DRIM modulates Src activation and regulates angiogenic functions in vascular endothelial cells.

Downregulated in Metastasis Protein (DRIM) was discovered in malignant epithelial cells and was thought to be mainly a nucleus protein affecting cancer cells. Recent single-cell sequencing analysis suggests that DRIM is abundantly expressed in vascular endothelial cells. There has been no knowledge of the role of DRIM in the endothelium. In the present study, using protein fraction method and cell imaging, we identified that the DRIM protein was abundantly present in both nucleus and the cytoskeletal fractions of human vascular endothelial cells. Knockdown of DRIM in the endothelial cells significantly affected growth, migration, and angiogenic tubule formation. Proteomics analyses revealed that Src was an important direct target protein of DRIM, a finding further confirmed by protein interaction assay. Silencing DRIM activated the tyrosine 419 site phosphorylation of Src kinase in endothelial cells, thereby affecting the downstream proteins of Src including p-FAK and p-STAT3, and exerting biological effects. To conclude, our results provide evidence of DRIM being a nuclear and cytoskeletal-associated protein, having a novel key role of the protein in vascular endothelial cells.