title: The 19-kDa Mycobacterium tuberculosis protein induces macrophage apoptosis through Toll-like receptor-2.
abstract: Macrophages infected with Mycobacterium tuberculosis undergo increased rates of apoptosis. Important objectives are to define the microbial factors that cause apoptosis, the mechanisms involved and the impact on infection. The 19-kDa M. tuberculosis glycolipoprotein (p19) is both cell wall-associated and secreted and is a candidate virulence factor. We investigated the potential of recombinant, His-tagged p19 lacking the secretion/acylation signal to induce macrophage apoptosis. The TUNEL assay and annexin V binding to membrane phosphatidylserine were used to measure apoptosis. The results show that p19 does act to induce apoptosis in differentiated THP-1 cells and monocyte-derived macrophages and that this effect is both dose- and time-dependent. Furthermore, this effect of p19 is Toll-like receptor (TLR)-2-mediated because preincubation of either THP-1 cells or TLR-2-expressing CHO cells with anti-TLR-2 mAb inhibited apoptosis induced by p19. Apoptosis of macrophages in response to p19 was found to be caspase-8 dependent and caspase-9 independent consistent with a transmembrane pathway signaling cell death through TLR-2. The viability of M. tuberculosis in cells undergoing apoptosis induced by p19 was significantly reduced suggesting the possibility that this may favor containment of infection. Although native p19 is a mycobacterial glycolipoprotein, based upon the use of recombinant p19 where the acylation signal had been removed, we conclude that it is the polypeptide component of p19 that is responsible for signaling through TLR-2 and that the lipid moiety is not required.
authors.affiliation: Department of Medicine, Division of Infectious Diseases, University of British Columbia, Faculty of Medicine and Science, The Research Institute of the Vancouver Hospital and Health Sciences Center, Vancouver, British Columbia, Canada.
authors.forename: Martín
authors.initials: M
authors.lastname: López
authors.forename: Laura M
authors.initials: LM
authors.lastname: Sly
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Luu
authors.forename: Douglas
authors.initials: D
authors.lastname: Young
authors.forename: Howard
authors.initials: H
authors.lastname: Cooper
authors.forename: Neil E
authors.initials: NE
authors.lastname: Reiner
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D016466:CHO Cells; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000502:physiology; D006224:Cricetinae; D029721:Drosophila Proteins; D004340:Drug Contamination; D006639:Histidine / Q000235:genetics; D006801:Humans; D007424:Intracellular Fluid / Q000276:immunology / Q000382:microbiology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008074:Lipoproteins / Q000235:genetics / Q000502:physiology*; D008264:Macrophages / Q000166:cytology / Q000201:enzymology / Q000276:immunology* / Q000382:microbiology*; D008562:Membrane Glycoproteins / Q000502:physiology*; D008970:Molecular Weight; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000254:growth & development / Q000276:immunology*; D011956:Receptors, Cell Surface / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology; D015398:Signal Transduction / Q000276:immunology; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D014407:Tumor Cells, Cultured
chemical_list: C087864:19 kDa antigen, Mycobacterium; D001426:Bacterial Proteins; D029721:Drosophila Proteins; D008070:Lipopolysaccharides; D008074:Lipoproteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D006639:Histidine; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases