Phosphorylation of syntenin-1 by TBK1 promotes proliferation and migration of non-small cell lung cancer cells.

Syntenin-1 is a promising therapeutic target for cancer, as its inhibitors have shown positive efficacy in preclinical models of various cancer types. Posttranslational modifications, including phosphorylation, play an important role in regulating syntenin-1 activity, but the underlying molecular mechanisms have not been completely understood. To figure out the enzymes that catalyze syntenin-1 modifications, we performed mass spectrometry proteomics analysis of immunoprecipitated syntenin-1 and identified TANK-binding kinase 1 (TBK1) as a binding partner. Using biochemical and cellular assays, we demonstrated that TBK1 directly interacted with syntenin-1 and phosphorylated it at residue S6. ULK1, the reported kinase to catalyze syntenin-1 S6 phosphorylation, was shown in our assays to indirectly trigger syntenin-1 phosphorylation by activating TBK1. We also found that syntenin-1 was upregulated in non-small cell lung cancer (NSCLC) cells, and TBK1-catalyzed syntenin-1 phosphorylation promoted cell growth and metastasis of the NSCLC cell line A549. Transcriptome sequencing revealed that syntenin-1 phosphorylation by TBK1 activated the MAPK signaling pathway. Our study illuminated a new mechanism in which syntenin-1 phosphorylation, regulated by upstream TBK1 signaling, controls NSCLC progression.