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

<i>Mycobacterium bovis</i> is a major cause of animal tuberculosis that is also highly dangerous to human health. Autophagic isolation and degradation of intracellular pathogens are employed by host cells as primary innate immune defence mechanisms to control intercellular <i>M. bovis</i> infection. In this study, RNA-Seq technology was used to obtain the total mRNA from bone marrow-derived macrophages (BMDMs) infected with <i>M. bovis</i> 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) signalling and AMP-activated protein kinase (AMPK) signalling. The results of in vivo and in vitro experiments showed significant up-regulation of GBP2b during <i>M. bovis</i> 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. Further studies revealed that the activation of AMPK signalling was essential for the regulation of autophagy during <i>M. bovis</i> infection, and the down-regulation of GBP2b promoted the intracellular survival of <i>M. bovis</i>. These findings were validated on two types of macrophages, which extended the knowledge about the involvement of GBP2b in the autophagic process. Based on these observations, GBP2b should be developed as a promising molecular target for intervening on host–pathogen interactions to develop novel therapeutic strategies to control <i>M. bovis</i> infections in humans and animals.