title: PstS-1, the 38-kDa Mycobacterium tuberculosis glycoprotein, 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 α-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 α-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.
authors.affiliation: Departamento de Inmunología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México City, México.
authors.forename: M
authors.initials: M
authors.lastname: Esparza
authors.forename: B
authors.initials: B
authors.lastname: Palomares
authors.forename: T
authors.initials: T
authors.lastname: García
authors.forename: P
authors.initials: P
authors.lastname: Espinosa
authors.forename: E
authors.initials: E
authors.lastname: Zenteno
authors.forename: R
authors.initials: R
authors.lastname: Mancilla
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000276:immunology*; D000117:Acetylglucosamine / Q000494:pharmacology; D000217:Acyltransferases / Q000276:immunology; D018829:Adhesins, Bacterial / Q000276:immunology*; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology; D001422:Bacterial Adhesion / Q000276:immunology; D001426:Bacterial Proteins / Q000276:immunology*; D045744:Cell Line, Tumor; D002473:Cell Wall / Q000276:immunology; D003208:Concanavalin A / Q000737:chemistry; D047468:Immunoprecipitation; D037181:Lectins, C-Type / Q000276:immunology*; D008264:Macrophages / Q000276:immunology*; D008351:Mannans / Q000494:pharmacology; D008358:Mannose / Q000378:metabolism; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000276:immunology*; D008565:Membrane Proteins / Q000276:immunology; D008766:Methylmannosides / Q000494:pharmacology; D051379:Mice; D009169:Mycobacterium tuberculosis / Q000276:immunology* / Q000472:pathogenicity; D010504:Periodic Acid / Q000378:metabolism; D010587:Phagocytosis / Q000276:immunology; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000276:immunology*; D014397:Tuberculosis, Pulmonary / Q000473:pathology; D043323:alpha-Mannosidase / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D018829:Adhesins, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D037181:Lectins, C-Type; D008351:Mannans; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins; D008766:Methylmannosides; C581205:PstS-1 protein, Mycobacterium tuberculosis; D011956:Receptors, Cell Surface; D010504:Periodic Acid; D003208:Concanavalin A; C008466:methylmannoside; C009288:metaperiodate; D000217:Acyltransferases; C112580:antigen 85A, Mycobacterium tuberculosis; D043323:alpha-Mannosidase; D008358:Mannose; D000117:Acetylglucosamine