Abstract
Protein O-mannosyltransferase (PMT) catalyzes an initial step of protein O-mannosylation of Mycobacterium tuberculosis (Mtb) and plays a crucial role for Mtb survival in the host. To better understand the role of PMT in the host innate immune response during mycobacterial infection, in this study, we utilized Mycobacterium smegmatis pmt (MSMEG_5447) gene knockout strain, ΔM5447, to infect THP-1 cells. Our results revealed that the lack of MSMEG_5447 not only impaired the growth of M. smegmatis in 7H9 medium but also reduced the resistance of M. smegmatis against lysozyme and acidic stress in vitro. Macrophage infection assay showed that ΔM5447 displayed attenuated growth in macrophages at 24 h post-infection. The production of TNF-α and IL-6 and the activation of transcription factor NF-κB were decreased in ΔM5447-infected macrophages, which were further confirmed by transcriptomic analysis. Moreover, ΔM5447 failed to inhibit phagosome–lysosome fusion in macrophages. These findings revealed that PMT played a role in modulating the innate immune responses of the host, which broaden our understanding for functions of protein O-mannosylation in mycobacterium–host interaction.
Highlights
Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the top 10 causes of death and the leading cause of death from a single infectious agent
We found that the level of O-mannosylation of proteins around 70 kD had no differences in all fractions except cell membrane (CM) of the Wt and M5447 strains
Among 23 genes, NF-κB, JUN, and CXCL8 played a core role in enriched pathways. These results demonstrated that Protein O-mannosyltransferase (PMT) deficiency reduced the intracellular survival of M. smegmatis, which was associated with failure of inhibiting the phagosome–lysosome fusion in macrophages
Summary
Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the top 10 causes of death and the leading cause of death from a single infectious agent. The burden of TB is still in a phase of high level, largely due to the TB/HIV coinfection and emergence of high drug-resistant Mtb strains (WHO, 2020). Under this situation, efforts for understanding pathogenicity of Mtb become eagerly important. Role of Mycobacterial Protein O-Mannosyltransferase provides an impermeable barrier for antimicrobial drugs resistance and is crucial for Mtb pathogenicity and survival in infected host (Abrahams and Besra, 2016; Turner and Torrelles, 2018). Recent studies showed that many cell envelope proteins and secreted proteins of Mtb were frequently O-mannosylated (Espitia et al, 2010; Mehaffy et al, 2019). The protective capacity of Mycobacterium bovis BCG was improved by boosting with the O-mannosylated protein of BCG (Deng et al, 2020)
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