Protein O‐mannosyltransferase Rv1002c contributes to low cell permeability, biofilm formation in vitro, and mycobacterial survival in mice

Abstract

Mycobacterium tuberculosis (M. tuberculosis) Rv1002c encodes the protein O‐mannosyltransferase (PMT), which catalyzes the transfer of mannose to serine or threonine residues of proteins. We explored the function of PMT in vitro and in vivo. Rv1002c protein was heterogeneously overexpressed in nonpathogenic Mycobacterium smegmatis (named as MS_Rv1002c). A series of trials including mass spectrometry, transmission electron microscope, biofilm formation and antibiotics susceptibility were performed to explore the function of PMT on bacterial survival in vitro. Mouse experiments were carried out to evaluate the virulence of PMT in vivo. PMT decreased the cell envelope permeability and promoted microbial biofilm formation. PMT enhanced the mycobacterial survival in vivo and inhibited the release of pro‐inflammatory cytokines in serum. The function might be associated with an increased abundance of some mannoproteins in culture filtrate (CF). PMT is likely to be involved in mycobacterial survival both in vivo and in vitro due to increasing the mannoproteins abundance in CF.

Defining the Genes Required for Survival of Mycobacterium bovis in the Bovine Host Offers Novel Insights into the Genetic Basis of Survival of Pathogenic Mycobacteria

“…Genes that are involved in post-translational modifications such as glycosylation were attenuating in M. bovis AF2122/97 but not required in vivo in M. tuberculosis H37Rv . Rv1002c is thought to add mannose groups to secreted proteins, and overexpression of this protein in M. smegmatis was recently shown to enhance survival in vivo and inhibit proinflammatory cytokine production ( 57 ). The substrates of the protein mannosyltransferase are thought to be several secreted lipoproteins, including LpqW, which is involved in the insertion of the virulence lipid LAM at the mycobacterial cell surface ( 57 , 58 ).…”

Enhanced Glycosylation Caused by Overexpression of Rv1002c in a Recombinant BCG Promotes Immune Response and Protects against Mycobacterium tuberculosis Infection

“…Additionally, intracellular persistence and proliferation of Rv1002c mutants in mouse and human macrophages and virulence in SCID mice were impaired, suggesting that O-mannosylation is an important pathway for successful host–pathogen interactions and establishing infectivity by M. tb [ 27 ]. M.sm overexpressing Rv1002c also demonstrated better in vivo survival than the wild-type strain [ 28 ]. Reduced immunodominant glycosylated protein levels in ΔRv1002c strains, many of which are known TLR-2 agonists, may directly impact the host’s ability to recognize pathogens and respond appropriately to infection [ 36 , 37 ].…”

“…Rv1002c is the only O-mannosyltransferase in M. tb that catalyzes the transfer of mannose to the Ser or Thr residues of the peptide chain [ 26 , 27 ]. Most O-mannosylated proteins are secreted, and bacterial surface proteins in M. tb are related to virulence [ 27 , 28 ].…”

Mycobacterium tuberculosis Biofilms: Immune Responses, Role in TB Pathology, and Potential Treatment

“… 19 Additionally, the Protein O-mannosyltransferase Rv1002c decreases cell permeability and promotes biofilm formation. 20 …”