[miR-15b-5p affects PIK3CA/AKT1 pathway through USP9X to alleviate airway inflammation in asthma]

Objective To investigate whether miR-15b-5p can alleviate airway inflammation in asthma by negatively regulating ubiquitin specific peptidase 9X (USP9X) to down-regulate the expression of phosphatidylinositol 4, 5-diphosphate 3-kinase catalytic subunit α/AKT serine/threonine kinase 1 (PIK3CA/AKT1) pathway. Methods USP9X was predicted to be a direct target of miR-15b-5p by using an online database (miRWalk), and the luciferase reporter gene assay was performed to verify it. Co-immunoprecipitation (CO-IP) was used to verify the direct binding between USP9X and PIK3CA and the role of USP9X and its small molecule inhibitor WP1130 in the deubiquitination of PIK3CA. C57 mice were randomly divided into Control group, OVA group, OVA combined with NC group and miR-15b-5p agomir group, with 10 mice in each group. BEAS-2B cells were induced with interleukin 13 (IL-13) and treated with miR-15b-5p mimic. HE, Masson, PAS, immunohistochemistry, immunofluorescence staining, flow cytometry, Western blot and quantitative real-time PCR(qRT-PCR) were performed. Results It was found that the administration of miR-15b-5p agomir and mimic could reduce peribronchial inflammatory cells and improve airway inflammation, and miR-15b-5p could target negative regulation of USP9X. USP9X could directly bind to PIK3CA and regulate PIK3CA level in a proteasome-dependent manner, and USP9X could deubiquitinate K29-linked PIK3CA protein. Down-regulation of USP9X could increase PIK3CA ubiquitination level. WP1130, a small molecule inhibitor of USP9X, has the same effect as knockdown of USP9X, both of which could increase the ubiquitination level of PIK3CA and reduce the protein level of PIK3CA. Conclusion The miR-15b-5p/USP9X/PIK3CA/AKT1 signaling pathway may provide potential therapeutic targets for asthma.