STATUS OF YOPM AND YOPN IN THE YERSINIA YOP VIRULON - YOPM OF YERSINIA-ENTEROCOLITICA IS INTERNALIZED INSIDE THE CYTOSOL OF PU5-1.8 MACROPHAGES BY THE YOPB, YOPD, YOPN DELIVERY APPARATUS

The Yersinia Yop virulon is an anti-host system made up of four elemen ts: (i) a type III secretion system called Ysc; (ii) a system designed to deliver bacterial proteins into eukaryotic target cells (YopB, Yop D); (iii) a control element (YopN); and (iv) a set of intracellularly delivered proteins designed to disarm these cells or disrupt their com munications (YopE, YopH and possibly others), YopM, another Yop protei n, binds thrombin and is thus presumed to act as an extracellular effe ctor. Here, we analyzed YopM from Y.enterocolitica and we wondered whe ther it could also be delivered inside eukaryotic cells, To answer thi s question we applied the Yop-Cya reporter strategy, Hybrids made of 1 41 or 100 N-terminal residues of YopM fused to Cya were delivered insi de PU5-1.8 macrophages by recombinant Y.enterocolitica strains, YopB a nd YopD were required as translocators. Leakage of the reporters into the macrophage culture supernatant during the bacterial infection incr eased strongly when YopN was missing, showing that YopN is involved in the control of delivery of YopM inside eukaryotic cells. YopN itself was not delivered into the macrophages, Zn conclusion, YopM is translo cated inside the eukaryotic cells and its physiopathological role shou ld be revised or completed.