Phosphoproteomics reveals alternative roles of PknG in mycobacterial pathogenesis

ABSTRACT: Pathogenic mycobacteria, such as Mycobacterium tuberculosis, modulate the host immune system to evade clearance and promote long-term persistence, resulting in disease progression or latent infection. Understanding the mechanisms pathogenic mycobacteria use to evade the host immune system is critical to better understanding the pathogenesis of mycobacterial infection. Protein kinase G (PknG) in pathogenic mycobacteria has been shown to play an important role in avoiding clearance by macrophages through blocking phagosome-lysosome fusion; however, the exact mechanism is not completely understood. Here, to investigate the influence of mycobacterial PknG on the phosphoprotein signalling cascades triggered during early events prior to phagocytosis, RAW 264.7 macrophage cell lines were stimulated with M. bovis BCG wild-type and PknG knock-out mutant strains and harvested prior to uptake. After proteolysis, phosphopeptides were enriched via TiO2 columns and subjected to LC-MS/MS to identify differentially phosphorylated peptides between macrophages exposed to the wild-type and PknG knock-out mutant. A total of 1401 phosphosites on 914 unique host proteins were identified. Following phosphoproteome normalisation and differential expression analysis, a total of 149 phosphosites were differentially phosphorylated in the RAW 264.7 macrophages exposed to the wild-type versus the PknG knock-out mutant. A subset of 95 phosphosites was differentially up-regulated in the presence of PknG. In addition, a presence/absence analysis identified 34 phosphosites on 27 host proteins to be exclusively phosphorylated in the presence of PknG. Functional analysis of our data revealed that PknG kinase activity in mycobacteria primes an altered phosphorylation state in host macrophages prior to establishment of infection, through interfering with host spliceosomal and translational machinery, actin cytoskeletal organisation, pro-inflammatory cytokine induction, and programmed cell death, thus establishing a new role for PknG in directing the fate of mycobacteria in macrophage infections.

INSTRUMENT(S):

ORGANISM(S): Mycobacterium Tuberculosis Mus Musculus (mouse)

TISSUE(S): Macrophage

SUBMITTER: Matthys Potgieter  

LAB HEAD: Jonathan M. Blackburn

PROVIDER: PXD031055 | Pride | 2025-11-17

REPOSITORIES: Pride