A Metabolic Enzyme, Pyruvate Carboxylase, Functions as a Sequence-Selective Small RNA Sensor for Antiviral Immunity

Interleukin 27 (IL-27) is an anti-HIV cytokine that induces 14 novel microRNAs (miRNAs) in T cells. We previously reported that transfection of two of these miRNA mimics, miRTC10 and miRTC14, differentially induced interferons (IFN)A2, A8, A13, and L1 expression in human primary macrophages. However, the mechanism underlying this activation remains unclear. Here, we show that miRTC14 does not directly target IFN-regulatory genes but instead engages cytosolic RNA-sensing proteins. Using miRNA pull-down coupled with mass spectrometry and immunoblotting, we identified a metabolic enzyme, pyruvate carboxylase (PC) and laboratory of genetics and physiology 2 (LGP2/DHX58) as direct binding partners of miRTC14. Functional analyses revealed that miRTC14 induces IFN expression by more than100-fold (p < 0.001), whereas PC and LGP2 depletion markedly attenuated this response (50-100 fold reduction, p < 0.01). Reconstitution of PC and LGP2 in deficient HEK293 cells restored miRTC14-driven IFN induction. We found that miRTC14-induced IFN activation depends on sequence features at the duplex termini and is unlikely to arise from canonical miRNA-mediated gene silencing. These findings establish PC as a novel miRNA-binding protein and define a previously unrecognized RNA-sensing mechanism by which miRTC14 drives IFN production, linking metabolic enzymes to RNA sequence-dependent innate immunity.