Guanylate-Binding protein 2b regulates the AMPK/mTOR/ULK1 signalling pathway to induce autophagy during Mycobacterium bovis infection

Autophagic isolation and degradation of intracellular pathogens are employed by host cells as primary innate immune defense mechanisms to control intercellular M. bovis infection. In this study, RNA-Seq technology was used to obtain the total mRNA from bone marrow-derived macrophages (BMDMs) infected with M. bovis at 6 and 24 h after infection. One of the differential genes, GBP2b, was also investigated. Analysis of the significant pathway involved in GBP2b-coexpressed mRNA demonstrated that GBP2b was associated with autophagy and autophagy-related mammalian target of rapamycin (mTOR) signaling and AMP-activated protein kinase (AMPK) signaling. The results of in vivo and in vitro experiments showed significant up-regulation of GBP2b during M. bovis infection. For in vitro validation, small interfering RNA-GBP2b plasmids were transfected into BMDMs and RAW264.7 cells lines to down-regulate the expression of GBP2b. The results showed that the down-regulation of GBP2b impaired autophagy via the AMPK/mTOR/ULK1 pathway, thereby promoting the intracellular survival of M. bovis. Further studies revealed that the activation of AMPK signaling was essential for the regulation of autophagy during M. bovis infection. These findings expand the understanding of how GBP2b regulates autophagy and suggest that GBP2b may be a potential target for the treatment of diseases caused by M. bovis.