PstS‐1, the 38‐kDaMycobacterium tuberculosisGlycoprotein, is an Adhesin, Which Binds the Macrophage Mannose Receptor and Promotes Phagocytosis

Abstract

Mycobacterium tuberculosis, the primary causative agent of tuberculosis, infects macrophages and transforms the hostile intracellular environment into a permissive niche. M. tuberculosis infects macrophages using a variety of microbial ligand/cell receptor systems. In this study, binding assays with biotin-labelled mycobacterial cell wall proteins revealed five Concanavalin A-reactive proteins that bind macrophages. Among these proteins, we identified PstS-1, a 38-kDa M. tuberculosis mannosylated glycolipoprotein, and characterized it as an adhesin. Inhibition assays with mannan and immunoprecipitation demonstrated that PstS-1 binds the mannose receptor. We purified PstS-1 to 95.9% purity using ion exchange chromatography. The presence of mannose in purified PstS-1 was demonstrated by Concanavalin A interaction, which was abolished in the presence of sodium m-periodate and a-D-mannosidase. Gas chromatography revealed that purified PstS-1 contained 1% of carbohydrates by weight, which was mainly mannose. Finally, we used fluorescent microbeads coated with purified PstS-1 in phagocytosis assays and discovered that microbead uptake was inhibited by the pre-incubation of cells with GlcNAc, mannan and a-methyl mannoside. The interaction of PstS-1 coated beads with the mannose receptor was confirmed by confocal colocalization studies that showed high Pearson and Manders's colocalization coefficients. Our findings contribute to a better understanding of the strategies M. tuberculosis uses to infect host cells, the critical first step in the pathogenesis of tuberculosis.

Transcriptional Profiling of Mycobacterium tuberculosis Exposed toIn VitroLysosomal Stress

“…Finally, in iLivE M. tuberculosis we measured the upregulation of pstS1, which encodes a mycobacterial cell wall adhesin that has been demonstrated to promote phagocytosis of mycobacteria via binding to the mannose receptor (52). This implies an increased ability of bacilli to infect neighboring host cells when released from apoptotic macrophages.…”

Mycobacterium tuberculosis Phosphate Uptake System Component PstA2 Is Not Required for Gene Regulation or Virulence

“…Since complementation analysis was not performed in this previous study we cannot rule out this possibility. Finally, PstS1 may have a virulence function that is separable from its role in P i uptake, as it was recently suggested to promote macrophage phagocytosis by binding the mannose receptor [13]. …”

Macrophage Takeover and the Host–bacilli interplay During Tuberculosis

“…MR, DC-SIGN, Mincle, Dectin-1 and Dectin-2 are among some of the myeloid CLRs future science group www.futuremedicine.com known to interact with M. tuberculosis [21][22][23][24][25]. MR recognizes many glycosylated ligands of M. tuberculosis and facilitates its phagocytosis [22,26]. Interaction of ManLAM with MR is known to inhibit phagosome-lysosome fusion, resulting in enhanced survival of the bacilli inside macrophages [27].…”

“…M. tuberculosis cell wall being rich in glycoproreins, glycolipids, lipoglycans and polysaccharides [20] is efficiently recognized by CLRs. MR, DC-SIGN, Mincle, Dectin-1 and Dectin-2 are among some of the myeloid CLRs future science group www.futuremedicine.com known to interact with M. tuberculosis [21][22][23][24][25]. MR recognizes many glycosylated ligands of M. tuberculosis and facilitates its phagocytosis [22,26].…”