Recent studies have reported that the crosslinking of regulatory receptors (RRs), such as blood dendritic cell antigen 2 (BDCA-2) (CD303) or ILT7 (CD85g), of plasmacytoid dendritic cells (pDCs) efficiently suppresses the production of type I interferons (IFN-I, α/β/ω) and other cytokines in response to toll-like receptor 7 and 9 (TLR7/9) ligands. The exact mechanism of how this B cell receptor (BCR)-like signaling blocks TLR7/9-mediated IFN-I production is unknown. Here, we stimulated BCR-like signaling by ligation of RRs with BDCA-2 and ILT7 mAbs, hepatitis C virus particles, or BST2 expressing cells. We compared BCR-like signaling in proliferating pDC cell line GEN2.2 and in primary pDCs from healthy donors, and addressed the question of whether pharmacological targeting of BCR-like signaling can antagonize RR-induced pDC inhibition. To this end, we tested the TLR9-mediated production of IFN-I and proinflammatory cytokines in pDCs exposed to a panel of inhibitors of signaling molecules involved in BCR-like, MAPK, NF-ĸB, and calcium signaling pathways. We found that MEK1/2 inhibitors, PD0325901 and U0126 potentiated TLR9-mediated production of IFN-I in GEN2.2 cells. More importantly, MEK1/2 inhibitors significantly increased the TLR9-mediated IFN-I production blocked in both GEN2.2 cells and primary pDCs upon stimulation of BCR-like or phorbol 12-myristate 13-acetate-induced protein kinase C (PKC) signaling. Triggering of BCR-like and PKC signaling in pDCs resulted in an upregulation of the expression and phoshorylation of c-FOS, a downstream gene product of the MEK1/2-ERK pathway. We found that the total level of c-FOS was higher in proliferating GEN2.2 cells than in the resting primary pDCs. The PD0325901-facilitated restoration of the TLR9-mediated IFN-I production correlated with the abrogation of MEK1/2-ERK-c-FOS signaling. These results indicate that the MEK1/2-ERK pathway inhibits TLR9-mediated type I IFN production in pDCs and that pharmacological targeting of MEK1/2-ERK signaling could be a strategy to overcome immunotolerance of pDCs and re-establish their immunogenic activity.

• Klíčová slova
• B cell-like receptor signaling, MEK1/2, blood dendritic cell antigen 2, c-FOS, plasmacytoid dendritic cells, regulatory receptors, toll-like receptors 7 and 9 (TLR7/9), type I interferon,
• MeSH
• B-lymfocyty imunologie   MeSH
• buněčné linie MeSH
• dendritické buňky fyziologie   MeSH
• extracelulárním signálem regulované MAP kinasy metabolismus   MeSH
• interferon typ I metabolismus   MeSH
• lidé MeSH
• MAP kinasa-kinasa 1 metabolismus   MeSH
• MAP kinasa-kinasa 2 metabolismus   MeSH
• MAP kinasový signální systém MeSH
• NF-kappa B metabolismus   MeSH
• proteinkinasa C metabolismus   MeSH
• protoonkogenní proteiny c-fos metabolismus   MeSH
• receptory antigenů B-buněk genetika   metabolismus   MeSH
• toll-like receptor 9 metabolismus   MeSH
• vápníková signalizace MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• extracelulárním signálem regulované MAP kinasy MeSH
• interferon typ I MeSH
• MAP kinasa-kinasa 1 MeSH
• MAP kinasa-kinasa 2 MeSH
• NF-kappa B MeSH
• proteinkinasa C MeSH
• protoonkogenní proteiny c-fos MeSH
• receptory antigenů B-buněk MeSH
• toll-like receptor 9 MeSH