HEPARIN INTERFERES WITH TRANSLOCATION OF YOP PROTEINS INTO HELA-CELLSAND BINDS TO LCRG, A REGULATORY COMPONENT OF THE YERSINIA YOP APPARATUS

Yersiniae are equipped with the Yop virulon, an apparatus that allows extracellular bacteria to deliver toxic Yop proteins inside the host c ell cytosol in order to sabotage the communication networks of the hos t cell or even to cause cell death. LcrG is a component of the Yop vir ulon involved in the regulation of secretion of the Yops. In this pape r, we show that LcrG can bind HeLa cells, and we analyse the role of p roteoglycans in this phenomenon. Treatment of the HeLa cells with hepa rinase I, but not chondroitinase ABC, led to inhibition of binding. Co mpetition assays indicated that heparin and dextran sulphate strongly inhibited binding, but that other glycosaminoglycans did not. This dem onstrated that binding of HeLa cells to purified LcrG is caused by hep aran sulphate proteoglycans. LcrG could bind directly to heparin-agaro se beads and, in agreement with these results, analysis of the protein sequence of Yersinia enterocolitica LcrG revealed heparin-binding mot ifs. In vitro production and secretion by Y. enterocolitica of the Yop s was unaffected by the addition of heparin. However, the addition of exogenous heparin decreased the level of YopE-Cya translocation into H eLa cells. A similar decrease was seen with dextran sulphate, whereas the other glycosaminoglycans tested had no significant effect. Translo cation was also decreased by treatment of HeLa cells with heparinitase , but not with chondroitinase. Thus, heparan sulphate proteoglycans ha ve an important role to play in translocation. The interaction between LcrG and heparan sulphate anchored at the surface of HeLa cells could be a signal triggering deployment of the Yop translocation machinery. This is the first report of a eukaryotic receptor interacting with th e type III secretion and associated translocation machinery of Yersini a or of other bacteria.