ZDHHC11-Mediated Palmitoylation of PPM1A Regulates Lung Cancer Metastasis via the TGF-β1-Smad2/3 Signaling Pathway.

Abstract

Background: Lung cancer remains the most common cause of cancer-related mortality worldwide. The transforming growth factor-beta 1 (TGF-β1) pathway promotes epithelial-mesenchymal transition (EMT), invasion, and metastasis in advanced disease via mothers against decapentaplegic homolog 2 (Smad2) and Smad3. This study investigated how post-translational modifications regulate TGF-β1-Smad signaling.

Methods: Lung cancer cell lines and a mouse metastasis model were used to explore the roles of protein phosphatase magnesium-dependent 1A (PPM1A) palmitoylation, zinc finger DHHC-type palmitoyltransferase 11 (ZDHHC11), and ubiquitin-specific peptidase 5 (USP5) in regulating Smad2/3 signaling. Palmitoylation-deficient and wild-type PPM1A constructs were introduced by lentiviral transduction. Protein levels, modifications, and interactions were analyzed by western blot, immunoprecipitation, and immunofluorescence. Palmitoylation was measured using acyl-resin-assisted capture (Acyl-RAC). Cell invasion and migration were assessed using Transwell assays.

Results: Palmitoylation of PPM1A at cysteine 71 enhanced the interaction between PPM1A and Smad2/3, promoted Smad2/3 dephosphorylation, and suppressed lung cancer cell invasion and metastasis. ZDHHC11 was identified as the enzyme responsible for PPM1A palmitoylation; its loss diminished this modification and accelerated metastasis in vivo. TGF-β1 downregulated ZDHHC11 expression, weakened PPM1A-Smad2/3 binding, and increased cell migration. Additionally, USP5 stabilized Smad2/3 by preventing their ubiquitin-mediated degradation, and TGF-β1 further amplified this effect by limiting PPM1A access.

Conclusion: This study identified a novel palmitoylation-dependent mechanism regulating TGF-β1-Smad signaling in lung cancer. Upregulating the ZDHHC11-PPM1A axis or targeting USP5 may offer new strategies to inhibit metastasis in lung cancer.