A Critical Role for Tapasin in the Assembly and Function of Multimeric MHC Class I-TAP Complexes

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Science  29 Aug 1997:
Vol. 277, Issue 5330, pp. 1306-1309
DOI: 10.1126/science.277.5330.1306

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Newly assembled major histocompatibility complex (MHC) class I molecules, together with the endoplasmic reticulum chaperone calreticulin, interact with the transporter associated with antigen processing (TAP) through a molecule called tapasin. The molecular cloning of tapasin revealed it to be a transmembrane glycoprotein encoded by an MHC-linked gene. It is a member of the immunoglobulin superfamily with a probable cytoplasmic endoplasmic reticulum retention signal. Up to four MHC class I–tapasin complexes were found to bind to each TAP molecule. Expression of tapasin in a negative mutant human cell line (220) restored class I–TAP association and normal class I cell surface expression. Tapasin expression also corrected the defective recognition of virus-infected 220 cells by class I–restricted cytotoxic T cells, establishing a critical functional role for tapasin in MHC class I–restricted antigen processing.

  • * These authors contributed equally to this work.

  • Present address: Institute of Genetics, University of Cologne, Zuelpicher Strasse 47, D-50674 Köeln, Germany.

  • Present address: Samuel Lunenfeld Research Institute, Mt. Sinai Hospital, 600 University Avenue, Toronto, Ontario, Canada M5G1X5.

  • § Present address: Department of Immunology, Brigham and Women's Hospital, 250 Longwood Avenue, Boston, MA 02115, USA.

  • || Present address: Division of Immunology, Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK.

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