Identification of AXL interactome by proximity-dependent protein identification (BioID)

AXL is a receptor tyrosine kinase (RTK) which, together with TYRO3 and MER, belongs to the TAM receptor family. A ligand for AXL is growth arrest specific 6 (GAS6), which is able to bind all three TAMs with the highest affinity for AXL. AXL is overexpressed in a variety of different cancers, which correlates with poor prognosis, metastasis and drug resistance. However, its biology is still not fully understood and data concerning proteins that interact with this receptor are almost completely lacking. To identify mechanisms underlying the role of GAS6-AXL signaling in cancer, we established an AXL interactome using proximity-dependent biotin identification (BioID) assay. Experiments were conducted in HEK293 cells and human glioblastoma LN229 cells, which do not express and express AXL, respectively. The Gene Ontology (GO) analysis of biological processes indicated enrichment of proteins implicated in cell junction organization, axonogenesis, supramolecular fiber organization, angiogenesis and actin-related processes in bot, non-stimulated and GAS6-stimulated samples. Importantly, in samples with activated AXL, proteins implicated in actin-related processes were overrepresented. Consistent with this, we found that GAS6 stimulation triggered actin remodeling manifested by intense membrane ruffling and macropinocytosis. Our study provides comprehensive data about proteins interacting with AXL. Thus, the obtained results will help to understand the biology of the AXL receptor, particularly with respect to its involvement in cancer invasion.