The MUC5B promoter variant results in proteomic changes in the nonfibrotic lung.

The gain-of-function MUC5B promoter variant is the dominant risk factor for the development of idiopathic pulmonary fibrosis (IPF). However, its impact on protein expression in both nonfibrotic control and IPF lung specimens has not been well characterized. Utilizing laser capture microdissection coupled to mass spectrometry, we investigated the proteomic profiles of airway and alveolar epithelium in nonfibrotic controls (n = 12) and IPF specimens (n = 12), stratified by the MUC5B promoter variant. Through qualitative and quantitative analyses, as well as pathway analysis and immunohistological validation, we have identified a distinct MUC5B-associated protein profile. Notably, the nonfibrotic control alveoli exhibited substantial MUC5B-associated protein changes, with an increase in IL-3 signaling. Additionally, we found that epithelial cells overlying IPF fibroblastic foci clustered closely to alveolar epithelia and expressed proteins associated with cellular stress pathways. In conclusion, our findings suggest that the MUC5B promoter variant leads to protein changes in alveolar and airway epithelium that appear to be associated with initiation and progression of lung fibrosis.