RESUMO
Persistent Rel/nuclear factor-kappaB (NF-kappaB) activity is a hallmark of many human cancers, and the Rel proteins are implicated in leukemia/lymphomagenesis but the mechanism is not fully understood. Microarray analysis to identify transformation-impacting genes regulated by NF-kappaB's oncogenic v-Rel and c-Rel proteins uncovered that Rel protein expression leads to transcriptional repression of key B-cell receptor (BCR) components and signaling molecules like B-cell linker (BLNK), the B-cell adaptor for phosphoinositide 3-kinase (BCAP) and immunoglobulin lambda light chain (Ig lambda), and is accompanied by a block in BCR-mediated activation of extracellular signal-regulated kinase, Akt, and c-Jun-NH(2)-kinase in response to anti-IgM. The BLNK and BCAP proteins were also down-regulated in lymphoid cells expressing a transformation-competent chimeric RelA/v-Rel protein, suggesting a correlation with the capacity of Rel proteins to transform lymphocytes. DNA-binding studies identified functional NF-kappaB-binding sites, and chromatin immunoprecipitation (ChIP) data showed binding of Rel to the endogenous blnk and bcap promoters in vivo. Importantly, restoration of either BLNK or BCAP expression strongly inhibited transformation of primary chicken lymphocytes by the potent NF-kappaB oncoprotein v-Rel. These findings are interesting because blnk and other BCR components and signaling molecules are down-regulated in primary mediastinal large B-cell lymphomas and Hodgkin's lymphomas, which depend on c-Rel for survival, and are consistent with the tumor suppressor function of BLNK. Overall, our results indicate that down-regulation of BLNK and BCAP is an important contributing factor to the malignant transformation of lymphocytes by Rel and suggest that gene repression may be as important as transcriptional activation for Rel's transforming activity.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/imunologia , Linfócitos/imunologia , Proteínas Oncogênicas v-rel/imunologia , Proteínas Proto-Oncogênicas c-rel/imunologia , Fator de Transcrição RelA/imunologia , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Linfócitos B/imunologia , Galinhas , Cromatina/genética , Cromatina/metabolismo , DNA/genética , Regulação para Baixo , Humanos , Ativação Linfocitária , Camundongos , NF-kappa B/genética , Análise de Sequência com Séries de Oligonucleotídeos , Proteínas Oncogênicas v-rel/genética , Regiões Promotoras Genéticas , Proteínas Proto-Oncogênicas c-rel/genética , Fator de Transcrição RelA/genética , Ativação Transcricional , TransfecçãoRESUMO
The initiation of primary immune responses is the key function of specialized antigen presenting cells, the dendritic cells (DC). DC of myeloid origin capture antigens in tissues, migrate to lymphoid organs and stimulate T cell responses. A subset of DC has been described which expresses lymphoid determinants and has potential regulatory functions. Conditional transformation of chicken bone marrow progenitors with v-relER, a v-rel estrogen receptor (ER) fusion gene, allows expansion of progenitors that can be induced to differentiate into DC in vitro. In this paper we describe that v-relER cells exhibit both myeloid and lymphoid surface markers, while B cell, T cell and NK (natural killer)-specific surface markers are absent. v-relER DC express, however, cytoplasmic CD3 protein and mRNA for CD8alpha and the lymphoid transcription factor GATA-3. These data suggest that v-relER DC might be related to the lymphoid subset of DC described in mammals.
Assuntos
Células Dendríticas/imunologia , Proteínas Oncogênicas v-rel/imunologia , Receptores de Estrogênio/imunologia , Animais , Biomarcadores , Complexo CD3/genética , Antígenos CD8/genética , Linhagem Celular Transformada , Transformação Celular Neoplásica , Galinhas , Citoplasma/metabolismo , Proteínas de Ligação a DNA/genética , Fator de Transcrição GATA3 , Expressão Gênica , Células-Tronco Hematopoéticas/imunologia , Antígenos de Histocompatibilidade Classe II/análise , Proteínas Oncogênicas v-rel/genética , Receptores de Estrogênio/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia , Transativadores/genéticaRESUMO
Whereas most CD8+ T cells in lymph nodes and spleen express the CD8alpha beta heterodimer and depend absolutely on thymic competence for their development, a substantial population of T cells expressing CD8alpha alpha matures extrathymically. Although the existence of these CD8 sublineages is well established, relatively little is known about differences that might exist among CD8 cells in their requirement for particular transcriptional pathways during the development and maintenance of normal populations. Transgenic mice whose T lineage expresses an IkappaBalpha mutant exhibited decreased NF-kappaB signaling and a diminution in mature CD8 T cells. We now have determined that although TCR-dependent CD69 induction by CD8alpha alpha and CD8alpha beta T cells was unaffected by inhibition of NF-kappaB, TCRalpha beta CD8alpha beta T cells were preferentially reduced compared to their TCRalpha beta CD8alpha alpha or TCRgamma delta counterparts. This finding was most prominent in spleen, but was also apparent in Peyer's patches of transgenic mice. In addition, diminished antiviral cytotoxic responses of CD8alpha beta intraepithelial lymphocytes were observed after enteric reovirus infection. Taken together, these results indicate that NF-kappaB signaling is more important for the thymus-dependent TCRalpha beta CD8alpha beta population than for other CD8 lineages, and thus regulates the number, function, and normal balance of CD8 subsets in the periphery.
