Soluble tapasin restores MHC class I expression and function in the tapasin-negative cell line .220.
Tapasin forms a bridge between TAP (transporters associated with antigen processing) and MHC class I molecules and plays a critical role in class I assembly. In its absence, TAP and class I do not associate, and class I cell surface expression is reduced. We now identify two independent functions for tapasin. Tapasin increases TAP levels and allows more peptide to be translocated to the endoplasmic reticulum. Furthermore, when expressed in the tapasin-negative .220 cell line, recombinant soluble tapasin retains its association with class I and restores class I cell surface expression and function, even though it no longer binds TAP or increases TAP levels. This finding suggests that the association of tapasin with class I is sufficient to facilitate loading and assembly of class I molecules.
Lehner
P J
PJ
Section of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Surman
M J
MJ
Cresswell
P
P
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D017951:Antigen Presentation; D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015795:HLA-B8 Antigen / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D009154:Mutation; D010455:Peptides / Q000378:metabolism*; D011485:Protein Binding; D012995:Solubility; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters; D017920:Antiporters; D015795:HLA-B8 Antigen; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; D010455:Peptides; C073119:TAP1 protein, human; C107762:tapasin; C071692:TAP2 protein, human