Bruton’s Tyrosine Kinase Is Required for TLR2 and TLR4-Induced TNF, but Not IL-6, Production

Abstract

Bruton’s tyrosine kinase (Btk), the gene mutated in the human immunodeficiency X-linked agammaglobulinemia, is activated by LPS and is required for LPS-induced TNF production. In this study, we have investigated the role of Btk both in signaling via another TLR (TLR2) and in the production of other proinflammatory cytokines such as IL-1β, IL-6, and IL-8. Our data show that in X-linked agammaglobulinemia PBMCs, stimulation with TLR4 (LPS) or TLR2 (N-palmitoyl-S-[2, 3-bis(palmitoyloxy)-(2R)-propyl]-(R)-cysteine) ligands produces significantly less TNF and IL-1β than in normal controls. In contrast, a lack of Btk has no impact on the production of IL-6, IL-8, or the anti-inflammatory cytokine, IL-10. Our previous data suggested that Btk lies within a p38-dependent pathway that stabilizes TNF mRNA. Accordingly, TaqMan quantitative PCR analysis of actinomycin D time courses presented in this work shows that overexpression of Btk is able to stabilize TNF, but not IL-6 mRNA. Furthermore, using the p38 inhibitor SB203580, we show that the TLR4-induced production of TNF, but not IL-6, requires the activity of p38 MAPK. These data provide evidence for a common requirement for Btk in TLR2- and TLR4-mediated induction of two important proinflammatory cytokines, TNF and IL-1β, and reveal important differences in the TLR-mediated signals required for the production of IL-6, IL-8, and IL-10.

Signaling by Toll-like Receptors 8 and 9 Requires Bruton's Tyrosine Kinase

“…Heparinized blood samples were collected prior to the infusion of intravenous immunoglobulins. PBMCs were generated as described previously (17).…”

Selective Activation of the p38 MAPK Pathway by Synthetic Monophosphoryl Lipid A

“…One of the signaling pathways activated by both TRIF and MyD88 involves the MAPK family of signaling kinases (11). Growing evidence indicates that different MAPKs play different roles in mediating expression of MyD88-associated versus TRIF-associated genes at either transcriptional levels via activation of transcription factors or at post-transcriptional levels via mRNA transcript stabilization (13)(14)(15)(16)(17)(18)(19). We and others (1, 3, 20 -22) noted previously that MPLA increased levels of not only TRIF-associated transcripts, such as IFIT1 (interferon-induced protein with tetratricopeptide repeats) and IFIT2, but also significant levels of NF-B-associated IL-10, TNF␣, IL-12, and co-stimulatory molecules, despite comparatively weak NF-B activation.…”

TLR-induced activation of Btk – Role for endosomal MHC class II molecules revealed

“…Investigations into noncanonical pathways that are activated downstream of the TLRs have brought Bruton's tyrosine kinase (Btk), a nonreceptor tyrosine kinase, to the fore as key signaling molecule in this respect. In these studies Btk has been demonstrated to interact with the adaptor molecules MyD88 and Mal downstream of TLR4, 6, 8, and 9 resulting in NFκB activation and the production of TNF-α and IL-6 [3][4][5][6].…”