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Infect Immun, May 1998, p. 1878-1884, Vol. 66, No. 5
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Role of YopP in Suppression of Tumor Necrosis Factor Alpha Release by Macrophages during Yersinia Infection

Anne Boland and Guy R. Cornelis*

Microbial Pathogenesis Unit, Christian de Duve Institute of Cellular Pathology, and Faculté de Médecine, Université Catholique de Louvain, B-1200 Brussels, Belgium

Received 6 November 1997/Returned for modification 23 December 1997/Accepted 12 February 1998

The Yersinia plasmid-encoded Yop virulon enables extracellular adhering bacteria to deliver toxic effector proteins inside their target cells. It includes a type III secretion system (Ysc), at least two translocator proteins (YopB, YopD), and a set of intracellular Yop effectors (YopE, YopH, YopO, YopM, and YopP). Infection of macrophages with a wild-type strain leads to low levels of tumor necrosis factor alpha (TNF-alpha ) release compared to infection with plasmid-cured strains, suggesting that the virulence plasmid encodes a factor impairing the normal TNF-alpha response of infected macrophages. This effect is correlated with the inhibition of the macrophage mitogen-activated protein kinase (MAPK) activities. To identify the Yop protein responsible for the suppression of TNF-alpha release, we infected J774A.1 and PU5-1.8 macrophages with a battery of knockout Yersinia enterocolitica mutants and we quantified the TNF-alpha released. Mutants affected in secretion (yscN), in translocation (yopB and yopD), or in synthesis of all the known Yop effectors (yopH, yopO, yopP, yopE, and yopM polymutants) were unable to block the TNF-alpha response of the macrophages. In contrast, single yopE, yopH, yopO, and yopM mutants behaved like the wild-type strain. A yopP mutant elicited elevated TNF-alpha release, and complementation of the yopP mutant or the yop effector polymutant strain with yopP alone led to a drop in TNF-alpha release. In addition, YopP was also responsible for the inhibition of the extracellular signal-regulated kinase2 (ERK2) and p38 MAPK activities. These results show that YopP is the Yop effector responsible for the Yersinia-induced suppression of TNF-alpha release by infected macrophages.

* Corresponding author. Mailing address: Microbial Pathogenesis Unit, Avenue Hippocrate, 74, UCL Box 74-49, B-1200 Brussels, Belgium. Phone: 32 2 764 74 49. Fax: 32 2 764 74 98. E-mail: Cornelis{at}mipa.ucl.ac.be.

Infect Immun, May 1998, p. 1878-1884, Vol. 66, No. 5
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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