MST3 accelerates migration and invasion of non-small cell lung cancer cells by phosphorylating vimentin

Mammalian Sterile 20-like protein kinase 3 (MST3) has been implicated in the progression of non-small cell lung cancer (NSCLC). However, the molecular mechanisms regarding MST3-mediated regulation of NSCLC progression remain to be elucidated. In this study, we demonstrate that MST3 enhances the invasion and migration of NSCLC cells by phosphorylating vimentin. Specifically, phosphorylation at residues S39 and S205 of vimentin contributes to MST3-induced migratory and invasive phenotypes. The T190 and K65 residues, which are critical for MST3 kinase activity, are required for MST3-mediated vimentin phosphorylation, particularly at S39, as demonstrated by in vitro phosphorylation assays. Functional assays, including wound healing and transwell-based migration and invasion, further confirmed that the T190 and K65 residues are critical for MST3-driven cell motility and invasion. Immunofluorescence staining revealed co-localization of MST3 with vimentin, while co-immunoprecipitation and GST pull-down assays demonstrated a direct interaction between the two proteins. Collectively, these findings identify a novel mechanism by which MST3 drives NSCLC cell migration and invasion via vimentin phosphorylation, and suggest the MST3-vimentin axis as a potential therapeutic target for NSCLC intervention.