We speculate that the somewhat weaker pathogenic effect of YopJ may have been the basis of trouble in building a robust RNAi display using Y. pestis. In this examine, we describe a c KIT EGR1 signaling pathway that is certainly targeted by Yersinia throughout infection. Al even though c KIT and EGR1 haven’t been previously posi tioned experimentally during the very same pathway towards the greatest of our information, c KIT and EGR1 functions could be linked primarily based on convergence of multiple overlapping pathways. Activation of c KIT has been shown to stimu late the JNK, MEK ERK, and PI3K AKT signaling path means, which can feed into EGR1 and other transcription aspects to regulate cell development, differen tiation and inflammatory responses. In turn, EGR1 regulates expression of chemokines and cytokines and was uncovered to act synergistically with NF κB to stimulate IL 8 trans cription.
Our success help a model by which c KIT signaling is targeted our site by Yersinia T3SS to suppress pro inflam matory responses. Some kinases activated downstream of c KIT, this kind of as MEK and PI3K, happen to be shown for being inhibited from the Yersinia effectors YopJ and YopH, re spectively. YopJ has also been shown to inhibit phosphorylation of MKK4 SEK1 and attenuates JNK sig naling and subsequent EGR1 activation. Our findings recommend that downregulation of a receptor kinase function that prospects to NF κB activation can ameli orate the inhibitory result of Yersinia T3SS.
Considering the fact that we ob served the inhibition of a further signaling protein AKT1 also resulted in greater manufacturing of TNF by Yersinia infected macrophage cells, we hy pothesized that on bacterial infection, numerous signal transduction pathways are triggered kinase inhibitor by a variety of host extracellular and intracellular receptors of pathogen as sociated molecular patterns. Nonetheless, not all signaling pathways are inactivated by Yersinia through in fection, and inhibition of c KIT could cause redirection to different signaling pathways, this kind of since the LPS activated CD14 and TLR4 signaling to p38 and JNK, to recover NF KB driven gene expression. This hy pothesis is supported by our observations that phar macological inactivation of JNK1 working with the inhibitor BI 78D3 did not recover pro inflammatory gene ex pression in THP one cells contaminated with pathogenic Yer sinia, when AKT1 and c KIT inhibition resulted in greater TNF production in infected THP one and NHDC.
So, redistribution of signaling pathways can nevertheless bring about mitigation of NF κB regulated immune response during the course of Yersinia infection. The exact mechanism of Yersinia activation of c KIT stays unclear. The normal ligand of c KIT, SCF, is proven to activate c KIT phosphorylation inside 5 min of therapy. In response to Y. enteroco litica, c KIT exhibited maximal phosphorylation at 45 min publish infection in THP one cells by Western blot, demonstrating that Yersinia infection is cap in a position of stimulating c KIT activation, albeit by way of a delayed response when compared with SCF. Considering that, we observed this de layed phosphorylation in each virulent and attenuated Y. enterocolitica, it might be the situation that LPS or other bac terial cell surface molecule can mediate host receptor phosphorylation and or signaling, as opposed to solely the T3SS. We have also shown that inhibition of c KIT sig naling from the tiny molecule OSI 930 induced an altered inflammatory gene expression pattern in response to pathogenic Yersinia that resembled infection by a non virulent strain, even further supporting practical hyperlinks involving c KIT exercise and Yersinia virulence.