title: Physical and functional association of the major histocompatibility complex class I heavy chain alpha3 domain with the transporter associated with antigen processing.
abstract: CD8+ T lymphocytes recognize antigens as short, MHC class I-associated peptides derived by processing of cytoplasmic proteins. The transporter associated with antigen processing translocates peptides from the cytosol into the ER lumen, where they bind to the nascent class I molecules. To date, the precise location of the class I-TAP interaction site remains unclear. We provide evidence that this site is contained within the heavy chain alpha3 domain. Substitution of a 15 amino acid portion of the H-2Db alpha3 domain (aa 219-233) with the analogous MHC class II (H-2IAd) beta2 domain region (aa 133-147) results in loss of surface expression which can be partially restored upon incubation at 26 degrees C in the presence of excess peptide and beta2-microglobulin. Mutant H-2Db (Db219-233) associates poorly with the TAP complex, and cannot present endogenously-derived antigenic peptides requiring TAP-dependent translocation to the ER. However, this presentation defect can be overcome through use of an ER targeting sequence which bypasses TAP-dependent peptide translocation. Thus, the alpha3 domain serves as an important site of interaction (directly or indirectly) with the TAP complex and is necessary for TAP-dependent peptide loading and class I surface expression.
authors.affiliation: Michael Heidelberger Division of Immunology, the Department of Pathology and Kaplan Comprehensive Cancer Center, New York University Medical Center, New York 10016, USA.
authors.forename: K
authors.initials: K
authors.lastname: Kulig
authors.forename: D
authors.initials: D
authors.lastname: Nandi
authors.forename: I
authors.initials: I
authors.lastname: Bacik
authors.forename: J J
authors.initials: JJ
authors.lastname: Monaco
authors.forename: S
authors.initials: S
authors.lastname: Vukmanović
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation; D006183:H-2 Antigens / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D064532:Histocompatibility Antigen H-2D; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009154:Mutation; D013329:Structure-Activity Relationship; D013602:T-Lymphocytes, Cytotoxic / Q000502:physiology; D001613:beta 2-Microglobulin / Q000502:physiology
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters; D006183:H-2 Antigens; D064532:Histocompatibility Antigen H-2D; C073119:TAP1 protein, human; C486171:Tap1 protein, mouse; C489516:Tap2 protein, mouse; D001613:beta 2-Microglobulin; C071692:TAP2 protein, human