Yersinia outer protein YopE affects the actin cytoskeleton in Dictyostelium discoideum through targeting of multiple Rho family GTPases

The Yersinia pseudotuberculosis virulence factors YopE, YopH, YopM and YopJ were expressed de novo within Dictyostelium and their effects on growth in axenic medium and on bacterial lawns were analyzed. No severe effect was observed for YopH, YopJ and YopM, but expression of YopE, which is a GTPase activating protein for Rho GTPases, was found to be highly detrimental. GFP-tagged YopE expressing cells had less conspicuous cortical actin accumulation and decreased amounts of F-actin. The actin polymerization response upon cAMP stimulation was impaired, although chemotaxis was unaffected. YopE also caused reduced uptake of yeast particles. These alterations are probably due to impaired Rac1 activation. We also found that YopE predominantly associates with intracellular membranes including the Golgi apparatus and inhibits the function of moderately overexpressed RacH.The phenotype elicited by YopE in Dictyostelium can be explained, at least in part, by inactivation of one or more Rho family GTPases. It further demonstrates that the social amoeba Dictyostelium discoideum can be used as an efficient and easy-to-handle model organism in order to analyze the function of a translocated GAP protein of a human pathogen.In the genus Yersinia there are three pathogenic species that can cause different diseases such as bubonic plague or gastrointestinal disorders. Yersinia enterocolitica is an important human pathogen that can also provoke a variety of extraintestinal clinical syndromes, e. g. systemic arthritis. The main strategy used by Yersinia to overcome the host immune system is the blockage of phagocytosis by cells of the innate immune system and the silencing of inflammatory reactions [1]. For this purpose Yersinia translocates at least six so-called Yersinia Outer Proteins (Yops) into the host cell via a type III secretion system [2,3]. The Yop effector proteins interfere with different eukaryotic cell signaling pathways and/or disrupt the cytoskeleton in a specialized