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Although binge alcohol-induced gut leakage has been studied extensively in the context of reactive oxygen species-mediated signaling, it was recently revealed that post-transcriptional regulation plays an essential role as well. Ethanol (EtOH)-inducible cytochrome P450-2E1 (CYP2E1), a key enzyme in EtOH metabolism, promotes alcohol-induced hepatic steatosis and inflammatory liver disease, at least in part by mediating changes in intestinal permeability. For instance, gut leakage and elevated intestinal permeability to endotoxins have been shown to be regulated by enhancing CYP2E1 mRNA and CYP2E1 protein levels. Although it is understood that EtOH promotes CYP2E1 induction and activation, the mechanisms that regulate CYP2E1 expression in the context of intestinal damage remain poorly defined. Specific miRNAs, including miR-132, miR-212, miR-378, and miR-552, have been shown to repress the expression of CYP2E1, suggesting that these miRNAs contribute to EtOH-induced intestinal injury. Here, we have shown that CYP2E1 expression is regulated post-transcriptionally through miRNA-mediated degradation, as follows: (1) the RNA-binding protein AUbinding factor 1 (AUF1) binds mature miRNAs, including CYP2E1-targeting miRNAs, and this binding modulates the degradation of corresponding target mRNAs upon EtOH treatment; (2) the serine/threonine kinase mammalian Ste20-like kinase 1 (MST1) mediates oxidative stress-induced phosphorylation of AUF1. Those findings suggest that reactive oxygen species-mediated signaling modulates AUF1/miRNA interaction through MST1-mediated phosphorylation. Thus, our study demonstrates the critical functions of AUF1 phosphorylation by MST1 in the decay of miRNAs targeting CYP2E1, the stabilization of CYP2E1 mRNA in the presence of EtOH, and the relationship of this pathway to subsequent intestinal injury. [ABSTRACT FROM AUTHOR]

Argonaute (AGO), a component of RNA-induced silencing complexes (RISCs), is a representative RNA-binding protein (RBP) known to bind with mature microRNA (miRNA) and is directly involved in post-transcriptional gene silencing. However, despite the biological significance of miRNA, the roles of other micro RNA-binding proteins (miRBPs) remain unclear in regulation of miRNA loading, dissociation from RISC, and extracellular release. In this study, we perform protein arrays to profile miRBPs and identify 118 RNA-binding proteins directly binding with miRNAs. Among those proteins, RBP quaking (QKI) inhibits extracellular release of mature microRNA let-7b by controlling the loading of let-7b into extracellular vesicles via additional miRBPs such as hnRNPD/AUF1 and hnRNPK. The enhanced extracellular release of let-7b after QKI depletion activates the Toll-like Receptor 7 (TLR7) and promotes the production of proinflammatory cytokines in recipient cells, leading to brain inflammation in mouse cortex. Thus, this study reveals contribution of QKI to the inhibition of brain inflammation via regulation of extracellular let-7b release., (© 2024. Published by The Company of Biologists Ltd.)