Ac₂PIM-responsive miR-150 and miR-143 target receptor-interacting protein Kinase 2 and transforming growth factor beta-activated Kinase 1 to suppress NOD2-induced immunomodulators

Abstract

Specific and coordinated regulation of innate immune receptor-driven signaling networks often determines the net outcome of the immune responses. Here, we investigated the cross-regulation of toll-like receptor (TLR)2 and nucleotide-binding oligomerization domain (NOD)2 pathways mediated by Ac₂PIM, a tetra-acylated form of mycobacterial cell wall component and Muramyl Dipeptide (MDP), a peptidoglycan derivative respectively. While Ac₂PIM treatment of macrophages compromised their ability to induce NOD2-dependent immunomodulators like cyclooxygenase (COX)-2, suppressor of cytokine signaling (SOCS)-3 and matrix metalloproteinase (MMP)-9, no change in the NOD2-responsive NO, TNF-α, VEGF-A and IL-12 levels was observed. Further, genome-wide microRNA expression profiling identified Ac₂PIM-responsive miR-150 and miR-143 to target NOD2 signaling adaptors, RIP2 and TAK1 respectively. Interestingly, Ac₂PIM was found to activate the SRC-FAK-PYK2-CREB cascade via TLR2 to recruit CBP/P300 at the promoters of miR-150 and miR-143 and epigenetically induce their expression. Loss-of-function studies utilizing specific miRNA inhibitors establish that Ac₂PIM, via the miRNAs, abrogate NOD2-induced PI3K-PKCδ-MAPK pathway to suppress β-CATENIN-mediated expression of COX-2, SOCS-3 and MMP-9. Our investigation has thus underscored the negative regulatory role of Ac₂PIM-TLR2 signaling on NOD2 pathway which could broaden our understanding on vaccine potential or adjuvant utilities of Ac₂PIM and/or MDP.