Research Scholars Annex Hall

A mycobacterial phosphoribosyltransferase promotes bacillary survival by inhibiting oxidative stress and autophagy pathways in macrophages and zebrafish

Prof. Avinash Sonawane

KIIT University, Odisha

Mycobacterium tuberculosis (Mtb) employs various strategies to modulate host immune responses to facilitate its persistence in macrophages. The Mtb cell wall contains numerous glycoproteins with unknown role in pathogenesis. We have identified a novel mannosylated glycoprotein phosphoribosyltransferase, encoded by the Rv3242c, from Mtb cell walls. Homology modeling, bioinformatic analyses and assay of phosphoribosyltransferase activity measurement in Mycobacterium smegmatis expressing recombinant Rv3242c (MsmRv3242c) confirmed the mass spectrometry data. Using Mycobacterium marinum-zebrafish and the surrogate MsmRv3242c infection models, we proved that phosphoribosyltransferase is involved in mycobacterial virulence. Histological and infection assays showed that M. marinum mimG mutant, an Rv3242c orthologue in a pathogenic M. marinum strain, was strongly attenuated in adult zebrafish and also survived less in macrophages. In contrast, infection with wild-type and the complemented ∆mimG:Rv3242c M. marinum strains showed prominent pathological features such as severe emaciation, skin lesions, hemorrhaging, and more zebrafish death. Similarly, recombinant MsmRv3242c bacteria showed increased invasion in non-phagocytic epithelial cells and longer intracellular survival in macrophages as compared to wild-type and vector control M. smegmatis strains. Further mechanistic studies revealed that the Rv3242c and mimG mediated enhancement of intramacrophagic survival was due to inhibition of autophagy, reactive oxygen species and reduced activities of superoxide dismutase and catalase enzymes. Infection with MsmRv3242c also activated the MAPK pathway, NF-κB and inflammatory cytokines. In summary, we show that a novel mycobacterial mannosylated phosphoribosyltransferase acts as a virulence and immunomodulatory factors, suggesting that it may constitute a novel target for antimycobacterial drugs.