351
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Lopez-Verrilli MA, Court FA. Transfer of vesicles from schwann cells to axons: a novel mechanism of communication in the peripheral nervous system. Front Physiol 2012; 3:205. [PMID: 22707941 PMCID: PMC3374349 DOI: 10.3389/fphys.2012.00205] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 05/23/2012] [Indexed: 12/29/2022] Open
Abstract
Schwann cells (SCs) are the glial component of the peripheral nervous system, with essential roles during development and maintenance of axons, as well as during regenerative processes after nerve injury. SCs increase conduction velocities by myelinating axons, regulate synaptic activity at presynaptic nerve terminals and are a source of trophic factors to neurons. Thus, development and maintenance of peripheral nerves are crucially dependent on local signaling between SCs and axons. In addition to the classic mechanisms of intercellular signaling, the possibility of communication through secreted vesicles has been poorly explored to date. Interesting recent findings suggest the occurrence of lateral transfer mediated by vesicles from glial cells to axons that could have important roles in axonal growth and axonal regeneration. Here, we review the role of vesicular transfer from SCs to axons and propose the advantages of this means in supporting neuronal and axonal maintenance and regeneration after nerve damage.
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352
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Turola E, Furlan R, Bianco F, Matteoli M, Verderio C. Microglial microvesicle secretion and intercellular signaling. Front Physiol 2012; 3:149. [PMID: 22661954 PMCID: PMC3357554 DOI: 10.3389/fphys.2012.00149] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 05/02/2012] [Indexed: 01/02/2023] Open
Abstract
Microvesicles (MVs) are released from almost all cell brain types into the microenvironment and are emerging as a novel way of cell-to-cell communication. This review focuses on MVs discharged by microglial cells, the brain resident myeloid cells, which comprise ∼10–12% of brain population. We summarize first evidence indicating that MV shedding is a process activated by the ATP receptor P2X7 and that shed MVs represent a secretory pathway for the inflammatory cytokine IL-β. We then discuss subsequent findings which clarify how IL-1 β can be locally processed and released from MVs into the extracellular environment. In addition, we describe the current understanding about the mechanism of P2X7-dependent MV formation and membrane abscission, which, by involving sphingomyelinase activity and ceramide formation, may share similarities with exosome biogenesis. Finally we report our recent results which show that microglia-derived MVs can stimulate neuronal activity and participate to the propagation of inflammatory signals, and suggest new areas for future investigation.
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353
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Schneider A, Simons M. Exosomes: vesicular carriers for intercellular communication in neurodegenerative disorders. Cell Tissue Res 2012; 352:33-47. [PMID: 22610588 PMCID: PMC3602607 DOI: 10.1007/s00441-012-1428-2] [Citation(s) in RCA: 238] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 04/05/2012] [Indexed: 12/11/2022]
Abstract
The intercellular transfer of misfolded proteins has received increasing attention in various neurodegenerative diseases characterized by the aggregation of specific proteins, as observed in Alzheimer's, Parkinson's and Huntington's disease. One hypothesis holds that intercellular dissemination of these aggregates within the central nervous system results in the seeded assembly of the cognate soluble protein in target cells, similar to that proposed for transmissible prion diseases. The molecular mechanisms underlying the intercellular transfer of these proteinaceous aggregates are poorly understood. Various transfer modes of misfolded proteins including continuous cell-cell contacts such as nanotubes, unconventional secretion or microvesicle/exosome-associated dissemination have been suggested. Cells can release proteins, lipids and nucleic acids by vesicular exocytosis pathways destined for horizontal transfer. Encapsulation into microvesicular/exosomal vehicles not only protects these molecules from degradation and dilution in the extracellular space but also facilitates delivery over large distances, e.g. within the blood flow or interstitial fluid. Specific surface ligands might allow the highly efficient and targeted uptake of these vesicles by recipient cells. In this review, we focus on the cell biology and function of neuronal microvesicles/exosomes and discuss the evidence for pathogenic intercellular protein transfer mediated by vesicular carriers.
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Affiliation(s)
- Anja Schneider
- Department of Psychiatry and Psychotherapy, University Medicine Goettingen, Von-Siebold-Str.5, 37075, Goettingen, Germany.
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354
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Bellingham SA, Guo BB, Coleman BM, Hill AF. Exosomes: vehicles for the transfer of toxic proteins associated with neurodegenerative diseases? Front Physiol 2012; 3:124. [PMID: 22563321 PMCID: PMC3342525 DOI: 10.3389/fphys.2012.00124] [Citation(s) in RCA: 287] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 04/13/2012] [Indexed: 12/31/2022] Open
Abstract
Exosomes are small membranous vesicles secreted by a number of cell types including neurons and can be isolated from conditioned cell media or bodily fluids such as urine and plasma. Exosome biogenesis involves the inward budding of endosomes to form multivesicular bodies (MVB). When fused with the plasma membrane, the MVB releases the vesicles into the extracellular environment as exosomes. Proposed functions of these vesicles include roles in cell–cell signaling, removal of unwanted proteins, and the transfer of pathogens between cells. One such pathogen which exploits this pathway is the prion, the infectious particle responsible for the transmissible neurodegenerative diseases such as Creutzfeldt–Jakob disease (CJD) of humans or bovine spongiform encephalopathy (BSE) of cattle. Similarly, exosomes are also involved in the processing of the amyloid precursor protein (APP) which is associated with Alzheimer’s disease. Exosomes have been shown to contain full-length APP and several distinct proteolytically cleaved products of APP, including Aβ. In addition, these fragments can be modulated using inhibitors of the proteases involved in APP cleavage. These observations provide further evidence for a novel pathway in which PrP and APP fragments are released from cells. Other proteins such as superoxide dismutase I and alpha-synuclein (involved in amyotrophic lateral sclerosis and Parkinson’s disease, respectively) are also found associated with exosomes. This review will focus on the role of exosomes in neurodegenerative disorders and discuss the potential of these vesicles for the spread of neurotoxicity, therapeutics, and diagnostics for these diseases.
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Affiliation(s)
- Shayne A Bellingham
- Department of Biochemistry and Molecular Biology, The University of Melbourne Melbourne, VIC 3010, Australia
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355
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Frühbeis C, Fröhlich D, Krämer-Albers EM. Emerging roles of exosomes in neuron-glia communication. Front Physiol 2012; 3:119. [PMID: 22557979 PMCID: PMC3339323 DOI: 10.3389/fphys.2012.00119] [Citation(s) in RCA: 212] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 04/11/2012] [Indexed: 01/12/2023] Open
Abstract
Brain function depends on coordinated interactions between neurons and glial cells. Recent evidence indicates that these cells release endosome-derived microvesicles termed exosomes, which are 50-100 nm in size and carry specific protein and RNA cargo. Exosomes can interact with neighboring cells raising the concept that exosomes may mediate signaling between brain cells and facilitate the delivery of bioactive molecules. Oligodendrocytes myelinate axons and furthermore maintain axonal integrity by an yet uncharacterized pathway of trophic support. Here, we highlight the role of exosomes in nervous system cell communication with particular focus on exosomes released by oligodendrocytes and their potential implications in axon-glia interaction and myelin disease, such as multiple sclerosis. These secreted vesicles may contribute to eliminate overproduced myelin membrane or to transfer antigens facilitating immune surveillance of the brain. Furthermore, there is emerging evidence that exosomes participate in axon-glia communication.
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Affiliation(s)
- Carsten Frühbeis
- Department of Molecular Cell Biology, Johannes Gutenberg University Mainz Mainz, Germany
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356
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Microvesicle and tunneling nanotube mediated intercellular transfer of g-protein coupled receptors in cell cultures. Exp Cell Res 2012; 318:603-13. [PMID: 22266577 DOI: 10.1016/j.yexcr.2012.01.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 12/27/2011] [Accepted: 01/03/2012] [Indexed: 01/10/2023]
Abstract
Recent evidence shows that cells exchange collections of signals via microvesicles (MVs) and tunneling nano-tubes (TNTs). In this paper we have investigated whether in cell cultures GPCRs can be transferred by means of MVs and TNTs from a source cell to target cells. Western blot, transmission electron microscopy and gene expression analyses demonstrate that A(2A) and D(2) receptors are present in released MVs. In order to further demonstrate the involvement of MVs in cell-to-cell communication we created two populations of cells (HEK293T and COS-7) transiently transfected with D(2)R-CFP or A(2A)R-YFP. These two types of cells were co-cultured, and FRET analysis demonstrated simultaneously positive cells to the D(2)R-CFP and A(2A)R-YFP. Fluorescence microscopy analysis also showed that GPCRs can move from one cell to another also by means of TNTs. Finally, recipient cells pre-incubated for 24 h with A(2A)R positive MVs were treated with the adenosine A(2A) receptor agonist CGS-21680. The significant increase in cAMP accumulation clearly demonstrated that A(2A)Rs were functionally competent in target cells. These findings demonstrate that A(2A) receptors capable of recognizing and decoding extracellular signals can be safely transferred via MVs from source to target cells.
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357
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Quantitative and integrative proteome analysis of peripheral nerve myelin identifies novel myelin proteins and candidate neuropathy loci. J Neurosci 2012; 31:16369-86. [PMID: 22072688 DOI: 10.1523/jneurosci.4016-11.2011] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Peripheral nerve myelin facilitates rapid impulse conduction and normal motor and sensory functions. Many aspects of myelin biogenesis, glia-axonal interactions, and nerve homeostasis are poorly understood at the molecular level. We therefore hypothesized that only a fraction of all relevant myelin proteins has been identified so far. Combining gel-based and gel-free proteomic approaches, we identified 545 proteins in purified mouse sciatic nerve myelin, including 36 previously known myelin constituents. By mass spectrometric quantification, the predominant P0, periaxin, and myelin basic protein constitute 21, 16, and 8% of the total myelin protein, respectively, suggesting that their relative abundance was previously misestimated due to technical limitations regarding protein separation and visualization. Focusing on tetraspan-transmembrane proteins, we validated novel myelin constituents using immuno-based methods. Bioinformatic comparison with mRNA-abundance profiles allowed the categorization in functional groups coregulated during myelin biogenesis and maturation. By differential myelin proteome analysis, we found that the abundance of septin 9, the protein affected in hereditary neuralgic amyotrophy, is strongly increased in a novel mouse model of demyelinating neuropathy caused by the loss of prion protein. Finally, the systematic comparison of our compendium with the positions of human disease loci allowed us to identify several candidate genes for hereditary demyelinating neuropathies. These results illustrate how the integration of unbiased proteome, transcriptome, and genome data can contribute to a molecular dissection of the biogenesis, cell biology, metabolism, and pathology of myelin.
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358
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Kleemann P, Distler E, Wagner EM, Thomas S, Klobuch S, Aue S, Schnürer E, Schild H, Theobald M, Plachter B, Tenzer S, Meyer RG, Herr W. Varicella-zoster virus glycoproteins B and E are major targets of CD4+ and CD8+ T cells reconstituting during zoster after allogeneic transplantation. Haematologica 2011; 97:874-82. [PMID: 22207687 DOI: 10.3324/haematol.2011.052597] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND After allogeneic hematopoietic stem-cell transplantation patients are at increased risk for herpes zoster as long as varicella-zoster virus specific T-cell reconstitution is impaired. This study aimed to identify immunodominant varicella-zoster virus antigens that drive recovery of virus-specific T cells after transplantation. DESIGN AND METHODS Antigens were purified from a varicella-zoster virus infected cell lysate by high-performance liquid chromatography and were identified by quantitative mass spectrometric analysis. To approximate in vivo immunogenicity for memory T cells, antigen preparations were consistently screened with ex vivo PBMC of varicella-zoster virus immune healthy individuals in sensitive interferon-γ ELISpot assays. Candidate virus antigens identified by the approach were genetically expressed in PBMC using electroporation of in vitro transcribed RNA encoding full-length proteins and were then analyzed for recognition by CD4(+) and CD8(+) memory T cells. RESULTS Varicella-zoster virus encoded glycoproteins B and E, and immediate early protein 62 were identified in immunoreactive lysate material. Predominant CD4(+) T-cell reactivity to these proteins was observed in healthy virus carriers. Furthermore, longitudinal screening in allogeneic stem-cell transplantation patients showed strong expansions of memory T cells recognizing glycoproteins B and E after onset of herpes zoster, while immediate early protein 62 reactivity remained moderate. Reactivity to viral glycoproteins boosted by acute zoster was mediated by both CD4(+) and CD8(+) T cells. CONCLUSIONS Our data demonstrate that glycoproteins B and E are major targets of varicella-zoster virus specific CD4(+) and CD8(+) T-cell reconstitution occurring during herpes zoster after allogeneic stem-cell transplantation. Varicella-zoster virus glycoproteins B and E might form the basis for novel non-hazardous zoster subunit vaccines suitable for immunocompromised transplant patients.
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Affiliation(s)
- Patrick Kleemann
- Department of Medicine III, University Medical Center, Mainz, Germany
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359
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Miller LK, Hou X, Rodriguiz RM, Gagnidze K, Sweedler JV, Wetsel WC, Devi LA. Mice deficient in endothelin-converting enzyme-2 exhibit abnormal responses to morphine and altered peptide levels in the spinal cord. J Neurochem 2011; 119:1074-85. [PMID: 21972895 DOI: 10.1111/j.1471-4159.2011.07513.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An increasing body of evidence suggests that endothelin-converting enzyme-2 (ECE-2) is a non-classical neuropeptide processing enzyme. Similar to other neuropeptide processing enzymes, ECE-2 exhibits restricted neuroendocrine distribution, intracellular localization, and an acidic pH optimum. However, unlike classical neuropeptide processing enzymes, ECE-2 exhibits a non-classical cleavage site preference for aliphatic and aromatic residues. We previously reported that ECE-2 cleaves a number of neuropeptides at non-classical sites in vitro; however its role in peptide processing in vivo is poorly understood. Given the recognized roles of neuropeptides in pain and opiate responses, we hypothesized that ECE-2 knockout (KO) mice might show altered pain and morphine responses compared with wild-type mice. We find that ECE-2 KO mice show decreased response to a single injection of morphine in hot-plate and tail-flick tests. ECE-2 KO mice also show more rapid development of tolerance with prolonged morphine treatment and fewer signs of naloxone-precipitated withdrawal. Peptidomic analyses revealed changes in the levels of a number of spinal cord peptides in ECE-2 KO as compared to wild-type mice. Taken together, our findings suggest a role for ECE-2 in the non-classical processing of spinal cord peptides and morphine responses; however, the precise mechanisms through which ECE-2 influences morphine tolerance and withdrawal remain unclear.
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Affiliation(s)
- Lydia K Miller
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, New York, USA
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360
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Aggarwal S, Yurlova L, Simons M. Central nervous system myelin: structure, synthesis and assembly. Trends Cell Biol 2011; 21:585-93. [DOI: 10.1016/j.tcb.2011.06.004] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 06/01/2011] [Accepted: 06/07/2011] [Indexed: 01/13/2023]
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361
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Fitzner D, Schnaars M, van Rossum D, Krishnamoorthy G, Dibaj P, Bakhti M, Regen T, Hanisch UK, Simons M. Selective transfer of exosomes from oligodendrocytes to microglia by macropinocytosis. J Cell Sci 2011; 124:447-58. [PMID: 21242314 DOI: 10.1242/jcs.074088] [Citation(s) in RCA: 607] [Impact Index Per Article: 46.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The transfer of antigens from oligodendrocytes to immune cells has been implicated in the pathogenesis of autoimmune diseases. Here, we show that oligodendrocytes secrete small membrane vesicles called exosomes, which are specifically and efficiently taken up by microglia both in vitro and in vivo. Internalisation of exosomes occurs by a macropinocytotic mechanism without inducing a concomitant inflammatory response. After stimulation of microglia with interferon-γ, we observe an upregulation of MHC class II in a subpopulation of microglia. However, exosomes are preferentially internalised in microglia that do not seem to have antigen-presenting capacity. We propose that the constitutive macropinocytotic clearance of exosomes by a subset of microglia represents an important mechanism through which microglia participate in the degradation of oligodendroglial membrane in an immunologically 'silent' manner. By designating the capacity for macropinocytosis and antigen presentation to distinct cells, degradation and immune function might be assigned to different subtypes of microglia.
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Affiliation(s)
- Dirk Fitzner
- Max-Planck Institute for Experimental Medicine, Hermann-Rein-Str., D-37075 Göttingen, Germany
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362
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Abstract
Exosomes are small membrane vesicles of endocytic origin secreted by most cell types, and are thought to play important roles in intercellular communications. Although exosomes were originally described in 1983, interest in these vesicles has really increased dramatically in the last 3 years, after the finding that they contain mRNA and microRNA. This discovery sparked renewed interest for the general field of membrane vesicles involved in intercellular communications, and research on these structures has grown exponentially over the last few years, probing their composition and function, as well as their potential value as biomarkers.
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363
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Matros A, Kaspar S, Witzel K, Mock HP. Recent progress in liquid chromatography-based separation and label-free quantitative plant proteomics. PHYTOCHEMISTRY 2011; 72:963-74. [PMID: 21176926 DOI: 10.1016/j.phytochem.2010.11.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 11/05/2010] [Accepted: 11/09/2010] [Indexed: 05/26/2023]
Abstract
Recent innovations in liquid chromatography-mass spectrometry (LC-MS)-based methods have facilitated quantitative and functional proteomic analyses of large numbers of proteins derived from complex samples without any need for protein or peptide labelling. Regardless of its great potential, the application of these proteomics techniques to plant science started only recently. Here we present an overview of label-free quantitative proteomics features and their employment for analysing plants. Recent methods used for quantitative protein analyses by MS techniques are summarized and major challenges associated with label-free LC-MS-based approaches, including sample preparation, peptide separation, quantification and kinetic studies, are discussed. Database search algorithms and specific aspects regarding protein identification of non-sequenced organisms are also addressed. So far, label-free LC-MS in plant science has been used to establish cellular or subcellular proteome maps, characterize plant-pathogen interactions or stress defence reactions, and for profiling protein patterns during developmental processes. Improvements in both, analytical platforms (separation technology and bioinformatics/statistical analysis) and high throughput nucleotide sequencing technologies will enhance the power of this method.
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Affiliation(s)
- A Matros
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Department of Physiology and Cell Biology, Corrensstrasse 3, D-06466 Gatersleben, Germany
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364
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Bobrie A, Colombo M, Raposo G, Théry C. Exosome Secretion: Molecular Mechanisms and Roles in Immune Responses. Traffic 2011; 12:1659-68. [DOI: 10.1111/j.1600-0854.2011.01225.x] [Citation(s) in RCA: 747] [Impact Index Per Article: 57.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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365
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Bello-Morales R, Pérez-Hernández M, Rejas MT, Matesanz F, Alcina A, López-Guerrero JA. Interaction of PLP with GFP-MAL2 in the human oligodendroglial cell line HOG. PLoS One 2011; 6:e19388. [PMID: 21573057 PMCID: PMC3090389 DOI: 10.1371/journal.pone.0019388] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 03/28/2011] [Indexed: 11/18/2022] Open
Abstract
The velocity of the nerve impulse conduction of vertebrates relies on the myelin sheath, an electrically insulating layer that surrounds axons in both the central and peripheral nervous systems, enabling saltatory conduction of the action potential. Oligodendrocytes are the myelin-producing glial cells in the central nervous system. A deeper understanding of the molecular basis of myelination and, specifically, of the transport of myelin proteins, will contribute to the search of the aetiology of many dysmyelinating and demyelinating diseases, including multiple sclerosis. Recent investigations suggest that proteolipid protein (PLP), the major myelin protein, could reach myelin sheath by an indirect transport pathway, that is, a transcytotic route via the plasma membrane of the cell body. If PLP transport relies on a transcytotic process, it is reasonable to consider that this myelin protein could be associated with MAL2, a raft protein essential for transcytosis. In this study, carried out with the human oligodendrocytic cell line HOG, we show that PLP colocalized with green fluorescent protein (GFP)-MAL2 after internalization from the plasma membrane. In addition, both immunoprecipitation and immunofluorescence assays, indicated the existence of an interaction between GFP-MAL2 and PLP. Finally, ultrastructural studies demonstrated colocalization of GFP-MAL2 and PLP in vesicles and tubulovesicular structures. Taken together, these results prove for the first time the interaction of PLP and MAL2 in oligodendrocytic cells, supporting the transcytotic model of PLP transport previously suggested.
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Affiliation(s)
- Raquel Bello-Morales
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid/Consejo Superior de Investigaciones Científicas, Cantoblanco, Madrid, Spain
| | - Marta Pérez-Hernández
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid/Consejo Superior de Investigaciones Científicas, Cantoblanco, Madrid, Spain
| | - María Teresa Rejas
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid/Consejo Superior de Investigaciones Científicas, Cantoblanco, Madrid, Spain
| | - Fuencisla Matesanz
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Antonio Alcina
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - José Antonio López-Guerrero
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid/Consejo Superior de Investigaciones Científicas, Cantoblanco, Madrid, Spain
- * E-mail:
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366
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van der Vos KE, Balaj L, Skog J, Breakefield XO. Brain tumor microvesicles: insights into intercellular communication in the nervous system. Cell Mol Neurobiol 2011; 31:949-59. [PMID: 21553248 DOI: 10.1007/s10571-011-9697-y] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 04/12/2011] [Indexed: 02/03/2023]
Abstract
Brain tumors are heterogeneous tumors composed of differentiated tumor cells that resemble various neural cells and a small number of multipotent cancer stem cells. These tumors modify normal cells in their environment to promote tumor growth, invasion and metastases by various ways. Recent publications show that glioblastoma cells release microvesicles that contain a select subset of cellular proteins and RNAs. These microvesicles are avidly taken up by normal cells in cell culture and can change the translational profile of these cells through delivery of tumor-derived mRNAs, which are translated into functional proteins. In addition to mRNA and proteins, microvesicles have been shown to contain microRNAs, non-coding RNAs and DNA. This commentary explores the recent advances in this novel intercellular communication route and discusses the potential physiological role of microvesicles in brain tumorigenesis.
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367
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Tu-Sekine B, Raben DM. Regulation and roles of neuronal diacylglycerol kinases: a lipid perspective. Crit Rev Biochem Mol Biol 2011; 46:353-64. [PMID: 21539478 DOI: 10.3109/10409238.2011.577761] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Diacylglycerol kinases (DGKs) are a class of enzymes that catalyze the ATP-dependent conversion of diacylglycerol (DAG) to phosphatidic acid (PtdOH), resulting in the coordinate regulation of these two lipid second messengers. This regulation is particularly important in the nervous system where it is now well-established that DAG and PtdOH serve very important roles in modulating a variety of neurological functions. There are currently 10 identified mammalian DGKs, organized into five classes or "Types" based upon similarities in their primary sequences. A number of studies have identified eight of these isoforms in various regions of the mammalian central nervous system (CNS): DGK-α, DGK-β, DGK-γ, DGK-η, DGK-ζ, DGK-ι, DGK-ϵ, and DGK-θ. Further studies have provided compelling evidence supporting roles for these enzymes in neuronal spine density, myelination, synaptic activity, neuronal plasticity, epileptogenesis and neurotransmitter release. The physiological regulation of these enzymes is less clear. Like all interfacial enzymes, DGKs metabolize their hydrophobic substrate (DAG) at a membrane-aqueous interface. Therefore, these enzymes can be regulated by alterations in their subcellular localization, enzymatic activity, and/or membrane association. In this review, we summarize what is currently understood about the localization and regulation of the neuronal DGKs in the mammalian CNS.
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Affiliation(s)
- Becky Tu-Sekine
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, 21205 MD, USA
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368
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Von Bartheld CS, Altick AL. Multivesicular bodies in neurons: distribution, protein content, and trafficking functions. Prog Neurobiol 2011; 93:313-40. [PMID: 21216273 DOI: 10.1016/j.pneurobio.2011.01.003] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 12/22/2010] [Accepted: 01/03/2011] [Indexed: 11/27/2022]
Abstract
Multivesicular bodies (MVBs) are intracellular endosomal organelles characterized by multiple internal vesicles that are enclosed within a single outer membrane. MVBs were initially regarded as purely prelysosomal structures along the degradative endosomal pathway of internalized proteins. MVBs are now known to be involved in numerous endocytic and trafficking functions, including protein sorting, recycling, transport, storage, and release. This review of neuronal MVBs summarizes their research history, morphology, distribution, accumulation of cargo and constitutive proteins, transport, and theories of functions of MVBs in neurons and glia. Due to their complex morphologies, neurons have expanded trafficking and signaling needs, beyond those of "geometrically simpler" cells, but it is not known whether neuronal MVBs perform additional transport and signaling functions. This review examines the concept of compartment-specific MVB functions in endosomal protein trafficking and signaling within synapses, axons, dendrites and cell bodies. We critically evaluate reports of the accumulation of neuronal MVBs based on evidence of stress-induced MVB formation. Furthermore, we discuss potential functions of neuronal and glial MVBs in development, in dystrophic neuritic syndromes, injury, disease, and aging. MVBs may play a role in Alzheimer's, Huntington's, and Niemann-Pick diseases, some types of frontotemporal dementia, prion and virus trafficking, as well as in adaptive responses of neurons to trauma and toxin or drug exposure. Functions of MVBs in neurons have been much neglected, and major gaps in knowledge currently exist. Developing truly MVB-specific markers would help to elucidate the roles of neuronal MVBs in intra- and intercellular signaling of normal and diseased neurons.
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Affiliation(s)
- Christopher S Von Bartheld
- Department of Physiology and Cell Biology, Mailstop 352, University of Nevada School of Medicine, Reno, NV 89557, USA.
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369
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Bakhti M, Winter C, Simons M. Inhibition of myelin membrane sheath formation by oligodendrocyte-derived exosome-like vesicles. J Biol Chem 2011; 286:787-96. [PMID: 20978131 PMCID: PMC3013037 DOI: 10.1074/jbc.m110.190009] [Citation(s) in RCA: 182] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Indexed: 01/06/2023] Open
Abstract
Myelin formation is a multistep process that is controlled by a number of different extracellular factors. During the development of the central nervous system (CNS), oligodendrocyte progenitor cells differentiate into mature oligodendrocytes that start to enwrap axons with myelin membrane sheaths after receiving the appropriate signal(s) from the axon or its microenvironment. The signals required to initiate this process are unknown. Here, we show that oligodendrocytes secrete small membrane vesicles, exosome-like vesicles, into the extracellular space that inhibit both the morphological differentiation of oligodendrocytes and myelin formation. The inhibitory effects of exosome-like vesicles were prevented by treatment with inhibitors of actomyosin contractility. Importantly, secretion of exosome-like vesicles from oligodendrocytes was dramatically reduced when cells were incubated by conditioned neuronal medium. In conclusion, our results provide new evidence for small and diffusible oligodendroglial-derived vesicular carriers within the extracellular space that have inhibitory properties on cellular growth. We propose that neurons control the secretion of autoinhibitory oligodendroglial-derived exosomes to coordinate myelin membrane biogenesis.
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Affiliation(s)
- Mostafa Bakhti
- From the Max Planck Institute for Experimental Medicine, D-37075 Göttingen, Germany and
| | - Christine Winter
- From the Max Planck Institute for Experimental Medicine, D-37075 Göttingen, Germany and
- the Department of Neurology, University of Göttingen, D-37075 Göttingen, Germany
| | - Mikael Simons
- From the Max Planck Institute for Experimental Medicine, D-37075 Göttingen, Germany and
- the Department of Neurology, University of Göttingen, D-37075 Göttingen, Germany
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370
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Release of exosomes from differentiated neurons and its regulation by synaptic glutamatergic activity. Mol Cell Neurosci 2010; 46:409-18. [PMID: 21111824 DOI: 10.1016/j.mcn.2010.11.004] [Citation(s) in RCA: 421] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 10/15/2010] [Accepted: 11/12/2010] [Indexed: 12/21/2022] Open
Abstract
Exosomes are microvesicles released into the extracellular medium upon fusion to the plasma membrane of endosomal intermediates called multivesicular bodies. They represent ways for discarding proteins and metabolites and also for intercellular transfer of proteins and RNAs. In the nervous system, it has been hypothesized that exosomes might be involved in the normal physiology of the synapse and possibly allow the trans-synaptic propagation of pathogenic proteins throughout the tissue. As a first step to validate this concept, we used biochemical and morphological approaches to demonstrate that mature cortical neurons in culture do indeed secrete exosomes. Using electron microscopy, we observed exosomes being released from somato-dendritic compartments. The endosomal origin of exosomes was demonstrated by showing that the C-terminal domain of tetanus toxin specifically endocytosed by neurons and accumulating inside multivesicular bodies, is released in the extracellular medium in association with exosomes. Finally, we found that exosomal release is modulated by glutamatergic synaptic activity, suggesting that this process might be part of normal synaptic physiology. Thus, our study paves the way towards the demonstration that exosomes take part in the physiology of the normal and pathological nervous system.
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371
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Mathivanan S, Ji H, Simpson RJ. Exosomes: extracellular organelles important in intercellular communication. J Proteomics 2010; 73:1907-20. [PMID: 20601276 DOI: 10.1016/j.jprot.2010.06.006] [Citation(s) in RCA: 1857] [Impact Index Per Article: 132.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 05/26/2010] [Accepted: 06/18/2010] [Indexed: 12/12/2022]
Abstract
In addition to intracellular organelles, eukaryotic cells also contain extracellular organelles that are released, or shed, into the microenvironment. These membranous extracellular organelles include exosomes, shedding microvesicles (SMVs) and apoptotic blebs (ABs), many of which exhibit pleiotropic biological functions. Because extracellular organelle terminology is often confounding, with many preparations reported in the literature being mixtures of extracellular vesicles, there is a growing need to clarify nomenclature and to improve purification strategies in order to discriminate the biochemical and functional activities of these moieties. Exosomes are formed by the inward budding of multivesicular bodies (MVBs) and are released from the cell into the microenvironment following the fusion of MVBs with the plasma membrane (PM). In this review we focus on various strategies for purifying exosomes and discuss their biophysical and biochemical properties. An update on proteomic analysis of exosomes from various cell types and body fluids is provided and host-cell specific proteomic signatures are also discussed. Because the ectodomain of ~42% of exosomal integral membrane proteins are also found in the secretome, these vesicles provide a potential source of serum-based membrane protein biomarkers that are reflective of the host cell. ExoCarta, an exosomal protein and RNA database (http://exocarta.ludwig.edu.au), is described.
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Affiliation(s)
- Suresh Mathivanan
- Ludwig Institute for Cancer Research, Parkville, Victoria, Australia
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372
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Hsu C, Morohashi Y, Yoshimura SI, Manrique-Hoyos N, Jung S, Lauterbach MA, Bakhti M, Grønborg M, Möbius W, Rhee J, Barr FA, Simons M. Regulation of exosome secretion by Rab35 and its GTPase-activating proteins TBC1D10A-C. ACTA ACUST UNITED AC 2010; 189:223-32. [PMID: 20404108 PMCID: PMC2856897 DOI: 10.1083/jcb.200911018] [Citation(s) in RCA: 606] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A screen in oligodendrocytes establishes a Rab family member and its GAPs as regulators of exosome secretion by controlling endocytic vesicle docking with the plasma membrane. Oligodendrocytes secrete vesicles into the extracellular space, where they might play a role in neuron–glia communication. These exosomes are small vesicles with a diameter of 50–100 nm that are formed within multivesicular bodies and are released after fusion with the plasma membrane. The intracellular pathways that generate exosomes are poorly defined. Because Rab family guanosine triphosphatases (GTPases) together with their regulators are important membrane trafficking organizers, we investigated which Rab GTPase-activating proteins interfere with exosome release. We find that TBC1D10A–C regulate exosome secretion in a catalytic activity–dependent manner. We show that Rab35 is the target of TBC1D10A–C and that the inhibition of Rab35 function leads to intracellular accumulation of endosomal vesicles and impairs exosome secretion. Rab35 localizes to the surface of oligodendroglia in a GTP-dependent manner, where it increases the density of vesicles, suggesting a function in docking or tethering. These findings provide a basis for understanding the biogenesis and function of exosomes in the central nervous system.
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Affiliation(s)
- Chieh Hsu
- Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
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373
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Lo Turco EG, Souza GHMF, Garcia JS, Ferreira CR, Eberlin MN, Bertolla RP. Effect of endometriosis on the protein expression pattern of follicular fluid from patients submitted to controlled ovarian hyperstimulation for in vitro fertilization. Hum Reprod 2010; 25:1755-66. [DOI: 10.1093/humrep/deq102] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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374
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Novel approaches for scanning near-field optical microscopy imaging of oligodendrocytes in culture. Neuroimage 2010; 49:517-24. [DOI: 10.1016/j.neuroimage.2009.07.035] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Accepted: 07/15/2009] [Indexed: 11/22/2022] Open
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375
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Simpson RJ, Lim JW, Moritz RL, Mathivanan S. Exosomes: proteomic insights and diagnostic potential. Expert Rev Proteomics 2009; 6:267-83. [PMID: 19489699 DOI: 10.1586/epr.09.17] [Citation(s) in RCA: 815] [Impact Index Per Article: 54.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Exosomes are 40-100-nm diameter membrane vesicles of endocytic origin that are released by most cell types upon fusion of multivesicular bodies with the plasma membrane, presumably as a vehicle for cell-free intercellular communication. While early studies focused on their secretion from diverse cell types in vitro, exosomes have now been identified in body fluids such as urine, amniotic fluid, malignant ascites, bronchoalveolar lavage fluid, synovial fluid, breast milk, saliva and blood. Exosomes have pleiotropic biological functions, including immune response, antigen presentation, intracellular communication and the transfer of RNA and proteins. While they have also been implicated in the transport and propagation of infectious cargo, such as prions, and retroviruses, including HIV, suggesting a role in pathological situations, recent studies suggest that the presence of such infectious cargo may be artefacts of exosome-purification strategies. Improvements in mass spectrometry-based proteomic tools, both hardware and software, coupled with improved purification schemes for exosomes, has allowed more in-depth proteome analyses, contributing immensely to our understanding of the molecular composition of exosomes. Proteomic cataloguing of exosomes from diverse cell types has revealed a common set of membrane and cytosolic proteins, suggesting the evolutionary importance of these membrane particles. Additionally, exosomes express an array of proteins that reflect the originating host cell. Recent findings that exosomes contain inactive forms of both mRNA and microRNA that can be transferred to another cell and be functional in that new environment, have initiated many microRNA profiling studies of exosomes circulating in blood. These studies highlight the potential of exosomal microRNA profiles for use as diagnostic biomarkers of disease through a noninvasive blood test. The exacerbated release of exosomes in tumor cells, as evidenced by their increased levels in blood during the late stage of a disease and their overexpression of certain tumor cell biomarkers, suggests an important role of exosomes in diagnosis and biomarker studies. The aim of this article is to provide a brief overview of exosomes, including methods used to isolate and characterize exosomes. New advances in proteomic methods, and both mass spectrometry hardware and informatics tools will be covered briefly.
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Affiliation(s)
- Richard J Simpson
- Ludwig Institute for Cancer Research, PO Box 2008, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia.
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376
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Myelin proteomics: molecular anatomy of an insulating sheath. Mol Neurobiol 2009; 40:55-72. [PMID: 19452287 PMCID: PMC2758371 DOI: 10.1007/s12035-009-8071-2] [Citation(s) in RCA: 218] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Accepted: 04/14/2009] [Indexed: 12/12/2022]
Abstract
Fast-transmitting vertebrate axons are electrically insulated with multiple layers of nonconductive plasma membrane of glial cell origin, termed myelin. The myelin membrane is dominated by lipids, and its protein composition has historically been viewed to be of very low complexity. In this review, we discuss an updated reference compendium of 342 proteins associated with central nervous system myelin that represents a valuable resource for analyzing myelin biogenesis and white matter homeostasis. Cataloging the myelin proteome has been made possible by technical advances in the separation and mass spectrometric detection of proteins, also referred to as proteomics. This led to the identification of a large number of novel myelin-associated proteins, many of which represent low abundant components involved in catalytic activities, the cytoskeleton, vesicular trafficking, or cell adhesion. By mass spectrometry-based quantification, proteolipid protein and myelin basic protein constitute 17% and 8% of total myelin protein, respectively, suggesting that their abundance was previously overestimated. As the biochemical profile of myelin-associated proteins is highly reproducible, differential proteome analyses can be applied to material isolated from patients or animal models of myelin-related diseases such as multiple sclerosis and leukodystrophies.
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377
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Geromanos SJ, Vissers JPC, Silva JC, Dorschel CA, Li GZ, Gorenstein MV, Bateman RH, Langridge JI. The detection, correlation, and comparison of peptide precursor and product ions from data independent LC-MS with data dependant LC-MS/MS. Proteomics 2009; 9:1683-95. [PMID: 19294628 DOI: 10.1002/pmic.200800562] [Citation(s) in RCA: 390] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The detection, correlation, and comparison of peptide and product ions from a data independent LC-MS acquisition strategy with data dependent LC-MS/MS is described. The data independent mode of acquisition differs from an LC-MS/MS data acquisition since no ion transmission window is applied with the first mass analyzer prior to collision induced disassociation. Alternating the energy applied to the collision cell, between low and elevated energy, on a scan-to-scan basis, provides accurate mass precursor and associated product ion spectra from every ion above the LOD of the mass spectrometer. The method therefore provides a near 100% duty cycle, with an inherent increase in signal intensity due to the fact that both precursor and product ion data are collected on all isotopes of every charge-state across the entire chromatographic peak width. The correlation of product to precursor ions, after deconvolution, is achieved by using reconstructed retention time apices and chromatographic peak shapes. Presented are the results from the comparison of a simple four protein mixture, in the presence and absence of an enzymatically digested protein extract from Escherichia coli. The samples were run in triplicate by both data dependant analysis (DDA) LC-MS/MS and data-independent, alternate scanning LC-MS. The detection and identification of precursor and product ions from the combined DDA search results of the four protein mixture were used for comparison to all other data. Each individual set of data-independent LC-MS data provides a more comprehensive set of detected ions than the combined peptide identifications from the DDA LC-MS/MS experiments. In the presence of the complex E. coli background, over 90% of the monoisotopic masses from the combined LC-MS/MS identifications were detected at the appropriate retention time. Moreover, the fragmentation pattern and number of associated elevated energy product ions in each replicate experiment was found to be very similar to the DDA identifications. In the case of the corresponding individual DDA LC-MS/MS experiment, 43% of the possible detectable peptides of interest were identified. The presented data illustrates that the time-aligned data from data-independent alternate scanning LC-MS experiments is highly comparable to the data obtained via DDA. The obtained information can therefore be effectively and correctly deconvolved to correlate product ions with parent precursor ions. The ability to generate precursor-product ion tables from this information and subsequently identify the correct parent precursor peptide will be illustrated in a companion manuscript.
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378
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Absence of 2-hydroxylated sphingolipids is compatible with normal neural development but causes late-onset axon and myelin sheath degeneration. J Neurosci 2008; 28:9741-54. [PMID: 18815260 DOI: 10.1523/jneurosci.0458-08.2008] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Sphingolipids containing 2-hydroxylated fatty acids are among the most abundant lipid components of the myelin sheath and therefore are thought to play an important role in formation and function of myelin. To prove this hypothesis, we generated mice lacking a functional fatty acid 2-hydroxylase (FA2H) gene. FA2H-deficient (FA2H(-/-)) mice lacked 2-hydroxylated sphingolipids in the brain and in peripheral nerves. In contrast, nonhydroxylated galactosylceramide was increased in FA2H(-/-) mice. However, oligodendrocyte differentiation examined by in situ hybridization with cRNA probes for proteolipid protein and PDGFalpha receptor and the time course of myelin formation were not altered in FA2H(-/-) mice compared with wild-type littermates. Nerve conduction velocity measurements of sciatic nerves revealed no significant differences between FA2H(-/-) and wild-type mice. Moreover, myelin of FA2H(-/-) mice up to 5 months of age appeared normal at the ultrastructural level, in the CNS and peripheral nervous system. Myelin thickness and g-ratios were normal in FA2H(-/-) mice. Aged (18-month-old) FA2H(-/-) mice, however, exhibited scattered axonal and myelin sheath degeneration in the spinal cord and an even more pronounced loss of stainability of myelin sheaths in sciatic nerves. These results show that structurally and functionally normal myelin can be formed in the absence of 2-hydroxylated sphingolipids but that its long-term maintenance is strikingly impaired. Because axon degeneration appear to start rather early with respect to myelin degenerations, these lipids might be required for glial support of axon function.
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379
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Simpson RJ, Jensen SS, Lim JWE. Proteomic profiling of exosomes: Current perspectives. Proteomics 2008; 8:4083-99. [DOI: 10.1002/pmic.200800109] [Citation(s) in RCA: 641] [Impact Index Per Article: 40.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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380
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Medic N, Vita F, Abbate R, Soranzo MR, Pacor S, Fabbretti E, Borelli V, Zabucchi G. Mast cell activation by myelin through scavenger receptor. J Neuroimmunol 2008; 200:27-40. [PMID: 18657868 DOI: 10.1016/j.jneuroim.2008.05.019] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Revised: 05/29/2008] [Accepted: 05/30/2008] [Indexed: 10/21/2022]
Abstract
A role for mast cells (MC) in the pathogenesis of multiple sclerosis (MS) has been suggested, based on the analysis of human lesions and on an animal model of the disease (EAE). What role MC play in the development of MS is not well understood. We hypothesized that the link connecting MC with demyelinating diseases may be represented by their interaction with myelin. Here we show that myelin can activate mast cells. This process could be a key event in the mast cell function required for inducing EAE in mice and possibly in MS in man.
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Affiliation(s)
- Nevenka Medic
- Department of Physiology and Pathology, University of Trieste, via A. Fleming 22, 34127 Trieste Italy
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381
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Weinzierl A, Rudolf D, Hillen N, Tenzer S, van Endert P, Schild H, Rammensee HG, Stevanović S. Features of TAP-independent MHC class I ligands revealed by quantitative mass spectrometry. Eur J Immunol 2008; 38:1503-10. [DOI: 10.1002/eji.200838136] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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382
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Kippert A, Trajkovic K, Fitzner D, Opitz L, Simons M. Identification of Tmem10/Opalin as a novel marker for oligodendrocytes using gene expression profiling. BMC Neurosci 2008; 9:40. [PMID: 18439243 PMCID: PMC2396630 DOI: 10.1186/1471-2202-9-40] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Accepted: 04/25/2008] [Indexed: 01/06/2023] Open
Abstract
Background During the development of the central nervous system, oligodendrocytes generate large amounts of myelin, a multilayered insulating membrane that ensheathes axons, thereby allowing the fast conduction of the action potential and maintaining axonal integrity. Differentiation of oligodendrocytes to myelin-forming cells requires the downregulation of RhoA GTPase activity. Results To gain insights into the molecular mechanisms of oligodendrocyte differentiation, we performed microarray expression profiling of the oligodendroglial cell line, Oli-neu, treated with the Rho kinase (ROCK) inhibitor, Y-27632 or with conditioned neuronal medium. This resulted in the identification of the transmembrane protein 10 (Tmem10/Opalin), a novel type I transmembrane protein enriched in differentiating oligodendrocytes. In primary cultures, Tmem10 was abundantly expressed in O4-positive oligodendrocytes, but not in oligodendroglial precursor cells, astrocytes, microglia or neurons. In mature oligodendrocytes Tmem10 was enriched in the rims and processes of the cells and was only found to a lesser extent in the membrane sheets. Conclusion Together, our results demonstrate that Tmem10 is a novel marker for in vitro generated oligodendrocytes.
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Affiliation(s)
- Angelika Kippert
- Centre for Biochemistry and Molecular Cell Biology, University of Göttingen Humboldtallee 23, Göttingen, Germany.
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383
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Lakkaraju A, Rodriguez-Boulan E. Itinerant exosomes: emerging roles in cell and tissue polarity. Trends Cell Biol 2008; 18:199-209. [PMID: 18396047 DOI: 10.1016/j.tcb.2008.03.002] [Citation(s) in RCA: 305] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Revised: 03/05/2008] [Accepted: 03/06/2008] [Indexed: 12/11/2022]
Abstract
Cells use secreted signals (e.g. chemokines and growth factors) and sophisticated vehicles such as argosomes, cytonemes, tunneling nanotubes and exosomes to relay important information to other cells, often over large distances. Exosomes, 30-100-nm intraluminal vesicles of multivesicular bodies (MVB) released upon exocytic fusion of the MVB with the plasma membrane, are increasingly recognized as a novel mode of cell-independent communication. Exosomes have been shown to function in antigen presentation and tumor metastasis, and in transmitting infectious agents. However, little is known about the biogenesis and function of exosomes in polarized cells. In this review, we discuss new evidence suggesting that exosomes participate in the transport of morphogens and RNA, and thus influence cell polarity and developmental patterning of tissues.
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Affiliation(s)
- Aparna Lakkaraju
- Margaret M. Dyson Vision Research Institute, Department of Ophthalmology, Weill Medical College of Cornell University, New York, NY 10021, USA.
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384
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From Our Sister Journal: Proteomics 24/2007. Proteomics 2007. [DOI: 10.1002/pmic.200790101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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