Interferon-gamma （IFN-γ） is a major proinflammatory effector and regulatory cytokine produced by activated T cells and NK cells. IFN-γ has been shown to play pivotal roles in fundamental immunological processes su...Interferon-gamma （IFN-γ） is a major proinflammatory effector and regulatory cytokine produced by activated T cells and NK cells. IFN-γ has been shown to play pivotal roles in fundamental immunological processes such as inflammatory reactions, cell-mediated immunity and autoimmunity. A variety of human disorders have now been linked to irregular IFN-γ expression. In order to achieve proper IFN-γ-mediated immunological effects, IFN-γ expression in T cells is subject to both positive and negative regulation. In this study, we report for the first time the negative regulation of IFN-γ expression by Prospero-related Homeobox （Proxl）. In Jurkat T cells and primary human CD4＋ T cells, Proxl expression decreases quickly upon T cell activation, concurrent with a dramatic increase in IFN-γ expression. Reporter analysis and chromatin immunoprecipitation （CHIP） revealed that Proxl associates with and inhibits the transcription activity of IFN-γ promoter in activated Jurkat T cells. Co-immunoprecipitation and GST pull-down assay demonstrated a direct binding between Proxl and the nuclear receptor peroxisome proliferator-activated receptor gamma （PPARγ）, which is also an IFN-γ repressor in T cells. By introducing deletions and mutations into Proxl, we show that the repression of IFN-γ promoter by Proxl is largely dependent upon the physical interaction between Proxl and PPARγ. Furthermore, PPARγ antagonist treatment removes Proxl from IFN-γ promoter and attenuates repression of IFN-γ expression by Proxl. These findings establish Proxl as a new negative regulator of IFN-γ expression in T cells and will aid in the understanding of IFN-γ transcription regulation mechanisms.展开更多
Lymphangiogenesis, the growth of new lymphatic vessels, has long been regarded as a putative efficient pathway to neoplastic metastization. Recent results have shown the necessity of lymphatic molecular markers and gr...Lymphangiogenesis, the growth of new lymphatic vessels, has long been regarded as a putative efficient pathway to neoplastic metastization. Recent results have shown the necessity of lymphatic molecular markers and growth factors for lymphangiogenesis. Importantly, lymphatic endothelial receptor tyrosine kinase VEGFR-3 and its ligands VEGF-C and VEGF-D play crucial roles in promoting lymphatic vascular growth both during development and in pathological conditions. Isolation of pure cultures of lymphatic and blood vascular endothelial cells and systematic characterization of their transcriptomes provide useful cell culture models and novel potential vascular markers and offer further insights into the lymphatic vascular biology. Ectopic expression of the lymphatic endothelial specific homeobox transcription factor Prox1 in blood endothelial cells results in a shift in the gene expression profile towards the lymphatic endothelial phenotype. It demonstrates the plasticity of endothelial cells and offers the possibility of transcriptional reprogramming of vascular endothelial cells as future putative therapeutic applications.展开更多
文摘Interferon-gamma （IFN-γ） is a major proinflammatory effector and regulatory cytokine produced by activated T cells and NK cells. IFN-γ has been shown to play pivotal roles in fundamental immunological processes such as inflammatory reactions, cell-mediated immunity and autoimmunity. A variety of human disorders have now been linked to irregular IFN-γ expression. In order to achieve proper IFN-γ-mediated immunological effects, IFN-γ expression in T cells is subject to both positive and negative regulation. In this study, we report for the first time the negative regulation of IFN-γ expression by Prospero-related Homeobox （Proxl）. In Jurkat T cells and primary human CD4＋ T cells, Proxl expression decreases quickly upon T cell activation, concurrent with a dramatic increase in IFN-γ expression. Reporter analysis and chromatin immunoprecipitation （CHIP） revealed that Proxl associates with and inhibits the transcription activity of IFN-γ promoter in activated Jurkat T cells. Co-immunoprecipitation and GST pull-down assay demonstrated a direct binding between Proxl and the nuclear receptor peroxisome proliferator-activated receptor gamma （PPARγ）, which is also an IFN-γ repressor in T cells. By introducing deletions and mutations into Proxl, we show that the repression of IFN-γ promoter by Proxl is largely dependent upon the physical interaction between Proxl and PPARγ. Furthermore, PPARγ antagonist treatment removes Proxl from IFN-γ promoter and attenuates repression of IFN-γ expression by Proxl. These findings establish Proxl as a new negative regulator of IFN-γ expression in T cells and will aid in the understanding of IFN-γ transcription regulation mechanisms.
文摘Lymphangiogenesis, the growth of new lymphatic vessels, has long been regarded as a putative efficient pathway to neoplastic metastization. Recent results have shown the necessity of lymphatic molecular markers and growth factors for lymphangiogenesis. Importantly, lymphatic endothelial receptor tyrosine kinase VEGFR-3 and its ligands VEGF-C and VEGF-D play crucial roles in promoting lymphatic vascular growth both during development and in pathological conditions. Isolation of pure cultures of lymphatic and blood vascular endothelial cells and systematic characterization of their transcriptomes provide useful cell culture models and novel potential vascular markers and offer further insights into the lymphatic vascular biology. Ectopic expression of the lymphatic endothelial specific homeobox transcription factor Prox1 in blood endothelial cells results in a shift in the gene expression profile towards the lymphatic endothelial phenotype. It demonstrates the plasticity of endothelial cells and offers the possibility of transcriptional reprogramming of vascular endothelial cells as future putative therapeutic applications.
