A novel and evolutionarily conserved PtdIns(3,4,5)P3-binding domain is necessary for DOCK180 signalling

Abstract

The evolutionarily conserved DOCK180 protein has an indispensable role in cell migration by functioning as an exchange factor for Rac GTPase via its DOCK homology region (DHR)-2 domain. We report here that the conserved DHR-1 domain also has an important signalling role. A form of DOCK180 that lacks DHR-1 fails to promote cell migration, although it is capable of inducing Rac GTP-loading. The DHR-1 domain interacts with PtdIns(3,4,5)P₃ in vitro and in vivo, and mediates the DOCK180 signalling complex localization at sites of PtdIns(3,4,5)P₃ accumulation in the cell's leading edge. A form of DOCK180 in which the DHR-1 domain has been replaced by a canonical PtdIns(3,4,5)P₃-binding pleckstrin homology domain is fully functional at inducing cell elongation and migration, suggesting that the main function of DHR-1 is to bind PtdIns(3,4,5)P₃. These results demonstrate that DOCK180, via its DHR-1 and DHR-2 domains, couples PtdIns(3,4,5)P₃ signalling to Rac GTP-loading, which is essential for directional cell movement.