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The adaptive immune system involves antigen-specific host defense mechanisms mediated by T and B cells. In particular, CD4+ T cells play a central role in the elimination of pathogens. Immunological tolerance in the thymus regulates T lymphocytes to avoid self-components, including induction of cell death in immature T cells expressing the self-reactive T-cell receptor repertoire. In the periphery, mature T cells are also regulated by tolerance, e.g., via induction of anergy or regulatory T cells. Thus, T cells strictly control intrinsic signal transduction to prevent excessive responses or self-reactions. If the inhibitory effects of T cells on these mechanisms are disrupted, T cells may incorrectly attack self-components, which can lead to autoimmune disease. The functions of T cells are supported by post-translational modifications, particularly phosphorylation, of signaling molecules, the proper regulation of which is controlled by endogenous mechanisms within the T cells themselves. In recent years, molecular targeted agents against kinases have been developed for treatment of autoimmune diseases. In this review, we discuss T-cell signal transduction in autoimmune disease and provide an overview of acetylation-mediated regulation of T-cell signaling pathways. [ABSTRACT FROM AUTHOR]

T cell functions are regulated by multiple signaling cascades, including the MKK4-JNK (c-Jun NH 2 terminal kinase) pathway. However, the mechanism regulating the MKK4-JNK axis in T cells remains unclear. Herein, we demonstrated that protein acetylation modulates JNK activity induced by T cell receptor (TCR) activation. The acetyltransferase, CREB-binding protein (CBP), is transported from the nucleus to the cytoplasm in response to TCR cross-linking. To investigate the role of CBP in TCR signaling, we overexpressed CBP in the cytoplasm of Jurkat cells, a human T lymphocyte line. Enforced expression of cytoplasmic CBP led to MKK4 acetylation and interfered with MKK4-mediated JNK phosphorylation. Insufficient JNK activity decreased the activity of the transcription factor, AP-1. In contrast, other transcription factors, NF-κB and NFAT, stimulated with anti-CD3 and anti-CD28 antibodies were activated normally in the presence of cytoplasmic-CBP. These results provide valuable insights into the role of acetylation in MKK4-JNK signaling in T cells. [ABSTRACT FROM AUTHOR]

Interleukin-7 (IL-7) is essential for lymphocyte development. To identify the functional subdomains in the cytoplasmic tail of the IL-7 receptor (IL-7R) α chain, here, we constructed a series of IL-7Rα deletion mutants. We found that IL-7Rα-deficient hematopoietic progenitor cells (HPCs) gave rise to B cells both in vitro and in vivo when a wild-type (WT) IL-7Rα chain was introduced; however, no B cells were observed under the same conditions from IL-7Rα-deficient HPCs with introduction of the exogenous IL-7Rα subunit, which lacked the amino acid region at positions 414–441 (d414–441 mutant). Signal transducer and activator of transcription 5 (STAT5) was phosphorylated in cells with the d414–441 mutant, similar to that in WT cells, in response to IL-7 stimulation. In contrast, more truncated STAT5 (tSTAT5) was generated in cells with the d414–441 mutant than in WT cells. Additionally, the introduction of exogenous tSTAT5 blocked B lymphopoiesis but not myeloid cell development from WT HPCs in vivo. These results suggested that amino acids 414–441 in the IL-7Rα chain formed a critical subdomain necessary for the supportive roles of IL-7 in B-cell development. [ABSTRACT FROM AUTHOR]