ABSTRACT
CYLD is a lysine 63-deubiquitinating enzyme that inhibits NF-κB and JNK signaling. Here, we show that CYLD knock-out mice have markedly increased numbers of regulatory T cells (Tregs) in peripheral lymphoid organs but not in the thymus. In vitro stimulation of CYLD-deficient naive T cells with anti-CD3/28 in the presence of TGF-ß led to a marked increase in the number of Foxp3-expressing T cells when compared with stimulated naive control CD4(+) cells. Under endogenous conditions, CYLD formed a complex with Smad7 that facilitated CYLD deubiquitination of Smad7 at lysine 360 and 374 residues. Moreover, this site-specific ubiquitination of Smad7 was required for activation of TAK1 and p38 kinases. Finally, knockdown of Smad7 or inhibition of p38 activity in primary T cells impaired Treg differentiation. Together, our results show that CYLD regulates TGF-ß signaling function in T cells and the development of Tregs through deubiquitination of Smad7.
Subject(s)
Cysteine Endopeptidases/metabolism , Signal Transduction , Smad7 Protein/metabolism , T-Lymphocytes, Regulatory/cytology , Transforming Growth Factor beta/metabolism , Animals , CD4-Positive T-Lymphocytes/cytology , CD4-Positive T-Lymphocytes/drug effects , CD4-Positive T-Lymphocytes/metabolism , Cysteine Endopeptidases/deficiency , Cysteine Endopeptidases/genetics , Deubiquitinating Enzyme CYLD , Forkhead Transcription Factors/genetics , Gene Knockout Techniques , HeLa Cells , Humans , Interleukin-2 Receptor alpha Subunit/metabolism , Lymph Nodes/immunology , MAP Kinase Kinase Kinases/metabolism , MAP Kinase Signaling System/drug effects , Mice , Promoter Regions, Genetic , Protein Binding , Signal Transduction/drug effects , T-Lymphocytes, Regulatory/drug effects , T-Lymphocytes, Regulatory/metabolism , Transforming Growth Factor beta/pharmacology , Ubiquitination/drug effects , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
X-linked hyper IgM syndrome (XHM) is a combined immune deficiency disorder caused by genetic alterations in CD40 ligand. The purpose of this study was to investigate the safety and efficacy of recombinant CD40 ligand (rCD40L) in the treatment of the disease. Three children were administered rCD40L subcutaneously 3 times per week at 0.03 mg/kg for 22 weeks, and after a 12-week drug-free interval, the dose was increased to 0.05 mg/kg for an additional 22 weeks of treatment. Although specific antibody responses to T cell-dependent antigens was lacking, administration of rCD40 resulted in acquisition of the capacity to mount cutaneous delayed type hypersensitivity reactions that disappeared during the drug-free interval as well as the postbiologic follow-up period. With rCD40L treatment, patient T cells developed a new capacity to respond to T-cell mitogens with synthesis of IFN-γ and TNF-α. Intracellular cytokine staining studies showed that both CD4(+) and CD8(+) T cells participated in this response. Finally, CD40L therapy was associated with changes in lymph node size and architecture based on comparison of biopsies taken before and after therapy. This clinical study showed that rCD40L is capable of improving T cell-immune function in patients with XHM.
