Pathogenic Escherichia coli Hijacks GTPase-Activated p21-Activated Kinase for Actin Pedestal Formation

Enteropathogenic Escherichia coli and enterohemorrhagic E. coli (EPEC and EHEC, respectively) are extracellular pathogens that reorganize the host cell cytoskeleton to form “actin pedestals” beneath the tightly adherent bacteria, a critical step in pathogenesis. EPEC and EHEC inject effector proteins that manipulate host cell signaling cascades to trigger pedestal assembly. One such effector, EspG, has been reported to bind and activate p21-activated kinase (PAK), a key cytoskeletal regulator, but the function of this interaction and whether it impacts pedestal assembly are unknown. Here, we demonstrate that deletion of espG significantly impairs pedestal formation and attachment by both EPEC and EHEC. This role of EspG is shown to be dependent on its interaction with PAK. Unexpectedly, EspG was able to subvert PAK only in the presence of Rho family small GTPases, which function to both concentrate PAK at the membrane and stimulate PAK activation. Our findings reveal a novel mechanism by which EspG hijacks PAK and sustains its active state to drive bacterial attachment to host cells.