RESUMO
TLRs function as molecular sensors to detect pathogen-derived products and trigger protective responses ranging from secretion of cytokines that increase the resistance of infected cells and chemokines that recruit immune cells to cell death that limits microbe spreading. Viral dsRNA participate in virus-infected cell apoptosis, but the signaling pathway involved remains unclear. In this study we show that synthetic dsRNA induces apoptosis of human breast cancer cells in a TLR3-dependent manner, which involves the molecular adaptor Toll/IL-1R domain-containing adapter inducing IFN-beta and type I IFN autocrine signaling, but occurs independently of the dsRNA-activated kinase. Moreover, detailed molecular analysis of dsRNA-induced cell death established the proapoptotic role of IL-1R-associated kinase-4 and NF-kappaB downstream of TLR3 as well as the activation of the extrinsic caspases. The direct proapoptotic activity of endogenous human TLR3 expressed by cancerous cells reveals a novel aspect of the multiple-faced TLR biology, which may open new clinical prospects for using TLR3 agonists as cytotoxic agents in selected cancers.
Assuntos
Apoptose/imunologia , Neoplasias da Mama/imunologia , Neoplasias da Mama/patologia , Receptor 3 Toll-Like/metabolismo , Sequência de Bases , Neoplasias da Mama/genética , Caspases/metabolismo , Linhagem Celular Tumoral , DNA de Neoplasias/genética , Feminino , Humanos , Interferon Tipo I/metabolismo , Quinases Associadas a Receptores de Interleucina-1 , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , NF-kappa B/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , RNA Interferente Pequeno/genética , Transdução de Sinais , Fator 6 Associado a Receptor de TNF/metabolismo , Receptor 3 Toll-Like/agonistas , Receptor 3 Toll-Like/genética , eIF-2 Quinase/metabolismoRESUMO
Human plasmacytoid dendritic cells (pDCs), also called type 2 dendritic cell precursors or natural interferon (IFN)-producing cells, represent a cell type with distinctive phenotypic and functional features. They are present in the thymus and probably share a common precursor with T and natural killer (NK) cells. In an effort to identify genes that control pDC development we searched for genes of which the expression is restricted to human pDC using a cDNA subtraction technique with activated monocyte-derived DCs (Mo-DCs) as competitor. We identified the transcription factor Spi-B to be expressed in pDCs but not in Mo-DCs. Spi-B expression in pDCs was maintained on in vitro maturation of pDCs. Spi-B was expressed in early CD34(+)CD38(-) hematopoietic progenitors and in CD34(+)CD1a(-) thymic precursors. Spi-B expression is down-regulated when uncommitted CD34(+)CD1a(-) thymic precursors differentiate into committed CD34(+)CD1a(+) pre-T cells. Overexpression of Spi-B in hematopoietic progenitor cells resulted in inhibition of development of T cells both in vitro and in vivo. In addition, development of progenitor cells into B and NK cells in vitro was also inhibited by Spi-B overexpression. Our results indicate that Spi-B is involved in the control of pDC development by limiting the capacity of progenitor cells to develop into other lymphoid lineages.
Assuntos
Proteínas de Ligação a DNA/fisiologia , Células Dendríticas/citologia , Células Dendríticas/metabolismo , Fatores de Transcrição/fisiologia , Apoptose/efeitos dos fármacos , Linfócitos B/citologia , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Linhagem da Célula/efeitos dos fármacos , Proteínas de Ligação a DNA/análise , Proteínas de Ligação a DNA/genética , Células Dendríticas/classificação , Humanos , Imunofenotipagem , Células Matadoras Naturais/citologia , Linfócitos T/citologia , Fatores de Transcrição/análise , Fatores de Transcrição/genética , Transdução GenéticaRESUMO
Human plasmacytoid dendritic cells represent a rare population of leukocytes which produce high amounts of type I interferon in response to certain viruses. Although those cells were first described in 1958, there are still unsolved issues related to their origin and function. Recently, a leukemic counterpart of plasmacytoid dendritic cells was identified. Molecular approaches using either normal or leukemic plasmacytoid dendritic cells provide some new insights into the controversial lymphoid origin of those cells. The need for specific markers is still a critical aspect for the identification of plasmacytoid dendritic cells, whatever stage of differentiation, in normal as well as in pathological conditions. Hopefully, novel markers will allow delineation of the relationships between dendritic cells at different stages of differentiation/maturation along the myeloid and lymphoid lineages.
Assuntos
Antígenos CD/biossíntese , Diferenciação Celular/imunologia , Células Dendríticas/imunologia , Interferon Tipo I/biossíntese , Animais , Células Dendríticas/citologia , Humanos , Plasmócitos , Linfócitos T/citologia , Linfócitos T/imunologiaRESUMO
Recent studies in humans have highlighted the importance of a distinct cellular entity, the plasmacytoid dendritic cell (PDC). To identify genes for which expression is restricted to human PDCs, a cDNA subtraction technique was applied using cDNA from activated monocyte-derived DCs (MDDCs) as competitor. In the 650 sequences analyzed, 25% were for B-cell transcripts. We also found lymphoid-related genes, immunoglobulinlike transcript 7 (ILT7), granzyme B (GrB), Spi-B, and the receptor tyrosine kinase Eph-B1. Granzyme B was up-regulated on activation, and protein was detected only in PDCs. Eph-B1 protein was expressed in the cytoplasm and the nuclei of PDCs and MDDCs, respectively. Interestingly, several novel molecules have been identified that were predicted to encode for a type 2 transmembrane protein (BRI(3)), a putative cytokine (C-15, a cysteine-rich-secreted protein), and a type 1 leucine-rich repeat protein (MAPA). The identification of genes expressed in PDCs provides new insights into their function and origin.
