SMAD4 and pemphigus foliaceus: This study revealed the following points: (1) GA could protect against BLM-induced PF; (2) GA could reduce PF induced by the increased SUMOylation of SMAD4 through SENP1; (3) SMAD4 SUMOylation participated in TGF-β1-mediated lung EMT, which was accompanied by increased ROS production.