Yersinia pseudotuberculosis binds to
beta1 integrin receptors, and uses the type III secretion
proteins YopB and YopD to introduce pores and to translocate Yop effectors directly into host cells. Y. pseudotuberculosis lacking effectors that inhibit
Rho GTPases, YopE and YopT, have high pore forming activity. Here, we present evidence that Y. pseudotuberculosis selectively modulates Rho activity to induce cellular changes that control pore formation and effector translocation. Inhibition of actin polymerization decreased pore formation and YopE translocation in HeLa cells infected with Y. pseudotuberculosis. Inactivation of Rho, Rac, and Cdc42 by treatment with
Clostridium difficile toxin B inhibited pore formation and YopE translocation in infected HeLa cells. Expression of a dominant negative form of Rac did not reduce the uptake of membrane impermeable
dyes in HeLa cells infected with a pore forming strain YopEHJT(-). Similarly, the Rac inhibitor
NSC23766 did not decrease pore formation or translocation, although it efficiently hindered Rac-dependent bacterial uptake. In contrast, C. botulinum C3 potently reduced pore formation and translocation, implicating Rho A, B, and/or C in the control of the Yop delivery. An invasin mutant (Y. pseudotuberculosis invD911E) that binds to beta1
integrins, but inefficiently transduces signals through the receptors, was defective for YopE translocation. Interfering with the
beta1 integrin signaling pathway, by inhibiting
Src kinase activity, negatively affected YopE translocation. Additionally, Y. pseudotuberculosis
infection activated Rho by a mechanism that was dependent on YopB and on high affinity bacteria interaction with
beta1 integrin receptors. We propose that Rho activation, mediated by signals triggered by the YopB/YopD translocon and from engagement of
beta1 integrin receptors, stimulates actin polymerization and activates the translocation process, and that once the Yops are translocated, the action of YopE or YopT terminate delivery of Yops and prevents pore formation.