Identification of sequences in the human peptide transporter subunit TAP1 required for transporter associated with antigen processing (TAP) function

• Published in: International immunology 2001-01, Vol.13 (1), p.31-41
• Main Authors: Ritz, Ulrike, Momburg, Frank, Pircher, Hans-Peter, Strand, Dennis, Huber, Christoph, Seliger, Barbara
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; antigen presentation; Antigen Presentation - genetics; antigen processing; ATP Binding Cassette Transporter, Subfamily B, Member 2; ATP Binding Cassette Transporter, Subfamily B, Member 3; ATP-Binding Cassette Transporters - genetics; ATP-Binding Cassette Transporters - immunology; ATP-Binding Cassette Transporters - metabolism; ATP-Binding Cassette Transporters - physiology; Biological Transport, Active - genetics; Biological Transport, Active - immunology; Con A concanavalin A; CTL cytotoxic T lymphocytes; Cytotoxicity Tests, Immunologic; Dimerization; Epitopes, T-Lymphocyte - immunology; Epitopes, T-Lymphocyte - metabolism; ER endoplasmic reticulum; Genetic Vectors - chemical synthesis; Histocompatibility Antigens Class I - biosynthesis; Histocompatibility Antigens Class I - genetics; Humans; LCMV lymphocytic choriomeningitis virus; Lymphocytic choriomeningitis virus - immunology; MCA methylcholanthrene; MHC; Mice; Mice, Inbred C57BL; Mice, Knockout; Mutagenesis, Site-Directed; Peptide Fragments - genetics; Peptide Fragments - immunology; Peptide Fragments - physiology; peptide transporter; Sequence Deletion; SLO streptolysin O; T cell response; T-Lymphocytes, Cytotoxic - immunology; T-Lymphocytes, Cytotoxic - metabolism; T-Lymphocytes, Cytotoxic - virology; TAP transporter associated with antigen processing; TAP1 protein; TBS Tris-buffered saline; Transfection; Tumor Cells, Cultured; β2m β2-microglobulin
• ISSN: 0953-8178; 1460-2377
• DOI: 10.1093/intimm/13.1.31

The heterodimeric peptide transporter associated with antigen processing (TAP) consisting of the subunits TAP1 and TAP2 mediates the transport of cytosolic peptides into the lumen of the endoplasmic reticulum (ER). In order to accurately define domains required for peptide transporter function, a molecular approach based on the construction of a panel of human TAP1 mutants and their expression in TAP1–/– cells was employed. The characteristics and biological activity of the various TAP1 mutants were determined, and compared to that of wild-type TAP1 and TAP1–/– control cells. All mutant TAP1 proteins were localized in the ER and were capable of forming complexes with the TAP2 subunit. However, the TAP1 mutants analyzed transported peptides with different efficiencies and displayed a heterogeneous MHC class I surface expression pattern which was directly associated with their susceptibility to cytotoxic T lymphocyte-mediated lysis. Based on this study, the TAP1 mutants can be divided into three categories: those expressing a similar phenotype compared to TAP1–/– or wild-type TAP1 cells respectively, and those representing an intermediate phenotype in terms of peptide transport rate, MHC class I surface expression and immune recognition. Thus, the results provide evidence that specific regions in the TAP1 subunit are crucial for the proper processing and presentation of cytosolic antigens to MHC class I-restricted T cells, whereas others may play a minor role in this process.