Abstract Rationale Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibroproliferative interstitial lung disease whose molecular mechanisms are not fully understood. Protein palmitoylation is a dynamic lipid modification orchestrated by opposing enzymes: zDHHC palmitoyltransferases (“writers”) and acyl-protein thioesterases (“erasers”). Several central signaling proteins of fibroblast activation and organ fibrosis, including STAT3, ERK1/2, and p53, are subject to palmitoylation, which suggests that the enzymes controlling this modification are potent regulators of pro-fibrotic signaling. However, the direct involvement of zDHHCs in the pathogenesis of pulmonary fibrosis has not been investigated. Methods Protein palmitoylation was assessed in transforming growth factor-beta1 (TGF-β1) stimulated lung fibroblasts by Acyl-Resin Assisted Capture (RAC) assay. To evaluate the role of zDHHC21 in profibrotic responses of lung fibroblasts, cells were isolated from wild-type (WT) and zDHHC21dep/dep mice, characterized by the in-frame deletion of the phenylalanine in position 233 (DF233), resulting in a loss-of-function mutation. Then their pro-fibrotic phenotype was assessed by measuring collagen 1a1 (Col1a1), fibronectin (Fn), and alpha-smooth muscle actin expressions. To assess the role of zDHHC21 in pulmonary fibrosis, WT and zDHHC21dep/dep mice were subjected to bleomycin (Bleo)-induced lung fibrosis. At twenty-one days after Bleo exposure, lungs were subjected to measurement of hydroxyproline content as well as histological analysis. Results We found that zDHHC21 loss of function enhances TGF-β1-mediated lung fibroblast activation. zDHHC21dep/dep mice were more susceptible to Bleo-induced lung fibrosis compared to WT counterparts. Finally, we found that zDHHC21 regulates PI3K/Akt/mTOR signaling by palmitoylating PTEN in lung fibroblasts. Conclusions zDHHC21 plays an important role in regulating key profibrotic signaling pathways in lung fibroblasts and pulmonary fibrosis. These findings suggest that protein palmitoylation may play an important role in the pathobiology of IPF. This abstract is funded by: NIH
Shayahati et al. (Fri,) studied this question.