TPL-2 Inhibits IFN-β Expression via an ERK1/2-TCF-FOS Axis in TLR4-Stimulated Macrophages

Abstract

TPL-2 kinase plays an important role in innate immunity, activating ERK1/2 MAPKs in myeloid cells following TLR stimulation. We investigated how TPL-2 controls transcription in TLR4-stimulated mouse macrophages. TPL-2 activation of ERK1/2 regulated expression of genes encoding transcription factors, cytokines, chemokines, and signaling regulators. Bioinformatics analysis of gene clusters most rapidly induced by TPL-2 suggested that their transcription was mediated by the ternary complex factor (TCF) and FOS transcription factor families. Consistently, TPL-2 induced ERK1/2 phosphorylation of the ELK1 TCF and the expression of TCF target genes. Furthermore, transcriptomic analysis of TCF-deficient macrophages demonstrated that TCFs mediate approximately half of the transcriptional output of TPL-2 signaling, partially via induced expression of secondary transcription factors. TPL-2 signaling and TCFs were required for maximal TLR4-induced FOS expression. Comparative analysis of the transcriptome of TLR4-stimulated Fos−/− macrophages indicated that TPL-2 regulated a significant fraction of genes by controlling FOS expression levels. A key function of this ERK1/2-TCF-FOS pathway was to mediate TPL-2 suppression of type I IFN signaling, which is essential for host resistance against intracellular bacterial infection.

Selective Regulation of a Defined Subset of Inflammatory and Immunoregulatory Genes by an NF-κB p50-IκBζ Pathway

“…Tpl2 stability requires association with the ankyrin repeat-containing p105 precursor protein encoded by the Nfkb1 gene (Beinke et al 2003; Waterfield et al 2003; Gantke et al 2011). RNA-seq analyses with lipid A-stimulated Map3k8 D270A/D270A (kinase-inactive Tpl2 mutant) BMDMs (Blair et al 2022), and with lipid A-stimulated WT BMDMs in the presence of an ERK1/2 inhibitor (Supplemental Figure S1), demonstrated that Egr1 is by far the most strongly impacted gene in both settings. Thus, Egr1 deficiency in Nfkb1 -/- BMDMs is likely due to the absence of Tpl2 (note that ERK and the p38 MAPK activate many other TLR4-induced genes in a redundant manner) (Tong et al 2016).…”

Selective regulation of a defined subset of inflammatory and immunoregulatory genes by an NF-κB p50–IκBζ pathway

“…Tpl2 stability requires association with the ankyrin repeat-containing p105 precursor protein encoded by the Nfkb1 gene ( Waterfield et al 2003 ; Beinke et al 2004 ; Gantke et al 2011 ). RNA-seq analyses with lipid A-stimulated Map3k8 D270A/D270A (kinase-inactive Tpl2 mutant) BMDMs ( Blair et al 2022 ) and with lipid A-stimulated WT BMDMs in the presence of an ERK1/2 inhibitor ( Supplemental Fig. S1 ) demonstrated that Egr1 is the most strongly impacted gene in both settings.…”

p38γ and p38δ modulate innate immune response by regulating MEF2D activation

“…RNA was isolated from 1 × 10 6 BMDM from WT or p38γ/δKIKO male mice using the RNeasy kit (QIAGEN). Biological replicate libraries were prepared using the TruSeq RNA library prep kit (Illumina) and were single-end sequenced on the Illumina HiSeq 2500 platform as described in Blair et al, 2022 .…”