A role for N-WASP in invasin-promoted internalisation.

Phagocytosis of Yersinia pseudotuberculosis occurs through interaction of the bacterial protein invasin with beta1-integrins. Here we report that N-WASP plays a role in internalisation of an invasin-expressing, avirulent strain of Y. pseudotuberculosis. Ectopic expression of N-WASP mutants, which affect recruitment of the Arp2/3 complex to the phagosome, reduces uptake of Yersinia. In addition, expression of the Cdc42/Rac-binding (CRIB) region of N-WASP has an inhibitory effect on uptake. Using GFP-tagged Rho GTPase mutants, we provide evidence that Rac1, but not Cdc42, is important for internalisation. Furthermore, activated Rac1 rescues Toxin B, CRIB and Src family kinase inhibitor PP2-mediated impairment of uptake. Our observations indicate that invasin-mediated phagocytosis occurs via a Src and WASP family-dependent mechanism(s), involving the Arp2/3 complex and Rac, but does not require Cdc42.