Proteasome dysfunction in alveolar type 2 epithelial cells is associated with acute respiratory distress syndrome

Proteasomes are a critical component of quality control that regulates turnover of short-lived, unfolded, and misfolded proteins. Proteasome activity has been therapeutically targeted and considered as a treatment option for several chronic lung disorders including pulmonary fibrosis. Though pharmacologic inhibition of proteasome activity effectively prevents the transformation of fibroblasts to myofibroblasts, the effect on alveolar type 2 (AT2) epithelial cells is not clear. To address this knowledge gap, we generated a genetic model in which a proteasome subunit, RPT3, which promotes assembly of active 26S proteasome, was conditionally deleted in AT2 cells of mice. Targeted deletion of RPT3 in AT2 cells resulted in 26S proteasome dysfunction, leading to augmented cell stress and death. Acute loss of AT2 cells resulted in depletion of alveolar surfactant, disruption of the alveolar epithelial barrier and, ultimately, lethal acute respiratory distress syndrome. This study underscores the need for further investigation into the differential effect of proteasome inhibition in lung cell types. Overall design: RPT3AT2?/? and SftpcWT/CreER mice (n=3 mice /genotype) were fed tamoxifen chow for 7 days followed by extraction of RNA from freshly isolated alveolar type 2 epithelial cells. RNA sequencing was performed on Illumina platform.