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Biogenesis of extracellular vesicles (EV): exosomes, microvesicles, retrovirus-like vesicles, and apoptotic bodies. J Neurooncol 2013; 113:1-11. [PMID: 23456661 DOI: 10.1007/s11060-013-1084-8] [Citation(s) in RCA: 963] [Impact Index Per Article: 87.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 02/13/2013] [Indexed: 12/14/2022]
Abstract
Recent studies suggest both normal and cancerous cells secrete vesicles into the extracellular space. These extracellular vesicles (EVs) contain materials that mirror the genetic and proteomic content of the secreting cell. The identification of cancer-specific material in EVs isolated from the biofluids (e.g., serum, cerebrospinal fluid, urine) of cancer patients suggests EVs as an attractive platform for biomarker development. It is important to recognize that the EVs derived from clinical samples are likely highly heterogeneous in make-up and arose from diverse sets of biologic processes. This article aims to review the biologic processes that give rise to various types of EVs, including exosomes, microvesicles, retrovirus like particles, and apoptotic bodies. Clinical pertinence of these EVs to neuro-oncology will also be discussed.
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102
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Koppers-Lalic D, Hogenboom MM, Middeldorp JM, Pegtel DM. Virus-modified exosomes for targeted RNA delivery; a new approach in nanomedicine. Adv Drug Deliv Rev 2013; 65:348-56. [PMID: 22820525 PMCID: PMC7103310 DOI: 10.1016/j.addr.2012.07.006] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 07/04/2012] [Accepted: 07/08/2012] [Indexed: 12/21/2022]
Abstract
A major goal in biomedical research is to clinically reverse the cause of disease rather than treating the symptoms. Gene therapy has the potential to meet this goal and the discovery of RNA interference (RNAi) has lead to a new class of highly selective therapeutics. However, initial enthusiasm is reduced due to safety concerns associated with virus-based delivery vectors that are used for in vivo delivery. Viral vectors for siRNA delivery into target cells are used because of their high target specificity and delivery efficacy (endosomal escape). Recent discoveries suggest that a specialized form of nano-sized lipid vesicles called exosomes can incorporate and transport functional RNAs into target cells and may serve as an attractive alternative. Evidence is accumulating that most pluricellular organisms sustain exosome-based communications via inter-cellular exchange of mRNA and miRNAs between cells. We discovered that viruses have found ways to exploit this communication pathway and we argue here that adaptations of exosomes imposed by viruses maybe exploited for superior delivery of RNA in vivo. We discuss recent discoveries in exosome biogenesis their physical properties, targeting and delivery strategies and how the knowledge of exosome production in virus infected cells could propel their entry into clinical settings.
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Key Words
- abc, atp-binding cassette
- ago, argonaute
- bace1, β-site app-cleaving enzyme 1
- bbb, blood brain barrier
- dex, dendritic cell- derived exosome
- ebv, epstein–barr virus
- ee, early endosome
- escrt, endosomal sorting complexes required for transport
- hcc, hepatocellular carcinoma
- ilv, intralumenal vesicles
- imdc, immature dendritic cell
- imdex, immature dendritic cell-derived exosome
- lcl, latency type iii lymphoblastoid b cell line
- le, late endosome
- lmp1, latent membrane protein 1
- mdex, mature dendritic cell-derived exosome
- mdr1, multidrug resistance protein 1
- mirna, microrna
- mrna, messenger rna
- mvb, multivesicular body
- p-body, processing body
- peg, poly(ethylene glycol)
- pirna, piwi-interacting rna
- risc, rna-induced silencing complex
- rnai, rna interference
- sirna, small interference rna
- vlp, virus-like particles
- vsv-g, g protein of vesicular stomatitis virus
- exosomes
- microrna
- genetic-transfer
- virus
- gene-therapy
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Affiliation(s)
- Danijela Koppers-Lalic
- Department of Pathology, Cancer Center Amsterdam, VU University Medical Center, de Boelelaan 1117HV Amsterdam, The Netherlands
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103
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Malik ZA, Kott KS, Poe AJ, Kuo T, Chen L, Ferrara KW, Knowlton AA. Cardiac myocyte exosomes: stability, HSP60, and proteomics. Am J Physiol Heart Circ Physiol 2013; 304:H954-65. [PMID: 23376832 DOI: 10.1152/ajpheart.00835.2012] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exosomes, which are 50- to 100-nm-diameter lipid vesicles, have been implicated in intercellular communication, including transmitting malignancy, and as a way for viral particles to evade detection while spreading to new cells. Previously, we demonstrated that adult cardiac myocytes release heat shock protein (HSP)60 in exosomes. Extracellular HSP60, when not in exosomes, causes cardiac myocyte apoptosis via the activation of Toll-like receptor 4. Thus, release of HSP60 from exosomes would be damaging to the surrounding cardiac myocytes. We hypothesized that 1) pathological changes in the environment, such as fever, change in pH, or ethanol consumption, would increase exosome permeability; 2) different exosome inducers would result in different exosomal protein content; 3) ethanol at "physiological" concentrations would cause exosome release; and 4) ROS production is an underlying mechanism of increased exosome production. We found the following: first, exosomes retained their protein cargo under different physiological/pathological conditions, based on Western blot analyses. Second, mass spectrometry demonstrated that the protein content of cardiac exosomes differed significantly from other types of exosomes in the literature and contained cytosolic, sarcomeric, and mitochondrial proteins. Third, ethanol did not affect exosome stability but greatly increased the production of exosomes by cardiac myocytes. Fourth, ethanol- and hypoxia/reoxygenation-derived exosomes had different protein content. Finally, ROS inhibition reduced exosome production but did not completely inhibit it. In conclusion, exosomal protein content is influenced by the cell source and stimulus for exosome formation. ROS stimulate exosome production. The functions of exosomes remain to be fully elucidated.
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Affiliation(s)
- Z A Malik
- Molecular and Cellular Cardiology, Department of Medicine, University of California, Davis, CA 95616, USA
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104
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Fowler VM. The human erythrocyte plasma membrane: a Rosetta Stone for decoding membrane-cytoskeleton structure. CURRENT TOPICS IN MEMBRANES 2013; 72:39-88. [PMID: 24210427 DOI: 10.1016/b978-0-12-417027-8.00002-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The mammalian erythrocyte, or red blood cell (RBC), is a unique experiment of nature: a cell with no intracellular organelles, nucleus or transcellular cytoskeleton, and a plasma membrane with uniform structure across its entire surface. By virtue of these specialized properties, the RBC membrane has provided a template for discovery of the fundamental actin filament network machine of the membrane skeleton, now known to confer mechanical resilience, anchor membrane proteins, and organize membrane domains in all cells. This chapter provides a historical perspective and critical analysis of the biochemistry, structure, and physiological functions of this actin filament network in RBCs. The core units of this network are nodes of ~35-37 nm-long actin filaments, interconnected by long strands of (α1β1)₂-spectrin tetramers, forming a 2D isotropic lattice with quasi-hexagonal symmetry. Actin filament length and stability is critical for network formation, relying upon filament capping at both ends: tropomodulin-1 at pointed ends and αβ-adducin at barbed ends. Tropomodulin-1 capping is essential for precise filament lengths, and is enhanced by tropomyosin, which binds along the short actin filaments. αβ-adducin capping recruits spectrins to sites near barbed ends, promoting network formation. Accessory proteins, 4.1R and dematin, also promote spectrin binding to actin and, with αβ-adducin, link to membrane proteins, targeting actin nodes to the membrane. Dissection of the molecular organization within the RBC membrane skeleton is one of the paramount achievements of cell biological research in the past century. Future studies will reveal the structure and dynamics of actin filament capping, mechanisms of precise length regulation, and spectrin-actin lattice symmetry.
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Affiliation(s)
- Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, USA.
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105
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Peters LL, Paw BH, Blanc L. The scat mouse model highlights RASA3, a GTPase activating protein, as a key regulator of vertebrate erythropoiesis and megakaryopoiesis. Small GTPases 2012; 4:47-50. [PMID: 23221813 DOI: 10.4161/sgtp.23013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Although significant progress has been made in the past decades in our understanding of bone marrow failure syndromes and anemia, many pathological conditions of unknown origin remain. Mouse models have significantly contributed to our understanding of normal erythropoiesis and the pathogenesis of erythroid disorders. Recently, we identified in the scat (severe combined anemia and thrombocytopenia) mouse model a missense mutation (G125V) in the Rasa3 gene, encoding a Ras GTPase activating protein (GAP). RASA3 is lost during reticulocyte maturation through the exosomal pathway and is therefore absent in mature erythrocytes. In wild-type reticulocytes, RASA3 is bound to the plasma membrane, a prerequisite for its GAP activity, but is mislocalized to the cytosol in scat. This mislocalization leads to RASA3 loss of function and higher levels of Ras-GTP, the active form of Ras, are consistently found in scat mature red cells. Finally, RASA3 function is conserved among vertebrates, since erythropoiesis and thrombopoiesis are impaired in zebrafish in which rasa3 is knocked-down by morpholinos, and RASA3 is expressed in human erythroleukemia cells as well as in primary cells. In this commentary, we highlight the critical, conserved and non-redundant function of RASA3 in the context of vertebrate erythropoiesis and megakaryopoiesis. We notably discuss the mechanism of RASA3 downregulation and speculate on the most intriguing part of the phenotype observed in scat; the transient remission period.
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106
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Microvesicles and exosomes: Opportunities for cell-derived membrane vesicles in drug delivery. J Control Release 2012; 161:635-44. [DOI: 10.1016/j.jconrel.2011.11.021] [Citation(s) in RCA: 298] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 11/17/2011] [Accepted: 11/19/2011] [Indexed: 01/19/2023]
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107
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Simpson RJ, Kalra H, Mathivanan S. ExoCarta as a resource for exosomal research. J Extracell Vesicles 2012; 1:18374. [PMID: 24009883 PMCID: PMC3760644 DOI: 10.3402/jev.v1i0.18374] [Citation(s) in RCA: 267] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Revised: 03/19/2012] [Accepted: 03/20/2012] [Indexed: 12/14/2022] Open
Abstract
Exosomes are a class of extracellular vesicles that are secreted by various cell types. Unlike other extracellular vesicles (ectosomes and apoptotic blebs), exosomes are of endocytic origin. The roles of exosomes in vaccine/drug delivery, intercellular communication and as a possible source of disease biomarkers have sparked immense interest in them, resulting in a plethora of studies. Whilst multidimensional datasets are continuously generated, it is difficult to harness the true potential of the data until they are compiled and made accessible to the biomedical researchers. Here, we describe ExoCarta (http://www.exocarta.org), a manually curated database of exosomal proteins, RNA and lipids. Datasets currently present in ExoCarta are integrated from both published and unpublished exosomal studies. Since its launch in 2009, ExoCarta has been accessed by more than 16,000 unique users. In this article, we discuss the utility of ExoCarta for exosomal research and urge biomedical researchers in the field to deposit their datasets directly to ExoCarta.
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Affiliation(s)
- Richard J Simpson
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
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108
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Koles K, Nunnari J, Korkut C, Barria R, Brewer C, Li Y, Leszyk J, Zhang B, Budnik V. Mechanism of evenness interrupted (Evi)-exosome release at synaptic boutons. J Biol Chem 2012; 287:16820-34. [PMID: 22437826 DOI: 10.1074/jbc.m112.342667] [Citation(s) in RCA: 207] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Wnt signaling plays critical roles during synaptic development and plasticity. However, the mechanisms by which Wnts are released and travel to target cells are unresolved. During synaptic development, the secretion of Drosophila Wnt1, Wingless, requires the function of Evenness Interrupted (Evi)/Wls, a Wingless-binding protein that is secreted along with Wingless at the neuromuscular junction. Given that Evi is a transmembrane protein, these studies suggested the presence of a novel vesicular mechanism of trans-synaptic communication, potentially in the form of exosomes. To establish the mechanisms for the release of Evi vesicles, we used a dsRNA assay in cultured cells to screen for genes that when down-regulated prevent the release of Evi vesicles. We identified two proteins, Rab11 and Syntaxin 1A (Syx1A), that were required for Evi vesicle release. To determine whether the same mechanisms were used in vivo at the neuromuscular junction, we altered the activity of Rab11 and Syx1A in motoneurons and determined the impact on Evi release. We found that Syx1A, Rab11, and its effector Myosin5 were required for proper Evi vesicle release. Furthermore, ultrastructural analysis of synaptic boutons demonstrated the presence of multivesicular bodies, organelles involved in the production and release of exosomes, and these multivesicular bodies contained Evi. We also used mass spectrometry, electron microscopy, and biochemical techniques to characterize the exosome fraction from cultured cells. Our studies revealed that secreted Evi vesicles show remarkable conservation with exosomes in other systems. In summary, our observations unravel some of the in vivo mechanisms required for Evi vesicle release.
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Affiliation(s)
- Kate Koles
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
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109
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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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110
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Multiple recognition assay reveals prostasomes as promising plasma biomarkers for prostate cancer. Proc Natl Acad Sci U S A 2011; 108:8809-14. [PMID: 21555566 DOI: 10.1073/pnas.1019330108] [Citation(s) in RCA: 174] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Prostasomes are microvesicles (mean diameter, 150 nm) that are produced and secreted by normal and malignant prostate acinar cells. It has been hypothesized that invasive growth of malignant prostate cells may cause these microvesicles, normally released into seminal fluid, to appear in interstitial space and therewith into peripheral circulation. The suitability of prostasomes as blood biomarkers in patients with prostate cancer was tested by using an expanded variant of the proximity ligation assay (PLA). We developed an extremely sensitive and specific assay (4PLA) for detection of complex target structures such as microvesicles in which the target is first captured via an immobilized antibody and subsequently detected by using four other antibodies with attached DNA strands. The requirement for coincident binding by five antibodies to generate an amplifiable reporter results in both increased specificity and sensitivity. The assay successfully detected significantly elevated levels of prostasomes in blood samples from patients with prostate cancer before radical prostatectomy, compared with controls and men with benign biopsy results. The medians for prostasome levels in blood plasma of patients with prostate cancer were 2.5 to sevenfold higher compared with control samples in two independent studies, and the assay also distinguished patients with high and medium prostatectomy Gleason scores (8/9 and 7, respectively) from those with low score (≤ 6), thus reflecting disease aggressiveness. This approach that enables detection of prostasomes in peripheral blood may be useful for early diagnosis and assessment of prognosis in organ-confined prostate cancer.
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111
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Duijvesz D, Luider T, Bangma CH, Jenster G. Exosomes as biomarker treasure chests for prostate cancer. Eur Urol 2010; 59:823-31. [PMID: 21196075 DOI: 10.1016/j.eururo.2010.12.031] [Citation(s) in RCA: 218] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Accepted: 12/20/2010] [Indexed: 01/07/2023]
Abstract
CONTEXT Although progress has been made with regard to types of markers (protein, DNA, RNA, and metabolites) and implementation of improved technologies (mass spectrometry, arrays, and deep sequencing), the discovery of novel biomarkers for prostate cancer (PCa) in complex fluids, such as serum and urine, remains a challenge. Meanwhile, recent studies have reported that many cancer-derived proteins and RNAs are secreted through small vesicles known as exosomes. OBJECTIVE This narrative review describes recent progress in exosome research, focusing on the potential role of exosomes as novel biomarkers for PCa. The purpose of this review is to acquaint clinicians and researchers in the field of urology with the potential role of exosomes as biomarker treasure chests and with their clinical value. EVIDENCE ACQUISITION Medline and Embase entries between 1966 and September 2010 were searched using the keywords exosomes, microvesicles, prostasomes, biomarkers, prostate cancer, and urology. Leading publications and articles constructively contributing to exosome research were selected for this review. EVIDENCE SYNTHESIS Exosomes are small vesicles (50-100 nm) secreted by almost all tissues; they represent their tissue origin. Purification of prostate- and PCa-derived exosomes will allow us to profile exosomes, providing a promising source of protein and RNA biomarkers for PCa. This profiling will contribute to the discovery of novel markers for the early diagnosis and reliable prognosis of PCa. CONCLUSIONS Although the initial results are promising, further investigations are required to assess the clinical value of these exosomes in PCa.
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Affiliation(s)
- Diederick Duijvesz
- Department of Urology, Erasmus Medical Centre, Rotterdam, The Netherlands
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112
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113
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Abstract
Interactions between the essential dietary metals, iron and copper, have been known for many years. This review highlights recent advances in iron-copper interactions with a focus on tissues and cell types important for regulating whole-body iron and copper homeostasis. Cells that mediate dietary assimilation (enterocytes) and storage and distribution (hepatocytes) of iron and copper are considered, along with the principal users (erythroid cells) and recyclers of red cell iron (reticuloendothelial macrophages). Interactions between iron and copper in the brain are also discussed. Many unanswered questions regarding the role of these metals and their interactions in health and disease emerge from this synopsis, highlighting extensive future research opportunities.
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Affiliation(s)
- James F Collins
- Food Science and Human Nutrition Department, University of Florida, Gainesville, Florida 32611, USA
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114
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Circulating nucleic acids as a new diagnostic tool. Cell Mol Biol Lett 2010; 15:242-59. [PMID: 20186496 PMCID: PMC6275674 DOI: 10.2478/s11658-010-0004-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 02/10/2010] [Indexed: 02/06/2023] Open
Abstract
The discovery of circulating nucleic acids in the 1940s opened up new possibilities for the non-invasive detection, monitoring and screening of various human disorders. Several tumour markers that enable early cancer detection or tumour behaviour prediction have been detected in the plasma of cancer patients. Maternal plasma analysis can be used to detect certain fetal abnormalities, with the quantification of cell-free nucleic acids used to screen for several pregnancy-associated disorders. Some other applications are in transplant monitoring and graft rejection assessment, and in certain medical emergencies such as trauma and burn severity stratification. Many studies have yielded promising results in this field, but the techniques have yet to be applied in routine clinical practice. Large-scale studies using similar technologies and a broad spectrum of patients are still needed to verify the results of the various studies.
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115
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The water channel aquaporin-1 partitions into exosomes during reticulocyte maturation: implication for the regulation of cell volume. Blood 2009; 114:3928-34. [PMID: 19724054 DOI: 10.1182/blood-2009-06-230086] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aquaporin-1 (AQP-1), the universal water channel, is responsible for rapid response of cell volume to changes in plasma tonicity. In the membrane of the red cell the concentration of the protein is tightly controlled. Here, we show that AQP-1 is partially lost during in vitro maturation of mouse reticulocytes and that it is associated with exosomes, released throughout this process. AQP-1 in young reticulocytes localizes to the plasma membrane and also in endosomal compartments and exosomes, formed both in vitro and in vivo. During maturation a part of the total pool of AQP-1 is differentially sorted and released via the exosomal pathway. A proteasome inhibitor, MG132, suppresses secretion of AQP-1, implying that ubiquitination is a sorting signal for its release. We further show that modulation of medium tonicity in vitro regulates the secretion of AQP-1, thus showing that extracellular osmotic conditions can drive sorting of selected proteins by the exosomal pathway. These results lead us to suggest that AQP-1 sorting into exosomes may be the mechanism by which the reticulocyte adapts to environmental changes during its maturation.
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116
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Locke JA, Fazli L, Adomat H, Smyl J, Weins K, Lubik AA, Hales DB, Nelson CC, Gleave ME, Tomlinson Guns ES. A novel communication role for CYP17A1 in the progression of castration-resistant prostate cancer. Prostate 2009; 69:928-37. [PMID: 19267349 DOI: 10.1002/pros.20940] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND CYP17A1 is currently a target for total androgen blockade in advanced prostate cancer (CaP) patients. After castration, or removal of testicular androgens, CYP17A1 can act as a rate-limiting enzyme in androgen synthesis from cholesterol or other adrenal precursors within the tumor microenvironment ultimately contributing to disease progression. Herein we provide evidence that CYP17A1 could also be a mediator of cell-to-cell communication within the CaP tumor microenvironment. METHODS CYP17A1 expression was evaluated by immunohistochemical analysis of human tumor sections and Western blot analysis of CaP patients' serum and exosome isolates. CYP17A1 activity assays were conducted in human serum (and positive control human liver and kidney microsomes) using progesterone as a precursor and an LC-MS endpoint. RESULTS These studies revealed that the expression pattern of CYP17A1 is typical of a secretory protein as it is localized to the luminal pole of the cells in exocrine secretory mode. CYP17A1 is expressed in human serum and in fact is elevated in the serum of CaP patients as compared to healthy controls. Serum CYP17A1 activity could not be confirmed, however, verification of CYP17A1 expression in exosomes suggests a role in cell-to-cell communication within the tumor microenvironment. CONCLUSIONS CYP17A1 is a crucial enzyme for de novo androgen synthesis within the tumor microenvironment after removal of testicular androgens by castration. We provide evidence for a novel role for CYP17A1 in serum and further reiterate the importance of targeting this enzyme in CaP progression.
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Affiliation(s)
- Jennifer A Locke
- Department of Urologic Sciences, University of British Columbia, The Prostate Centre at Vancouver General Hospital, Vancouver, British Columbia, Canada
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117
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Conde-Vancells J, Rodriguez-Suarez E, Embade N, Gil D, Matthiesen R, Valle M, Elortza F, Lu SC, Mato JM, Falcon-Perez JM. Characterization and comprehensive proteome profiling of exosomes secreted by hepatocytes. J Proteome Res 2009; 7:5157-66. [PMID: 19367702 DOI: 10.1021/pr8004887] [Citation(s) in RCA: 447] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Exosomes represent a discrete population of vesicles that are secreted from various cell types to the extracellular media. Their protein and lipid composition are a consequence of sorting events at the level of the multivesicular body, a central organelle which integrates endocytic and secretory pathways. Characterization of exosomes from different biological samples has shown the presence of common as well as cell-type specific proteins. Remarkably, the protein content of the exosomes is modified upon pathological or stress conditions. Hepatocytes play a central role in the body response to stress metabolizing potentially harmful endogenous substances as well as xenobiotics. In the present study, we described and characterized for the first time exosome secretion in nontumoral hepatocytes, and with the use of a systematic proteomic approach, we establish the first extensive proteome of a hepatocyte-derived exosome population which should be useful in furthering our understanding of the hepatic function and in the identification of components that may serve as biomarkers for hepatic alterations. Our analysis identifies a significant number of proteins previously described among exosomes derived from others cell types as well as proteins involved in metabolizing lipoproteins, endogenous compounds and xenobiotics, not previously described in exosomes. Furthermore, we demonstrated that exosomal membrane proteins can constitute an interesting tool to express nonexosomal proteins into exosomes with therapeutic purposes.
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Affiliation(s)
- Javier Conde-Vancells
- Metabolomics Unit, CICbioGUNE, CIBERehd, Bizkaia Technology Park, Derio, 48160, Bizkaia, Spain
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118
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Gatto C, Milanick M. Red blood cell Na pump: Insights from species differences. Blood Cells Mol Dis 2009; 42:192-200. [PMID: 19268612 DOI: 10.1016/j.bcmd.2009.01.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Accepted: 01/06/2009] [Indexed: 01/21/2023]
Abstract
The red blood cell membrane is specialized to exchange chloride and bicarbonate; usually the pH gradient, the chloride ratio, and the membrane potential are tightly coupled. We review the evidence that led to the ability to separately vary inside and outside pH in red cells. The effect of pH on Na pump activity and on the selectivity of the inside and the outside transport sites is reviewed. In red blood cells, at high pH, the outside site is not selective. An increase in protons leads to an increase in K(+) affinity, thus making the site more selective. The pK for this site is different in rats and humans; because of the high conservation of residues in these two species, there are only a few possible residues that can account for this difference. On the inside, work from unsided preparations suggests that, at high pH, the transport site is highly selective for Na(+). Once again, an increase in protons leads to an increase in K(+) affinity, but now the result is a less selective site. During their maturation, reticulocytes lose many membrane proteins. The type and fractional loss is species dependent. For example, most reticulocytes lose most of their Na pumps, retaining about 100 pumps per cell, but animals from the order Carnivora lose all their pumps. We review some of the evidence that PKC phosphorylation of N-terminus serines is responsible for endocytosis in other cell types and species variation in this region.
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Affiliation(s)
- Craig Gatto
- Division of Biomedical Sciences, School of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA
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Wang GJ, Liu Y, Qin A, Shah SV, Deng ZB, Xiang X, Cheng Z, Liu C, Wang J, Zhang L, Grizzle WE, Zhang HG. Thymus exosomes-like particles induce regulatory T cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2008; 181:5242-8. [PMID: 18832678 PMCID: PMC4319673 DOI: 10.4049/jimmunol.181.8.5242] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Exosomes released from different types of cells have been proposed to contribute to intercellular communication. We report that thymic exosome-like particles (ELPs) released from cells of the thymus can induce the development of Foxp3(+) regulatory T (Treg) cells in the lung and liver. Thymic ELPs also induce the conversion of thymic CD4(+)CD25(-) T cells into Tregs. Tregs induced by thymic ELPs suppress the proliferation of CD4(+)CD25(-) T cells in vitro and in vivo. We further show that neutralization of TGF-beta in ELPs partially reverses thymic ELP-mediated induction of CD4(+)Foxp3(+) T cells in the lung and liver. This study demonstrates that thymic ELPs participate in the induction of Foxp3(+) Tregs. Also, TGF-beta of thymic ELPs might be required for the generation of Tregs in the peripheral tissues.
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Affiliation(s)
- Gui-Jun Wang
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Yuelong Liu
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Aijian Qin
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Spandan V. Shah
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Zhong-bin Deng
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Xiaoyu Xiang
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Ziqiang Cheng
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Cunren Liu
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Jianhua Wang
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Liming Zhang
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - William E. Grizzle
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Huang-Ge Zhang
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
- Birmingham Veterans Administration Medical Center, Birmingham, AL 35233
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120
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Exosome secretion, including the DNA damage-induced p53-dependent secretory pathway, is severely compromised in TSAP6/Steap3-null mice. Cell Death Differ 2008; 15:1723-33. [PMID: 18617898 DOI: 10.1038/cdd.2008.104] [Citation(s) in RCA: 264] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
TSAP6 (tumor suppressor-activated pathway 6), also known as Steap3, is a direct p53 transcriptional target gene. It regulates protein secretion, for example translationally controlled tumor protein (TCTP), which is implicated in tumor reversion. In keeping with the latter, we show herein that TSAP6 is a glycosylated protein present in the trans-Golgi network, endosomal-vesicular compartment and cytoplasmic membrane. To further investigate the physiological function of TSAP6, we have generated TSAP6-deficient mice. These mice exhibit microcytic anemia with abnormal reticulocyte maturation and deficient transferrin receptor downregulation, a process known to be dependent on exosomal secretion. Moreover, we provide direct evidence that exosome production is severely compromised in TSAP6-null cells. Finally, we show that the DNA damage-induced p53-dependent nonclassical exosomal secretory pathway is abrogated in TSAP6-null cells. Given the fact that exosomes are used as cell-free vaccines against cancer and that they could be involved in the biogenesis and spread of human immunodeficiency virus, it is important to understand their regulation. The results presented here provide the first genetic demonstration that exosome formation is a tightly controlled biological process dependent of TSAP6.
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121
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Increased exosome production from tumour cell cultures using the Integra CELLine Culture System. J Immunol Methods 2008; 335:98-105. [PMID: 18423480 DOI: 10.1016/j.jim.2008.03.001] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Revised: 03/03/2008] [Accepted: 03/05/2008] [Indexed: 11/23/2022]
Abstract
Exosomes are nanometer-sized vesicles, secreted from most cell types, with documented immune-modulatory functions. Exosomes can be purified from cultured cells but to do so effectively, requires maintenance of cells at high density in order to obtain sufficient accumulation of exosomes in the culture medium, prior to purification. Whilst high density cultures can be achieved with cells in suspension, this remains difficult with adherent cells, resulting in low quantity of exosomes for subsequent study. We have used the Integra CELLine culture system, originally designed for hybridoma cultures, to achieve a significant increase in obtainable exosomes from adherent and non-adherent tumour cells. Traditional cultures of mesothelioma cells (cultured in 75 cm(2) flasks) gave an average yield of 0.78 microg+/-0.14 microg exosome/ml of conditioned medium. The CELLine Adhere 1000 (CLAD1000) flask, housing the same cell line, increased exosome yield approximately 12 fold to 10.06 microg+/-0.97 microg/ml. The morphology, phenotype and immune function of these exosomes were compared, and found to be identical in all respects. Similarly an 8 fold increase in exosome production was obtained from NKL cells (a suspension cell line) using a CELLine 1000 (CL1000) flask. The CELLine system also incurred ~5.5 fold less cost and reduced labour for cell maintenance. This simple culture system is a cost effective, useful method for significantly increasing the quantity of exosomes available from cultured cells, without detrimental effects. This tool should prove advantageous in future studies of exosome-immune modulation in cancer and other settings.
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122
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Smalley DM, Sheman NE, Nelson K, Theodorescu D. Isolation and identification of potential urinary microparticle biomarkers of bladder cancer. J Proteome Res 2008; 7:2088-96. [PMID: 18373357 DOI: 10.1021/pr700775x] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Bladder cancer leads to approximately 13,000 deaths annually in the United States. Early disease is often treated with minimal morbidity and has good prognosis, while the opposite is true for advanced disease. Currently, no tools exist for early detection of this cancer. Microparticles are small, subcellular particles released by essentially all cells upon activation and are known to be produced constitutively by cancer cells. Since most bladder cancers originate in the urothelial cells lining the lumen of the organ, we hypothesize that these cells will release microparticles into the urine. The goal of this study was to identify potential biomarkers in the urinary microparticles of individuals with bladder cancer. Urine microparticles from five healthy individuals and four individuals with bladder cancer were isolated. Samples were delipidated by PAGE and trypsin-digested, peptides were extracted, and the proteome was examined by LC-MS/MS using a Thermo Finnigan LTQ and LTQ-FT ion trap mass spectrometer. Protein identification was determined by SEQUEST and relative quantitation was assessed by comparing spectral counts. Eight proteins were elevated in the microparticles from individuals with bladder cancer. They include five proteins associated with the epidermal growth factor receptor pathway, the alpha subunit of GsGTP binding protein, resistin, and retinoic acid-induced protein 3. Further studies will be needed to validate these potential biomarkers.
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Affiliation(s)
- David M Smalley
- Mellon Medical Biomarker Discovery Laboratory, W. M. Keck Laboratory for Mass Spectrometry, Department of Urology, University of Virginia, Charlottesville, Virginia 22908, USA
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Abache T, Le Naour F, Planchon S, Harper F, Boucheix C, Rubinstein E. The transferrin receptor and the tetraspanin web molecules CD9, CD81, and CD9P-1 are differentially sorted into exosomes after TPA treatment of K562 cells. J Cell Biochem 2008; 102:650-64. [PMID: 17407154 DOI: 10.1002/jcb.21318] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Here we show that treatment of K562 cells with the phorbol ester TPA induces the down-modulation of various surface antigens. Among them, the transferrin receptor (TfR), the tetraspanin CD81, and a CD81-associated protein, CD9P-1, were unique in that their expression levels were lower after 24 h incubation than after 3 h. We demonstrated that like the TfR, CD81 was internalized at early times, and was less synthesized at latter times. Despite the association of a fraction of the TfR with CD81, these two molecules were subjected to different fates. TPA increased targeting of CD81 and CD9P-1 into exosomes but strongly reduced the localization of the TfR in these vesicles. Using this model we have shown that a fraction of CD81 and CD9P-1 in exosomes comes from a surface pool and that these molecules remain associated in exosomes. However, CD9P-1 could be targeted to exosomes in the absence of CD81 and of another tetraspanin, CD9. The targeting of CD9 into exosomes did not require palmitoylation of the protein. J. Cell. Biochem. 102: 650-664, 2007. (c) 2007 Wiley-Liss, Inc.
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Toth B, Lok CAR, Böing A, Diamant M, van der Post JAM, Friese K, Nieuwland R. Microparticles and exosomes: impact on normal and complicated pregnancy. Am J Reprod Immunol 2007; 58:389-402. [PMID: 17922691 DOI: 10.1111/j.1600-0897.2007.00532.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Eukaryotic cells release vesicles into their environment by membrane shedding (ectosomes or microparticles) and secretion (exosomes). Microparticles and exosomes occur commonly in vitro and in vivo. The occurrence, composition and function(s) of these vesicles change during disease (progression). During the last decade, the scientific and clinical interest increased tremendously. Evidence is accumulating that microparticles and exosomes may be of pathophysiological relevance in autoimmune, cardiovascular and thromboembolic diseases, as well as inflammatory and infectious disorders. In this review, we will summarize the discovery, biology, structure and function of microparticles and exosomes, and discuss their (patho-) physiological role during normal and complicated pregnancy.
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Affiliation(s)
- Bettina Toth
- Department of Obstetrics and Gynaecology, Ludwig-Maximilians University, Grosshadern, Munich, Germany.
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125
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Vingtdeux V, Hamdane M, Loyens A, Gelé P, Drobeck H, Bégard S, Galas MC, Delacourte A, Beauvillain JC, Buée L, Sergeant N. Alkalizing drugs induce accumulation of amyloid precursor protein by-products in luminal vesicles of multivesicular bodies. J Biol Chem 2007; 282:18197-18205. [PMID: 17468104 DOI: 10.1074/jbc.m609475200] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amyloid precursor protein (APP) metabolism is central to the pathogenesis of Alzheimer disease. We showed recently that the amyloid intracellular domain (AICD), which is released by gamma-secretase cleavage of APP C-terminal fragments (CTFs), is strongly increased in cells treated with alkalizing drugs (Vingtdeux, V., Hamdane, M., Bégard, S., Loyens, A., Delacourte, A., Beauvillain, J.-C., Buée, L., Marambaud, P., and Sergeant, N. (2007) Neurobiol. Dis. 25, 686-696). Herein, we aimed to determine the cell compartment in which AICD accumulates. We show that APP-CTFs and AICD are present in multivesicular structures. Multivesicular bodies contain intraluminal vesicles (known as exosomes) when released in the extracellular space. We demonstrate that APP, APP-CTFs, and AICD are integrated and secreted within exosomes in differentiated neuroblastoma and primary neuronal culture cells. Together with recent data showing that amyloid-beta is also found in exosomes, our data show that multivesicular bodies are essential organelles for APP metabolism and that all APP metabolites can be secreted in the extracellular space.
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Affiliation(s)
- Valérie Vingtdeux
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France
| | - Malika Hamdane
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France
| | - Anne Loyens
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France
| | - Patrick Gelé
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France
| | - Hervé Drobeck
- CNRS, UMR 8161, "Lille Institute of Biology," University of Lille 1, Pasteur Institute of Lille, 1, rue du Professeur Calmette, F-59021 Lille Cedex, France
| | - Séverine Bégard
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France
| | - Marie-Christine Galas
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France
| | - André Delacourte
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France
| | - Jean-Claude Beauvillain
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France
| | - Luc Buée
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France
| | - Nicolas Sergeant
- INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France; Facultéde Médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, Centre de Recherches Jean-Pierre Aubert, Université Lille 2, Place de Verdun, F-59045 Lille, France.
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Abstract
The heat shock proteins (HSP) are a highly conserved family of proteins with critical functions in protein folding, protein trafficking, and cell signaling. These proteins also protect the cell against injury. HSP60 has been found in the extracellular space and has been identified in the plasma of some individuals. HSP60 is thought to be a "danger signal" to the immune system and is also highly immunogenic. Thus extracellular HSP60 is possibly toxic to the cell. The mechanism by which HSP60 is released into the extracellular space is unknown, as is whether it is released by cardiac myocytes. We investigated several different pathways controlling protein release including the classic, Golgi-mediated pathway. We found that HSP60 is released via exosomes, and that within the exosome, HSP60 is tightly attached to the exosome membrane.
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Affiliation(s)
- Sanjiv Gupta
- Molecular and Cellular Cardiology, Cardiovascular Division, University of California, Davis, One Shields Ave., Davis, CA 95616, USA
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127
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Abstract
A few years after the first description of free-circulating DNA in plasma and serum, the detection of tumor-associated overexpressed mRNA in plasma was also reported. This observation has been confirmed and it seems to be clear that the presence of free-circulating RNA is a ubiquitous phenomenon. In this short review I will discuss some basic aspects of the release mechanisms for the RNA, its biological meaning, and clinical value.
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Affiliation(s)
- Michael Fleischhacker
- Charité-Universitätsmedizin Berlin, Medizinische Klinik m.S. Onkologie u. Hämatologie, Molekularbiologisches Labor, Alte Apotheke, Schumannstr. 20-21, 10117 Berlin, Germany.
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128
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Calzolari A, Raggi C, Deaglio S, Sposi NM, Stafsnes M, Fecchi K, Parolini I, Malavasi F, Peschle C, Sargiacomo M, Testa U. TfR2 localizes in lipid raft domains and is released in exosomes to activate signal transduction along the MAPK pathway. J Cell Sci 2006; 119:4486-98. [PMID: 17046995 DOI: 10.1242/jcs.03228] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Transferrin receptor 2 (TfR2) possesses a YQRV motif similar to the YTRF motif of transferrin receptor 1 (TfR1) responsible for the internalization and secretion through the endosomal pathway. Raft biochemical dissection showed that TfR2 is a component of the low-density Triton-insoluble (LDTI) plasma membrane domain, able to co-immunoprecipitate with caveolin-1 and CD81, two structural raft proteins. In addition, subcellular fractionation experiments showed that TfR1, which spontaneously undergoes endocytosis and recycling, largely distributed to intracellular organelles, whereas TfR2 was mainly associated with the plasma membrane. Given the TfR2 localization in lipid rafts, we tested its capability to activate cell signalling. Interaction with an anti-TfR2 antibody or with human or bovine holotransferrin showed that it activated ERK1/ERK2 and p38 MAP kinases. Integrity of lipid rafts was required for MAPK activation. Co-localization of TfR2 with CD81, a raft tetraspanin exported through exosomes, prompted us to investigate exosomes released by HepG2 and K562 cells into culture medium. TfR2, CD81 and to a lesser extent caveolin-1, were found to be part of the exosomal budding vesicles. In conclusion, the present study indicates that TfR2 localizes in LDTI microdomains, where it promotes cell signalling, and is exported out of the cells through the exosome pathway, where it acts as an intercellular messenger.
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Affiliation(s)
- Alessia Calzolari
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
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129
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Yount G, Taft RJ, Luu T, Rachlin K, Moore D, Zhang W. Independent motile microplast formation correlates with glioma cell invasiveness. J Neurooncol 2006; 81:113-21. [PMID: 16850105 DOI: 10.1007/s11060-006-9211-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Accepted: 06/08/2006] [Indexed: 10/24/2022]
Abstract
Diffuse brain invasion contributes to the poor prognosis for patients with gliomas. Analyzing glioma cell migration in vitro, we have demonstrated the spontaneous shedding of anucleate cell fragments that separate from glioma cell bodies and maintain viability from hours to days. Unlike previously described cell fragments that are released from cells as diffusible vectors, glioma cell fragments are independently motile. We used computerized time-lapse microscopy to characterize the formation of these independent motile microplasts (IMMPs) in human cell cultures derived from the most highly invasive glial tumor, glioblastoma. IMMPs were larger than previously described cell fragments, ranging in size from approximately 2% to nearly half of the area of their parent cells. Complex cell-like behaviors-including establishment of polarity, extension of lamellipodia and filopodia, and change in direction of movement-remained intact in IMMPs. The average direction and velocity of the IMMPs were indistinguishable from those of their parent cells. IMMPs formed at a significantly higher rate in glioma cell lines rendered more invasive by overexpression of invasion-related genes than in vector-transfected controls. The correlation with cell invasiveness indicates that IMMP formation may be related to the cell-invasive phenotype. Further investigation will determine whether IMMPs represent a novel addition to the growing list of viable cell fragments with biological relevance.
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Affiliation(s)
- Garret Yount
- California Pacific Medical Center Research Institute, 475 Brannan Street, Suite 220, San Francisco, CA 94107, USA.
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130
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Johnstone RM. Exosomes biological significance: A concise review. Blood Cells Mol Dis 2006; 36:315-21. [PMID: 16487731 DOI: 10.1016/j.bcmd.2005.12.001] [Citation(s) in RCA: 268] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Accepted: 12/07/2005] [Indexed: 01/12/2023]
Abstract
Exosomes were initially thought to be a mechanism for removing unneeded membrane proteins from reticulocytes. Current studies have shown that the process of exosome formation extends to many mammalian cells. This concise review highlights the findings reported at a Workshop on Exosomes. Full knowledge of the contribution of exosomes to intercellular information transmission and the potential medical application of this knowledge will depend on the ingenuity of future investigators and their insight into biological processes.
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Affiliation(s)
- Rose M Johnstone
- Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada H3G 1Y6.
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