PIM1 Inhibition Alleviates <i>Aspergillus fumigatus</i> Keratitis by Regulating DDX41-Mediated STING Signaling Pathway

Purpose: Fungal keratitis (FK) is a severe, sight-threatening infection with limited therapeutic options. Although the proto-oncogene PIM1 has been implicated in various inflammatory diseases, its role and underlying mechanisms in FK remain unknown. Methods: We investigated the expression and function of PIM1 in human corneal epithelial cells (HCECs) and a mouse model of Aspergillus fumigatus keratitis using genetic and pharmacologic approaches. Protein-protein interactions and phosphorylation events were analyzed by co-immunoprecipitation, GST pull-down, and in vitro kinase assays. Inflammatory cytokine production and signaling pathway activation were assessed using ELISA, quantitative RT-PCR, and Western blot. Results: A. fumigatus infection significantly upregulated PIM1 expression in both HCECs and mouse corneas. PIM1 overexpression enhanced the fungus-induced inflammatory response, whereas PIM1 knockdown or pharmacologic inhibition attenuated the production of proinflammatory cytokines (TNF-α, IL-6, IL-1β, IFN-β). Mechanistically, PIM1 directly interacted with and promoted serine phosphorylation of the DNA sensor DDX41. This PIM1-DDX41 interaction was essential for activating the downstream STING-TBK1-IRF3 signaling pathway. The proinflammatory effects of PIM1 were abolished by DDX41 knockdown or STING inhibition. Importantly, both genetic silencing and pharmacologic inhibition of PIM1 alleviated disease severity, reduced fungal load, and suppressed the DDX41/STING-mediated inflammatory cascade in the mouse model of FK. Conclusions: Our findings reveal a novel mechanism by which PIM1 aggravates A. fumigatus keratitis through activation of the DDX41-STING signaling axis, highlighting PIM1 as a promising therapeutic target for FK.