The GAS6-AXL signaling pathway triggers actin remodeling that drives membrane ruffling, macropinocytosis, and cancer-cell invasion

Abstract

AXL, a member of the TAM (TYRO3, AXL, MER) receptor tyrosine kinase family, and its ligand, GAS6, are implicated in oncogenesis and metastasis of many cancer types. However, the exact cellular processes activated by GAS6-AXL remain largely unexplored. Here, we identified an interactome of AXL and revealed its associations with proteins regulating actin dynamics. Consistently, GAS6-mediated AXL activation triggered actin remodeling manifested by peripheral membrane ruffling and circular dorsal ruffles (CDRs). This further promoted macropinocytosis that mediated the internalization of GAS6-AXL complexes and sustained survival of glioblastoma cells grown under glutamine-deprived conditions. GAS6-induced CDRs contributed to focal adhesion turnover, cell spreading, and elongation. Consequently, AXL activation by GAS6 drove invasion of cancer cells in a spheroid model. All these processes required the kinase activity of AXL, but not TYRO3, and downstream activation of PI3K and RAC1. We propose that GAS6-AXL signaling induces multiple actin-driven cytoskeletal rearrangements that contribute to cancer-cell invasion.

Bemcentinib and Gilteritinib Inhibit Cell Growth and Impair the Endo-Lysosomal and Autophagy Systems in an AXL-Independent Manner

“…AXL KO clones were isolated from nonclonally selected population of AXL KO LN229 cells generated using sgRNA target sequence 5'CCCGAAGCCAATGTACCTCG-3' as described previously (16). To isolate single clones, 100 cells of nonclonally selected population of AXL KO in 20 mL of DMEM medium were seeded into a 96-well plate (200 µl/well), and single clones were picked when colonies had formed.…”

“…Moreover, AXL and GAS6 were reported to be frequently overexpressed in malignant human gliomas, and glioblastoma patients with high levels of AXL and/or GAS6 showed a significantly shorter time to tumor progression (15). Recently, we demonstrated that at the cellular level GAS6-mediated AXL activation triggered multiple actin-dependent processes such as membrane ruffling, macropinocytosis and focal adhesion turnover that jointly contributed to invasion of glioblastoma cells (16). An activation of similar actin-dependent processes by GAS6-AXL signaling was also reported in other cancer cells (16,17).…”

“…Recently, we demonstrated that at the cellular level GAS6-mediated AXL activation triggered multiple actin-dependent processes such as membrane ruffling, macropinocytosis and focal adhesion turnover that jointly contributed to invasion of glioblastoma cells (16). An activation of similar actin-dependent processes by GAS6-AXL signaling was also reported in other cancer cells (16,17). Importantly, AXL activation constitutes a mechanism of acquired resistance to both conventional and targeted cancer therapies, and increased AXL level has been reported in many drug-resistant cancer cell lines (13,14).…”

Therapeutic Targeting of the Gas6/Axl Signaling Pathway in Cancer

“…Axl also mediates key components of the metastatic cascade, including, but not limited to, epithelial-to-mesenchymal transition, migration and invasion, proliferation, survival, stemness, angiogenesis, and immune evasion [ 19 , 20 , 22 , 27 ] ( Figure 1 ). A study by Zdzalik-Bielecka and colleagues demonstrated that the Gas6/Axl pathway mediates actin cytoskeleton remodeling for cell migration and invasion via formations of peripheral ruffles and circular dorsal ruffles [ 28 ]. Such Gas6-induced Axl activation contributes to focal adhesion turnover, cell spreading, and elongation through the activation of PI3K and RAC1 [ 28 , 29 ].…”

“…A study by Zdzalik-Bielecka and colleagues demonstrated that the Gas6/Axl pathway mediates actin cytoskeleton remodeling for cell migration and invasion via formations of peripheral ruffles and circular dorsal ruffles [ 28 ]. Such Gas6-induced Axl activation contributes to focal adhesion turnover, cell spreading, and elongation through the activation of PI3K and RAC1 [ 28 , 29 ]. Another study similarly demonstrated that Axl mediates cell invasion through the regulation of lysosome peripheral distribution [ 30 ].…”