Â© 2018 Pandey, Lin, Cabello, da Costa, Feng, Feng, Zhang, Iwawaki, Rice-Ficht, Ficht, de Figueiredo and Qin. Brucella spp. are intracellular vacuolar pathogens that causes brucellosis, a worldwide zoonosis of profound importance. We previously demonstrated that the activity of host unfolded protein response (UPR) sensor IRE1Î± (inositol-requiring enzyme 1) and ER-associated autophagy confer susceptibility to Brucella melitensis and Brucella abortus intracellular replication. However, the mechanism by which host IRE1Î± regulates the pathogen intracellular lifestyle remains elusive. In this study, by employing a diverse array of molecular approaches, including biochemical analyses, fluorescence microscopy imaging, and infection assays using primary cells derived from Ern1 (encoding IRE1) conditional knockout mice, we address this gap in our understanding by demonstrating that a novel IRE1Î± to ULK1, an important component for autophagy initiation, signaling axis confers susceptibility to Brucella intracellular parasitism. Importantly, deletion or inactivation of key signaling components along this axis, including IRE1Î±, BAK/BAX, ASK1, and JNK as well as components of the host autophagy system ULK1, Atg9a, and Beclin 1, resulted in striking disruption of Brucella intracellular trafficking and replication. Host kinases in the IRE1Î±-ULK1 axis, including IRE1Î±, ASK1, JNK1, and/or AMPKa as well as ULK1, were also coordinately phosphorylated in an IRE1Î±-dependent fashion upon the pathogen infection. Taken together, our findings demonstrate that the IRE1Î±-ULK1 signaling axis is subverted by the bacterium to promote intracellular parasitism, and provide new insight into our understanding of the molecular mechanisms of intracellular lifestyle of Brucella.
- Unfolded Protein Response (upr)
- Intracellular Trafficking And Replication
- Inositol-requiring Enzyme 1 (ire1)
- Brucella Melitensis