that Ras activation in response to EGF was significantly lowered when C62B cells overexpressed a construct encoding both CSRD + GRD. Moreover, when PKC-alpha was downregulated, the Ras-GAP activity of CSRD + GRD was significantly diminished, whereas overexpressed GRD alone acted as a weaker GAP and in a PKC-independent manner. Most importantly, functional Ras inhibition and EGF signaling shifts were established at the single cell level in C6-derived cell lines stably overexpressing CSRD + GRD, when transient co-overexpression of Ras and PKC-depletion prior to stimulation with EGF-induced mitosis. Taken together, these data provide the first evidence of a functional, allosteric regulation of GRD by CSRD, which requires neurofibromin phosphorylation by PKC and association with the actin cytoskeleton. Our data may suggest a novel mechanism for regulating biological responses to EGF and provide a new aspect for the understanding of the aberrant proliferation seen in the CNS of children with NF1.
Collapse
Affiliation(s)
- D Mangoura
- Department of Pediatrics, The University of Chicago, Chicago, IL, USA. and Neurosciences Division, Institute for Biomedical Research, Athens, Greece
| | | | | | | | | | | | | | | |
Collapse
|
133
|
Sens P, Turner MS. Budded membrane microdomains as tension regulators. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:031918. [PMID: 16605569 DOI: 10.1103/physreve.73.031918] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Revised: 11/30/2005] [Indexed: 05/08/2023]
Abstract
We propose a mechanism by which changes of the mechanical tension of a composite lipid membrane are buffered by the invagination of membrane domains. We show that domain invagination, driven by differences in chemical composition, is a first-order transition controlled by membrane tension. The invaginated domains play the role of a membrane reservoir, exchanging area with the main membrane, and impose an equilibrium tension entirely controlled by their mechanical properties. The dynamical response of the reservoir reflects the tension-dependent kinetics of the domain shape transition, so that the tension of such a composite membrane is inherently transient and dynamical. The implications of this phenomenon for the mechanical properties of the membranes of living cells, where invaginated membrane domains are known to exist, are discussed.
Collapse
Affiliation(s)
- Pierre Sens
- UMR 168, Physico-Chimie Curie, Institut Curie, Paris cedex 05, France.
| | | |
Collapse
|
134
|
Titushkin I, Cho M. Distinct membrane mechanical properties of human mesenchymal stem cells determined using laser optical tweezers. Biophys J 2006; 90:2582-91. [PMID: 16399828 PMCID: PMC1403190 DOI: 10.1529/biophysj.105.073775] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The therapeutic efficacy of mesenchymal stem cells (MSCs) in tissue engineering and regenerative medicine is determined by their unique biological, mechanical, and physicochemical characteristics, which are yet to be fully explored. Cell membrane mechanics, for example, has been shown to critically influence MSC differentiation. In this study, we used laser optical tweezers to measure the membrane mechanics of human MSCs and terminally differentiated fibroblasts by extracting tethers from the outer cell membrane. The average tether lengths were 10.6+/-1.1 microm (hMSC) and 3.0+/-0.5 microm (fibroblasts). The tether extraction force did not increase during tether formation, which suggests existence of a membrane reservoir intended to buffer membrane tension fluctuations. Cytoskeleton disruption resulted in a fourfold tether length increase in fibroblasts but had no effect in hMSCs, indicating weak association between the cell membrane and hMSC actin cytoskeleton. Cholesterol depletion, known to decrease lipid bilayer stiffness, caused an increase in the tether length both in fibroblasts and hMSCs, as does the treatment of cells with DMSO. We postulate that whereas fibroblasts use both the membrane rigidity and membrane-cytoskeleton association to regulate their membrane reservoir, hMSC cytoskeleton has only a minor impact on stem cell membrane mechanics.
Collapse
Affiliation(s)
- Igor Titushkin
- Department of Bioengineering, University of Illinois, Chicago, Illinois 60607, USA
| | | |
Collapse
|
135
|
Abstract
Membrane curvature is no longer seen as a passive consequence of cellular activity but an active means to create membrane domains and to organize centres for membrane trafficking. Curvature can be dynamically modulated by changes in lipid composition, the oligomerization of curvature scaffolding proteins and the reversible insertion of protein regions that act like wedges in membranes. There is an interplay between curvature-generating and curvature-sensing proteins during vesicle budding. This is seen during vesicle budding and in the formation of microenvironments. On a larger scale, membrane curvature is a prime player in growth, division and movement.
Collapse
Affiliation(s)
- Harvey T McMahon
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
| | | |
Collapse
|
136
|
Shen SS, Steinhardt RA. The mechanisms of cell membrane resealing in rabbit corneal epithelial cells. Curr Eye Res 2005; 30:543-54. [PMID: 16020288 DOI: 10.1080/02713680590968574] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE To examine membrane repair mechanisms in rabbit corneal epithelial (RCE) cells. METHODS Microneedle puncture and fluorescent dye loss were used to wound membranes and assay resealing, respectively. Different repair mechanisms were detected pharmacologically and with antisense oligonucleotides. RESULTS The RCE cells rapidly reseal plasma membranes by calcium-dependent exocytotic mechanisms that exhibit both facilitated and potentiated responses to multiple wounding. The facilitated response was inhibited by specific inhibitors of protein kinase C (PKC) and brefeldin A, and the potentiated response was blocked by inhibitors of cAMP-dependent protein kinase (PKA). Reduction of myosin IIA inhibited the facilitated response, and reduction of IIB inhibited the initial resealing. CONCLUSIONS RCE cells rapidly repair plasma membrane disruptions. At a second wound at the same site, PKC stimulated vesicle formation from the Golgi apparatus, resulting in more rapid membrane resealing for a facilitated response. The RCE cell also contains a PKA-dependent global potentiation of membrane resealing.
Collapse
Affiliation(s)
- Sheldon S Shen
- Department of Genetics, Development and Cellular Biology, Iowa State University, Ames, Iowa, USA
| | | |
Collapse
|
137
|
Männistö M, Rönkkö S, Mättö M, Honkakoski P, Hyttinen M, Pelkonen J, Urtti A. The role of cell cycle on polyplex-mediated gene transfer into a retinal pigment epithelial cell line. J Gene Med 2004; 7:466-76. [PMID: 15619286 DOI: 10.1002/jgm.693] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Retinal pigment epithelium (RPE) maintains the function of photoreceptors and eyesight and is an important target for gene delivery. Since in some diseases RPE cells proliferate uncontrollably, we investigated the role of cell cycle in non-viral gene delivery into a RPE cell line (D407). METHODS D407 (human) cells were transfected with cationic DNA complexes. Cells were synchronized into different phases of the cell cycle and transfected using poly-L-lysine (PLL) or polyethyleneimine (PEI) carriers for 3 h. The effects of different reporters (beta-galactosidase, luciferase) or promoters (CMV, SV40, tk, PDE-beta) on gene expression were evaluated 43 h later. Cellular uptake of ethidium monoazide/DNA complexes with PLL or PEI was determined by flow cytometry. Fluorescent DNA and the complexes were localized with a confocal microscope. The role of cell cycle in transcription was evaluated by stable luciferase-expressing cells. RESULTS PLL showed lower transfection levels than PEI in synchronized cells and only slight dependence on cell cycle. PEI showed minimal efficiency at G1 phase and maximum level at S phase. All promoters and reporter genes showed dependence on cell cycle. Cellular uptake of polyplexes was highest at S phase (80-90%) and lowest at G1 phase (5-30%). Confocal microscopy showed minor differences of free DNA between groups in the nucleus, where it was largely carrier-bound. Cell cycle effects on luciferase expression were clear in stable cell line CONCLUSIONS Transfection by polyplexes in the RPE cell line is influenced by cellular uptake and transcription, and both processes are cell-cycle-dependent. The results have implications in retinal gene therapy.
Collapse
Affiliation(s)
- Marjo Männistö
- Department of Pharmaceutics, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland.
| | | | | | | | | | | | | |
Collapse
|
138
|
Puig-de-Morales M, Millet E, Fabry B, Navajas D, Wang N, Butler JP, Fredberg JJ. Cytoskeletal mechanics in adherent human airway smooth muscle cells: probe specificity and scaling of protein-protein dynamics. Am J Physiol Cell Physiol 2004; 287:C643-54. [PMID: 15175221 DOI: 10.1152/ajpcell.00070.2004] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We probed elastic and loss moduli in the adherent human airway smooth muscle cell through a variety of receptor systems, each serving as a different molecular window on cytoskeletal dynamics. Coated magnetic microbeads were attached to the cell surface via coating-receptor binding. A panel of bead coatings was investigated: a peptide containing the sequence RGD, vitronectin, urokinase, activating antibody against beta(1)-integrin, nonactivating antibody against beta(1)-integrin, blocking antibody against beta(1)-integrin, antibody against beta(1)-integrin, and acetylated low-density lipoprotein. An oscillatory mechanical torque was applied to the bead, and resulting lateral displacements were measured at baseline, after actin disruption by cytochalasin D, or after contractile activation by histamine. As expected, mechanical moduli depended strongly on bead type and bead coating, differing at the extremes by as much as two orders of magnitude. In every case, however, elastic and loss moduli increased with frequency f as a weak power law, f( x-1). Moreover, with few exceptions, data could be scaled such that elastic and frictional responses depended solely on the power law exponent x. Taken together, these data suggest that power law behavior represents a generic feature of underlying protein-protein dynamics.
Collapse
Affiliation(s)
- Marina Puig-de-Morales
- Physiology Program, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115.
| | | | | | | | | | | | | |
Collapse
|
139
|
Wilhelm C, Cebers A, Bacri JC, Gazeau F. Deformation of intracellular endosomes under a magnetic field. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2003; 32:655-60. [PMID: 12811432 DOI: 10.1007/s00249-003-0312-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2003] [Revised: 04/25/2003] [Accepted: 04/25/2003] [Indexed: 10/26/2022]
Abstract
We present a non-invasive method to monitor the membrane tension of intracellular organelles using a magnetic field as an external control parameter. By exploiting the spontaneous endocytosis of anionic colloidal ferromagnetic nanoparticles, we obtain endosomes possessing a superparamagnetic lumen in eukaryotic cells. Initially flaccid, the endosomal membrane undulates because of thermal fluctuations, restricted in zero field by the resting tension and the curvature energy of the membrane. When submitted to a uniform magnetic field, the magnetized endosomes elongate along the field, resulting in the flattening of the entropic membrane undulations. The quantification of the endosome deformation for different magnetic fields allows in situ measurement of the resting tension and the bending stiffness of the membrane enclosing the intracellular organelle.
Collapse
Affiliation(s)
- C Wilhelm
- Laboratoire des Milieux Désordonnés et Hétérogènes, UMR7603, and FR2438 CNRS Matière et Systèmes Complexes, Université Pierre et Marie Curie, Tour 13, Case 86, 4 place Jussieu, 75005 Paris, France
| | | | | | | |
Collapse
|
140
|
van der Wijk T, Tomassen SFB, Houtsmuller AB, de Jonge HR, Tilly BC. Increased vesicle recycling in response to osmotic cell swelling. Cause and consequence of hypotonicity-provoked ATP release. J Biol Chem 2003; 278:40020-5. [PMID: 12871943 DOI: 10.1074/jbc.m307603200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Osmotic swelling of Intestine 407 cells leads to an immediate increase in cell surface membrane area as determined using the fluorescent membrane dye FM 1-43. In addition, as measured by tetramethylrhodamine isothiocyanate (TRITC)-dextran uptake, a robust (>100-fold) increase in the rate of endocytosis was observed, starting after a discrete lag time of 2-3 min and lasting for approximately 10-15 min. The hypotonicity-induced increase in membrane surface area, like the cell swelling-induced release of ATP (Van der Wijk, T., De Jonge, H. R., and Tilly, B. C. (1999) Biochem. J. 343, 579-586), was diminished after 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester loading or cytochalasin B treatment. Uptake of TRITC-dextrans, however, was not affected. Treatment of the cells with the vesicle-soluble N-ethylmaleimide-sensitive factor attachment protein receptor-specific protease Clostridium botulinum toxin F not only nearly eliminated the hypotonicity-induced increase in membrane surface area but also strongly diminished the release of ATP, indicating the involvement of regulated exocytosis. Both the ATP hydrolase apyrase and the MEK inhibitor PD098059 diminished the osmotic swelling-induced increase in membrane surface area as well as the subsequent uptake of TRITC-dextrans. Taken together, the results indicate that extracellular ATP is required for the hypotonicity-induced vesicle recycling and suggest that a positive feedback loop, involving purinergic activation of the Erk-1/2 pathway, may contribute to the release of ATP from hypo-osmotically stimulated cells.
Collapse
Affiliation(s)
- Thea van der Wijk
- Department of Biochemistry, Erasmus University Medical Center, 3000DR Rotterdam, The Netherlands
| | | | | | | | | |
Collapse
|
141
|
Abstract
The chemical synapse is a specialized intercellular junction that operates nearly autonomously to allow rapid, specific, and local communication between neurons. Focusing our attention on the presynaptic terminal, we review the current understanding of how synaptic morphology is maintained and then the mechanisms in synaptic vesicle exocytosis and recycling.
Collapse
Affiliation(s)
- Venkatesh N Murthy
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
| | | |
Collapse
|
142
|
Burroughs NJ, Wülfing C. Differential segregation in a cell-cell contact interface: the dynamics of the immunological synapse. Biophys J 2002; 83:1784-96. [PMID: 12324401 PMCID: PMC1302272 DOI: 10.1016/s0006-3495(02)73944-1] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Receptor-ligand couples in the cell-cell contact interface between a T cell and an antigen-presenting cell form distinct geometric patterns and undergo spatial rearrangement within the contact interface. Spatial segregation of the antigen and adhesion receptors occurs within seconds of contact, central aggregation of the antigen receptor then occurring over 1-5 min. This structure, called the immunological synapse, is becoming a paradigm for localized signaling. However, the mechanisms driving its formation, in particular spatial segregation, are currently not understood. With a reaction diffusion model incorporating thermodynamics, elasticity, and reaction kinetics, we examine the hypothesis that differing bond lengths (extracellular domain size) is the driving force behind molecular segregation. We derive two key conditions necessary for segregation: a thermodynamic criterion on the effective bond elasticity and a requirement for the seeding/nucleation of domains. Domains have a minimum length scale and will only spontaneously coalesce/aggregate if the contact area is small or the membrane relaxation distance large. Otherwise, differential attachment of receptors to the cytoskeleton is required for central aggregation. Our analysis indicates that differential bond lengths have a significant effect on synapse dynamics, i.e., there is a significant contribution to the free energy of the interaction, suggesting that segregation by differential bond length is important in cell-cell contact interfaces and the immunological synapse.
Collapse
|
143
|
Mogilner A, Edelstein-Keshet L. Regulation of actin dynamics in rapidly moving cells: a quantitative analysis. Biophys J 2002; 83:1237-58. [PMID: 12202352 PMCID: PMC1302225 DOI: 10.1016/s0006-3495(02)73897-6] [Citation(s) in RCA: 226] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We develop a mathematical model that describes key details of actin dynamics in protrusion associated with cell motility. The model is based on the dendritic-nucleation hypothesis for lamellipodial protrusion in nonmuscle cells such as keratocytes. We consider a set of partial differential equations for diffusion and reactions of sequestered actin complexes, nucleation, and growth by polymerization of barbed ends of actin filaments, as well as capping and depolymerization of the filaments. The mechanical aspect of protrusion is based on an elastic polymerization ratchet mechanism. An output of the model is a relationship between the protrusion velocity and the number of filament barbed ends pushing the membrane. Significantly, this relationship has a local maximum: too many barbed ends deplete the available monomer pool, too few are insufficient to generate protrusive force, so motility is stalled at either extreme. Our results suggest that to achieve rapid motility, some tuning of parameters affecting actin dynamics must be operating in the cell.
Collapse
Affiliation(s)
- Alex Mogilner
- Department of Mathematics and Institute of Theoretical Dynamics, University of California, Davis, California 95616 USA.
| | | |
Collapse
|
144
|
Rauch C, Brunet AC, Deleule J, Farge E. C2C12 myoblast/osteoblast transdifferentiation steps enhanced by epigenetic inhibition of BMP2 endocytosis. Am J Physiol Cell Physiol 2002; 283:C235-43. [PMID: 12055092 DOI: 10.1152/ajpcell.00234.2001] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the modulation of critical transcriptional steps of C2C12 myoblast/osteoblast transdifferentiation triggered by the bone morphogenetic protein 2 (BMP2) signaling protein, in response to epigenetic inhibition of the endocytotic internalization of exogenous BMP2. BMP2 endocytosis was inhibited chemically with polyethylene glycol-50 (PEG-Chol) and cyclodextrin and mechanically by mild hyposmotic treatment. BMP2-dependent nuclear translocation of the mother against Dpp (Smad1) transcription factor was ten times faster if BMP2 endocytosis was inhibited. Smad1-dependent expression of the JunB gene, the first transcriptional step in myoblast dedifferentiation, was increased by a factor of three to four. JunB-dependent levels of myogenin repression, one of the critical markers of terminal myoblastic differentiation, was amplified by a factor of three. Smad1-dependent levels of alkaline phosphatase expression, one of the C2C12 osteoblast differentiation markers, were 3.5 to 5 times higher. The same behavior was observed for osteopontin, the other C2C12 osteoblast differentiation marker. These results suggest that the cell genome could "sense" tissue mechanical deformations by mechanical inhibition of signaling protein endocytosis, thereby translating mechanical strains into transcription events involved in cell differentiation.
Collapse
Affiliation(s)
- Cyril Rauch
- Mechanics and Genetics of Developmental Embryogenesis Group, Unité Mixte de Recherche 168 Physico-Chimie Curie, Curie Institut, 75005 Paris, France
| | | | | | | |
Collapse
|
145
|
Ludtke JJ, Sebestyén MG, Wolff JA. The effect of cell division on the cellular dynamics of microinjected DNA and dextran. Mol Ther 2002; 5:579-88. [PMID: 11991749 DOI: 10.1006/mthe.2002.0581] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Gene delivery is a multistep process that is being studied to increase its efficiency, a major hurdle for effective gene therapy. Our study focused on the nuclear entry step by microinjecting a mixture of fluorescent dextran and the pEYFP-Nuc plasmid (encoding a nuclear-targeted, enhanced GFP) into the cytoplasm of nondividing and dividing cells that were selected using non-chemical means. After 10 and 1000 ng/microl of plasmid DNA (pDNA) were cytoplasmically injected, 28% and 50% of the cells that had not divided expressed GFP, respectively, compared with 50% and 90% for the cells that had divided. This result suggested that pDNA can enter the nonmitotic nuclei of mononucleated cells, albeit at a lower efficiency than mitotic nuclei. The ability of pDNA to enter the intact nuclei of nondividing cells is consistent with our previous experience using multinucleated myotubes and digitonin-permeabilized cells in culture and using intravascular naked pDNA delivery in vivo. An explanation for the small effect of cell division was provided by studies using fluorescently labeled molecules and confocal fluorescent microscopy. They showed that the bulk of large dextran, and similarly pDNA, was excluded from re-formed nuclei after mitosis, thereby limiting the effect of cell division on the nuclear entry of pDNA.
Collapse
Affiliation(s)
- James J Ludtke
- Departments of Pediatrics and Medical Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
| | | | | |
Collapse
|
146
|
Truschel ST, Wang E, Ruiz WG, Leung SM, Rojas R, Lavelle J, Zeidel M, Stoffer D, Apodaca G. Stretch-regulated exocytosis/endocytosis in bladder umbrella cells. Mol Biol Cell 2002; 13:830-46. [PMID: 11907265 PMCID: PMC99602 DOI: 10.1091/mbc.01-09-0435] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The epithelium of the urinary bladder must maintain a highly impermeable barrier despite large variations in urine volume during bladder filling and voiding. To study how the epithelium accommodates these volume changes, we mounted bladder tissue in modified Ussing chambers and subjected the tissue to mechanical stretch. Stretching the tissue for 5 h resulted in a 50% increase in lumenal surface area (from approximately 2900 to 4300 microm(2)), exocytosis of a population of discoidal vesicles located in the apical cytoplasm of the superficial umbrella cells, and release of secretory proteins. Surprisingly, stretch also induced endocytosis of apical membrane and 100% of biotin-labeled membrane was internalized within 5 min after stretch. The endocytosed membrane was delivered to lysosomes and degraded by a leupeptin-sensitive pathway. Last, we show that the exocytic events were mediated, in part, by a cyclic adenosine monophosphate, protein kinase A-dependent process. Our results indicate that stretch modulates mucosal surface area by coordinating both exocytosis and endocytosis at the apical membrane of umbrella cells and provide insight into the mechanism of how mechanical forces regulate membrane traffic in non-excitable cells.
Collapse
Affiliation(s)
- Steven T Truschel
- Renal-Electrolyte Division, Department of Medicine, Laboratory of Epithelial Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
147
|
Abstract
All cells experience and respond to mechanical stimuli, such as changes in plasma membrane tension, shear stress, hydrostatic pressure, and compression. This review is an examination of the changes in membrane traffic that occur in response to mechanical forces. The plasma membrane has an associated tension that modulates both exocytosis and endocytosis. As membrane tension increases, exocytosis is stimulated, which acts to decrease membrane tension. In contrast, increased membrane tension slows endocytosis, whereas decreased tension stimulates internalization. In most cases, secretion is stimulated by external mechanical stimuli. However, in some cells mechanical forces block secretion. External stimuli also enhance membrane and fluid endocytosis in several cell types. Transduction of mechanical stimuli into changes in exocytosis/endocytosis may involve the cytoskeleton, stretch-activated channels, integrins, phospholipases, tyrosine kinases, and cAMP.
Collapse
Affiliation(s)
- Gerard Apodaca
- Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
| |
Collapse
|
148
|
Abstract
Sperm of the nematode, Ascaris suum, crawl using lamellipodial protrusion, adhesion and retraction, a process analogous to the amoeboid motility of other eukaryotic cells. However, rather than employing an actin cytoskeleton to generate locomotion, nematode sperm use the major sperm protein (MSP). Moreover, nematode sperm lack detectable molecular motors or the battery of actin-binding proteins that characterize actin-based motility. The Ascaris system provides a simple ‘stripped down’ version of a crawling cell in which to examine the basic mechanism of cell locomotion independently of other cellular functions that involve the cytoskeleton. Here we present a mechanochemical analysis of crawling in Ascaris sperm. We construct a finite element model wherein (a) localized filament polymerization and bundling generate the force for lamellipodial extension and (b) energy stored in the gel formed from the filament bundles at the leading edge is subsequently used to produce the contraction that pulls the rear of the cell forward. The model reproduces the major features of crawling sperm and provides a framework in which amoeboid cell motility can be analyzed. Although the model refers primarily to the locomotion of nematode sperm, it has important implications for the mechanics of actin-based cell motility.Movies available on-line.
Collapse
Affiliation(s)
- Dean Bottino
- Department of Molecular and Cellular Biology, University of California, Berkeley, CA 94720-3112, USA
| | | | | | | | | |
Collapse
|
149
|
Raucher D, Sheetz MP. Phospholipase C activation by anesthetics decreases membrane-cytoskeleton adhesion. J Cell Sci 2001; 114:3759-66. [PMID: 11707527 DOI: 10.1242/jcs.114.20.3759] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many different amphiphilic compounds cause an increase in the fluid-phase endocytosis rates of cells in parallel with a decrease in membrane-cytoskeleton adhesion. These compounds, however, do not share a common chemical structure, which leaves the mechanism and even site of action unknown. One possible mechanism of action is through an alteration of inositol lipid metabolism by modifying the cytoplasmic surface of the plasma membrane bilayer. By comparing permeable amphiphilic amines used as local anesthetics with their impermeable analogs, we find that access to the cytoplasmic surface is necessary to increase endocytosis rate and decrease membrane-cytoskeleton adhesion. In parallel, we find that the level of phosphatidylinositol 4,5-bisphosphate (PIP2) in the plasma membrane is decreased and cytoplasmic Ca2+ is increased only by permeable amines. The time course of both the decrease in plasma membrane PIP2 and the rise in Ca2+ parallels the decrease in cytoskeleton-membrane adhesion. Inositol labeling shows that phosphatidylinositol-4-phosphate levels are increased by the permeable anesthetics, indicating that lipid turnover is increased. Consistent with previous observations, phospholipase C (PLC) inhibitors block anesthetic effects on the PIP2 and cytoplasmic Ca2+ levels, as well as the drop in adhesion. Therefore, we suggest that PLC activity is increased by amine anesthetics at the cytoplasmic surface of the plasma membrane, which results in a decrease in membrane-cytoskeleton adhesion.
Collapse
Affiliation(s)
- D Raucher
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
| | | |
Collapse
|
150
|
Tammi R, Rilla K, Pienimaki JP, MacCallum DK, Hogg M, Luukkonen M, Hascall VC, Tammi M. Hyaluronan enters keratinocytes by a novel endocytic route for catabolism. J Biol Chem 2001; 276:35111-22. [PMID: 11451952 DOI: 10.1074/jbc.m103481200] [Citation(s) in RCA: 190] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hyaluronan synthesized in the epidermis has an exceptionally short half-life, indicative of its catabolism by epidermal keratinocytes. An intracellular pool of endogenously synthesized hyaluronan, from 1 to 20 fg/cell, inversely related to cell density, was observed in cultured rat epidermal keratinocytes. More than 80% of the intracellular hyaluronan was small (<90 kDa). Approximately 25% of newly synthesized hyaluronan was endocytosed by the keratinocytes and had a half-life of 2-3 h. A biotinylated aggrecan G(1) domain/link protein probe demonstrated hyaluronan in small vesicles of approximately 100 nm diameter close to the plasma membrane, and in large vesicles and multivesicular bodies up to 1300 nm diameter around the nucleus. Hyaluronan did not co-localize with markers of lysosomes. However, inhibition of lysosomal acidification with NH(4)Cl or chloroquine, or treating the cells with the hyaluronidase inhibitor apigenin increased intracellular hyaluronan staining, suggesting that it resided in prelysosomal endosomes. Competitive displacement of hyaluronan from surface receptors using hyaluronan decasaccharides, resulted in a rapid disappearance of this endosomal hyaluronan (t(12) approximately 5 min), indicating its transitory nature. The ultrastructure of the hyaluronan-containing vesicles, co-localization with marker proteins for different vesicle types, and application of specific uptake inhibitors demonstrated that the formation of hyaluronan-containing vesicles did not involve clathrin-coated pits or caveolae. Treatment of rat epidermal keratinocytes with the OX50 monoclonal antibody against the hyaluronan receptor CD44 increased endosomal hyaluronan. However, no CD44-hyaluronan co-localization was observed intracellularly unless endosomal trafficking was retarded by monensin, or cultivation at 20 degrees C, suggesting CD44 recycling. Rat epidermal keratinocytes thus internalize a large proportion of their newly synthesized hyaluronan into non-clathrin-coated endosomes in a receptor mediated way, and rapidly transport it to slower degradation in the endosomal/lysosomal system.
Collapse
Affiliation(s)
- R Tammi
- Department of Anatomy, University of Kuopio, P. O. Box 1627, FIN-70211 Kuopio, Finland.
| | | | | | | | | | | | | | | |
Collapse
|