MAPPING CHANGES OF MIRNA-MRNA NETWORKS INLEISHMANIA-INFECTEDMACROPHAGES PREDICTS REGULATORY MIRNA-TF LOOPS AS NOVEL TARGETS OF PARASITE IMMUNE SUBVERSION

Abstract

AbstractMicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level and play a crucial role in numerous disease processes, including infections. Although intracellular microbial pathogens are known to modulate host cell gene expression to establish permissive conditions for infection, the specific role of host-encoded miRNAs underlying such subversion remains poorly understood. In this study, we employed the protozoan parasiteLeishmania amazonensisas a model system to investigate how infection of macrophages modifies the host cell miRNA profile to evade antimicrobial functions and to establish permissive conditions for intracellular proliferation. Dual RNA-seq analyses using matched mRNA and miRNA-enriched samples from uninfected andL. amazonensis-infected bone marrow-derived macrophages (BMDMs) revealed 102 differentially expressed miRNAs (padj<0.05), with 18 miRNAs showing reduced and 84 miRNAs showing increased abundance in infected BMDMs. Mapping putative networks of miRNA-mRNA interactions based on the observed expression changes, combined with Gene Ontology enrichment analyses, allowed us to identify potential miRNA target genes involved in key biological processes and metabolic pathways that permit parasite intracellular survival and proliferation. Our analyses predict the existence of a large miRNA-mRNA network affecting the expression level of numerous transcription factors that indicates inhibition of the NF-κB-dependent inflammatory response or the promotion of cholesterol biosynthesis during infection. In particular, the over 10e3-fold increase in the abundance of mmu-miR-686 in infected BMDMs was correlated with a reduced abundance of putative target transcripts implicated in miRNA biogenesis itself, in RNA binding, and in regulation of apoptosis, such asCaspase 12, the mRNA decay activator proteinZfp36l1orLeukemia Inhibitory Factor Receptor Alpha. Likewise, the over 200-fold increase in abundance of mmu-miR-6546-3p was associated with a reduced abundance of putative target mRNAs implicated in cytokine-mediated signaling, positive regulation of apoptotic process and regulation of gene expression, affecting, for example, theMADS box transcription enhancer factor 2, thetransformation related protein 53 inducible nuclear protein 1, or theG protein-coupled receptor 35. Interestingly, both miRNAs are predicted to simultaneously target 32 mRNAs that showed reduced abundance in infected BMDMs, includingMaturin Neural Progenitor Differentiation Regulator(Mturn), a regulator of NF-κB transcription factor activity. In conclusion, our approach provides novel insight into molecular mechanisms that may govern macrophage subversion and intracellularLeishmaniasurvival. Our results shed new light on the complex relationship among miRNAs, macrophage gene expression andLeishmaniainfection, proposing regulatory feed-forward loops (FFLs) and feedback loops (FBLs) between miRNAs and TFs as a novel target ofLeishmaniaimmune subversion. These findings open exciting new avenues for the development of intervention strategies aimed at disrupting such crucial interactions, for example using an anti-miR (antagomir) approach against mmu-miR-686 and mmu-miR-6546-3p.