enterocolitica pYV+ or (C) Y. enterocolitica pYV- at MOI 40 for the indicated time points. Cell lysates were immunoprecipitated with anti-c-KIT antibody followed by Protein A Sepharose and were resolved by 8% SDS-PAGE. Western blots were probed with
anti-c-KIT and p-Tyr (PY20) antibodies. Results from three independent experiments were quantified and are presented as percentage of phosphorylated versus total c-KIT. We also show that ~95% depletion of c-KIT transcript levels by siRNA treatment (Figure 5B) rescued EGR1, VCAM1, CCL20, and IL-8 gene expression in response to Y. enterocolitica WA infection in THP-1 cells, compared to infected Selleckchem AZD7762 control cells treated with non-targeting siRNA (si-CTL) (Figure 5C). Similarly,
expression levels of the NF-κB transcription factors, NF-κB1/p50 and RelA/p65, were recovered in c-KIT-silenced cells in response to Y. enterocolitica WA Bioactive Compound Library research buy infection. In the absence of infection, silencing of c-KIT expression by siRNA did not induce any significant change in the expression levels of EGR1 or the tested cytokines and transcription factors (Figure 5B). To further investigate the interplay between c-KIT signaling and pathogenic Yersinia, we measured RelA levels in purified nuclei isolated from untreated or Y. enterocolitica-infected THP-1 cells SN-38 purchase (Figure 5D, left panel). In response to inflammatory stimuli, RelA is normally released from its cytoplasmic inhibitor, IκBα, and transported to the nucleus to modulate gene expression . Based on flow cytometric analysis, RelA protein levels were shown to increase by ~2-fold in the nuclei of THP-1 cells infected with Y. enterocolitica WA, compared to uninfected cells. (Figure 5D, middle and right panels) Interestingly, pre-treatment of THP-1 cells with OSI-930 led to a higher 4-fold increase of nuclear RelA levels, suggesting that Yersinia targets the c-KIT signaling pathway to suppress post-transcriptional activation of RelA. Collectively, our data demonstrate that virulent Yersinia inhibits both Methamphetamine transcription and post-transcriptional regulation of key inflammatory proteins
via the c-KIT signaling pathway. c-KIT phosphorylation is induced upon Yersinia infection independently of T3SS We next investigated c-KIT phosphorylation to assess kinase activation in response to Yersinia infection. The binding of natural ligand SCF to c-KIT has been shown to induce receptor dimerization, rapid auto-phosphorylation of tyrosine residues in the intracellular domain, and subsequent recruitment of signaling proteins to activate multiple downstream pathways [34, 35]. We examined c-KIT phosphorylation in THP1 cells using Western blots, in response to infection with both Y. enterocolitica virulent (pYV+) and attenuated (pYV-) strains (Figure 6) c-KIT exhibited maximal phosphorylation at ~45 min post-infection in both Y.