RNA m6A demethylase ALKBH5 drives emergency granulopoiesis and neutrophil mobilization by upregulating G-CSFR expression

Abstract

Abstract Emergency granulopoiesis and neutrophil mobilization that can be triggered by granulocyte colony-stimulating factor (G-CSF) through its receptor G-CSFR are essential for antibacterial innate defense. Yet the epigenetic modifiers crucial for intrinsically regulating G-CSFR expression and neutrophil innate response against bacterial infection remain largely unclear. N6-methyladenosine (m6A) RNA modification and its demethylase alkB homolog 5 (ALKBH5) are key epigenetic regulators of immunity and inflammation, whereas their roles in neutrophil generation and mobilization are still unknown. Using cecal ligation and puncture (CLP)-induced polymicrobial sepsis to model systemic bacterial infection, here we report that ALKBH5 is required for emergency granulopoiesis and neutrophil mobilization. ALKBH5 depletion significantly impaired the generation of immature neutrophils in bone marrow of sepsis mice. Meanwhile, Alkbh5-deficient mice exhibited higher retention of mature neutrophils in bone marrow and defective neutrophil release into blood, leading to less neutrophils in the infected site than wild-type littermates undergoing sepsis. Mechanistically, ALKBH5 imprinted generation- and mobilization-promoting transcriptome signatures in both mouse and human neutrophils during bacterial infection, especially upregulated G-CSFR expression by erasing m6A methylation on CSF3R mRNAs to inhibit their decay, consequently increasing the cell-surface G-CSFR expression and JAK-STAT signaling. RIP-qPCR confirmed a direct binding of ALKBH5 to CSF3R mRNAs and the binding strength was declined upon bacterial infection, accounting for the decreased G-CSFR on bacteria-infected neutrophils. Together, we define a new role of ALKBH5 in intrinsically driving neutrophil generation and mobilization through m6A demethylation-dependent post-transcriptional regulation, indicating neutrophil m6A RNA modification as the potential target for treating bacterial infections and neutropenia.