title: Secreted proteins from Mycobacterium tuberculosis gain access to the cytosolic MHC class-I antigen-processing pathway.
abstract: CD8+ T cells play an important role in the host response to infection with Mycobacterium tuberculosis (Mtb). Mtb resides in an arrested phagosome that is phenotypically similar to an early endosome. The mechanisms by which Mtb-derived Ags gain access to the HLA-I-processing pathway are incompletely characterized. Studies with CD8+ T cell lines have suggested that Mtb Ags gain access to the HLA-I pathway in an alternate vacuolar pathway that is both brefeldin A (BFA) and TAP independent. To define the requirements of entry of Ag into the HLA-I pathway, we have used human CD8+ T cell clones specific for the secreted Mtb Ag CFP10. Human monocyte-derived dendritic cells were pulsed with CFP10 expressed in a recombinant adenovirus, surface adsorbed to microspheres, or in its native form by Mtb. When delivered by adenovirus, processing and presentation of CFP10 were blocked by both BFA and the proteasomal blocker lactacystin. In contrast, processing of CFP10 adsorbed to the surface of microspheres was not affected by either of these Ag-processing inhibitors. BFA, lactacystin, and TAP inhibition blocked the recognition of Mtb-infected dendritic cells, suggesting that processing was via a cytosolic pathway for this secreted protein Ag. We conclude that secreted proteins from Mtb can be processed in a BFA- and proteasome-dependent manner, consistent with egress of Ag into the cytosol and subsequent loading of proteasomally derived peptides.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Oregon Health Sciences University/Portland Veterans Affairs (VA) Medical Center, 3710 U.S. Veterans Road, Portland, OR 97239, USA. lewinsod@OHSU.edu
authors.forename: David M
authors.initials: DM
authors.lastname: Lewinsohn
authors.forename: Jeff E
authors.initials: JE
authors.lastname: Grotzke
authors.forename: Amy S
authors.initials: AS
authors.lastname: Heinzel
authors.forename: Liqing
authors.initials: L
authors.lastname: Zhu
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Ovendale
authors.forename: Mark
authors.initials: M
authors.lastname: Johnson
authors.forename: Mark R
authors.initials: MR
authors.lastname: Alderson
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors; D000260:Adenoviruses, Human / Q000235:genetics / Q000276:immunology; D000595:Amino Acid Sequence; D017951:Antigen Presentation / Q000187:drug effects / Q000276:immunology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D002460:Cell Line; D002461:Cell Line, Transformed; D002999:Clone Cells; D003600:Cytosol / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology* / Q000378:metabolism*; D006801:Humans; D017874:Immediate-Early Proteins / Q000502:physiology; D019344:Lactic Acid / Q000276:immunology / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D008863:Microspheres; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000276:immunology* / Q000472:pathogenicity; D011100:Polyglycolic Acid / Q000378:metabolism; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000378:metabolism; D061988:Proteasome Inhibitors; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D014764:Viral Proteins / Q000502:physiology
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; D015395:Histocompatibility Antigens Class I; C105843:ICP47 protein, Herpes simplex virus; D017874:Immediate-Early Proteins; D007976:Leupeptins; D011108:Polymers; D061988:Proteasome Inhibitors; D014764:Viral Proteins; C063261:acetylleucyl-leucyl-norleucinal; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D020126:Brefeldin A; D011100:Polyglycolic Acid; D019344:Lactic Acid