The effect of TASL knockout on murine B cells following TLR9 stimulation
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE302697 | GEO | 2025/12/24
REPOSITORIES: GEO
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Project description:Plasmacytoid dendritic cells (pDCs) can be activated by the endosomal TLRs, and contribute to the pathogenesis of systemic lupus erythematosus (SLE) by producing type I IFNs. Thus, blocking TLR-mediated pDC activation may represent a useful approach for the treatment of SLE. In an attempt to identify a therapeutic target for blocking TLR signaling in pDCs, we investigated the contribution of Bruton's tyrosine kinase (Btk) to the activation of pDCs by TLR7 and TLR9 stimulation by using a selective Btk inhibitor RN486. Stimulation of TLR7 and 9 with their respective agonist, namely, gardiquimod and type A CpG ODN2216, resulted in the activation of human pDCs, as demonstrated by the expression of activation markers (CD69, CD40, and CD86), elevated production of IFN-alpha and other inflammatory cytokines, as well as up-regulation of numerous genes including IFN-alpha-inducible genes and activation of interferon regulatory factor 7 (IRF7) and NF-kB. RN486 inhibited all of these events induced by TLR9, but not TLR7 stimulation, with a nanomolar potency for inhibiting type A CpG ODN2216-mediated production of cytokines (e.g., IC50=386 nM for inhibiting IFN-alpha). Our data reveal Btk as an important regulatory enzyme in the TLR9 pathway, and a potential therapeutic target for SLE and other TLR-driven diseases. pDCs from healthy donors (n=4) were treated with gardiquimod (TLR7 agonist) or ODN 2216 (TLR9 agonist) with or without BTK inhibitor for 3 hours.
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Project description:Synthetic oligonucleotides (ODNs) containing CpG motifs stimulate human plasmacytoid dendritic cells (pDCs) to produce type-1 interferons (IFN) and pro-inflammatory cytokines. Previous studies demonstrated that interferon regulatory factors (IRFs) played a central role in mediating CpG-induced pDC activation. This work explores the inverse effects of IRF-5 and IRF-8 on CpG dependent gene expression. Results from RNA interference and microarray studies indicate that IRF-5 up-regulates TLR9-driven gene expression whereas IRF-8 down-regulates the same genes. Several findings support the conclusion that IRF-8 inhibits TLR9 dependent gene expression by directly blocking the activity of IRF-5. First, the inhibitory activity of IRF-8 is only observed when IRF-5 is present. Second, proximity ligation analysis shows that IRF-8 and IRF-5 co-localize within the cytoplasm of resting human pDC and co-translocate to the nucleus after CpG stimulation. Taken together, these findings suggest that two transcription factors with opposing functions control TLR9 signaling in human pDCs. CAL-1 cells were transfected with siRNA targeting IRF-5 (IRF-5si) and left unstimulated (n=4, technical repeats) or stimulated with K-type CpG ODN (n=4, technical repeats). CAL-1 cells were transfected with siRNA targeting IRF-8 (IRF-8si) and left unstimulated (n=4, technical repeats) or stimulated with K-type CpG ODN (n=4, technical repeats). CAL-1 cells were transfected with control siRNA (Contsi) and left unstimulated (n=4, technical repeats) or stimulated with K-type CpG ODN (n=4, technical repeats).
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Project description:Nucleic acid sensing by endolysosomal TLR7-9 results in the induction of antiviral and proinflammatory transcriptional responses. We recently identified TASL as the innate immune adaptor mediating TLR7-9-induced IRF5 activation via the interaction with SLC15A4, but its relevance in primary murine cells remained unexplored. Here we assessed the impact of deficiency in TASL and/or its previously uncharacterized paralogue Gm6377, named here TASL2, on endolysosomal TLR responses in primary bone-marrow-derived pDCs and splenic B cells. Double knockout TASLxTASL2 (TASLDKO) phenocopied the strong impairement observed in cells from SLC15A4-deficient feeble mice, while single TASL or TASL2 deficiency showed partial effect. Altogether, this study demonstrates that the SLC15A4-TASL/TASL2 complex play a critical role for TLR7-9-driven inflammatory responses.
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Project description:Toll-like receptors (TLRs) have a crucial role in the recognition of pathogens and initiation of immune responses. Here we show that a previously uncharacterized protein encoded by CXorf21—a gene that is associated with systemic lupus erythematosus—interacts with the endolysosomal transporter SLC15A4, an essential but poorly understood component of the endolysosomal TLR machinery also linked to autoimmune disease. Loss of this type-I-interferon-inducible protein, which we refer to as ‘TLR adaptor interacting with SLC15A4 on the lysosome’ (TASL), abrogated responses to endolysosomal TLR agonists in both primary and transformed human immune cells. Deletion of SLC15A4 or TASL specifically impaired the activation of the IRF pathway without affecting NF-κB and MAPK signalling, which indicates that ligand recognition and TLR engagement in the endolysosome occurred normally. Extensive mutagenesis of TASL demonstrated that its localization and function relies on the interaction with SLC15A4. TASL contains a conserved pLxIS motif (in which p denotes a hydrophilic residue and x denotes any residue) that mediates the recruitment and activation of IRF5. This finding shows that TASL is an innate immune adaptor for TLR7, TLR8 and TLR9 signalling, revealing a clear mechanistic analogy with the IRF3 adaptors STING, MAVS and TRIF. The identification of TASL as the component that links endolysosomal TLRs to the IRF5 transcription factor via SLC15A4 provides a mechanistic explanation for the involvement of these proteins in systemic lupus erythematosus.
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Project description:Plasmacytoid dendritic cells (pDCs) can be activated by the endosomal TLRs, and contribute to the pathogenesis of systemic lupus erythematosus (SLE) by producing type I IFNs. Thus, blocking TLR-mediated pDC activation may represent a useful approach for the treatment of SLE. In an attempt to identify a therapeutic target for blocking TLR signaling in pDCs, we investigated the contribution of Bruton's tyrosine kinase (Btk) to the activation of pDCs by TLR7 and TLR9 stimulation by using a selective Btk inhibitor RN486. Stimulation of TLR7 and 9 with their respective agonist, namely, gardiquimod and type A CpG ODN2216, resulted in the activation of human pDCs, as demonstrated by the expression of activation markers (CD69, CD40, and CD86), elevated production of IFN-alpha and other inflammatory cytokines, as well as up-regulation of numerous genes including IFN-alpha-inducible genes and activation of interferon regulatory factor 7 (IRF7) and NF-kB. RN486 inhibited all of these events induced by TLR9, but not TLR7 stimulation, with a nanomolar potency for inhibiting type A CpG ODN2216-mediated production of cytokines (e.g., IC50=386 nM for inhibiting IFN-alpha). Our data reveal Btk as an important regulatory enzyme in the TLR9 pathway, and a potential therapeutic target for SLE and other TLR-driven diseases.
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