Cadherin-26 drives macrophage alternative activation via suppressing STUB1-mediated IL-4Rα ubiquitination in asthma

Rationale：IL-4 receptor (IL-4R)-mediated alternative activation of macrophage drives type 2 airway inflammation. Cadherin-26 (CDH26) upregulates epithelial type II IL-4R signaling in asthma. However, whether CDH26 contributes to type I IL-4R-mediated macrophage activation and the mechanism by which CDH26 upregulates IL-4R expression remains unknown. Objectives: To investigate whether CDH26 promotes macrophage alternative activation via suppressing IL-4Rα ubiquitination-proteasomal degradation. Methods: CDH26 expression in bronchoalveolar lavage cells of asthma patients was examined using quantitative PCR and immunostaining. Airway inflammation and macrophage activation were assessed in ovalbumin-sensitized and challenged macrophage-specific Cdh26-deficient mice. Mechanistic experiments included IL-4Rα degradation and ubiquitination assay, CDH26 co-immunoprecipitation and mass spectrometry analysis. Cdh26 siRNA encapsulated lipid nanoparticles were used to treat the mouse model. Measurements and Results: CDH26 expression was enhanced in bronchoalveolar lavage cells from patients with eosinophilic asthma and was localized to lung macrophages. Airway eosinophilia, mucus overproduction and macrophage alternative activation were significantly suppressed in ovalbumin-challenged macrophage-specific Cdh26-deficient mice compared to control mice. Cdh26 deficiency inhibits IL-4Rα expression and STAT6 phosphorylation in macrophages in vitro. Furthermore, CDH26 knockdown enhances whereas CDH26 overexpression suppresses IL-4Rα ubiquitination and proteasomal degradation. Mechanistically, CDH26 directly interacts with STUB1 and suppresses the binding of STUB1 to IL-4Rα and subsequent ubiquitination-proteasomal degradation. Cdh26 siRNA encapsulated lipid nanoparticles markedly alleviate airway inflammation, mucus overproduction and macrophage alternative activation in the mouse model. Conclusions: CDH26 interacts with STUB1 and suppresses STUB1-mediated IL-4Rα ubiquitination-proteasomal degradation, thereby amplifying IL-4R signaling in macrophages in asthma. CDH26 is a potential therapeutic target for asthma.