Long noncoding RNA AL109754.1 Regulates Myeloid Dendritic Cell Differentiation and Potentiates TLR signaling

Dendritic cells (DCs) are key antigen presentation cells (APC) that bridge innate and adaptive immune functions to contain the pathogenic threats. Long noncoding RNAs (lncRNAs) are implicated in functional regulation of various biological processes including inflammation and immunity. However, the knowledge on myeloid DC expressed lncRNA repertoire and their regulatory functions is limited. In this study, we have reconnoitered the time-kinetics of lncRNA expression profiles during monocyte-to-DC differentiation and their roles in shaping DC functions. Our RNA-seq data identified thousands of differentially expressed lncRNAs associated with primary human monocyte-to-DC differentiation in vitro. We selected two lncRNAs viz., AL109754.1 and AC093278.2 that were enriched during DC differentiation. Knockdown of AL109754.1 but not AC093278 affects DCs differentiation as observed by marked reduction of surface markers CD1a, CD93 and CD209. These DCs also exhibit significant reduction in the expression of TLR 2, 4, 5, 7 and 9, suggesting that AL109754.1 expression is critical in maintaining TLR expression in DCs. Furthermore, reduced phosphorylation of NF-{kappa}B, IRF3 and IRF7 in AL109754.1 knockdown DCs treated with TLR agonists further substantiate their role in potentiating TLR signaling. Mechanistically, AL109754.1 knockdown DC showed significant downregulation of multiple NF-{kappa}B-induced genes and time-dependent inhibition of pro-inflammatory cytokine (IL-1{beta}, IL-6, IL-8 and TNF) secretion upon challenge with TLR 4, 5, or 7 agonists. Overall, this study characterized novel functions of AL109754.1 that regulates DC differentiation, and TLR-dependent innate immune activation.