Bruton's tyrosine kinase separately regulates NFkappaB p65RelA activation and cytokine interleukin (IL)-10/IL-12 production in TLR9-stimulated B Cells

• Published in: The Journal of biological chemistry 2008-04, Vol.283 (17), p.11189-11198
• Main Authors: Lee, Koon-Guan, Xu, Shengli, Wong, Ee-Tsin, Tergaonkar, Vinay, Lam, Kong-Peng
• Format: Article
• Language: English
• Subjects: Agammaglobulinaemia Tyrosine Kinase; Animals; B-Lymphocytes - cytology; B-Lymphocytes - metabolism; CpG Islands; Cytosol - metabolism; Interleukin-10 - metabolism; Interleukin-12 - metabolism; Mice; Mice, Inbred C57BL; Models, Biological; Models, Genetic; Oligonucleotides - chemistry; Protein-Tyrosine Kinases - metabolism; Protein-Tyrosine Kinases - physiology; Signal Transduction; Toll-Like Receptor 9 - metabolism; Transcription Factor RelA - metabolism
• ISSN: 0021-9258
• DOI: 10.1074/jbc.M708516200

B lymphocytes express both B cell receptor and Toll-like receptors (TLR). We show here that Bruton's tyrosine kinase (Btk), a critical component in B cell receptor signaling, is also involved in TLR9 signaling in B cells. Stimulation of B cells with TLR9 ligand CpG oligodeoxynucleotide (ODN) leads to transient phosphorylation of Btk, and in the absence of Btk, TLR9-induced proliferation of B cells is impaired. Interestingly, Btk(-/-) B cells secrete significantly more interleukin (IL)-12 but much less IL-10 compared with wild type B cells upon TLR9 stimulation. Immunization of Btk(-/-) mice with CpG ODN also leads to elevated levels of IL-12 in vivo and consequently, a greater -fold increment in the production of Th1 type IgG2b and IgG3 antibodies in these mice compared with wild type controls. The addition of exogenous recombinant IL-10 could suppress IL-12 production by TLR9-activated Btk(-/-) B cells, suggesting that in B cells, Btk negatively regulates IL-12 through the induction of autocrine IL-10 production. TLR9 signaling also leads to the activation of NFkappaB, including the p65RelA subunit in wild type B cells. The lack of Btk signaling affects the activation of NFkappaB and impairs the translocation of the p65RelA subunit to the nucleus of B cells upon TLR9 stimulation. However, p65RelA(-/-) B cells could respond similarly to wild type B cells in terms of IL-10 and IL-12 secretion when stimulated with CpG ODN, suggesting that the defect in NFkappaB p65RelA activation is additional to the impairment in cytokine production in TLR9-activated Btk(-/-) B cells. Thus, Btk plays an important role in TLR9 signaling and acts separately to regulate NFkappaB RelA activation as well as IL-10 and IL-12 production in B cells.