Ral GTPases: corrupting the exocyst in cancer cells

The Ras-like small G-proteins RaIA and RaIB have achieved some notoriety as components of one of a growing variety of candidate Ras effector pathways. Recent work has demonstrated that Rai GTPase activation is required to support both the initiation and maintenance of tumorigenic transformation of human cells. The mechanistic basis for this support remains to be defined. However, the discovery that the exocyst is a direct effector complex for activated Rai proteins suggests that mobilization of polarized exocytosis might be a basic component of the biological framework supporting tumorigenic progression.