title: Mycobacterium tuberculosis 38-kDa antigen induces endoplasmic reticulum stress-mediated apoptosis via toll-like receptor 2/4.
abstract: Endoplasmic reticulum (ER) stress responses play critical roles in the pathogenesis of tuberculosis. To investigate the regulatory role of the ER stress response in 38-kDa antigen-induced apoptosis, we examined the relationship between the ER stress response and apoptosis in bone marrow-derived macrophages (BMDMs) stimulated with Mycobacterium tuberculosis antigen (38-kDa Ag). The expression of ER molecular chaperones, including C/EBP homologous protein (CHOP), glucose-regulated protein (Bip) and phosphorylated alpha subunit of eukaryotic initiation factor 2, was induced in BMDMs stimulated with the 38-kDa Ag. Interestingly, 38-kDa Ag-stimulation induced apoptosis via activation of caspase-12, -9 and -3. However, 38-kDa Ag-induced apoptosis was significantly reduced in TLR2- and TLR4-deficient macrophages. Because toll-like receptors (TLRs) initiate the activation of mitogen-activated protein kinase (MAPK) signaling cascades, we evaluated the effect of MAPK activation on ER stress. The 38-kDa Ag activated Jun N-terminal kinase, extracellular signal-regulated kinase and p38 phosphorylation. MAPK signaling induced the secretion of proinflammatory cytokines such as MCP-1, TNF-α and IL-6. The 38-kDa Ag-induced MCP-1 was especially associated with the induction of MCP-1-induced protein (MCPIP), which increased the generation of reactive oxygen species (ROS) and ER stress. To investigate the role of MCPIP in ROS-induced ER stress by 38-kDa Ag stimulation, we transfected MCPIP siRNA into RAW264.7 cells before 38-kDa Ag stimulation, and measured the generation of ROS and expression of ER molecular chaperones. ROS production and CHOP expression were decreased by the silencing of MCPIP induction. Our results demonstrate that the expression of MCPIP by 38-kDa Ag stimulation is increased through a TLR-MAPK-dependent signaling pathway, and leads to ER stress-induced apoptosis. In conclusion, MCPIP is important for host defense mechanisms in mycobacterial pathogenesis.
authors.affiliation: Department of Microbiology, College of Medicine, Chungnam National University, 266 Munhwa-ro, Jung-gu, Daejeon, 301-747, South Korea.
authors.forename: Yun-Ji
authors.initials: YJ
authors.lastname: Lim
authors.forename: Ji-Ae
authors.initials: JA
authors.lastname: Choi
authors.forename: Jeong-Hwan
authors.initials: JH
authors.lastname: Lee
authors.forename: Chul Hee
authors.initials: CH
authors.lastname: Choi
authors.forename: Hwa-Jung
authors.initials: HJ
authors.lastname: Kim
authors.forename: Chang-Hwa
authors.initials: CH
authors.lastname: Song
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects* / Q000235:genetics; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D009169:Mycobacterium tuberculosis / Q000737:chemistry; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012260:Ribonucleases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051195:Toll-Like Receptor 2 / Q000235:genetics* / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics* / Q000378:metabolism; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D000942:Antigens, Bacterial; D016207:Cytokines; C497250:Ddit3 protein, mouse; D000091342:Endoplasmic Reticulum Chaperone BiP; D015852:Eukaryotic Initiation Factor-2; D006360:Heat-Shock Proteins; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C072681:Mycobacterium tuberculosis antigens; D051742:Transcription Factor CHOP; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D012260:Ribonucleases; C541320:Zc3h12a protein, mouse; D020169:Caspases