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1.
EMBO J ; 36(20): 3012-3028, 2017 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-28923825

RESUMO

Exosomes, nano-sized secreted extracellular vesicles (EVs), are actively studied for their diagnostic and therapeutic potential. In particular, exosomes secreted by dendritic cells (DCs) have been shown to carry MHC-peptide complexes allowing efficient activation of T lymphocytes, thus displaying potential as promoters of adaptive immune responses. DCs also secrete other types of EVs of different size, subcellular origin and protein composition, whose immune capacities have not been yet compared to those of exosomes. Here, we show that large EVs (lEVs) released by human DCs are as efficient as small EVs (sEVs), including exosomes, to induce CD4+ T-cell activation in vitro When released by immature DCs, however, lEVs and sEVs differ in their capacity to orient T helper (Th) cell responses, the former favouring secretion of Th2 cytokines, whereas the latter promote Th1 cytokine secretion (IFN-γ). Upon DC maturation, however, these functional differences are abolished, and all EVs become able to induce IFN-γ. Our results highlight the need to comprehensively compare the functionalities of EV subtypes in all patho/physiological systems where exosomes are claimed to perform critical roles.


Assuntos
Linfócitos T CD4-Positivos/efeitos dos fármacos , Linfócitos T CD4-Positivos/imunologia , Células Dendríticas/imunologia , Células Dendríticas/metabolismo , Vesículas Extracelulares/metabolismo , Ativação Linfocitária , Humanos
2.
Immunity ; 35(3): 361-74, 2011 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-21820334

RESUMO

Engagement of the B cell receptor (BCR) by surface-tethered antigens (Ag) leads to formation of a synapse that promotes Ag uptake for presentation onto major histocompatibility complex class II (MHCII) molecules. We have highlighted the membrane trafficking events and associated molecular mechanisms involved in Ag extraction and processing at the B cell synapse. MHCII-containing lysosomes are recruited to the synapse where they locally undergo exocytosis, allowing synapse acidification and the extracellular release of hydrolases that promote the extraction of the immobilized Ag. Lysosome recruitment and secretion results from the polarization of the microtubule-organizing center (MTOC), which relies on the cell division cycle (Cdc42)-downstream effector, atypical protein kinase C (aPKCζ). aPKCζ is phosphorylated upon BCR engagement, associates to lysosomal vesicles, and is required for their polarized secretion at the B cell synapse. Regulation of B lymphocyte polarity therefore emerges as a central mechanism that couples Ag extraction to Ag processing and presentation.


Assuntos
Apresentação de Antígeno , Linfócitos B/imunologia , Sinapses Imunológicas , Lisossomos , Receptores de Antígenos de Linfócitos B/fisiologia , Animais , Polaridade Celular , Lisossomos/metabolismo , Camundongos , Proteína Quinase C/imunologia , Receptores de Antígenos de Linfócitos B/imunologia , Proteína cdc42 de Ligação ao GTP/imunologia
3.
Sci Data ; 10(1): 401, 2023 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-37353541

RESUMO

Cell polarity is an essential and highly conserved process governing cell function. Cell polarization is generally triggered by an external signal that induces the relocation of the centrosome, thus defining the polarity axis of the cell. Here, we took advantage of B cells as a model to study cell polarity and perform a medium-throughput siRNA-based imaging screen to identify new molecular regulators of polarization. We first identified candidates based on a quantitative proteomic analysis of proteins differentially associated with the centrosome of resting non-polarized and stimulated polarized B cells. We then targeted 233 candidates in a siRNA screen and identified hits regulating the polarization of the centrosome and/or lysosomes in B cells upon stimulation. Our dataset of proteomics, images, and polarity indexes provides a valuable source of information for a broad community of scientists interested in the molecular mechanisms regulating cell polarity.


Assuntos
Linfócitos B , RNA Interferente Pequeno , Centrossomo/metabolismo , Proteômica , Humanos , Animais
4.
J Cell Biol ; 176(7): 1007-19, 2007 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-17389233

RESUMO

Antigen (Ag) capture and presentation onto major histocompatibility complex (MHC) class II molecules by B lymphocytes is mediated by their surface Ag receptor (B cell receptor [BCR]). Therefore, the transport of vesicles that carry MHC class II and BCR-Ag complexes must be coordinated for them to converge for processing. In this study, we identify the actin-associated motor protein myosin II as being essential for this process. Myosin II is activated upon BCR engagement and associates with MHC class II-invariant chain complexes. Myosin II inhibition or depletion compromises the convergence and concentration of MHC class II and BCR-Ag complexes into lysosomes devoted to Ag processing. Accordingly, the formation of MHC class II-peptides and subsequent CD4 T cell activation are impaired in cells lacking myosin II activity. Therefore, myosin II emerges as a key motor protein in BCR-driven Ag processing and presentation.


Assuntos
Apresentação de Antígeno/imunologia , Linfócitos B/metabolismo , Antígenos de Histocompatibilidade Classe II/metabolismo , Miosina Tipo II/metabolismo , Receptores de Antígenos de Linfócitos B/metabolismo , Vesículas Transportadoras/metabolismo , Actinas/metabolismo , Animais , Linfócitos B/imunologia , Linfócitos T CD4-Positivos/imunologia , Células Cultivadas , Antígenos de Histocompatibilidade Classe II/imunologia , Ativação Linfocitária/imunologia , Lisossomos/imunologia , Lisossomos/metabolismo , Substâncias Macromoleculares/imunologia , Substâncias Macromoleculares/metabolismo , Camundongos , Camundongos Transgênicos , Miosina Tipo II/imunologia , Transporte Proteico/imunologia , Receptores de Antígenos de Linfócitos B/imunologia , Vesículas Transportadoras/imunologia
5.
Traffic ; 10(6): 629-36, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19416472

RESUMO

The onset of an adaptive immune response requires the activation of T and B lymphocytes by antigen-presenting cells, through a specialized form of intercellular communication, known as the immunological synapse (IS). In B lymphocytes the IS promotes efficient recognition and acquisition of membrane-bound Ags, while in T cells, it modulates the T cell response upon exposure to peptide-major histocompatibility complexes. In this review, we highlight the similarities that determine B and T cell activation, focusing on immune receptor downstream signaling events that lead to synapse formation. We stress the notion that polarization of T and B lymphocytes characterized by global changes in cytoskeleton and membrane trafficking modulates synapse structure and function, thus determining lymphocyte effector functions and fate.


Assuntos
Sinapses Imunológicas/fisiologia , Receptores de Antígenos de Linfócitos B/fisiologia , Receptores de Antígenos de Linfócitos T/fisiologia , Endocitose , Exocitose , Transporte Proteico , Receptores de Antígenos de Linfócitos B/metabolismo , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais
6.
Nat Commun ; 12(1): 4389, 2021 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-34282141

RESUMO

Despite their roles in intercellular communications, the different populations of extracellular vesicles (EVs) and their secretion mechanisms are not fully characterized: how and to what extent EVs form as intraluminal vesicles of endocytic compartments (exosomes), or at the plasma membrane (PM) (ectosomes) remains unclear. Here we follow intracellular trafficking of the EV markers CD9 and CD63 from the endoplasmic reticulum to their residency compartment, respectively PM and late endosomes. We observe transient co-localization at both places, before they finally segregate. CD9 and a mutant CD63 stabilized at the PM are more abundantly released in EVs than CD63. Thus, in HeLa cells, ectosomes are more prominent than exosomes. By comparative proteomic analysis and differential response to neutralization of endosomal pH, we identify a few surface proteins likely specific of either exosomes (LAMP1) or ectosomes (BSG, SLC3A2). Our work sets the path for molecular and functional discrimination of exosomes and small ectosomes in any cell type.


Assuntos
Exossomos/metabolismo , Tetraspanina 29/metabolismo , Tetraspanina 30/metabolismo , Comunicação Celular , Membrana Celular/metabolismo , Endossomos/metabolismo , Vesículas Extracelulares/metabolismo , Cadeia Pesada da Proteína-1 Reguladora de Fusão , Técnicas de Inativação de Genes , Células HeLa , Humanos , Proteínas de Membrana/metabolismo , Transporte Proteico , Proteômica
7.
J Exp Med ; 195(4): 461-72, 2002 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-11854359

RESUMO

Antigen recognition by clonotypic B cell receptor (BcR) is the first step of B lymphocytes differentiation into plasmocytes. This B cell function is dependent on efficient major histocompatibility complex (MHC) class II-restricted presentation of BcR-bound antigens. In this work, we analyzed the subcellular mechanisms underlying antigen presentation after BcR engagement on B cells. In quiescent B cells, we found that MHC class II molecules mostly accumulated at the cell surface and in an intracellular pool of tubulovesicular structures, whereas H2-M molecules were mostly detected in distinct lysosomal compartments devoid of MHC class II. BcR stimulation induced the transient intracellular accumulation of MHC class II molecules in newly formed multivesicular bodies (MVBs), to which H2-M was recruited. The reversible downregulation of cathepsin S activity led to the transient accumulation of invariant chain-MHC class II complexes in MVBs. A few hours after BcR engagement, cathepsin S activity increased, the p10 invariant chain disappeared, and MHC class II-peptide complexes arrived at the plasma membrane. Thus, BcR engagement induced the transient formation of antigen-processing compartments, enabling antigen-specific B cells to become effective antigen-presenting cells.


Assuntos
Linfócitos B/imunologia , Linfócitos B/metabolismo , Antígenos de Histocompatibilidade Classe II/imunologia , Antígenos de Histocompatibilidade Classe II/metabolismo , Ativação Linfocitária , Receptores de Antígenos de Linfócitos B/imunologia , Animais , Apresentação de Antígeno , Antígenos de Diferenciação de Linfócitos B/metabolismo , Linfócitos B/citologia , Linfócitos B/ultraestrutura , Catepsinas/metabolismo , Diferenciação Celular , Membrana Celular/metabolismo , Vesículas Citoplasmáticas/imunologia , Vesículas Citoplasmáticas/metabolismo , Regulação para Baixo , Endocitose , Membranas Intracelulares/metabolismo , Camundongos , Microscopia Imunoeletrônica , Transporte Proteico , Fatores de Tempo , Células Tumorais Cultivadas
8.
Curr Opin Immunol ; 19(1): 93-8, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17140785

RESUMO

Antigen capture and presentation onto MHC class II molecules by B lymphocytes is mediated by their surface antigen receptor - the B-cell receptor (BCR). The BCR must therefore coordinate the transport of MHC class II- and antigen-containing vesicles for them to converge and ensure efficient processing. Recently, progress has been made in understanding which and how these vesicular transport events are molecularly linked to BCR signaling. In particular, recent studies have emphasized the key roles of membrane microdomains and the actin cytoskeleton in regulation of membrane trafficking upon BCR engagement.


Assuntos
Apresentação de Antígeno/imunologia , Linfócitos B/imunologia , Membrana Celular/imunologia , Receptores de Antígenos de Linfócitos B/fisiologia , Transdução de Sinais/imunologia , Linfócitos B/metabolismo , Transporte Biológico Ativo/imunologia , Membrana Celular/metabolismo
9.
Mol Biol Cell ; 18(9): 3451-62, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17596518

RESUMO

Antigen binding to the B-cell receptor (BCR) induces multiple signaling cascades that ultimately lead to B lymphocyte activation. In addition, the BCR regulates the key trafficking events that allow the antigen to reach endocytic compartments devoted to antigen processing, i.e., that are enriched for major histocompatibility factor class II (MHC II) and accessory molecules such as H2-DM. Here, we analyze the role in antigen processing and presentation of the tyrosine kinase Syk, which is activated upon BCR engagement. We show that convergence of MHC II- and H2-DM-containing compartments with the vesicles that transport BCR-uptaken antigens is impaired in cells lacking Syk activity. This defect in endocytic trafficking compromises the ability of Syk-deficient cells to form MHC II-peptide complexes from BCR-internalized antigens. Altered endocytic trafficking is associated to a failure of Syk-deficient cells to properly reorganize their actin cytoskeleton in response to BCR engagement. We propose that, by modulating the actin dynamics induced upon BCR stimulation, Syk regulates the positioning and transport of the vesicles that carry the molecules required for antigen processing and presentation.


Assuntos
Actinas/metabolismo , Apresentação de Antígeno/imunologia , Endocitose , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Tirosina Quinases/metabolismo , Receptores de Antígenos de Linfócitos B/metabolismo , Animais , Linhagem Celular Tumoral , Citoesqueleto/metabolismo , Antígenos de Histocompatibilidade Classe II/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/deficiência , Ativação Linfocitária , Lisossomos/metabolismo , Lisossomos/ultraestrutura , Camundongos , Peptídeos/metabolismo , Transporte Proteico , Proteínas Tirosina Quinases/deficiência , Proteínas Tirosina Quinases/ultraestrutura , Baço/citologia , Baço/metabolismo , Quinase Syk
10.
Nat Commun ; 10(1): 2870, 2019 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-31253773

RESUMO

An important channel of cell-to-cell communication is direct contact. The immune synapse is a paradigmatic example of such type of interaction: it forms upon engagement of antigen receptors in lymphocytes by antigen-presenting cells and allows the local exchange of molecules and information. Although mechanics has been shown to play an important role in this process, how forces organize and impact on synapse function is unknown. We find that mechanical forces are spatio-temporally patterned at the immune synapse: global pulsatile myosin II-driven tangential forces are observed at the synapse periphery while localised forces generated by invadosome-like F-actin protrusions are detected at its centre. Noticeably, we observe that these force-producing actin protrusions constitute the main site of antigen extraction and endocytosis and require myosin II contractility to form. The interplay between global and local forces dictated by the organization of the actomyosin cytoskeleton therefore controls endocytosis at the immune synapse.


Assuntos
Citoesqueleto de Actina/fisiologia , Actomiosina/metabolismo , Linfócitos B/fisiologia , Endocitose/fisiologia , Miosina Tipo II/metabolismo , Actomiosina/genética , Animais , Comunicação Celular , Cruzamentos Genéticos , Integrases/genética , Integrases/metabolismo , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Miosina Tipo II/genética , Receptores de Complemento 3d
11.
Cell Rep ; 25(11): 3110-3122.e6, 2018 12 11.
Artigo em Inglês | MEDLINE | ID: mdl-30540943

RESUMO

Complete activation of B cells relies on their capacity to extract tethered antigens from immune synapses by either exerting mechanical forces or promoting their proteolytic degradation through lysosome secretion. Whether antigen extraction can also be tuned by local cues originating from the lymphoid microenvironment has not been investigated. We here show that the expression of Galectin-8-a glycan-binding protein found in the extracellular milieu, which regulates interactions between cells and matrix proteins-is increased within lymph nodes under inflammatory conditions where it enhances B cell arrest phases upon antigen recognition in vivo and promotes synapse formation during BCR recognition of immobilized antigens. Galectin-8 triggers a faster recruitment and secretion of lysosomes toward the B cell-antigen contact site, resulting in efficient extraction of immobilized antigens through a proteolytic mechanism. Thus, extracellular cues can determine how B cells sense and extract tethered antigens and thereby tune B cell responses in vivo.


Assuntos
Apresentação de Antígeno/imunologia , Antígenos de Superfície/metabolismo , Linfócitos B/imunologia , Galectinas/metabolismo , Sinapses Imunológicas/metabolismo , Animais , Linfócitos B/citologia , Pontos de Checagem do Ciclo Celular , Linhagem Celular , Galinhas , Linfonodos/metabolismo , Lisossomos/metabolismo , Camundongos Endogâmicos C57BL , Ligação Proteica , Proteólise , Ratos , Receptores de Antígenos de Linfócitos B/metabolismo , Linfócitos T/citologia
12.
Mol Biol Cell ; 28(7): 890-897, 2017 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-28179460

RESUMO

Recognition of surface-tethered antigens (Ags) by B-cells leads to the formation of an immune synapse that promotes Ag uptake for presentation onto MHC-II molecules. Extraction of immobilized Ags at the immune synapse of B-cells relies on the local secretion of lysosomes, which are recruited to the Ag contact site by polarization of their microtubule network. Although conserved polarity proteins have been implicated in coordinating cytoskeleton remodeling with lysosome trafficking, the cellular machinery associated with lysosomal vesicles that regulates their docking and secretion at the synaptic interface has not been defined. Here we show that the v-SNARE protein Vamp-7 is associated with Lamp-1+ lysosomal vesicles, which are recruited and docked at the center of the immune synapse of B-cells. A decrease in Vamp-7 expression does not alter lysosome transport to the synaptic interface but impairs their local secretion, a defect that compromises the ability of B-cells to extract, process, and present immobilized Ag. Thus our results reveal that B-cells rely on the SNARE protein Vamp-7 to promote the local exocytosis of lysosomes at the immune synapse, which is required for efficient Ag extraction and presentation.


Assuntos
Linfócitos B/metabolismo , Proteínas R-SNARE/metabolismo , Proteínas R-SNARE/fisiologia , Animais , Apresentação de Antígeno/imunologia , Antígenos/metabolismo , Linfócitos B/fisiologia , Linhagem Celular , Linhagem Celular Tumoral , Movimento Celular , Exocitose , Lisossomos/metabolismo , Camundongos , Transporte Proteico , Proteínas SNARE/metabolismo , Sinapses/metabolismo
13.
Sci Immunol ; 2(16)2017 10 27.
Artigo em Inglês | MEDLINE | ID: mdl-29079589

RESUMO

Dendritic cells (DCs) patrol their environment by linking antigen acquisition by macropinocytosis to cell locomotion. DC activation upon bacterial sensing inhibits macropinocytosis and increases DC migration, thus promoting the arrival of DCs to lymph nodes for antigen presentation to T cells. The signaling events that trigger such changes are not fully understood. We show that lysosome signaling plays a critical role in this process. Upon bacterial sensing, lysosomal calcium is released by the ionic channel TRPML1 (transient receptor potential cation channel, mucolipin subfamily, member 1), which activates the actin-based motor protein myosin II at the cell rear, promoting fast and directional migration. Lysosomal calcium further induces the activation of the transcription factor EB (TFEB), which translocates to the nucleus to maintain TRPML1 expression. We found that the TRPML1-TFEB axis results from the down-regulation of macropinocytosis after bacterial sensing by DCs. Lysosomal signaling therefore emerges as a hitherto unexpected link between macropinocytosis, actomyosin cytoskeleton organization, and DC migration.


Assuntos
Movimento Celular , Células Dendríticas/imunologia , Lisossomos/metabolismo , Transdução de Sinais , Animais , Apresentação de Antígeno , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Cálcio/metabolismo , Diferenciação Celular , Núcleo Celular/metabolismo , Citoesqueleto/metabolismo , Células Dendríticas/fisiologia , Regulação para Baixo , Lisossomos/imunologia , Camundongos , Miosina Tipo II/genética , Miosina Tipo II/metabolismo , Pinocitose , Canais de Potencial de Receptor Transitório/deficiência , Canais de Potencial de Receptor Transitório/genética , Canais de Potencial de Receptor Transitório/metabolismo
14.
J Immunol Methods ; 432: 30-4, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26684937

RESUMO

Cell migration is a hallmark of dendritic cells (DCs) function. It is needed for DCs to scan their environment in search for antigens as well as to reach lymphatic organs in order to trigger T lymphocyte's activation. Such interaction leads to tolerance in the case of DCs migrating under homeostatic conditions or to immunity in the case of DCs migrating upon encounter with pathogen-associated molecular patterns. Cell migration is therefore essential for DCs to transfer information from peripheral tissues to lymphoid organs, thereby linking innate to adaptive immunity. This stresses the need to unravel the molecular mechanisms involved. However, the tremendous complexity of the tissue microenvironment as well as the limited spatio-temporal resolution of in vivo imaging techniques has made this task difficult. To bypass this problem, we have developed microfabrication-based experimental tools that are compatible with high-resolution imaging. Here, we will discuss how such devices can be used to study DC migration under controlled conditions that mimic their physiological environment in a robust quantitative manner.


Assuntos
Microambiente Celular , Quimiotaxia , Células Dendríticas/imunologia , Microscopia , Microtecnologia , Imunidade Adaptativa , Animais , Polaridade Celular , Citocinas/imunologia , Citocinas/metabolismo , Células Dendríticas/metabolismo , Desenho de Equipamento , Humanos , Imunidade Inata , Microscopia/instrumentação , Microscopia/métodos , Microtecnologia/instrumentação , Microtecnologia/métodos , Miniaturização , Fenótipo , Transdução de Sinais , Fatores de Tempo
15.
Nat Cell Biol ; 18(1): 43-53, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26641718

RESUMO

Dendritic cell (DC) migration in peripheral tissues serves two main functions: antigen sampling by immature DCs, and chemokine-guided migration towards lymphatic vessels (LVs) on maturation. These migratory events determine the efficiency of the adaptive immune response. Their regulation by the core cell locomotion machinery has not been determined. Here, we show that the migration of immature DCs depends on two main actin pools: a RhoA-mDia1-dependent actin pool located at their rear, which facilitates forward locomotion; and a Cdc42-Arp2/3-dependent actin pool present at their front, which limits migration but promotes antigen capture. Following TLR4-MyD88-induced maturation, Arp2/3-dependent actin enrichment at the cell front is markedly reduced. Consequently, mature DCs switch to a faster and more persistent mDia1-dependent locomotion mode that facilitates chemotactic migration to LVs and lymph nodes. Thus, the differential use of actin-nucleating machineries optimizes the migration of immature and mature DCs according to their specific function.


Assuntos
Actinas/metabolismo , Diferenciação Celular/fisiologia , Movimento Celular/fisiologia , Quimiotaxia/fisiologia , Células Dendríticas/metabolismo , Animais , Células Cultivadas , Camundongos
16.
Mol Biol Cell ; 26(7): 1273-85, 2015 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-25631815

RESUMO

B-cell receptor (BCR) engagement with surface-tethered antigens leads to the formation of an immune synapse, which facilitates antigen uptake for presentation to T-lymphocytes. Antigen internalization and processing rely on the early dynein-dependent transport of BCR-antigen microclusters to the synapse center, as well as on the later polarization of the microtubule-organizing center (MTOC). MTOC repositioning allows the release of proteases and the delivery of MHC class II molecules at the synapse. Whether and how these events are coordinated have not been addressed. Here we show that the ancestral polarity protein Par3 promotes BCR-antigen microcluster gathering, as well as MTOC polarization and lysosome exocytosis, at the synapse by facilitating local dynein recruitment. Par3 is also required for antigen presentation to T-lymphocytes. Par3 therefore emerges as a key molecule in the coupling of the early and late events needed for efficient extraction and processing of immobilized antigen by B-cells.


Assuntos
Apresentação de Antígeno/imunologia , Antígenos/metabolismo , Linfócitos B/imunologia , Moléculas de Adesão Celular/fisiologia , Sinapses Imunológicas/imunologia , Receptores de Antígenos de Linfócitos B/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Animais , Antígenos/imunologia , Linfócitos B/metabolismo , Proteínas de Ciclo Celular , Camundongos , Receptores de Antígenos de Linfócitos B/imunologia
17.
Nat Commun ; 6: 7526, 2015 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-26109323

RESUMO

The immune response relies on the migration of leukocytes and on their ability to stop in precise anatomical locations to fulfil their task. How leukocyte migration and function are coordinated is unknown. Here we show that in immature dendritic cells, which patrol their environment by engulfing extracellular material, cell migration and antigen capture are antagonistic. This antagonism results from transient enrichment of myosin IIA at the cell front, which disrupts the back-to-front gradient of the motor protein, slowing down locomotion but promoting antigen capture. We further highlight that myosin IIA enrichment at the cell front requires the MHC class II-associated invariant chain (Ii). Thus, by controlling myosin IIA localization, Ii imposes on dendritic cells an intermittent antigen capture behaviour that might facilitate environment patrolling. We propose that the requirement for myosin II in both cell migration and specific cell functions may provide a general mechanism for their coordination in time and space.


Assuntos
Antígenos de Diferenciação de Linfócitos B/metabolismo , Antígenos/metabolismo , Movimento Celular/fisiologia , Células Dendríticas/metabolismo , Antígenos de Histocompatibilidade Classe II/metabolismo , Miosina Tipo II/metabolismo , Ovalbumina/metabolismo , Animais , Antígenos de Diferenciação de Linfócitos B/genética , Células da Medula Óssea , Catepsinas/genética , Catepsinas/metabolismo , Feminino , Antígenos de Histocompatibilidade Classe II/genética , Masculino , Camundongos , Técnicas Analíticas Microfluídicas , Miosina Tipo II/genética
18.
FEBS Lett ; 572(1-3): 11-4, 2004 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-15304316

RESUMO

Exosomes are small vesicles secreted by different immune cells and which display anti-tumoral properties. Stimulation of RBL-2H3 cells with ionomycin triggered phospholipase D2 (PLD2) translocation from plasma membrane to intracellular compartments and the release of exosomes. Although exosomes carry the two isoforms of PLD, PLD2 was enriched and specifically sorted on exosomes when overexpressed in cells. PLD activity present on exosomes was clearly increased following PLD2 overexpression. PLD2 activity in cells was correlated to the amount of exosome released, as measured by FACS. Therefore, the present work indicates that exosomes can vehicle signaling enzymes.


Assuntos
Vesículas Citoplasmáticas/ultraestrutura , Fosfolipase D/metabolismo , Animais , Linhagem Celular Tumoral , Cromograninas/análise , Cinética , Ratos
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