Fig. 5. Lack of Nedd4-2 causes misprocessing of proSP-C in alveolar type 2 (AT2) cells, but genetic deletion of Sftpc does not prevent pulmonary fibrosis in conditional Nedd4-2^−/− mice.

a Representative immunofluorescence images of lungs from conditional Nedd4-2^−/− mice and littermate controls stained with anti-proSP-C antibodies. The subcellular distribution of proSP-C in control lungs represents predominantly large subplasma membrane organelles consistent with lamellar bodies (white arrowheads) while expression of proSP-C in conditional Nedd4-2^−/− lungs also occurs in smaller cytosolic vesicles (n = 3/group). Scale bars, 50 and 10 µm (insets). b Western blot of isolated AT2 cells demonstrating aberrations in the proSP-C processing profile in conditional Nedd4-2^−/− compared to control mice (n = 3/group). c, d Representative Western blot (c) and densitometric analysis (d) of mature SP-C in bronchoalveolar lavage fluid from conditional Nedd4-2^−/− mice and littermate controls (n = 3/group). e–g Micrographs of representative hematoxylin and eosin (H&E) stained lung sections (scale bars, 1 mm) (e) and measurements of pressure–volume curves (n = 13/group) (f) and static lung compliance (g) from conditional Nedd4-2^−/− (n = 7 mice), conditional Nedd4-2^−/−/Sftpc^−/− (n = 10 mice), littermate Sftpc^−/− (n = 11 mice), and control mice (n = 7 mice) induced with doxycycline for an average of 4 months. *P < 0.05, **P < 0.01, ***P < 0.001. Statistical analysis was performed with unpaired two-tailed t test in d and ANOVA with Tukey’s post hoc test in g. Data are shown as mean ± S.E.M. Source data are provided in the Source Data file.