F-actin binding region of SPIN90 C-terminus is essential for actin polymerization and lamellipodia formation

We recently reported that SPIN90 is able to bind with several proteins involved in regulating actin cytoskeleton networks, including dynamin, WASP, β PIX, and Nck. Based on these findings, we investigated how SPIN90 regulates the actin cytoskeleton and promotes actin assembly. This study demonstrated that aluminium fluoride-induced localization of SPIN90 to lamellipodia requires amino acids 582-722 at the SPIN90 C-terminus, which is also essential for F-actin binding and Arp2/3 complex mediated polymerization of actin into branched actin filaments. Furthermore, after deletion of the F-actin binding region (582-722 SPIN90) failed to localize at the membrane edge and was unable to promote lamellipodia formation, suggesting that the F-actin binding region in the SPIN90 C-terminus is essential for the formation of branched actin networks and regulation of the actin cytoskeleton at the leading edge of cells.