Mycobacteria Manipulate G-Protein-Coupled Receptors to Increase Mucosal Rac1 Expression in the Lungs

Abstract

Mycobacterium bovis bacille Calmette-Guérin (BCG) is currently the only approved vaccine against tuberculosis (TB). BCG mimics M. tuberculosis (Mtb) in its persistence in the body and is used as a benchmark to compare new vaccine candidates. BCG was originally designed for mucosal vaccination, but comprehensive knowledge about its interaction with epithelium is currently lacking. We used primary airway epithelial cells (AECs) and a murine model to investigate the initial events of mucosal BCG interactions. Furthermore, we analysed the impact of the G-protein-coupled receptors (GPCRs), CXCR1 and CXCR2, in this process, as these receptors were previously shown to be important during TB infection. BCG infection of AECs induced GPCR-dependent Rac1 up-regulation, resulting in actin redistribution. Thealtered distribution of the actin cytoskeleton involved the MAPK signalling pathway. Blocking of the CXCR1 or CXCR2 prior to infection decreased Rac1 expression, and increased epithelial transcriptional activity and epithelial cytokine production. BCG infection did not result in epithelial cell death as measured by p53 phosphorylation and annexin. This study demonstrated that BCG infection of AECs manipulated the GPCRs to suppress epithelial signalling pathways. Future vaccine strategies could thus be improved by targeting GPCRs.

P53 in the impaired lungs

“…Bcl-2-associated athanogene 2 (Bag2) in macrophages interacts with P53 to reduce apoptosis, whereas miR-27b directly targets Bag2 and increases P53 activity [ 165 ]. The suppression of the epithelial STAT and NF-kB were abolished by the inhibition of Rac1 in Mtb infected AECs [ 166 ]. DNA damage-regulated autophagy modulator 1 (DRAM1) silencing resulted in an increased mycobacterium burden [ 167 ].…”

Innate Immune Responses of Galleria mellonella to Mycobacterium bovis BCG Challenge Identified Using Proteomic and Molecular Approaches

“…The increased abundance of β-actin at 4 h pi (+3.5 fold), may reflect the cytoskeletal redistribution and remodelling which takes place during phagocytosis ( Rougerie et al., 2013 ). In line with this observation, infection of primary murine epithelial and lung cells with BCG has been shown to up-regulate actin redistribution ( Alaridah et al., 2017 ). Studies of early granuloma structures in larval zebrafish found extensive reorganization of the actin cytoskeleton in granulomatous macrophages ( Cronan et al., 2016 ).…”

The Cholinergic System Contributes to the Immunopathological Progression of Experimental Pulmonary Tuberculosis

“…For example, the parainfluenza virus potentiates lung ACh concentrations through mRNA degradation and cleavage of sialic acid residues of the inhibitory mAChR2 which regulates both neuronal ( 38 ), and non-neuronal ACh secretion ( 38 , 40 ). Although we did not measure mAChR2 expression, previous reports suggest that Mtb is capable of altering G-protein-coupled receptor expression during infection ( 41 ). Alternatively, cytokines such as TNF-α and IFN-γ which are induced under LPS challenge ( 39 ), and are also highly induced in our model ( 20 ) should be able to increase ACh availability through mechanisms such as the inhibition of acetylcholinesterase, the ACh degrading enzyme ( 38 , 39 ).…”