101
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Yu D, Cook MC, Shin D, Silva DG, Marshall J, Toellner K, Havran WL, Caroni P, Cooke MP, Morse HC, MacLennan ICM, Goodnow CC, Vinuesa CG. Axon growth and guidance genes identify T‐dependent germinal centre B cells. Immunol Cell Biol 2007; 86:3-14. [DOI: 10.1038/sj.icb.7100123] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Di Yu
- Division of Immunology and Genetics, John Curtin School of Medical Research, The Australian National UniversityCanberraAustralia
| | - Matthew C Cook
- Australian National University Medical SchoolCanberraAustralia
| | - Dong‐Mi Shin
- Laboratory of Immunopathology, National Institute of Allergy and Infectious Diseases, National Institute of HealthRockvilleMDUSA
| | - Diego G Silva
- Division of Immunology and Genetics, John Curtin School of Medical Research, The Australian National UniversityCanberraAustralia
| | - Jennifer Marshall
- MRC Centre for Immune Regulation, University of BirminghamBirminghamUK
| | | | - Wendy L Havran
- Department of Immunology, The Scripps Research InstituteLa JollaCAUSA
| | - Pico Caroni
- Friedrich Miescher InstituteBaselSwitzerland
| | - Michael P Cooke
- The Genomics Institute of the Novartis Research FoundationSan DiegoCAUSA
| | - Herbert C Morse
- Laboratory of Immunopathology, National Institute of Allergy and Infectious Diseases, National Institute of HealthRockvilleMDUSA
| | - Ian CM MacLennan
- MRC Centre for Immune Regulation, University of BirminghamBirminghamUK
| | - Christopher C Goodnow
- Division of Immunology and Genetics, John Curtin School of Medical Research, The Australian National UniversityCanberraAustralia
- Australian Phenomics FacilityCanberraACTAustralia
| | - Carola G Vinuesa
- Division of Immunology and Genetics, John Curtin School of Medical Research, The Australian National UniversityCanberraAustralia
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102
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Sengupta P, Hammond A, Holowka D, Baird B. Structural determinants for partitioning of lipids and proteins between coexisting fluid phases in giant plasma membrane vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:20-32. [PMID: 17936718 DOI: 10.1016/j.bbamem.2007.08.028] [Citation(s) in RCA: 177] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 08/15/2007] [Accepted: 08/20/2007] [Indexed: 12/11/2022]
Abstract
The structural basis for organizational heterogeneity of lipids and proteins underlies fundamental questions about the plasma membrane of eukaryotic cells. A current hypothesis is the participation of liquid ordered (Lo) membrane domains (lipid rafts) in dynamic compartmentalization of membrane function, but it has been difficult to demonstrate the existence of these domains in live cells. Recently, giant plasma membrane vesicles (GPMVs) obtained by chemically induced blebbing of cultured cells were found to phase separate into optically resolvable, coexisting fluid domains containing Lo-like and liquid disordered (Ld)-like phases as identified by fluorescent probes. In the present study, we used these GPMVs to investigate the structural bases for partitioning of selected lipids and proteins between coexisting Lo-like/Ld-like fluid phases in compositionally complex membranes. Our results with lipid probes show that the structure of the polar headgroups, in addition to acyl chain saturation, can significantly affect partitioning. We find that the membrane anchor of proteins and the aggregation state of proteins both significantly influence their distributions between coexisting fluid phases in these biological membranes. Our results demonstrate the value of GPMVs for characterizing the phase preference of proteins and lipid probes in the absence of detergents and other perturbations of membrane structure.
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Affiliation(s)
- Prabuddha Sengupta
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA
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103
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Tong J, Nguyen L, Vidal A, Simon SA, Skene JHP, McIntosh TJ. Role of GAP-43 in sequestering phosphatidylinositol 4,5-bisphosphate to Raft bilayers. Biophys J 2007; 94:125-33. [PMID: 17827240 PMCID: PMC2134862 DOI: 10.1529/biophysj.107.110536] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The lipid phosphatidylinositol 4,5-bisphosphate (PIP(2)) is critical for a number of physiological functions, and its presence in membrane microdomains (rafts) appears to be important for several of these spatially localized events. However, lipids like PIP(2) that contain polyunsaturated hydrocarbon chains are usually excluded from rafts, which are enriched in phospholipids (such as sphingomyelin) containing saturated or monounsaturated chains. Here we tested a mechanism by which multivalent PIP(2) molecules could be transferred into rafts through electrostatic interactions with polybasic cytoplasmic proteins, such as GAP-43, which bind to rafts via their acylated N-termini. We analyzed the interactions between lipid membranes containing raft microdomains and a peptide (GAP-43P) containing the linked N-terminus and the basic effector domain of GAP-43. In the absence or presence of nonacylated GAP-43P, PIP(2) was found primarily in detergent-soluble membranes thought to correspond to nonraft microdomains. However, when GAP-43P was acylated by palmitoyl coenzyme A, both the peptide and PIP(2) were greatly enriched in detergent-resistant membranes that correspond to rafts; acylation of GAP-43P changed the free energy of transfer of PIP(2) from detergent-soluble membranes to detergent-resistant membranes by -1.3 kcal/mol. Confocal microscopy of intact giant unilamellar vesicles verified that in the absence of GAP-43P PIP(2) was in nonraft microdomains, whereas acylated GAP-43P laterally sequestered PIP(2) into rafts. These data indicate that sequestration of PIP(2) to raft microdomains could involve interactions with acylated basic proteins such as GAP-43.
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Affiliation(s)
- Jihong Tong
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA
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104
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Levitan I, Gooch KJ. Lipid rafts in membrane-cytoskeleton interactions and control of cellular biomechanics: actions of oxLDL. Antioxid Redox Signal 2007; 9:1519-34. [PMID: 17576163 DOI: 10.1089/ars.2007.1686] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Membrane-cytoskeleton coupling is known to play major roles in a plethora of cellular responses, such as cell growth, differentiation, polarization, motility, and others. In this review, the authors discuss the growing amount of evidence indicating that membrane-cytoskeleton interactions are regulated by the lipid composition of the plasma membrane, suggesting that cholesterol-rich membrane domains (lipid rafts), including caveolae, are essential for membrane-cytoskeleton coupling. Several models for raft-cytoskeleton interactions are discussed. Also described is the evidence suggesting that raft-cytoskeleton interactions play key roles in several cytoskeleton-dependent processes, particularly in the regulation of cellular biomechanical properties. To address further the physiological significance of raft-cytoskeleton coupling, the authors focus on the impact of oxidized low density lipoproteins, one of the major cholesterol carriers and proatherogenic factors, on the integrity of lipid rafts/caveolae, and on the organization of the cytoskeleton. Finally, the authors review the recent studies showing that oxLDL and cholesterol depletion have similar impacts on the biomechanical properties of vascular endothelial cells, which in turn affect endothelial angiogenic potential.
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Affiliation(s)
- Irena Levitan
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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105
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Lu Y, Tian QB, Endo S, Suzuki T. A role for LRP4 in neuronal cell viability is related to apoE-binding. Brain Res 2007; 1177:19-28. [PMID: 17889837 DOI: 10.1016/j.brainres.2007.08.035] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Revised: 06/12/2007] [Accepted: 08/09/2007] [Indexed: 11/16/2022]
Abstract
The distribution pattern of apolipoprotein E (apoE) in cortical neurons in culture resembles that of low-density lipoprotein receptor-related protein 4 (LRP4). Both proteins are distributed in a punctate manner on the cell surface throughout neurons, including somas and dendrites. This finding prompted us to examine whether apoE is a ligand for LRP4 in the rat brain. ApoE and LRP4 from both Cos7 cells heterologous expressing LRP4 and brain homogenate were co-immunoprecipitated. We then examined the effect of antibody against the ligand-binding domain of LRP4 (anti-LB). Anti-LB applied to neuronal cells in culture down-regulated MAP2-immunoreactive neurons, reduced the viability of neurons and impaired synaptic structure. This effect was possibly due to a blockade of the binding of extraneuronal ligands, such as apoE/cholesterol, to LRP4 protein, since anti-LB suppressed binding of apoE to the LRP4 heterologously expressed in Cos7 cells. These results suggest that apoE is an endogenous ligand for LRP4 and may play a role as a receptor for extracellular signals, including those from glial cells, in the maintenance of the viability of neurons.
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Affiliation(s)
- Yonghao Lu
- Department of Neuroplasticity, Institute on Aging and Adaptation, Shinshu University Graduate School of Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan
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106
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Lázaro-Diéguez F, Colonna C, Cortegano M, Calvo M, Martínez SE, Egea G. Variable actin dynamics requirement for the exit of different cargo from thetrans-Golgi network. FEBS Lett 2007; 581:3875-81. [PMID: 17651738 DOI: 10.1016/j.febslet.2007.07.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 07/06/2007] [Accepted: 07/08/2007] [Indexed: 01/16/2023]
Abstract
Efficient post-Golgi trafficking depends on microtubules, but actin filaments and actin-associated proteins are also postulated. Here we examined, by inverse fluorescence recovery after photobleaching, the role of actin dynamics in the exit from the TGN of fluorescent-tagged apical or basolateral and raft or non-raft-associated cargoes. Either the actin-stabilizing jasplakinolide or the actin-depolymerising latrunculin B variably but significantly inhibited post-Golgi traffic of non-raft associated apical p75NTR and basolateral VSV-G cargoes. The TGN-exit of the apical-destined VSV-G mutant was impaired only by latrunculin B. Strikingly, the raft-associated GPI-anchor protein was not affected by either actin toxin. Results indicate that actin dynamics participates in the TGN egress of both apical- and basolateral-targeted proteins but is not needed for apical raft-associated cargo.
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Affiliation(s)
- Francisco Lázaro-Diéguez
- Departament de Biologia Cellular i Anatomia Patològica, Facultat de Medicina, Universitat de Barcelona, C/Casanova 143, E-08036 Barcelona, Spain
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107
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Sanxaridis PD, Cronin MA, Rawat SS, Waro G, Acharya U, Tsunoda S. Light-induced recruitment of INAD-signaling complexes to detergent-resistant lipid rafts in Drosophila photoreceptors. Mol Cell Neurosci 2007; 36:36-46. [PMID: 17689976 PMCID: PMC2034437 DOI: 10.1016/j.mcn.2007.05.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Revised: 05/19/2007] [Accepted: 05/31/2007] [Indexed: 12/01/2022] Open
Abstract
Here, we reveal a novel feature of the dynamic organization of signaling components in Drosophila photoreceptors. We show that the multi-PDZ protein INAD and its target proteins undergo light-induced recruitment to detergent-resistant membrane (DRM) rafts. Reduction of ergosterol, considered to be a key component of lipid rafts in Drosophila, resulted in a loss of INAD-signaling complexes associated with DRM fractions. Genetic analysis demonstrated that translocation of INAD-signaling complexes to DRM rafts requires activation of the entire phototransduction cascade, while constitutive activation of the light-activated channels resulted in recruitment of complexes to DRM rafts in the dark. Mutations affecting INAD and TRP showed that PDZ4 and PDZ5 domains of INAD, as well as the INAD-TRP interaction, are required for translocation of components to DRM rafts. Finally, selective recruitment of phosphorylated, and therefore activatable, eye-PKC to DRM rafts suggests that DRM domains are likely to function in signaling, rather than trafficking.
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Affiliation(s)
| | - Michelle A. Cronin
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA
| | - Satinder S. Rawat
- Program is Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA
| | - Girma Waro
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA
| | - Usha Acharya
- Program is Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA
| | - Susan Tsunoda
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA
- *Address correspondence to: Susan Tsunoda, Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, Telephone: 617-358-1756, FAX: 617-353-8484,
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108
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Holahan MR, Honegger KS, Tabatadze N, Routtenberg A. GAP-43 gene expression regulates information storage. Learn Mem 2007; 14:407-15. [PMID: 17554085 PMCID: PMC1896091 DOI: 10.1101/lm.581907] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Previous reports have shown that overexpression of the growth- and plasticity-associated protein GAP-43 improves memory. However, the relation between the levels of this protein to memory enhancement remains unknown. Here, we studied this issue in transgenic mice (G-Phos) overexpressing native, chick GAP-43. These G-Phos mice could be divided at the behavioral level into "spatial bright" and "spatial dull" groups based on their performance on two hidden platform water maze tasks. G-Phos dull mice showed both acquisition and retention deficits on the fixed hidden platform task, but were able to learn a visible platform task. G-Phos bright mice showed memory enhancement relative to wild type on the more difficult movable hidden platform spatial memory task. In the hippocampus, the G-Phos dull group showed a 50% greater transgenic GAP-43 protein level and a twofold elevated transgenic GAP-43 mRNA level than that measured in the G-Phos bright group. Unexpectedly, the dull group also showed an 80% reduction in hippocampal Tau1 staining. The high levels of GAP-43 seen here leading to memory impairment find its histochemical and behavioral parallel in the observation of Rekart et al. (Neuroscience 126: 579-584) who described elevated levels of GAP-43 protein in the hippocampus of Alzheimer's patients. The present data suggest that moderate overexpression of a phosphorylatable plasticity-related protein can enhance memory, while excessive overexpression may produce a "neuroplasticity burden" leading to degenerative and hypertrophic events culminating in memory dysfunction.
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Affiliation(s)
- Matthew R. Holahan
- Departments of Psychology and Neurobiology and Physiology in the Northwestern University Interdepartmental Neuroscience (NUIN) Program, Northwestern University, Evanston, Illinois 60208, USA
- Corresponding authors.E-mail ; fax (613) 520-3667.E-mail ; fax (847) 491-3557
| | - Kyle S. Honegger
- Departments of Psychology and Neurobiology and Physiology in the Northwestern University Interdepartmental Neuroscience (NUIN) Program, Northwestern University, Evanston, Illinois 60208, USA
| | - Nino Tabatadze
- Departments of Psychology and Neurobiology and Physiology in the Northwestern University Interdepartmental Neuroscience (NUIN) Program, Northwestern University, Evanston, Illinois 60208, USA
| | - Aryeh Routtenberg
- Departments of Psychology and Neurobiology and Physiology in the Northwestern University Interdepartmental Neuroscience (NUIN) Program, Northwestern University, Evanston, Illinois 60208, USA
- Corresponding authors.E-mail ; fax (613) 520-3667.E-mail ; fax (847) 491-3557
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109
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110
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Zakharov VV, Mosevitsky MI. M-calpain-mediated cleavage of GAP-43 near Ser41 is negatively regulated by protein kinase C, calmodulin and calpain-inhibiting fragment GAP-43-3. J Neurochem 2007; 101:1539-51. [PMID: 17326767 DOI: 10.1111/j.1471-4159.2007.04452.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Neuronal protein GAP-43 performs multiple functions in axon guidance, synaptic plasticity and regulation of neuronal death and survival. However, the molecular mechanisms of its action in these processes are poorly understood. We have shown that in axon terminals GAP-43 is a substrate for calcium-activated cysteine protease m-calpain, which participates in repulsion of axonal growth cones and induction of neuronal death. In pre-synaptic terminals in vivo, in synaptosomes, and in vitro, m-calpain cleaved GAP-43 in a small region near Ser41, on either side of this residue. In contrast, micro-calpain cleaved GAP-43 in vitro at several other sites, besides Ser41. Phosphorylation of Ser41 by protein kinase C or GAP-43 binding to calmodulin strongly suppressed GAP-43 proteolysis by m-calpain. A GAP-43 fragment, lacking about forty N-terminal residues (named GAP-43-3), was produced by m-calpain-mediated cleavage of GAP-43 and inhibited m-calpain, but not micro-calpain. This fragment prevented complete cleavage of intact GAP-43 by m-calpain as a negative feedback. GAP-43-3 also blocked m-calpain activity against casein, a model calpain substrate. This implies that GAP-43-3, which is present in axon terminals in high amount, can play important role in regulation of m-calpain activity in neurons. We suggest that GAP-43-3 and another (N-terminal) GAP-43 fragment produced by m-calpain participate in modulation of neuronal response to repulsive and apoptotic signals.
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Affiliation(s)
- Vladislav V Zakharov
- Division of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute of Russian Academy of Sciences, Gatchina, Leningrad District, Russia.
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111
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Abstract
The dissection of mechanisms that regulate glucose transport by insulin has revealed an intricate network of signaling molecules scattered from the insulin receptor to the intracellular glucose transporter GLUT4. It is also appreciated that some insulin receptor signals jaunt in different directions to regulate events essential for the efficient redistribution of GLUT4 to the plasma membrane. Moreover key assists in the process appear to be arranged by membrane lipids and cytoskeletal proteins. Following current considerations of insulin signals regulating GLUT4, this review will focus on in vitro and in vivo evidence that supports an essential role for phosphoinositides and actin filaments in the control of glucose transport. The discussion will visit recent cell culture, whole animal, and human data highlighting membrane and cytoskeletal aspects of insulin resistance.
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Affiliation(s)
- Joseph T Brozinick
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
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112
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Rajala RVS, Elliott MH, McClellan ME, Anderson RE. Localization of the insulin receptor and phosphoinositide 3-kinase in detergent-resistant membrane rafts of rod photoreceptor outer segments. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 572:491-7. [PMID: 17249614 DOI: 10.1007/0-387-32442-9_68] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Affiliation(s)
- Raju V S Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, USA.
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113
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Gómez-Moutón C, Mañes S. Establishment and maintenance of cell polarity during leukocyte chemotaxis. Cell Adh Migr 2007; 1:69-76. [PMID: 19329880 DOI: 10.4161/cam.1.2.4547] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The term polarity refers to the differential distribution of the macromolecular elements of a cell, resulting in its asymmetry in function, shape and/or content. Polarity is a fundamental property of all metazoan cells in at least some stages, and is pivotal to processes such as epithelial differentiation (apical/basal polarity), coordinated cell activity within the plane of a tissue (planar cell polarity), asymmetric cell division, and cell migration. In the last case, an apparently symmetric cell responds to directional cues provided by chemoattractants, creating a polarity axis that runs from the cell anterior, or leading edge, in which actin polymerization takes place, to the cell posterior (termed uropod in leukocytes), in which acto-myosin contraction occurs. Here we will review some of the molecular mechanisms through which chemoattractants break cell symmetry to trigger directed migration, focusing on cells of the immune system. We briefly highlight some common or apparently contradictory pathways reported as important for polarity in other cells, as this suggests conserved or cell type-specific mechanisms in eukaryotic cell chemotaxis.
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114
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Botto L, Masserini M, Palestini P. Changes in the composition of detergent-resistant membrane domains of cultured neurons following protein kinase C activation. J Neurosci Res 2007; 85:443-50. [PMID: 17086551 DOI: 10.1002/jnr.21111] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Changes in the composition of cell fractions, and in particular of detergent-resistant membranes (DRM) isolated from cultured rat cerebellar granule cells, were taken as possible changes in lipid raft composition during a signal transduction event. After activation of protein kinase C (PKC) with phorbol esters (PMA) or glutamate, the content of PKC and of proteins highly enriched (GAP43, Fyn, and PrP(c)) or not (MARCKS) in DRM was followed. PKC activation strongly increased its association with membranes (from 2% to 75%), causing its enrichment within DRM; the substrate GAP43, enriched in DRM, remained membrane associated, but its proportion in DRM dramatically decreased (from about 40% to 2.5%), suggesting its shift from raft to nonraft membranes, possibly as a consequence of phosphorylation by PKC. The distribution of Fyn and PrP(c) (DRM-enriched) and of MARCKS (present mainly outside DRM) did not change. PKC activation was followed by an increase of GAP43 and MARCKS phosphorylation (about 7- and 8-fold, respectively). Noteworthy was that, after cell treatment with the lipid raft-disrupting drug methyl-beta-cyclodextrin, PKC activation occurred normally, followed by MARCKS phosphorylation, but GAP43 phosphorylation did not occur. Taken altogether, these data suggest that the integrity of lipid rafts is necessary for PKC to affect GAP43 and catalyze its phosphorylation.
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Affiliation(s)
- L Botto
- Department of Experimental Medicine (DIMS), Medical School, University of Milano-Bicocca, Monza, Italy
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115
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Corbin JA, Evans JH, Landgraf KE, Falke JJ. Mechanism of specific membrane targeting by C2 domains: localized pools of target lipids enhance Ca2+ affinity. Biochemistry 2007; 46:4322-36. [PMID: 17367165 PMCID: PMC2896972 DOI: 10.1021/bi062140c] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The C2 domain is a ubiquitous, conserved protein signaling motif widely found in eukaryotic signaling proteins. Although considerable functional diversity exists, most C2 domains are activated by Ca2+ binding and then dock to a specific cellular membrane. The C2 domains of protein kinase Calpha (PKCalpha) and cytosolic phospholipase A2alpha (cPLA2alpha), for example, are known to dock to different membrane surfaces during an intracellular Ca2+ signal. Ca2+ activation targets the PKCalpha C2 domain to the plasma membrane and the cPLA2alpha C2 domain to the internal membranes, with no detectable spatial overlap. It is crucial to determine how such targeting specificity is achieved at physiological bulk Ca2+ concentrations that during a typical signaling event rarely exceed 1 muM. For the isolated PKCalpha C2 domain in the presence of physiological Ca2+ levels, the target lipids phosphatidylserine (PS) and phosphatidylinositol-4,5-bisphosphate (PIP2) are together sufficient to recruit the PKCalpha C2 domain to a lipid mixture mimicking the plasma membrane inner leaflet. For the cPLA2alpha C2 domain, the target lipid phosphatidylcholine (PC) appears to be sufficient to drive membrane targeting to an internal membrane mimic at physiological Ca2+ levels, although the results do not rule out a second, unknown target molecule. Stopped-flow kinetic studies provide additional information about the fundamental molecular events that occur during Ca2+-activated membrane docking. In principle, C2 domain-directed intracellular targeting, which requires coincidence detection of multiple signals (Ca2+ and one or more target lipids), can exhibit two different mechanisms: messenger-activated target affinity (MATA) and target-activated messenger affinity (TAMA). The C2 domains studied here both utilize the TAMA mechanism, in which the C2 domain Ca2+ affinity is too low to be activated by physiological Ca2+ signals in most regions of the cell. Only when the C2 domain nears its target membrane, which provides a high local concentration of target lipid, is the effective Ca2+ affinity increased by the coupled binding equilibrium to a level that enables substantial Ca2+ activation and target docking. Overall, the findings emphasize the importance of using physiological ligand concentrations in targeting studies because super-physiological concentrations can drive docking interactions even when an important targeting molecule is missing.
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Affiliation(s)
| | | | | | - Joseph J. Falke
- To whom correspondence should be addressed. Tel: 303-492-3597. Fax: 303-492-5894.
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116
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Holahan MR, Honegger KS, Routtenberg A. Expansion and retraction of hippocampal mossy fibers during postweaning development: strain-specific effects of NMDA receptor blockade. Hippocampus 2007; 17:58-67. [PMID: 17143904 DOI: 10.1002/hipo.20242] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We have recently discovered differences in the distribution of the mossy fiber terminal field (MFTF) between adult Long-Evans rats (LER) and Wistar rats(WR): the suprapyramidal MFTF extends into distal stratum oriens (dSO) in LER, but is nearly absent in WR (Holahan et al.,2006, Hippocampus 16:560-570). To our knowledge, there is no developmental evidence that sheds light on how this strain-dependent MFTF innervation in the adult is achieved. Accordingly, the present study examined the time course of MFTF development from postnatal days 0 to 40 and the effect of NMDA-receptor antagonist 3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP) on this developmental organization. In both LER and WR, a MFTF projection to dSO was observed between P18 and P21. By P24, the dSO projection in WR was no longer detectable whereas in LER, the dSO projection seen on P21 remained. We suggest that in WR a retraction of the MFTF projection from dSO to stratum lucidum between P21 and P24 leads to its adult pattern. In WR, CPP administration enhanced the dSO projection, possibly by blocking the retraction process. In LER, CPP administration reduced the dSO projection. Thus, in each strain, NMDA receptor blockade effectively reversed the developmental course of MFTF pattern of innervation. The present results lend strong support to the view that NMDA receptor regulation of input-dependent processes during development is of critical importance in promoting the motility and target selection of presynaptic MF axons. This regulation extends later into development than had previously been thought.
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Affiliation(s)
- Matthew R Holahan
- Department of Psychology, Northwestern University, Evanston, Illinois 60208, USA.
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117
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Jarquin-Pardo M, Fitzpatrick A, Galiano FJ, First EA, Davis JN. Phosphatidic acid regulates the affinity of the murine phosphatidylinositol 4-phosphate 5-kinase-Ibeta for phosphatidylinositol-4-phosphate. J Cell Biochem 2007; 100:112-28. [PMID: 16888807 DOI: 10.1002/jcb.21027] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Type I phosphatidylinositol 4-phosphate 5-kinase (PI4P5K) catalyzes the phosphorylation of phosphatidylinositol 4 phosphate [PI(4)P] at carbon 5, producing phosphatidylinositol 4,5 bisphosphate [PI(4,5)P2]. Phosphatidic acid (PA) activates PI4P5K in vitro and plays a central role in the activation of PIP5K pathways in vivo. This report demonstrates that actin fiber formation in murine fibroblasts involves PA activation of PIP5Ks and defines biochemical interactions between PA and the PIP5Ks. Inhibition of phospholipase D production of PA results in the loss of actin fibers. Overexpression of the beta isoform of the type I murine phosphatidylinositol 4-phosphate 5-kinase (mPIP5K-Ibeta) maintains actin fiber structure in the face of phospholipase D inhibition. PA activates mPIP5K-Ibeta by direct binding to mPIP5K-Ibeta through both electrostatic and hydrophobic interactions, with the fatty acid acyl chain length and degree of saturation acting as critical determinants of binding and activation. Furthermore, kinetic analysis suggests that phosphorylation of the PI(4)P substrate does not follow classical Michaelis-Menten kinetics. Instead, the kinetic data are consistent with a model in which mPIP5K-Ibeta initially binds to the lipid micelle and subsequently binds the PI(4)P substrate. In addition, the kinetics indicate substrate inhibition, suggesting that mPIP5K-Ibeta contains an inhibitory PI(4)P-binding site. These results suggest a model in which mPIP5K-Ibeta is surrounded by PI(4)P, but is unable to catalyze its conversion to PI(4,5)P2 unless PA is bound.
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Affiliation(s)
- Marta Jarquin-Pardo
- Feist-Weiller Cancer Center and Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, Louisiana 71130-3932, USA
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118
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Raivich G, Makwana M. The making of successful axonal regeneration: Genes, molecules and signal transduction pathways. ACTA ACUST UNITED AC 2007; 53:287-311. [PMID: 17079020 DOI: 10.1016/j.brainresrev.2006.09.005] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Revised: 09/12/2006] [Accepted: 09/18/2006] [Indexed: 12/16/2022]
Abstract
Unlike its central counterpart, the peripheral nervous system is well known for its comparatively good potential for regeneration following nerve fiber injury. This ability is mirrored by the de novo expression or upregulation of a wide variety of molecules including transcription factors, growth-stimulating substances, cell adhesion molecules, intracellular signaling enzymes and proteins involved in regulating cell-surface cytoskeletal interactions, that promote neurite outgrowth in cultured neurons. However, their role in vivo is less known. Recent studies using neutralizing antibodies, gene inactivation and overexpression techniques have started to shed light on those endogenous molecules that play a key role in axonal outgrowth and the process of successful functional repair in the injured nervous system. The aim of the current review is to provide a summary on this rapidly growing field and the experimental techniques used to define the specific effects of candidate signaling molecules on axonal regeneration in vivo.
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Affiliation(s)
- Gennadij Raivich
- Perinatal Brain Repair Group, Department of Obstetrics and Gynaecology, University College London, 86-96 Chenies Mews, London, UK.
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119
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Lou Y, Gou JY, Xue HW. PIP5K9, an Arabidopsis phosphatidylinositol monophosphate kinase, interacts with a cytosolic invertase to negatively regulate sugar-mediated root growth. THE PLANT CELL 2007; 19:163-81. [PMID: 17220200 PMCID: PMC1820962 DOI: 10.1105/tpc.106.045658] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Phosphatidylinositol monophosphate 5-kinase (PIP5K) plays an essential role in coordinating plant growth, especially in response to environmental factors. To explore the physiological function of PIP5K, we characterized Arabidopsis thaliana PIP5K9, which is constitutively expressed. We found that a T-DNA insertion mutant, pip5k9-d, which showed enhanced PIP5K9 transcript levels, had shortened primary roots owing to reduced cell elongation. Transgenic plants overexpressing PIP5K9 displayed a similar root phenotype. Yeast two-hybrid assays identified a cytosolic invertase, CINV1, that interacted with PIP5K9, and the physiological relevance of this interaction was confirmed by coimmunoprecipitation studies using plant extracts. CINV1-deficient plants, cinv1, had reduced activities of both neutral and acid invertases as well as shortened roots. Invertase activities in pip5k9-d seedlings were also reduced, suggesting a negative regulation of CINV1 by PIP5K9. In vitro studies showed that PIP5K9 interaction indeed repressed CINV1 activities. Genome-wide expression studies revealed that genes involved in sugar metabolism and multiple developmental processes were altered in pip5k9-d and cinv1, and the altered sugar metabolism in these mutants was confirmed by metabolite profiling. Together, our results indicate that PIP5K9 interacts with CINV1 to negatively regulate sugar-mediated root cell elongation.
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Affiliation(s)
- Ying Lou
- National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Science, Chinese Academy of Sciences, 200032 Shanghai, People's Republic of China
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120
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Allen JA, Halverson-Tamboli RA, Rasenick MM. Lipid raft microdomains and neurotransmitter signalling. Nat Rev Neurosci 2006; 8:128-40. [PMID: 17195035 DOI: 10.1038/nrn2059] [Citation(s) in RCA: 637] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Lipid rafts are specialized structures on the plasma membrane that have an altered lipid composition as well as links to the cytoskeleton. It has been proposed that these structures are membrane domains in which neurotransmitter signalling might occur through a clustering of receptors and components of receptor-activated signalling cascades. The localization of these proteins in lipid rafts, which is affected by the cytoskeleton, also influences the potency and efficacy of neurotransmitter receptors and transporters. The effect of lipid rafts on neurotransmitter signalling has also been implicated in neurological and psychiatric diseases.
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Affiliation(s)
- John A Allen
- Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, Chicago, Illinois, USA
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121
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Rossi F, Gianola S, Corvetti L. Regulation of intrinsic neuronal properties for axon growth and regeneration. Prog Neurobiol 2006; 81:1-28. [PMID: 17234322 DOI: 10.1016/j.pneurobio.2006.12.001] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Revised: 11/04/2006] [Accepted: 12/05/2006] [Indexed: 01/29/2023]
Abstract
Regulation of neuritic growth is crucial for neural development, adaptation and repair. The intrinsic growth potential of nerve cells is determined by the activity of specific molecular sets, which sense environmental signals and sustain structural extension of neurites. The expression and function of these molecules are dynamically regulated by multiple mechanisms, which adjust the actual growth properties of each neuron population at different ontogenetic stages or in specific conditions. The neuronal potential for axon elongation and regeneration are restricted at the end of development by the concurrent action of several factors associated with the final maturation of neurons and of the surrounding tissue. In the adult, neuronal growth properties can be significantly modulated by injury, but they are also continuously tuned in everyday life to sustain physiological plasticity. Strict regulation of structural remodelling and neuritic elongation is thought to be required to maintain specific patterns of connectivity in the highly complex mammalian CNS. Accordingly, procedures that neutralize such mechanisms effectively boost axon growth in both intact and injured nervous system. Even in these conditions, however, aberrant connections are only formed in the presence of unusual external stimuli or experience. Therefore, growth regulatory mechanisms play an essentially permissive role by setting the responsiveness of neural circuits to environmental stimuli. The latter exert an instructive action and determine the actual shape of newly formed connections. In the light of this notion, efficient therapeutic interventions in the injured CNS should combine targeted manipulations of growth control mechanisms with task-specific training and rehabilitation paradigms.
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Affiliation(s)
- Ferdinando Rossi
- Rita Levi Montalcini Centre for Brain Repair, Department of Neuroscience, University of Turin, Corso Raffaello 30, I-10125 Turin, Italy.
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122
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Honda ZI. Fcε- and Fcγ-receptor signaling in diseases. ACTA ACUST UNITED AC 2006; 28:365-75. [PMID: 17106671 DOI: 10.1007/s00281-006-0051-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 09/27/2006] [Indexed: 12/14/2022]
Abstract
It has become increasingly clear that receptors for the immunoglobulin Fc region play pivotal roles in immune homeostasis and disease. This review describes the fine regulation of the high-affinity IgE-receptor (FcepsilonRI) signaling, especially focusing on the early events that are coordinately regulated by Src family protein tyrosine kinases (PTKs), FcepsilonRI beta-subunit, and membrane lipid rafts. Because allergen-mediated FcepsilonRI cross-linking leads to the synthesis and release of a variety of proinflammatory mediators and cytokines, the duration and amplitude of the signal need to be strictly controlled, and the counterbalancing signaling is provided by specialized inhibitory receptors and molecules. However, recent work have revealed that Src family PTKs and FcepsilonRI beta-subunit transduce both positive and negative signaling with unexpectedly complex mechanisms. FcgammaRIIB exerts a unique inhibitory function on cell activation processes after the engagement of Fcgamma, FcepsilonRI and B cell receptors. Recent work has shown that FcgammaRIIB polymorphisms are associated with systemic lupus erythematosus, and that a transmembrane polymorphism in FcgammaRIIB results in an impaired distribution to lipid rafts and a reduced inhibitory function. Studies addressing the functions of disease-associated polymorphisms in the FcepsilonRI beta-subunit and low-affinity FcgammaRs are also considered.
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Affiliation(s)
- Zen-Ichiro Honda
- Department of Allergy and Rheumatology, Faculty of Medicine, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan,
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123
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Gorbatyuk VY, Nosworthy NJ, Robson SA, Bains NPS, Maciejewski MW, Dos Remedios CG, King GF. Mapping the Phosphoinositide-Binding Site on Chick Cofilin Explains How PIP2 Regulates the Cofilin-Actin Interaction. Mol Cell 2006; 24:511-22. [PMID: 17114056 DOI: 10.1016/j.molcel.2006.10.007] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 08/21/2006] [Accepted: 10/04/2006] [Indexed: 11/25/2022]
Abstract
Cofilin plays a key role in the choreography of actin dynamics via its ability to sever actin filaments and increase the rate of monomer dissociation from pointed ends. The exact manner by which phosphoinositides bind to cofilin and inhibit its interaction with actin has proven difficult to ascertain. We determined the structure of chick cofilin and used NMR chemical shift mapping and structure-directed mutagenesis to unambiguously locate its recognition site for phosphoinositides (PIs). This structurally unique recognition site requires both the acyl chain and head group of the PI for a productive interaction, and it is not inhibited by phosphorylation of cofilin. We propose that the interaction of cofilin with membrane-bound PIs abrogates its binding to both actin and actin-interacting protein 1, and facilitates spatiotemporal regulation of cofilin activity.
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Affiliation(s)
- Vitaliy Y Gorbatyuk
- Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA
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124
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Sánchez-Bautista S, Marín-Vicente C, Gómez-Fernández JC, Corbalán-García S. The C2 Domain of PKCα Is a Ca2+-dependent PtdIns(4,5)P2 Sensing Domain: A New Insight into an Old Pathway. J Mol Biol 2006; 362:901-14. [PMID: 16949603 DOI: 10.1016/j.jmb.2006.07.093] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2006] [Revised: 07/25/2006] [Accepted: 07/26/2006] [Indexed: 11/28/2022]
Abstract
The C2 domain is a targeting domain that responds to intracellular Ca2+ signals in classical protein kinases (PKCs) and mediates the translocation of its host protein to membranes. Recent studies have revealed a new motif in the C2 domain, named the lysine-rich cluster, that interacts with acidic phospholipids. The purpose of this work was to characterize the molecular mechanism by which PtdIns(4,5)P2 specifically interacts with this motif. Using a combination of isothermal titration calorimetry, fluorescence resonance energy transfer and time-lapse confocal microscopy, we show here that Ca2+ specifically binds to the Ca2+ -binding region, facilitating PtdIns(4,5)P2 access to the lysine-rich cluster. The magnitude of PtdIns(4,5)P2 binding is greater than in the case of other polyphosphate phosphatidylinositols. Very importantly, the residues involved in PtdIns(4,5)P2 binding are essential for the plasma membrane localization of PKCalpha when RBL-2H3 cells are stimulated through their IgE receptors. Additionally, CFP-PH and CFP-C1 domains were used as bioprobes to demonstrate the co-existence of PtdIns(4,5)P2 and diacylglycerol in the plasma membrane, and it was shown that although a fraction of PtdIns(4,5)P2 is hydrolyzed to generate diacylglycerol and IP3, an important amount still remains in the membrane where it is available to activate PKCalpha. These findings entail revision of the currently accepted model of PKCalpha recruitment to the membrane and its activation.
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Affiliation(s)
- Sonia Sánchez-Bautista
- Departamento de Bioquímica y Biología Molecular (A), Facultad de Veterinaria, Universidad de Murcia Apartado de Correos 4021, E-30100-Murcia, Spain
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125
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Santarius M, Lee C, Anderson R. Supervised membrane swimming: small G-protein lifeguards regulate PIPK signalling and monitor intracellular PtdIns(4,5)P2 pools. Biochem J 2006; 398:1-13. [PMID: 16856876 PMCID: PMC1525017 DOI: 10.1042/bj20060565] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Regulation of PIPK (phosphatidylinositol phosphate kinase) and PtdIns(4,5)P2 signalling by small G-proteins and their effectors is key to many biological functions. Through selective recruitment and activation of different PIPK isoforms, small G-proteins such as Rho, Rac and Cdc42 modulate actin dynamics and cytoskeleton-dependent cellular events in response to extracellular signalling. These activities affect a number of processes, including endocytosis, bacterial penetration into host cells and cytolytic granule-mediated targeted cell killing. Small G-proteins and their modulators are also regulated by phosphoinositides through translocation and conformational changes. Arf family small G-proteins act at multiple sites as regulators of membrane trafficking and actin cytoskeletal remodelling, and regulate a feedback loop comprising phospholipase D, phosphatidic acid, PIPKs and PtdIns(4,5)P2, contributing to enhancement of PtdIns(4,5)P2-mediated cellular events and receptor signalling. Na+, Kir (inwardly rectifying K+), Ca2+ and TRP (transient receptor potential) ion channels are regulated by small G-proteins and membrane pools of PtdIns(4,5)P2. Yeast phosphatidylinositol 4-phosphate 5-kinases Mss4 and Its3 are involved in resistance against disturbance of sphingolipid biosynthesis and maintenance of cell integrity through the synthesis of PtdIns(4,5)P2 and downstream signalling through the Rom2/Rho2 and Rgf1/Rho pathways. Here, we review models for regulated intracellular targeting of PIPKs by small G-proteins and other modulators in response to extracellular signalling. We also describe the spatial and temporal cross-regulation of PIPKs and small G-proteins that is critical for a number of cellular functions.
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Affiliation(s)
- Megan Santarius
- *Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison, 1300 University Avenue, Madison, WI 53706, U.S.A
| | - Chang Ho Lee
- †Department of Pharmacology, College of Medicine, Hanyang University, 17 Hengdang-dong, Seongdong-ku, Seoul, 133-791, South Korea
- To whom correspondence should be addressed (email )
| | - Richard A. Anderson
- *Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison, 1300 University Avenue, Madison, WI 53706, U.S.A
- ‡Department of Pharmacology, University of Wisconsin Medical School, 1300 University Avenue, Madison, WI 53706, U.S.A
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126
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Di Giovanni S. Regeneration following spinal cord injury, from experimental models to humans: where are we? Expert Opin Ther Targets 2006; 10:363-76. [PMID: 16706677 DOI: 10.1517/14728222.10.3.363] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Regeneration in the adult CNS following injury is extremely limited. Traumatic spinal cord injury causes a permanent neurological deficit followed by a very limited recovery due to failed regeneration attempts. In fact, it is now clear that the spinal cord intrinsically has the potential to regenerate, but cellular loss and the presence of an inhibitory environment strongly limit tissue regeneration and functional recovery. The molecular mechanisms responsible for failed regeneration are starting to be unveiled. This gain in knowledge led to the design of therapeutic strategies aimed to limit the tissue scar, to enhance the proregeneration versus the inhibitory environment, and to replace tissue loss, including the use of stem cells. They have been very successful in several animal models, although results are still controversial in humans. Nonetheless, novel experimental approaches hold great promise for use in humans.
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Affiliation(s)
- Simone Di Giovanni
- Laboratory for NeuroRegeneration and Repair, University of Tuebingen, Hertie-Institute for Clinical Brain Research, D-72076 Tuebingen, Germany.
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127
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Takeda S, Saitoh A, Furuta M, Satomi N, Ishino A, Nishida G, Sudo H, Hotani H, Takiguchi K. Opening of holes in liposomal membranes is induced by proteins possessing the FERM domain. J Mol Biol 2006; 362:403-13. [PMID: 16934293 DOI: 10.1016/j.jmb.2006.07.071] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Revised: 07/19/2006] [Accepted: 07/27/2006] [Indexed: 11/18/2022]
Abstract
The destabilization of vesicles caused by interactions between lipid bilayers and proteins was studied by direct, real-time observation using high-intensity dark-field microscopy. We previously reported that talin, a cytoskeletal submembranous protein, can reversibly open stable large holes in giant liposomes made of neutral and acidic phospholipids. Talin and other proteins belonging to the band 4.1 superfamily have the FERM domain at their N-terminal and interact with lipid membranes via that domain. Here, we observed that band 4.1, ezrin and moesin, members of the band 4.1 superfamily, are also able to open stable holes in liposomes. However, truncation of their C-terminal domains, which can interact with the N-terminal FERM domain, impaired their hole opening activities. Oligomeric states of ezrin affected the capability of the membrane hole formation. Phosphatidylinositol bisphosphate (PIP2), which binds to the FERM domain and disrupts the interaction between the N and C termini of the band 4.1 superfamily, down-regulates their membrane opening activity. These results suggest that the intermolecular interaction plays a key role in the observed membrane hole formation.
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Affiliation(s)
- Shuichi Takeda
- Department of Molecular Biology, School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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128
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Allen-Vercoe E, Waddell B, Livingstone S, Deans J, DeVinney R. Enteropathogenic Escherichia coli Tir translocation and pedestal formation requires membrane cholesterol in the absence of bundle-forming pili. Cell Microbiol 2006; 8:613-24. [PMID: 16548887 DOI: 10.1111/j.1462-5822.2005.00654.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Enteropathogenic Escherichia coli (EPEC) is a significant cause of paediatric diarrhoea worldwide. Virulence requires adherence to intestinal epithelial cells, mediated in part through type IV bundle-forming pili (BFP), and the EPEC protein Tir. Tir is inserted into the enterocyte plasma membrane (PM), resulting in the formation of actin-rich pedestals. Tir is translocated by the type III secretion system (TTSS), through a pore comprised of EPEC proteins inserted into the PM. Here, we demonstrate that in the absence of BFP, EPEC adherence, effector translocation and pedestal formation are dependent on lipid rafts. Lipid raft disruption using methyl-beta-cyclodextrin (MbetaCD) decreased adherence by an EPEC BFP-deficient strain from 85% to 1%. Translocation of the effectors Tir and EspF was blocked by MbetaCD treatment, although the TTSS pore still formed. MbetaCD treatment after Tir delivery decreased pedestal formation by EPEC from 40% to 5%, but not by the related pathogen E. coli O157:H7 which uses a different Tir-based mechanism. In contrast, EPEC expressing the BFP can circumvent the requirement for membrane cholesterol. This suggests that lipid rafts play a role in virulence of this medically important pathogen.
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Affiliation(s)
- Emma Allen-Vercoe
- University of Calgary Health Sciences Centre, Department of Microbiology and Infectious Diseases, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
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129
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Li S, Carmichael ST. Growth-associated gene and protein expression in the region of axonal sprouting in the aged brain after stroke. Neurobiol Dis 2006; 23:362-73. [PMID: 16782355 DOI: 10.1016/j.nbd.2006.03.011] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2005] [Revised: 02/27/2006] [Accepted: 03/31/2006] [Indexed: 01/30/2023] Open
Abstract
Aged individuals exhibit reduced functional recovery after stroke. We examined the expression profile in aged animals of a recently identified group of growth-associated genes that underlies post-stroke axonal sprouting in the young adult. Basal levels of most growth-promoting genes are higher in aged cortex compared with young adult, and are further induced after stroke. Compared with the young adult, these genes are induced at later time points after stroke. For growth-inhibitory molecules, myelin-associated glycoprotein and ephrin A5 are uniquely induced in the aged brain; chondroitin sulfate proteoglycans and oligodendrocyte myelin glycoprotein are induced at earlier time points; and Nogo-A, semaphorin IIIa and NG2 decline in aged vs. young adult after stroke. The aged brain does not simply have a reduction in growth-associated molecules after stroke, but a completely unique molecular profile of post-stroke axonal sprouting.
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Affiliation(s)
- Songlin Li
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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130
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McIntosh TJ, Simon SA. ROLES OF BILAYER MATERIAL PROPERTIES IN FUNCTION AND DISTRIBUTION OF MEMBRANE PROTEINS. ACTA ACUST UNITED AC 2006; 35:177-98. [PMID: 16689633 DOI: 10.1146/annurev.biophys.35.040405.102022] [Citation(s) in RCA: 200] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Structural, compositional, and material (elastic) properties of lipid bilayers exert strong influences on the interactions of water-soluble proteins and peptides with membranes, the distribution of transmembrane proteins in the plane of the membrane, and the function of specific membrane channels. Theoretical and experimental studies show that the binding of either cytoplasmic proteins or extracellular peptides to membranes is regulated by the presence of charged lipids and that the sorting of transmembrane proteins into or out of membrane microdomains (rafts) depends on several factors, including bilayer material properties governed by the presence of cholesterol. Recent studies have also shown that bilayer material properties modify the permeability of membrane pores, formed either by protein channels or by cell-lytic peptides.
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Affiliation(s)
- Thomas J McIntosh
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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131
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Golebiewska U, Gambhir A, Hangyás-Mihályné G, Zaitseva I, Rädler J, McLaughlin S. Membrane-bound basic peptides sequester multivalent (PIP2), but not monovalent (PS), acidic lipids. Biophys J 2006; 91:588-99. [PMID: 16648167 PMCID: PMC1483118 DOI: 10.1529/biophysj.106.081562] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Several biologically important peripheral (e.g., myristoylated alanine-rich C kinase substrate) and integral (e.g., the epidermal growth factor receptor) membrane proteins contain clusters of basic residues that interact with acidic lipids in the plasma membrane. Previous measurements demonstrate that the polyvalent acidic lipid phosphatidylinositol 4,5-bisphosphate is bound electrostatically (i.e., sequestered) by membrane-adsorbed basic peptides corresponding to these clusters. We report here three experimental observations that suggest monovalent acidic lipids are not sequestered by membrane-bound basic peptides. 1), Binding of basic peptides to vesicles does not decrease when the temperature is lowered below the fluid-to-gel phase transition. 2), The binding energy of Lys-13 to lipid vesicles increases linearly with the fraction of monovalent acidic lipids. 3), Binding of basic peptides to vesicles produces no self-quenching of fluorescent monovalent acidic lipids. One potential explanation for these results is that membrane-bound basic peptides diffuse too rapidly for the monovalent lipids to be sequestered. Indeed, our fluorescence correlation spectroscopy measurements show basic peptides bound to phosphatidylcholine/phosphatidylserine membranes have a diffusion coefficient approximately twofold higher than that of lipids, and those bound to phosphatidylcholine/phosphatidylinositol 4,5-bisphosphate membranes have a diffusion coefficient comparable to that of lipids.
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Affiliation(s)
- Urszula Golebiewska
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794-8661, USA
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132
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Guerriero CJ, Weixel KM, Bruns JR, Weisz OA. Phosphatidylinositol 5-kinase stimulates apical biosynthetic delivery via an Arp2/3-dependent mechanism. J Biol Chem 2006; 281:15376-84. [PMID: 16601114 DOI: 10.1074/jbc.m601239200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The mechanisms by which polarized epithelial cells target distinct carriers enriched in newly synthesized proteins to the apical or basolateral membrane remain largely unknown. Here we investigated the effect of phosphatidylinositol metabolism and modulation of the actin cytoskeleton, two regulatory mechanisms that have individually been suggested to function in biosynthetic traffic, on polarized traffic in Madin-Darby canine kidney cells. Overexpression of phosphatidylinositol 5-kinase (PI5K) increased actin comet frequency in Madin-Darby canine kidney cells and concomitantly stimulated trans-Golgi network (TGN) to apical membrane delivery of the raft-associated protein influenza hemagglutinin (HA), but did not affect delivery of a non-raft-associated apical protein or a basolateral marker. Modulation of actin comet formation by pharmacologic means, by overexpression of the TGN-localized inositol polyphosphate 5-phosphatase Ocrl, or by blockade of Arp2/3 function had parallel effects on the rate of apical delivery of HA. Moreover, HA released from a TGN block was colocalized in transport carriers in association with PI5K and actin comets. Inhibition of Arp2/3 function in combination with microtubule depolymerization led to a virtual block in HA delivery, suggesting synergistic coordination of these cytoskeletal assemblies in membrane transport. Our results suggest a previously unidentified role for actin comet-mediated propulsion in the biosynthetic delivery of a subset of apical proteins.
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Affiliation(s)
- Christopher J Guerriero
- Laboratory of Epithelial Cell Biology, Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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133
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Milosevic I, Sørensen JB, Lang T, Krauss M, Nagy G, Haucke V, Jahn R, Neher E. Plasmalemmal phosphatidylinositol-4,5-bisphosphate level regulates the releasable vesicle pool size in chromaffin cells. J Neurosci 2006; 25:2557-65. [PMID: 15758165 PMCID: PMC6725155 DOI: 10.1523/jneurosci.3761-04.2005] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
During exocytosis, certain phospholipids may act as regulators of secretion. Here, we used several independent approaches to perturb the phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] level in bovine chromaffin cells to investigate how changes of plasmalemmal PI(4,5)P2 affect secretion. Membrane levels of PI(4,5)P2 were estimated by analyzing images of lawns of plasma membranes labeled with fluorescent probes specific for PI(4,5)P2. The specific PI(4,5)P2 signal was enriched in submicrometer-sized clusters. In parallel patch-clamp experiments on intact cells, we measured the secretion of catecholamines. Overexpression of phosphatidylinositol-4-phosphate-5-kinase I, or infusion of PI(4,5)P2 through the patch pipette, increased the PI(4,5)P2 level in the plasma membrane and potentiated secretion. Expression of a membrane-targeted inositol 5-phosphatase domain of synaptojanin 1 eliminated PI(4,5)P2 from the membrane and abolished secretion. An inhibitor of phosphatidylinositol-3 kinase, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one, led to a transient increase in the PI(4,5)P2 level that was associated with a potentiation of secretion. After prolonged incubation, the level of PI(4,5)P2 decreased and secretion was inhibited. Kinetic analysis showed that changes in PI(4,5)P2 levels led to correlated changes in the size of two releasable vesicle pools, whereas their fusion kinetics remained unaffected. We conclude that during both short- and long-term manipulations of PI(4,5)P2 level secretion scales with plasma membrane PI(4,5)P2 content and that PI(4,5)P2 has an early effect on secretion by regulating the number of vesicles ready for release.
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Affiliation(s)
- Ira Milosevic
- Department of Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
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134
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Paden CM, Watt JA, Selong TH, Paterson CL, Cranston HJ. The neuronal growth-associated protein (GAP)-43 is expressed by corticotrophs in the rat anterior pituitary after adrenalectomy. Endocrinology 2006; 147:952-8. [PMID: 16269460 DOI: 10.1210/en.2005-0715] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The neuronal growth-associated protein (GAP)-43 has been localized in both long fibers and punctate clusters by immunocytochemistry within the rat anterior pituitary (AP). After adrenalectomy (ADX), GAP-43 immunoreactivity (GAP-43-ir) is greatly increased and is associated with corticotrophs at the light microscopic level. We have undertaken an electron microscopic study to determine the cellular localization of GAP-43 in the post-ADX AP. Using preembedding immunocytochemistry, we found GAP-43-ir localized exclusively to the cytoplasmic surface of the plasmalemma within a subset of endocrine cells with ultrastructure typical of degranulated corticotrophs at 4 d after ADX. We combined preembedding immunoelectron microscopy for GAP-43 with immunogold labeling for ACTH and found that GAP-43-ir was invariably present only in cells containing ACTH-positive granules. The density of GAP-43-ir was highest within extensive processes emanating from the soma, suggesting that these processes are the basis for the punctate clusters of GAP-43 staining seen surrounding corticotrophs in the light microscope. We also observed rare synaptic-like contacts between GAP-43-ir processes and distant cell bodies. GAP-43 mRNA was detected in extracts of the AP 4 d after ADX using RT-PCR, and quantitative PCR confirmed that GAP-43 mRNA was significantly up-regulated in the AP in response to ADX. We postulate that increased expression of GAP-43 may stimulate process outgrowth and intercellular communication by activated corticotrophs.
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Affiliation(s)
- Charles M Paden
- Department of Cell Biology and Neuroscience, 513 Leon Johnson Hall, Montana State University, Bozeman, 59717-3148, USA.
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135
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Bulotta S, Cerullo A, Barsacchi R, De Palma C, Rotiroti D, Clementi E, Borgese N. Endothelial nitric oxide synthase is segregated from caveolin-1 and localizes to the leading edge of migrating cells. Exp Cell Res 2006; 312:877-89. [PMID: 16427620 DOI: 10.1016/j.yexcr.2005.12.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Revised: 11/04/2005] [Accepted: 12/02/2005] [Indexed: 11/28/2022]
Abstract
The enzyme endothelial Nitric Oxide Synthase (eNOS) is involved in key physiological and pathological processes, including cell motility and apoptosis. It is widely believed that at the cell surface eNOS is localized in caveolae, where caveolin-1 negatively regulates its activity, however, there are still uncertainties on its intracellular distribution. Here, we applied high resolution confocal microscopy to investigate the surface distribution of eNOS in transfected HeLa cells and in human umbilical vein endothelial cells (HUVEC) endogenously expressing the enzyme. In confluent and non-confluent HUVEC and HeLa cells, we failed to detect substantial colocalization between eNOS and caveolin-1 at the cell surface. Instead, in non-confluent cells, eNOS was concentrated in ruffles and at the leading edge of migrating cells, colocalizing with actin filaments and with the raft marker ganglioside G(M1), and well segregated from caveolin-1, which was restricted to the posterior region of the cells. Treatments that disrupted microfilaments caused loss of eNOS from the cell surface and decreased Ca(2+)-stimulated activity, suggesting a role of the cytoskeleton in the localization and function of the enzyme. Our results provide a morphological correlate for the role of eNOS in cell migration and raise questions on the site of interaction between eNOS and caveolin-1.
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Affiliation(s)
- Stefania Bulotta
- Department of Pharmaco-Biological Science, University of Catanzaro Magna Graecia, 88021 Catanzaro, Italy
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136
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Abstract
Eukaryotic cells have systems of internal organelles to synthesize lipids and membrane proteins, to release secreted proteins, to take up nutrients and to degrade membrane-bound and internalized molecules. Proteins and lipids move from organelle to organelle using transport vesicles. The accuracy of this traffic depends upon organelles being correctly recognized. In general, organelles are identified by the activated GTPases and specific lipid species that they display. These short-lived determinants provide organelles with an identity that is both unique and flexible. Recent studies have helped to establish how cells maintain and restrict these determinants and explain how this system is exploited by invading pathogens.
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Affiliation(s)
- Rudy Behnia
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
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137
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Carlton JG, Cullen PJ. Coincidence detection in phosphoinositide signaling. Trends Cell Biol 2005; 15:540-7. [PMID: 16139503 PMCID: PMC1904488 DOI: 10.1016/j.tcb.2005.08.005] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Revised: 07/06/2005] [Accepted: 08/19/2005] [Indexed: 11/20/2022]
Abstract
Phosphoinositide lipids function as both signaling molecules and as compartment-specific localization signals for phosphoinositide-binding proteins. In recent years, both phosphoinositides and phosphoinositide-binding proteins have been reported to display a restricted, rather than a uniform, distribution across intracellular membranes. Here, we examine recent data documenting the restricted distribution of both phosphoinositides and phosphoinositide-binding proteins and examine how phosphoinositide-binding proteins might engage multiple binding partners to achieve these restricted localizations, effectively acting as detectors of coincident localization signals.
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138
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Gasque G, Labarca P, Darszon A. Cholesterol-depleting compounds modulate K+-currents in Drosophila Kenyon cells. FEBS Lett 2005; 579:5129-34. [PMID: 16154131 DOI: 10.1016/j.febslet.2005.08.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Revised: 08/10/2005] [Accepted: 08/11/2005] [Indexed: 11/16/2022]
Abstract
Sterol-enriched lipid rafts have been involved in Drosophila membrane signalling such as Hedgehog targeting and glutamate receptor ligand-affinity regulation. Here, we show that the voltage-dependent K(+) currents expressed by the intrinsic neurons of the Mushroom bodies are upward-modulated by compounds that remove sterols from the plasma membrane. Modulation seems to rely on a fast-exchanging sterol-pool, which more strongly affects the slowly inactivating current. Our results provide the first evidence that sterols influence the operation of voltage-gated ion channels in Drosophila neurons and strengthen the importance of lipid rafts in this biological model.
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Affiliation(s)
- Gabriel Gasque
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad 2001, Colonia Chamilpa, Cuernavaca, Morelos 62210, México
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139
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Gokhale NA, Abraham A, Digman MA, Gratton E, Cho W. Phosphoinositide specificity of and mechanism of lipid domain formation by annexin A2-p11 heterotetramer. J Biol Chem 2005; 280:42831-40. [PMID: 16230353 DOI: 10.1074/jbc.m508129200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Annexin A2 is a phospholipid-binding protein that forms a heterotetramer (annexin II-p11 heterotetramer; A2t) with p11 (S100A10). It has been reported that annexin A2 is involved in binding to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) and in inducing membrane microdomain formation. To understand the mechanisms underlying these findings, we determined the membrane binding properties of annexin A2 wild type and mutants both as monomer and as A2t. Our results from surface plasmon resonance analysis showed that A2t and annexin A2 has modest selectivity for PtdIns(4,5)P2 over other phosphoinositides, which is conferred by conserved basic residues, including Lys279 and Lys281, on the convex surface of annexin A2. Fluorescence microscopy measurements using giant unilamellar vesicles showed that A2t of wild type, but not (K279A)2-(p11)2 or (K281A)2-(p11)2, specifically induced the formation of 1-microm-sized PtdIns(4,5)P2 clusters, which were stabilized by cholesterol. Collectively, these studies elucidate the structural determinant of the PtdIns(4,5)P2 selectivity of A2t and suggest that A2t may be involved in the regulation of PtdIns(4,5)P2 clustering in the cell.
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Affiliation(s)
- Nikhil A Gokhale
- Department of Chemistry, University of Illinois, Chicago, Illinois 60607-7061, USA
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140
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Ashton AC, Ushkaryov YA. Properties of synaptic vesicle pools in mature central nerve terminals. J Biol Chem 2005; 280:37278-88. [PMID: 16148008 DOI: 10.1074/jbc.m504137200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Readily releasable and reserve pools of synaptic vesicles play different roles in neurotransmission, and it is important to understand their recycling and interchange in mature central synapses. Using adult rat cerebrocortical synaptosomes, we have shown that 100 mosm hypertonic sucrose caused complete exocytosis of only the readily releasable pool (RRP) of synaptic vesicles containing glutamate or gamma-aminobutyric acid. Repetitive hypertonic stimulations revealed that this pool recycled (and reloaded the neurotransmitter from the cytosol) fully in <30 s and did so independently of the reserve pool. Multiple rounds of exocytosis could occur in the constant absence of extracellular Ca(2+). However, although each vesicle cycle includes a Ca(2+)-independent exocytotic step, some other stage(s) critically require an elevation of cytosolic [Ca(2+)], and this is supplied by intracellular stores. Repetitive recycling also requires energy, but not the activity of phosphatidylinositol 4-kinase, which maintains the normal level of phosphoinositides. By varying the length of hypertonic stimulations, we found that approximately 70% of the RRP vesicles fused completely with the plasmalemma during exocytosis and could then enter silent pools, probably outside active zones. The rest of the RRP vesicles underwent very fast local recycling (possibly by kiss-and-run) and did not leave active zones. Forcing the fully fused RRP vesicles into the silent pool enabled us to measure the transfer of reserve vesicles to the RRP and to show that this process requires intact phosphatidylinositol 4-kinase and actin microfilaments. Our findings also demonstrate that respective vesicle pools have similar characteristics and requirements in excitatory and inhibitory nerve terminals.
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Affiliation(s)
- Anthony C Ashton
- Department of Biological Sciences, Imperial College London, London SW7 2AZ, United Kingdom
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141
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Frêche B, Guillaumot P, Charmetant J, Pelletier L, Luquain C, Christiansen D, Billaud M, Manié SN. Inducible dimerization of RET reveals a specific AKT deregulation in oncogenic signaling. J Biol Chem 2005; 280:36584-91. [PMID: 16123037 DOI: 10.1074/jbc.m505707200] [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
Dominant-activating mutations in the RET (rearranged during transfection) proto-oncogene, a receptor tyrosine kinase, are causally associated with the development of multiple endocrine neoplasia type 2A (MEN2A) syndrome. Such oncogenic RET mutations induce its ligand-independent constitutive activation, but whether it spreads identical signaling to ligand-induced signaling is uncertain. To address this question, we designed a cellular model in which RET can be activated either by its natural ligand, or alternatively, by controlled dimerization of the protein that mimics MEN2A dimerization. We have shown that controlled dimerization leaves proximal RET signaling intact but impacts substantially on the tuning of the distal AKT kinase activation (delayed and sustained). In marked contrast, distal activation of ERK remained unaffected. We further demonstrated that specific temporal adjustment of ligand-induced AKT activation is dependent upon a lipid-based cholesterol-sensitive environment, and this control step is bypassed by MEN2A RET mutants. Therefore, these studies revealed that MEN2A mutations propagate previously unappreciated subtle differences in signaling pathways and unravel a role for lipid rafts in the temporal regulation of AKT activation.
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Affiliation(s)
- Barbara Frêche
- Laboratoire de Génétique moléculaire, Signalisation et Cancer, Unité Mixte de Recherche (UMR) 5201, Facultéde Médecine, 8 avenue Rockefeller, 69 373 LYON Cedex 08, France
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142
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Abstract
Peripheral nerve injury is normally followed by a robust regenerative response. Here we describe the early changes associated with injury from the initial rise in intracellular calcium and the subsequent activation of transcription factors and cytokines leading to an inflammatory reaction, and the expression of growth factors, cytokines, neuropeptides, and other secreted molecules involved in cell-to-cell communication promoting regeneration and neurite outgrowth. The aim of this review is to summarize the molecular mechanisms that play a part in executing successful regeneration.
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Affiliation(s)
- Milan Makwana
- Centre for Perinatal Brain Protection & Repair, Department of Obstetrics and Gynaecology, University College London, UK
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143
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Carmichael ST, Archibeque I, Luke L, Nolan T, Momiy J, Li S. Growth-associated gene expression after stroke: evidence for a growth-promoting region in peri-infarct cortex. Exp Neurol 2005; 193:291-311. [PMID: 15869933 DOI: 10.1016/j.expneurol.2005.01.004] [Citation(s) in RCA: 312] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2004] [Revised: 01/05/2005] [Accepted: 01/06/2005] [Indexed: 12/11/2022]
Abstract
Stroke induces axonal sprouting in peri-infarct cortex. A set of growth-associated genes important in axonal sprouting in peripheral nervous system regeneration and cortical development has recently been defined. The expression profiles of these growth-associated genes were defined during the post-stroke axonal sprouting response using a model of stroke in barrel field cortex. Stroke induces sequential waves of neuronal growth-promoting genes during the sprouting response: an early expression peak (SPRR1), a mid expression peak (p21, Ta1 tubulin, L1, MARCKS), a late peak (SCG10, SCLIP), and an early/sustained pattern (GAP43, CAP23, c-jun). These expression peaks correspond to specific time points in the sprouting response. The expression of the growth-inhibiting chondroitin sulfate proteoglycans aggrecan, brevican, versican, and phosphacan are induced late in the sprouting process; except neurocan, which is increased during the peak of the growth-promoting gene expression. The developmentally associated growth inhibitors ephrin-A5, ephB1, semaphorin IIIa, and neuropilin 1 are also induced in the early phases of the sprouting response. At the cellular level, chondroitin sulfate proteoglycans, in the form of peri-neuronal nets, are reduced in the region of axonal sprouting, during the peak of growth-promoting gene expression. These results identify a unique profile of growth-promoting gene expression in adult cortex after stroke, the inhibitory molecules that are present during the sprouting response, and a region in which growth-promoting genes are increased, growth-inhibitory proteins are diminished and axonal sprouting occurs. This region may be a growth-promoting zone after stroke.
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Affiliation(s)
- S Thomas Carmichael
- Department of Neurology, Geffen School of Medicine at UCLA, 710 Westwood Plaza, Los Angeles, CA 90095, USA.
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144
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Orr G, Hu D, Ozçelik S, Opresko LK, Wiley HS, Colson SD. Cholesterol dictates the freedom of EGF receptors and HER2 in the plane of the membrane. Biophys J 2005; 89:1362-73. [PMID: 15908575 PMCID: PMC1366621 DOI: 10.1529/biophysj.104.056192] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The flow of information through the epidermal growth factor receptor (EGFR) is shaped by molecular interactions in the plasma membrane. The EGFR is associated with lipid rafts, but their role in modulating receptor mobility and subsequent interactions is unclear. To investigate the role of nanoscale rafts in EGFR dynamics, we used single-molecule fluorescence imaging to track individual receptors and their dimerization partner, human epidermal growth factor receptor 2 (HER2), in the membrane of human mammary epithelial cells. We found that the motion of both receptors was interrupted by dwellings within nanodomains. EGFR was significantly less mobile than HER2. This difference was likely due to F-actin because its depolymerization led to similar diffusion patterns between the EGFR and HER2. Manipulations of membrane cholesterol content dramatically altered the diffusion pattern of both receptors. Cholesterol depletion led to almost complete confinement of the receptors, whereas cholesterol enrichment extended the boundaries of the restricted areas. Interestingly, F-actin depolymerization partially restored receptor mobility in cholesterol-depleted membranes. Our observations suggest that membrane cholesterol provides a dynamic environment that facilitates the free motion of EGFR and HER2, possibly by modulating the dynamic state of F-actin. The association of the receptors with lipid rafts could therefore promote their rapid interactions only upon ligand stimulation.
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Affiliation(s)
- Galya Orr
- Chemical and Biological Sciences Divisions, Pacific Northwest National Laboratory, Richland, Washington 99354, USA.
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145
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Vidal A, McIntosh TJ. Transbilayer peptide sorting between raft and nonraft bilayers: comparisons of detergent extraction and confocal microscopy. Biophys J 2005; 89:1102-8. [PMID: 15908585 PMCID: PMC1366595 DOI: 10.1529/biophysj.105.062380] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Membrane microdomains ("rafts") that sequester specific proteins and lipids are often characterized by their resistance to detergent extraction. Because rafts are enriched in sphingomyelin and cholesterol, raft bilayers are thicker and have larger area compressibility moduli than nonraft bilayers. It has been postulated that rafts concentrate proteins with long transmembrane domains (TMDs) because of "hydrophobic matching" between the TMDs and the thick raft bilayers. However, previous detergent extraction experiments with bilayers containing raft and nonraft domains have shown that the peptides P-23 and P-29, designed to have single TMDs matching the hydrocarbon thicknesses of detergent soluble membranes and detergent resistant membranes, respectively, are both localized to detergent soluble membranes. Those results imply that both peptides are preferentially located in nonraft domains. However, because the detergent solubilizes part of the bilayer, it has been unclear whether or not detergent extraction experiments provide an accurate indication of the location of peptides in intact bilayers. Here we use confocal microscopy to examine the distribution of these same peptides in intact bilayers containing both raft and nonraft domains. At 20 degrees C and 37 degrees C, P-23 and P-29 were both primarily localized in fluorescently labeled nonraft domains. These confocal results validate the previous detergent extraction experiments and demonstrate the importance of bilayer cohesive properties, compared to hydrophobic mismatch, in the sorting of these peptides that contain a single TMD.
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Affiliation(s)
- Adriana Vidal
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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146
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Szotowski B, Goldin-Lang P, Antoniak S, Bogdanov VY, Pathirana D, Pauschinger M, Dörner A, Kuehl U, Coupland S, Nemerson Y, Hummel M, Poller W, Hetzer R, Schultheiss HP, Rauch U. Alterations in myocardial tissue factor expression and cellular localization in dilated cardiomyopathy. J Am Coll Cardiol 2005; 45:1081-9. [PMID: 15808768 DOI: 10.1016/j.jacc.2004.12.061] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Revised: 11/29/2004] [Accepted: 12/06/2004] [Indexed: 11/22/2022]
Abstract
OBJECTIVES We investigated the myocardial localization and expression of tissue factor (TF) and alternatively spliced human tissue factor (asHTF) in patients with dilated cardiomyopathy (DCM). BACKGROUND Tissue factor is expressed in cardiac muscle and may play a role in maintaining myocardial structure. METHODS Myocardial biopsies were obtained from patients with a normal or mildly impaired ejection fraction (EF) (> or =50%) and moderate to severely reduced EF (<50%). Explanted DCM hearts were also examined. Myocardial TF expression level was assessed by real-time polymerase chain reaction, TF protein by enzyme-linked immunosorbent assay, and localization by immunohistochemistry. RESULTS We report the identification of asHTF in the human myocardium: it was located in cardiomyocytes and endothelial cells. Quantification of myocardial TF messenger ribonucleic acid in DCM revealed a decrease in the TF/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) ratio (1.76 x 10(-1) +/- 6.08 x 10(-2) for EF > or =50% [n = 19] vs. 1.06 x 10(-1) +/- 5.26 x 10(-2) for EF <50% [n = 27]; p < 0.001) and asHTF/GAPDH ratio (13.91 x 10(-5) +/- 11.20 x 10(-5) for EF > or =50% vs. 7.17 x 10(-5) +/- 3.82 x 10(-5) for EF <50%; p = 0.014). Tissue factor isoform expression level was also decreased in explanted DCM hearts (p < 0.01; n = 12). Total TF protein was reduced by 26% in DCM (p < 0.05). The TF/GAPDH ratio correlated positively with the EF (r = 0.504, p < 0.0001). Immunohistochemistry showed TF localized to the sarcolemma and Z-bands of the cardiomyocytes in patients with normal EF, whereas TF was found in the cardiomyocytic cytosol around the nucleus in DCM. CONCLUSIONS Tissue factor was down-regulated in the myocardium of DCM patients. The reduction in TF expression and change in localization may influence cell-to-cell contact stability and contractility, thereby contributing to cardiac dysfunction in DCM.
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Affiliation(s)
- Björn Szotowski
- Department of Cardiology and Pneumology, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany
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147
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van Rheenen J, Achame EM, Janssen H, Calafat J, Jalink K. PIP2 signaling in lipid domains: a critical re-evaluation. EMBO J 2005; 24:1664-73. [PMID: 15861130 PMCID: PMC1142585 DOI: 10.1038/sj.emboj.7600655] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Accepted: 03/24/2005] [Indexed: 11/09/2022] Open
Abstract
Microdomains such as rafts are considered as scaffolds for phosphatidylinositol (4,5) bisphosphate (PIP2) signaling, enabling PIP2 to selectively regulate different processes in the cell. Enrichment of PIP2 in microdomains was based on cholesterol-depletion and detergent-extraction studies. Here we show that two distinct phospholipase C-coupled receptors (those for neurokinin A and endothelin) share the same, homogeneously distributed PIP2 pool at the plasma membrane, even though the neurokinin A receptor is localized to microdomains and is cholesterol dependent in its PIP2 signaling whereas the endothelin receptor is not. Our experiments further indicate that detergent treatment causes PIP2 clustering and that cholesterol depletion interferes with basal, ligand-independent recycling of the neurokinin A receptor, thereby providing alternative explanations for the enrichment of PIP2 in detergent-insoluble membrane fractions and for the cholesterol dependency of PIP2 breakdown, respectively.
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Affiliation(s)
- Jacco van Rheenen
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
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148
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Marín-Vicente C, Gómez-Fernández JC, Corbalán-García S. The ATP-dependent membrane localization of protein kinase Calpha is regulated by Ca2+ influx and phosphatidylinositol 4,5-bisphosphate in differentiated PC12 cells. Mol Biol Cell 2005; 16:2848-61. [PMID: 15814842 PMCID: PMC1142429 DOI: 10.1091/mbc.e05-01-0067] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Signal transduction through protein kinase Cs (PKCs) strongly depends on their subcellular localization. Here, we investigate the molecular determinants of PKCalpha localization by using a model system of neural growth factor (NGF)-differentiated pheochromocytoma (PC12) cells and extracellular stimulation with ATP. Strikingly, the Ca2+ influx, initiated by the ATP stimulation of P2X receptors, rather than the Ca2+ released from the intracellular stores, was the driving force behind the translocation of PKCalpha to the plasma membrane. Furthermore, the localization process depended on two regions of the C2 domain: the Ca2+-binding region and the lysine-rich cluster, which bind Ca2+ and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], respectively. It was demonstrated that diacylglycerol was not involved in the localization of PKCalpha through its C1 domain, and in lieu, the presence of PtdIns(4,5)P2 increased the permanence of PKCalpha in the plasma membrane. Finally, it also was shown that ATP cooperated with NGF during the differentiation process of PC12 cells by increasing the length of the neurites, an effect that was inhibited when the cells were incubated in the presence of a specific inhibitor of PKCalpha, suggesting a possible role for this isoenzyme in the neural differentiation process. Overall, these results show a novel mechanism of PKCalpha activation in differentiated PC12 cells, where Ca2+ influx, together with the endogenous PtdIns(4,5)P2, anchor PKCalpha to the plasma membrane through two distinct motifs of its C2 domain, leading to enzyme activation.
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Affiliation(s)
- Consuelo Marín-Vicente
- Departamento de Bioquímica y Biología Molecular (A), Facultad de Veterinaria, Universidad de Murcia, E-30100 Murcia, Spain
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149
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Golub T, Caroni P. PI(4,5)P2-dependent microdomain assemblies capture microtubules to promote and control leading edge motility. ACTA ACUST UNITED AC 2005; 169:151-65. [PMID: 15809307 PMCID: PMC2171909 DOI: 10.1083/jcb.200407058] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The lipid second messenger PI(4,5)P2 modulates actin dynamics, and its local accumulation at plasmalemmal microdomains (rafts) might mediate regulation of protrusive motility. However, how PI(4,5)P2-rich rafts regulate surface motility is not well understood. Here, we show that upon signals promoting cell surface motility, PI(4,5)P2 directs the assembly of dynamic raft-rich plasmalemmal patches, which promote and sustain protrusive motility. The accumulation of PI(4,5)P2 at rafts, together with Cdc42, promotes patch assembly through N-WASP. The patches exhibit locally regulated PI(4,5)P2 turnover and reduced diffusion-mediated exchange with their environment. Patches capture microtubules (MTs) through patch IQGAP1, to stabilize MTs at the leading edge. Captured MTs in turn deliver PKA to patches to promote patch clustering through further PI(4,5)P2 accumulation in response to cAMP. Patch clustering restricts, spatially confines, and polarizes protrusive motility. Thus, PI(4,5)P2-dependent raft-rich patches enhance local signaling for motility, and their assembly into clusters is regulated through captured MTs and PKA, coupling local regulation of motility to cell polarity, and organization.
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Affiliation(s)
- Tamara Golub
- Friedrich Miescher Institut, Basel, 4058 Switzerland
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Chandrasekar I, Stradal TEB, Holt MR, Entschladen F, Jockusch BM, Ziegler WH. Vinculin acts as a sensor in lipid regulation of adhesion-site turnover. J Cell Sci 2005; 118:1461-72. [PMID: 15769850 DOI: 10.1242/jcs.01734] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The dynamics of cell adhesion sites control cell morphology and motility. Adhesion-site turnover is thought to depend on the local availability of the acidic phospholipid phosphatidylinositol-4,5-bisphosphate (PIP2). PIP2 can bind to many cell adhesion proteins such as vinculin and talin, but the consequences of this interaction are poorly understood. To study the significance of phospholipid binding to vinculin for adhesion-site turnover and cell motility, we constructed a mutant, vinculin-LD, deficient in acidic phospholipid binding yet with functional actin-binding sites. When expressed in cells, vinculin-LD was readily recruited to adhesion sites, as judged by fluorescence recovery after photobleaching (FRAP) analysis, but cell spreading and migration were strongly impaired, and PIP2-dependent disassembly of adhesions was suppressed. Thus, PIP2 binding is not essential for vinculin activation and recruitment, as previously suggested. Instead, we propose that PIP2 levels can regulate the uncoupling of adhesion sites from the actin cytoskeleton, with vinculin functioning as a sensor.
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Affiliation(s)
- Indra Chandrasekar
- Cell Biology, Zoological Institute, Technical University of Braunschweig, 38106 Braunschweig, Germany
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