WDR63 Promotes Pulmonary Fibrosis Through Facilitating K63 ‐Linked Ubiquitination of p53

BACKGROUND AND OBJECTIVE: Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease driven by dysregulated alveolar epithelial cells (AECs) and fibroblasts. While aberrant p53 signalling contributes to IPF pathogenesis, the precise mechanism of p53 activation is not well understood. WDR63, a WD40-repeat protein implicated in lung cancer and male infertility, may be functionally relevant in IPF. METHODS: The mouse model of bleomycin-induced pulmonary fibrosis was used to investigate the role of WDR63 in IPF. Immunofluorescent staining and Western blotting assays were performed to assess WDR63 expression in samples from IPF patients and lungs from mice with bleomycin-induced fibrosis. Senescence-associated β-galactosidase (SA-β-gal) staining and flow cytometry assays were performed to evaluate the role of WDR63 in the senescence and apoptosis of AECs and lung fibroblasts. Mass spectrometry (MS) and immunoprecipitation were employed to identify potential substrate proteins of WDR63. Ubiquitination assays were utilised to elucidate the mechanisms of p53 stabilisation. RESULTS: WDR63 is significantly upregulated in IPF patients. WDR63 inhibits proliferation and migration while promoting senescence and apoptosis in AECs. In lung fibroblasts, WDR63 increases cellular senescence and facilitates their differentiation into myofibroblasts. WDR63 promotes K63-linked polyubiquitination of p53, while reducing its K48-linked polyubiquitination, thereby stabilising p53 and activating its downstream signalling. Ectopic WDR63 expression exacerbates bleomycin-induced pulmonary fibrosis in vivo, whereas WDR63 silencing attenuates fibrotic progression. CONCLUSION: WDR63 stabilises p53 through K63-linked polyubiquitination, thereby driving pathological changes in AECs and lung fibroblasts and aggravating pulmonary fibrosis. These findings demonstrate that targeting WDR63 represents a novel therapeutic strategy for IPF.