Role of YopP in Suppression of Tumor Necrosis Factor Alpha Release by Macrophages duringYersiniaInfection

Abstract

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-α) release compared to infection with plasmid-cured strains, suggesting that the virulence plasmid encodes a factor impairing the normal TNF-α 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-α release, we infected J774A.1 and PU5-1.8 macrophages with a battery of knockout Yersinia enterocolitica mutants and we quantified the TNF-α released. Mutants affected in secretion (yscN), in translocation (yopB and yopD), or in synthesis of all the known Yop effectors (yopH,yopO, yopP, yopE, andyopM polymutants) were unable to block the TNF-α 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-α release, and complementation of the yopPmutant or the yop effector polymutant strain withyopP alone led to a drop in TNF-α 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 theYersinia-induced suppression of TNF-α release by infected macrophages.

A MAGE-A4 peptide presented by HLA-A2 is recognized by cytolytic T lymphocytes

“…Y. enterocolitica adheres to the surface of target cells and possesses a virulence apparatus, called the Yop virulon, which enables the translocation of toxic effector proteins, including YopE, into the cytosol of the host cell [40,41]. A new strain, MRS40 (pABL403), has recently been constructed, in which the genes encoding toxic Yop proteins are mutated or truncated [42]. Interestingly, this polymutant strain maintains its ability to translocate proteins in fusion with a truncated YopE into the cytosol of eukaryotic cells, but does not elicit cytotoxicity and can therefore be used as a vector to inject a protein into the cytosol of eukaryotic cells.…”

Type III secretion machines and the pathogenesis of enteric infections caused by Yersinia and Salmonella spp.

“…TNF-a production is activated by multiple signal transduction pathways requiring either mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase QNK), or extracellular signal-regulated kinase (ERK). Infection of wild-type Yersinia not only reduced kinase phosphorylation hut also kinase activity (145).…”

“…Although not an essential virulence factor, YopJ was shown to he required for the induction ofapoptosis in macrophages (87,88). In addition to causing apoptosis, YopJ also inhibits tumor necrosis factor (TNF)-a production hy macrophages (144,145). TNF-a production is activated by multiple signal transduction pathways requiring either mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase QNK), or extracellular signal-regulated kinase (ERK).…”

“…YopT was identified by sequencing the Yersinia virulence plasmid (86). YopT was not detected in the culture supernatant of wild-type Yersinia, but was found in low levels in a multiple yop mutant (yopEHMOP) (145). In this multiple deletion strain, over-expression of the YopT-Cya fusion resulted in accumulation of cAMP in the host cell, suggesting that YopT could be targeted into the eukaryotic cytosol (86).…”

Bacterial Interference of Ubiquitination and Deubiquitination

“…macrophages. By interfering with the NF-kB pathway through inhibition of MAPK (mitogen-activated protein kinase) kinases and IKKb, YopJ suppresses proinflammatory signaling via TNF and IL-8 production, as well as inducing apoptosis (Boland and Cornelis, 1998;Mills et al, 1997;Monack et al, 1997;Orth et al, 1999;Palmer et al, 1998;Yoon et al, 2003;Zhou et al, 2004). YopJ is a member of clan CE, family 55, and its substrate was originally thought to be SUMO-1, since expression of YopJ in mammalian cells decreased the cellular concentration of SUMO-1-conjugated proteins (Orth et al, 2000).…”