Emerging views on integrin signaling via Rac1 during invasin-promoted bacterial uptake

Enteropathogenic Yersinia species encode invasin, which promotes uptake into host cells by binding β1 integrins. Invasin may cluster integrin heterodimers extracellularly and cause the integrin α and β chains to splay apart in the cytoplasm. Cdc42 signaling is not essential for Yersinia uptake, whereas invasin crucially triggers Rac1-mediated signals that enable internalization. The signals linking invasin-mediated adhesion to Rac1 activation are not clear, but a novel kinase may release it from RhoGDI so that Rac1 can be activated, for example by Dock180. Rac1 may act via Arp2/3, phosphatidylinositol 4,5-bisphosphate and capping-proteins in the formation of nascent phagosomes during Yersinia uptake.