Abstract
The mycobacterial cell wall glycolipid trehalose-6,6-dimycolate (TDM) activates macrophages through the C-type lectin receptor MINCLE. Regulation of innate immune cells relies on miRNAs, which may be exploited by mycobacteria to survive and replicate in macrophages. Here, we have used macrophages deficient in the microprocessor component DGCR8 to investigate the impact of miRNA on the response to TDM. Deletion of DGCR8 in bone marrow progenitors reduced macrophage yield, but did not block macrophage differentiation. DGCR8-deficient macrophages showed reduced constitutive and TDM-inducible miRNA expression. RNAseq analysis revealed that they accumulated primary miRNA transcripts and displayed a modest type I IFN signature at baseline. Stimulation with TDM in the absence of DGCR8 induced overshooting expression of IFNβ and IFN-induced genes, which was blocked by antibodies to type I IFN. In contrast, signaling and transcriptional responses to recombinant IFNβ were unaltered. Infection with live Mycobacterium bovis Bacille Calmette-Guerin replicated the enhanced IFN response. Together, our results reveal an essential role for DGCR8 in curbing IFNβ expression macrophage reprogramming by mycobacteria.
Highlights
Specific miRNAs are required for proper development, differentiation and function of many immune cells (Kuipers et al, 2010; Dooley et al, 2013; Danger et al, 2014; Devasthanam & Tomasi, 2014)
bone marrow cells (BMCs) were cultured in the presence of M-CSF for 7 d to generate bone marrowderived macrophages (BMM); tamoxifen-metabolite 4-hydroxytamoxifen (TAM) was added to the cultures at day 1 (d1), d3, or d5 (Fig 1B), and the BMM harvested at d7 were analyzed for deletion of DGCR8
The abundance of the DGCR8 mRNA was reduced by 99% when TAM was added at d1 of the differentiation culture, whereas addition at d3 or d5 resulted in a reduction by 94% and 60%, respectively (Fig 1C)
Summary
Specific miRNAs are required for proper development, differentiation and function of many immune cells (Kuipers et al, 2010; Dooley et al, 2013; Danger et al, 2014; Devasthanam & Tomasi, 2014). They control innate immune cell activation and the magnitude of inflammatory responses at multiple layers by targeting common signaling pathway components, transcription factors and pattern recognition receptors and cytokines. MiRNAs represent a fundamental regulatory layer in innate immune responses by fine-tuning macrophage activation (O’Connell et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
