RESUMEN
HIV-1-infected macrophages participate in virus dissemination and establishment of virus reservoirs in host tissues, but the mechanisms for virus cell-to-cell transfer to macrophages remain unknown. Here, we reveal the mechanisms for cell-to-cell transfer from infected T cells to macrophages and virus spreading between macrophages. We show that contacts between infected T lymphocytes and macrophages lead to cell fusion for the fast and massive transfer of CCR5-tropic viruses to macrophages. Through the merge of viral material between T cells and macrophages, these newly formed lymphocyte-macrophage fused cells acquire the ability to fuse with neighboring noninfected macrophages. Together, these two-step envelope-dependent cell fusion processes lead to the formation of highly virus-productive multinucleated giant cells reminiscent of the infected multinucleated giant macrophages detected in HIV-1-infected patients and simian immunodeficiency virus-infected macaques. These mechanisms represent an original mode of virus transmission for viral spreading and a new model for the formation of macrophage virus reservoirs during infection.IMPORTANCE We reveal a very efficient mechanism involved in cell-to-cell transfer from infected T cells to macrophages and subsequent virus spreading between macrophages by a two-step cell fusion process. Infected T cells first establish contacts and fuse with macrophage targets. The newly formed lymphocyte-macrophage fused cells then acquire the ability to fuse with surrounding uninfected macrophages, leading to the formation of infected multinucleated giant cells that can survive for a long time, as evidenced in vivo in lymphoid organs and the central nervous system. This route of infection may be a major determinant for virus dissemination and the formation of macrophage virus reservoirs in host tissues during HIV-1 infection.
Asunto(s)
Linfocitos T CD4-Positivos/citología , Células Gigantes/virología , Infecciones por VIH/inmunología , VIH-1/fisiología , Macrófagos/citología , Animales , Linfocitos T CD4-Positivos/virología , Fusión Celular , Línea Celular , Células Gigantes/citología , Células HEK293 , VIH-1/patogenicidad , Humanos , Células Jurkat , Macaca mulatta , Macrófagos/virología , Virus de la Inmunodeficiencia de los Simios/patogenicidad , Virus de la Inmunodeficiencia de los Simios/fisiologíaRESUMEN
The variable regions (VHHs) of two heavy chain-only antibodies, JM2 and JM4, from llamas that have been immunized with a trimeric gp140 bound to a CD4 mimic have been recently isolated (here referred to as VHH JM2 and VHH JM4, respectively). JM2 binds the CD4-binding site of gp120 and neutralizes HIV-1 strains from subtypes B, C, and G. JM4 binds gp120 and neutralizes HIV-1 strains from subtypes A, B, C, A/E, and G in a CD4-dependent manner. In the present study, we constructed glycosylphosphatidylinositol (GPI)-anchored VHH JM2 and JM4 along with an E4 control and transduced them into human CD4+ cell lines and primary CD4 T cells. We report that by genetically linking the VHHs with a GPI attachment signal, VHHs are targeted to the lipid rafts of the plasma membranes. Expression of GPI-VHH JM4, but not GPI-VHH E4 and JM2, on the surface of transduced TZM.bl cells potently neutralizes multiple subtypes of HIV-1 isolates, including tier 2 or 3 strains, transmitted founders, quasispecies, and soluble single domain antibody (sdAb) JM4-resistant viruses. Moreover, transduction of CEMss-CCR5 cells with GPI-VHH JM4, but not with GPI-VHH E4, confers resistance to both cell-free and T cell-T cell transmission of HIV-1 and HIV-1 envelope-mediated fusion. Finally, GPI-VHH JM4-transduced human primary CD4 T cells efficiently resist both cell-free and T cell-T cell transmission of HIV-1. Thus, we conclude that VHH JM4, when targeted to the lipid rafts of the plasma membrane, efficiently neutralizes HIV-1 infection via both cell-free and T cell-T cell transmission. Our findings should have important implications for GPI-anchored antibody-based therapy against HIV-1. IMPORTANCE: Lipid rafts are specialized dynamic microdomains of the plasma membrane and have been shown to be gateways for HIV-1 budding as well as entry into T cells and macrophages. In nature, many glycosylphosphatidylinositol (GPI)-anchored proteins localize in the lipid rafts. In the present study, we developed GPI-anchored variable regions (VHHs) of two heavy chain-only antibodies, JM2 and JM4, from immunized llamas. We show that by genetically linking the VHHs with a GPI attachment signal, VHHs are targeted to the lipid rafts of the plasma membranes. GPI-VHH JM4, but not GPI-VHH JM2, in transduced CD4+ cell lines and human primary CD4 T cells not only efficiently blocks diverse HIV-1 strains, including tier 2 or 3 strains, transmitted founders, quasispecies, and soluble sdAb JM4-resistant strains, but also efficiently interferes T cell-T cell transmissions of HIV-1 and HIV-1 envelope-mediated fusion. Our findings should have important implications in GPI-anchored antibody-based therapy against HIV-1.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/virología , Camélidos del Nuevo Mundo/inmunología , Anticuerpos Anti-VIH/inmunología , VIH-1/inmunología , Animales , Anticuerpos Neutralizantes/genética , Anticuerpos Neutralizantes/inmunología , Camélidos del Nuevo Mundo/genética , Línea Celular , Sistema Libre de Células , Proteínas Ligadas a GPI/genética , Proteínas Ligadas a GPI/inmunología , Anticuerpos Anti-VIH/genética , Proteína gp120 de Envoltorio del VIH/inmunología , Infecciones por VIH/inmunología , Infecciones por VIH/terapia , Infecciones por VIH/virología , Humanos , Cadenas Pesadas de Inmunoglobulina/genética , Cadenas Pesadas de Inmunoglobulina/inmunología , Región Variable de Inmunoglobulina/genética , Región Variable de Inmunoglobulina/inmunología , Microdominios de Membrana/inmunología , Proteínas Recombinantes/genética , Proteínas Recombinantes/inmunologíaAsunto(s)
Enfermedades Autoinmunes/genética , Dermatitis Exfoliativa/genética , Inflamación/genética , Mutación/genética , FN-kappa B/metabolismo , Psoriasis/genética , Proteína de Unión al GTP cdc42/metabolismo , Actinas/metabolismo , Inhibidores de Disociación de Guanina Nucleótido/metabolismo , Humanos , Lactante , Lipoilación , Masculino , Linaje , Unión Proteica , Transducción de Señal , Síndrome , Secuenciación del Exoma , Proteína de Unión al GTP cdc42/genéticaRESUMEN
Forkhead box O (FOXO) transcription factors favor both T cell quiescence and trafficking through their control of the expression of genes involved in cell cycle progression, adhesion, and homing. In this article, we report that the product of the fam65b gene is a new transcriptional target of FOXO1 that regulates RhoA activity. We show that family with sequence similarity 65 member b (Fam65b) binds the small GTPase RhoA via a noncanonical domain and represses its activity by decreasing its GTP loading. As a consequence, Fam65b negatively regulates chemokine-induced responses, such as adhesion, morphological polarization, and migration. These results show the existence of a new functional link between FOXO1 and RhoA pathways, through which the FOXO1 target Fam65b tonically dampens chemokine-induced migration by repressing RhoA activity.
Asunto(s)
Movimiento Celular/genética , Factores de Transcripción Forkhead/metabolismo , Proteínas/genética , Transducción de Señal , Linfocitos T/inmunología , Linfocitos T/metabolismo , Proteína de Unión al GTP rhoA/metabolismo , Adhesión Celular/efectos de los fármacos , Adhesión Celular/genética , Moléculas de Adhesión Celular , Línea Celular , Movimiento Celular/efectos de los fármacos , Quimiocinas/farmacología , Proteína Forkhead Box O1 , Regulación de la Expresión Génica , Humanos , Unión Proteica , Proteínas/metabolismo , Activación TranscripcionalRESUMEN
Autoinflammatory diseases (AIDs) are conditions characterized by dysfunction of innate immunity, causing systemic inflammation and various clinical symptoms. The field of AIDs has expanded due to improved comprehension of pathophysiological mechanisms and advancements in genomics techniques. A new emerging category of AIDs is characterized by a significant increase in interleukin 18 (IL-18), a pro-inflammatory cytokine synthesized in macrophages and activated by caspase 1 via various inflammasomes. IL-18 plays a role in the regulation of innate and adaptive immunity. IL-18 is involved in various functions, such as the proliferation, survival, and differentiation of immune cells, tissue infiltration of immune cells, polarization of immune responses, and production of other pro-inflammatory cytokines. This review analyzes the literature on IL-18 regarding its functions and its implications in the diagnosis and treatment of AIDs. IL-18-associated AIDs comprise Still's disease and diseases associated with mutations in NLRC4, XIAP, CDC42, and PSTPIP1, as well as IL-18BP deficiencies. With the exception of PSTPIP1-associated diseases, these conditions all carry a risk of macrophagic activation syndrome. Measuring IL-18 levels in serum can aid in the diagnosis, prognosis, and monitoring of these diseases. Therapies targeting IL-18 and its signaling pathways are currently under investigation.
RESUMEN
Mutations in the N-terminal WD40 domain of coatomer protein complex subunit α (COPA) cause a type I interferonopathy, typically characterized by alveolar hemorrhage, arthritis, and nephritis. We described 3 heterozygous mutations in the C-terminal domain (CTD) of COPA (p.C1013S, p.R1058C, and p.R1142X) in 6 children from 3 unrelated families with a similar syndrome of autoinflammation and autoimmunity. We showed that these CTD COPA mutations disrupt the integrity and the function of coat protein complex I (COPI). In COPAR1142X and COPAR1058C fibroblasts, we demonstrated that COPI dysfunction causes both an anterograde ER-to-Golgi and a retrograde Golgi-to-ER trafficking defect. The disturbed intracellular trafficking resulted in a cGAS/STING-dependent upregulation of the type I IFN signaling in patients and patient-derived cell lines, albeit through a distinct molecular mechanism in comparison with mutations in the WD40 domain of COPA. We showed that CTD COPA mutations induce an activation of ER stress and NF-κB signaling in patient-derived primary cell lines. These results demonstrate the importance of the integrity of the CTD of COPA for COPI function and homeostatic intracellular trafficking, essential to ER homeostasis. CTD COPA mutations result in disease by increased ER stress, disturbed intracellular transport, and increased proinï¬ammatory signaling.
Asunto(s)
Proteína Coat de Complejo I , Proteína Coatómero , Niño , Humanos , Proteína Coatómero/genética , Proteína Coat de Complejo I/genética , Proteína Coat de Complejo I/metabolismo , Mutación , Síndrome , Aparato de Golgi/genética , Aparato de Golgi/metabolismoRESUMEN
A key feature in T lymphocyte biology is that Th cells rapidly polarize their secretory machinery toward cognate APCs. The molecular mechanisms of these dynamic Th cell responses and their impact on APC biology remain to be elucidated. In this study, we demonstrate that protein kinase Czeta (PKCzeta) is rapidly activated at the immunological synapse (IS) in human Th cells interacting with cognate dendritic cells (DCs) and that a functional PKCzeta is required for the polarization of Th cell secretory machinery toward DCs. We also show that PKCzeta-dependent Th cell polarization allows dedicated delivery of IFN-gamma and CD40L at the IS and is required for the activation of cognate DCs to IL-12 production. PKCzeta synaptic activation is a low-threshold phenomenon and, in Th cells interacting with multiple DCs, selectively occurs at the IS formed with the DCs offering the strongest stimulus leading to dedicated Th cell polarization. Our results identify the PKCzeta signaling pathway as a key component of the Th cell polarization machinery and provide a molecular basis for T cell-dedicated activation of cognate DCs.
Asunto(s)
Células Presentadoras de Antígenos/inmunología , Células Presentadoras de Antígenos/metabolismo , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/metabolismo , Polaridad Celular/inmunología , Sinapsis Inmunológicas/metabolismo , Activación de Linfocitos/inmunología , Proteína Quinasa C/metabolismo , Linfocitos T CD4-Positivos/enzimología , Ligando de CD40/metabolismo , Células Cultivadas , Técnicas de Cocultivo , Células Dendríticas/inmunología , Células Dendríticas/metabolismo , Activación Enzimática/inmunología , Humanos , Sinapsis Inmunológicas/enzimología , Sinapsis Inmunológicas/inmunología , Interferón gamma/metabolismo , Isoenzimas/metabolismo , Isoenzimas/fisiología , Fosforilación/inmunología , Proteína Quinasa C/fisiología , Receptores de Antígenos de Linfocitos T alfa-beta/metabolismo , Transducción de Señal/inmunologíaRESUMEN
Adenomatous polyposis coli (APC) is a tumor suppressor whose mutations underlie familial adenomatous polyposis (FAP) and colorectal cancer. Although its role in intestinal epithelial cells is well characterized, APC importance in T cell biology is ill defined. APC regulates cytoskeleton organization, cell polarity, and migration in various cell types. Here, we address whether APC plays a role in T lymphocyte migration. Using a series of cell biology tools, we unveiled that T cells from FAP patients carrying APC mutations display impaired adhesion and motility in constrained environments. We further dissected the cellular mechanisms underpinning these defects in APC-depleted CEM T cell line that recapitulate the phenotype observed in FAP T cells. We found that APC affects T cell motility by modulating integrin-dependent adhesion and cytoskeleton reorganization. Hence, APC mutations in FAP patients not only drive intestinal neoplasms but also impair T cell migration, potentially contributing to inefficient antitumor immunity.
Asunto(s)
Proteína de la Poliposis Adenomatosa del Colon , Poliposis Adenomatosa del Colon , Poliposis Adenomatosa del Colon/genética , Proteína de la Poliposis Adenomatosa del Colon/genética , Movimiento Celular , Humanos , Mutación , FenotipoRESUMEN
Ras homology (RHO) GTPases are signalling proteins that have crucial roles in triggering multiple immune functions. Through their interactions with a broad range of effectors and kinases, they regulate cytoskeletal dynamics, cell polarity and the trafficking and proliferation of immune cells. The activity and localization of RHO GTPases are highly controlled by classical families of regulators that share consensus motifs. In this Review, we describe the recent discovery of atypical modulators and partners of RHO GTPases, which bring an additional layer of regulation and plasticity to the control of RHO GTPase activities in the immune system. Furthermore, the development of large-scale genetic screening has now enabled researchers to identify dysregulation of RHO GTPase signalling pathways as a cause of many immune system-related diseases. We discuss the mutations that have been identified in RHO GTPases and their signalling circuits in patients with rare diseases. The discoveries of new RHO GTPase partners and genetic mutations in RHO GTPase signalling hubs have uncovered unsuspected layers of crosstalk with other signalling pathways and may provide novel therapeutic opportunities for patients affected by complex immune or broader syndromes.
Asunto(s)
Enfermedades del Sistema Inmune/enzimología , Enfermedades del Sistema Inmune/inmunología , Proteínas de Unión al GTP rho/inmunología , Proteínas de Unión al GTP rho/metabolismo , Humanos , Enfermedades del Sistema Inmune/genética , Modelos Genéticos , Modelos Inmunológicos , Mutación , Transducción de Señal/genética , Transducción de Señal/inmunología , Síndrome , Proteínas de Unión al GTP rho/genéticaRESUMEN
T lymphocyte migration is an essential step to mounting an efficient immune response. The rapid and random motility of these cells which favors their sentinel role is conditioned by chemokines as well as by the physical environment. Morphological changes, underlaid by dynamic actin cytoskeleton remodeling, are observed throughout migration but especially when the cell modifies its trajectory. However, the signaling cascade regulating the directional changes remains largely unknown. Using dynamic cell imaging, we investigated in this paper the signaling pathways involved in T cell directionality. We monitored cyclic adenosine 3'-5' monosphosphate (cAMP) variation concomitantly with actomyosin distribution upon T lymphocyte migration and highlighted the fact that spontaneous bursts in cAMP starting from the leading edge, are sufficient to promote actomyosin redistribution triggering trajectory modification. Although cAMP is commonly considered as an immunosuppressive factor, our results suggest that, when transient, it rather favors the exploratory behavior of T cells.
RESUMEN
We previously identified Fam65b as an atypical inhibitor of the small G protein RhoA. Using a conditional model of a Fam65b-deficient mouse, we first show that Fam65b restricts spontaneous RhoA activation in resting T lymphocytes and regulates intranodal T cell migration in vivo. We next aimed at understanding, at the molecular level, how the brake that Fam65b exerts on RhoA can be relieved upon signaling to allow RhoA activation. Here, we show that chemokine stimulation phosphorylates Fam65b in T lymphocytes. This post-translational modification decreases the affinity of Fam65b for RhoA and favors Fam65b shuttling from the plasma membrane to the cytosol. Functionally, we show that the degree of Fam65b phosphorylation controls some cytoskeletal alterations downstream active RhoA such as actin polymerization, as well as T cell migration in vitro. Altogether, our results show that Fam65b expression and phosphorylation can finely tune the amount of active RhoA in order to favor optimal T lymphocyte motility.
Asunto(s)
Proteínas Portadoras/inmunología , Movimiento Celular/inmunología , Proteínas de la Membrana/inmunología , Proteínas/inmunología , Linfocitos T/inmunología , Proteínas de Unión al GTP rho/inmunología , Proteína de Unión al GTP rhoA/inmunología , Citoesqueleto de Actina/genética , Citoesqueleto de Actina/inmunología , Animales , Proteínas Portadoras/genética , Moléculas de Adhesión Celular , Línea Celular Tumoral , Movimiento Celular/genética , Regulación de la Expresión Génica/inmunología , Humanos , Proteínas de la Membrana/genética , Ratones , Ratones Noqueados , Fosforilación/genética , Fosforilación/inmunología , Proteínas/genética , Linfocitos T/citología , Proteínas de Unión al GTP rho/genética , Proteína de Unión al GTP rhoA/genéticaRESUMEN
Despite being implicated in non-lymphoid tissues, non-recirculating T cells may also exist in secondary lymphoid organs (SLO). However, a detailed characterization of this lymphoid-resident T cell pool has not yet been done. Here we show that a substantial proportion of CD4 regulatory (Treg) and memory (Tmem) cells establish long-term residence in the SLOs of specific pathogen-free mice. Of these SLOs, only T cell residence within Peyer's patches is affected by microbiota. Resident CD4 Treg and CD4 Tmem cells from lymph nodes and non-lymphoid tissues share many phenotypic and functional characteristics. The percentage of resident T cells in SLOs increases considerably with age, with S1PR1 downregulation possibly contributing to this altered homeostasis. Our results thus show that T cell residence is not only a hallmark of non-lymphoid tissues, but can be extended to secondary lymphoid organs.
Asunto(s)
Envejecimiento/inmunología , Vida Libre de Gérmenes , Memoria Inmunológica , Tejido Linfoide/inmunología , Linfocitos T Reguladores , Animales , Femenino , Ratones Endogámicos C57BL , Microbiota , Receptores de Lisoesfingolípidos/metabolismo , Receptores de Esfingosina-1-Fosfato , Linfocitos T Reguladores/metabolismoRESUMEN
Cell quiescence is controlled by regulated genome-encoded programs that actively express genes which are often down-regulated or inactivated in transformed cells. Among them is FoxO1, a transcription factor that imposes quiescence in several cell types, including T lymphocytes. In these cells, the FAM65B encoding gene is a major target of FOXO1. Here, we show that forced expression of FAM65B in transformed cells blocks their mitosis because of a defect of the mitotic spindle, leading to G2 cell cycle arrest and apoptosis. Upon cell proliferation arrest, FAM65B is engaged in a complex containing two proteins well known to be involved in cell proliferation i.e. the HDAC6 deacetylase and the 14.3.3 scaffolding protein. In primary T cells, FAM65B is down-regulated upon T cell receptor engagement, and maintaining its expression blocks their proliferation, establishing that the decrease of FAM65B expression is required for proliferation. Conversely, inhibiting FAM65B expression in naive T lymphocytes decreases their activation threshold. These results identify FAM65B as a potential new target for controlling proliferation of both transformed and normal cells.
Asunto(s)
Proliferación Celular , Proteína Forkhead Box O1/metabolismo , Proteínas/metabolismo , Linfocitos T/citología , Moléculas de Adhesión Celular , Ciclo Celular , Línea Celular Transformada , Línea Celular Tumoral , Células Cultivadas , Regulación hacia Abajo , Fase G2 , Regulación de la Expresión Génica , Humanos , Leucemia/metabolismo , Mitosis , Fosforilación , Receptores de Antígenos de Linfocitos T/metabolismo , Transducción de Señal , Huso Acromático/metabolismo , Factores de Transcripción/metabolismoAsunto(s)
Enfermedades Autoinmunes/genética , Inflamación/genética , Lipoilación/genética , Ácido Palmítico/metabolismo , Proteína de Unión al GTP cdc42/genética , Proteína de Unión al GTP cdc42/metabolismo , Sustitución de Aminoácidos/genética , Arginina/genética , Enfermedades Autoinmunes/metabolismo , Cisteína/genética , Humanos , Inflamación/metabolismo , Lipoilación/fisiología , Mutación Missense , SíndromeRESUMEN
Cells respond to chemokine stimulation by losing their round shape in a process called polarization, and by altering the subcellular localization of many proteins. Classic imaging techniques have been used to study these phenomena. However, they required the manual acquisition of many cells followed by time consuming quantification of the morphology and the co-localization of the staining of tens of cells. Here, a rapid and powerful method is described to study these phenomena on samples consisting of several thousands of cells using an imaging flow cytometry technology that combines the advantages of a microscope with those of a cytometer. Using T lymphocytes stimulated with CCL19 and staining for MHC Class I molecules and filamentous actin, a gating strategy is presented to measure simultaneously the degree of shape alterations and the extent of co-localization of markers that are affected by CCL19 signaling. Moreover, this gating strategy allowed us to observe the segregation of filamentous actin (at the front) and phosphorylated Ezrin-Radixin-Moesin (phospho-ERM) proteins (at the rear) in polarized T cells after CXCL12 stimulation. This technique was also useful to observe the blocking effect on polarization of two different elements: inhibition of actin polymerization by a pharmacological inhibitor and expression of mutants of the Par6/atypical PKC signaling pathway. Thus, evidence is shown that this technique is useful to analyze both morphological alterations and protein redistributions.
Asunto(s)
Polaridad Celular/fisiología , Quimiocinas/farmacología , Linfocitos T/citología , Linfocitos T/metabolismo , Actinas/metabolismo , Animales , Polaridad Celular/efectos de los fármacos , Quimiocina CCL19/farmacología , Quimiocina CXCL12/farmacología , Quimiocinas/metabolismo , Proteínas del Citoesqueleto/metabolismo , Citometría de Flujo/métodos , Humanos , Proteínas de la Membrana/metabolismo , Ratones , Proteínas de Microfilamentos/metabolismo , Fosforilación , Transducción de Señal/efectos de los fármacos , Fracciones Subcelulares/metabolismo , Linfocitos T/efectos de los fármacosRESUMEN
Rho GTPases are key signal transducer elements activated in T cells by both chemokine and antigen receptors. These two signalling pathways control the two main functions of T lymphocytes: motility and activation. Rho GTPases are thus crucial for the development of an adequate immune response. In this review, we mostly focus on the roles of RhoA, Rac1 and Cdc42 in T cells. We show their importance in phenomena such as adhesion, morphological polarization, migration and antigen recognition.
Asunto(s)
Movimiento Celular , Activación de Linfocitos/inmunología , Linfocitos T/inmunología , Proteínas de Unión al GTP rho/metabolismo , Transducción de Señal , Linfocitos T/fisiologíaRESUMEN
Leukocyte locomotion is a polarized process with diverse regulatory assemblies segregating along an anterior-posterior axis that defines two regions within the cell, the leading edge and the uropod. However, the mechanisms that generate T cell asymmetry downstream of chemokine receptors are ill defined. In this study we show that the atypical protein kinases C (aPKCs), PKCiota and PKCzeta, are required for an early symmetry breaking step. Once the polarity is established, aPKCs also drive uropod formation. These effects depend on the interaction between Par6 and aPKCs. Finally, failure to transduce aPKC-dependent signals reduces T cell motility and their ability to scan dendritic cells. Altogether, our findings suggest that lymphocyte motor activity is regulated by a signaling cascade that relays chemokinetic input to aPKCs.
Asunto(s)
Polaridad Celular , Proteína Quinasa C/metabolismo , Linfocitos T/enzimología , Linfocitos T/inmunología , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Células Dendríticas/enzimología , Células Dendríticas/inmunología , Activación Enzimática , Humanos , Receptores CCR7/inmunología , Transducción de Señal/inmunología , Linfocitos T/citologíaRESUMEN
Bcl10 plays an essential role in the adaptive immune response, because Bcl10-deficient lymphocytes show impaired Ag receptor-induced NF-kappaB activation and cytokine production. Bcl10 is a phosphoprotein, but the physiological relevance of this posttranslational modification remains poorly defined. In this study, we report that Bcl10 is rapidly phosphorylated upon activation of human T cells by PMA/ionomycin- or anti-CD3 treatment, and identify Ser(138) as a key residue necessary for Bcl10 phosphorylation. We also show that a phosphorylation-deficient Ser(138)/Ala mutant specifically inhibits TCR-induced actin polymerization yet does not affect NF-kappaB activation. Moreover, silencing of Bcl10, but not of caspase recruitment domain-containing MAGUK protein-1 (Carma1) induces a clear defect in TCR-induced F-actin formation, cell spreading, and conjugate formation. Remarkably, Bcl10 silencing also impairs FcgammaR-induced actin polymerization and phagocytosis in human monocytes. These results point to a key role of Bcl10 in F-actin-dependent immune responses of T cells and monocytes/macrophages.
Asunto(s)
Actinas/metabolismo , Proteínas Adaptadoras Transductoras de Señales/fisiología , Receptores de Antígenos de Linfocitos T/inmunología , Receptores de IgG/inmunología , Linfocitos T/inmunología , Proteínas Adaptadoras Transductoras de Señales/antagonistas & inhibidores , Proteínas Adaptadoras Transductoras de Señales/genética , Proteína 10 de la LLC-Linfoma de Células B , Células Cultivadas , Humanos , Activación de Linfocitos , FN-kappa B/metabolismo , Fagocitosis/genética , Fosforilación , Proteínas Proto-Oncogénicas c-vav/metabolismo , Serina/genética , Serina/metabolismo , Proteína de Unión al GTP cdc42/metabolismo , Proteína de Unión al GTP rac1/metabolismoRESUMEN
The development of an effective immune response requires cell-cell contact between T cells and antigen-bearing cells of several types (dendritic cells, B cells, infected tissue cells). Recent advances in light microscopy have led to intense investigation of the molecular events that accompany these cell interactions, especially the redistribution of membrane proteins into discrete organized subdomains within the zone of cell-cell contact termed the 'immunological synapse'. Here we discuss two aspects of our own studies in this area. First, we highlight results from our in vitro analysis of the role of the cytoskeletal ezrin, radixin, moesin adapter proteins in the exclusion of CD43 from the well-defined T cell receptor (TCR) and integrin-rich zones of the synapse. Based on the molecular mechanism uncovered in this work, we propose a new model for how TCR-signaled changes in cytoskeletal organization indirectly influence both protein distributions and the efficiency of signaling between T cell and presenting cell. We then discuss the development of a new method for dynamic visualization of T cell - dendritic cell interactions in intact lymphoid tissue. The remarkable longevity of monogamous lymphocyte-presenting cell interactions is discussed, differences between our observations and those of others are laid out in detail, and prospects for future application of this technical approach to analysis of early immune responses in lymphoid organs and of effector lymphocyte function in tissues are presented.