RESUMO
Signal transducer and activator of transcription 3 (STAT3) is considered a negative regulator of inflammation, as inhibition of STAT3 signaling enhances antitumor immunity. However, STAT3 activation is a key oncogenic pathway in natural killer (NK)-lineage large granular lymphomas, and we recently reported enhanced proliferation and function of human NK cells activated with IL-21, which signals primarily through STAT3. These IL-21-expanded NK cells also have increased NKG2D expression, which led us to focus our investigation on whether STAT3 regulates NKG2D. In this study, we show that modulation of STAT3 phosphorylation with cytokines and small-molecule inhibitors correlates with NKG2D expression on human NK cells, leading to altered NK-cell degranulation. Moreover, NKG2D expression on murine NK cells having conditional STAT3 ablation is lower than on NK cells from wild-type mice, and human NK cells carrying dominant-negative STAT3 mutations have decreased baseline NKG2D expression and blunted responses to IL-10 and IL-21. Lastly, we show binding of STAT3 to a predicted STAT3 binding site upstream of the NKG2D gene, which is enhanced by IL-10 and IL-21 and decreased by STAT3 inhibition. Taken together, these data show that NKG2D expression in NK cells is regulated at the transcriptional level by STAT3, resulting in a functional NK cell defect in patients with STAT3 mutations.
Assuntos
Células Matadoras Naturais/imunologia , Células Matadoras Naturais/metabolismo , Subfamília K de Receptores Semelhantes a Lectina de Células NK/genética , Fator de Transcrição STAT3/metabolismo , Animais , Sequência de Bases , Sítios de Ligação/genética , DNA/genética , DNA/metabolismo , Humanos , Interleucina-10/metabolismo , Interleucina-15/metabolismo , Interleucinas/metabolismo , Síndrome de Job/genética , Síndrome de Job/imunologia , Síndrome de Job/metabolismo , Camundongos , Camundongos Knockout , Dados de Sequência Molecular , Mutação , Fosforilação , Fator de Transcrição STAT3/antagonistas & inibidores , Fator de Transcrição STAT3/deficiência , Fator de Transcrição STAT3/genética , Transdução de Sinais , Transcrição Gênica , Tirosina/metabolismoRESUMO
Neutrophil mobilization from the bone marrow is a critical aspect of the innate immune response, enabling a rapid deployment of phagocytes to infected or inflamed tissue. The cytokine G-CSF, which is induced rapidly during infection, elicits a swift and potent mobilizing response, yet its mechanisms of action remain poorly understood. Here, we studied the role of G-CSF and its principal signal transducer STAT3 in regulating expression of the neutrophil chemoattractant MIP-2. Our studies revealed Gr-1(hi) mature neutrophils as major sources of Cxcl2 (MIP-2) mRNA in bone marrow and G-CSF-responsive MIP-2 protein production. Induction of Cxcl2 was regulated directly by G-CSF-activated STAT3 via interaction at a STAT consensus element in the Cxcl2 promoter. G-CSF coordinately stimulated the association of STAT3, induction of the transcriptionally active H3K4me3 modification, and recruitment of RNA Pol II at the Cxcl2 proximal promoter, as well as the promoter region of Il8rb, encoding the MIP-2 receptor. These results suggest that the G-CSF-STAT3 pathway directly regulates transcriptional events that induce neutrophil mobilization.
