RESUMO
The adaptive immune response depends on the interaction of T cells and antigen-presenting cells at the immune synapse. Formation of the immune synapse and the subsequent T-cell activation are highly dependent on the actin cytoskeleton. In this work, we describe that T cells express drebrin, a neuronal actin-binding protein. Drebrin colocalizes with the chemokine receptor CXCR4 and F-actin at the peripheral supramolecular activation cluster in the immune synapse. Drebrin interacts with the cytoplasmic tail of CXCR4 and both proteins redistribute to the immune synapse with similar kinetics. Drebrin knockdown in T cells impairs the redistribution of CXCR4 and inhibits actin polymerization at the immune synapse as well as IL-2 production. Our data indicate that drebrin exerts an unexpected and relevant functional role in T cells during the generation of the immune response.
Assuntos
Actinas/metabolismo , Sinapses Imunológicas/metabolismo , Neuropeptídeos/metabolismo , Receptores CXCR4/metabolismo , Linfócitos T/metabolismo , Animais , Citoesqueleto/metabolismo , Humanos , Sinapses Imunológicas/genética , Interleucina-2/metabolismo , Células Jurkat , Ativação Linfocitária/genética , Complexos Multiproteicos/metabolismo , Neuropeptídeos/genética , Células PC12 , Ligação Proteica , Transporte Proteico , RNA Interferente Pequeno/genética , Ratos , Receptor Cross-Talk , Linfócitos T/imunologia , Linfócitos T/patologiaRESUMO
The human immunodeficiency virus 1 (HIV-1) envelope regulates the initial attachment of viral particles to target cells through its association with CD4 and either CXCR4 or CCR5. Although F-actin is required for CD4 and CXCR4 redistribution, little is known about the molecular mechanisms underlying this fundamental process in HIV infection. Using CD4(+) CXCR4(+) permissive human leukemic CEM T cells and primary lymphocytes, we have investigated whether HIV-1 Env might promote viral entry and infection by activating ERM (ezrin-radixin-moesin) proteins to regulate F-actin reorganization and CD4/CXCR4 co-clustering. The interaction of the X4-tropic protein HIV-1 gp120 with CD4 augments ezrin and moesin phosphorylation in human permissive T cells, thereby regulating ezrin-moesin activation. Moreover, the association and clustering of CD4-CXCR4 induced by HIV-1 gp120 requires moesin-mediated anchoring of actin in the plasma membrane. Suppression of moesin expression with dominant-negative N-moesin or specific moesin silencing impedes reorganization of F-actin and HIV-1 entry and infection mediated by the HIV-1 envelope protein complex. Therefore, we propose that activated moesin promotes F-actin redistribution and CD4-CXCR4 clustering and is also required for efficient X4-tropic HIV-1 infection in permissive lymphocytes.
Assuntos
Actinas/metabolismo , Antígenos CD4/metabolismo , Infecções por HIV/imunologia , HIV-1/imunologia , Linfócitos , Proteínas dos Microfilamentos/metabolismo , Receptores CXCR4/metabolismo , Internalização do Vírus , Animais , Antígenos CD4/genética , Linhagem Celular , Proteínas do Citoesqueleto/genética , Proteínas do Citoesqueleto/metabolismo , Proteína gp120 do Envelope de HIV/metabolismo , Humanos , Linfócitos/imunologia , Linfócitos/virologia , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Proteínas dos Microfilamentos/genética , Receptores CXCR4/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismoRESUMO
HIV-1 envelope (Env) triggers membrane fusion between the virus and the target cell. The cellular mechanism underlying this process is not well known. Phosphatidylinositol 4,5-bisphosphate (PIP(2)) is known to be important for the late steps of the HIV-1 infection cycle by promoting Gag localization to the plasma membrane during viral assembly, but it has not been implicated in early stages of HIV-1 membrane-related events. In this study, we show that binding of the initial HIV-1 Env-gp120 protein induces PIP(2) production in permissive lymphocytes through the activation of phosphatidylinositol-4-phosphate 5-kinase (PI4P5-K) Ialpha. Overexpression of wild-type PI4P5-K Ialpha increased HIV-1 Env-mediated PIP(2) production and enhanced viral replication in primary lymphocytes and CEM T cells, whereas PIP(2) production and HIV-1 infection were both severely reduced in cells overexpressing the kinase-dead mutant D227A (D/A)-PI4P5-K Ialpha. Similar results were obtained with replicative and single-cycle HIV-1 particles. HIV-1 infection was also inhibited by knockdown of endogenous expression of PI4P5-K Ialpha. These data indicate that PI4P5-K Ialpha-mediated PIP(2) production is crucial for HIV-1 entry and the early steps of infection in permissive lymphocytes.