Roles for calreticulin and a novel glycoprotein, tapasin, in the interaction of MHC class I molecules with TAP.
Assembly of MHC class I-beta 2 microglobulin (beta 2m) dimers in the endoplasmic reticulum involves two chaperones. Calnexin has previously been shown to interact with free class I heavy chains. Here, we show that the related chaperone, calreticulin, binds human class I-beta 2m dimers prior to peptide loading. Calreticulin remains ... associated with at least a subset of class I molecules when they, in turn, bind to TAP. Further evidence suggests that the interaction of class I-beta 2m dimers with TAP occurs via a novel uncharacterized 48 kDa glycoprotein, tapasin, which can bind independently to TAP and class I-beta 2m-calreticulin complexes. Tapasin is absent from the mutant cell line .220, in which class I-TAP association and peptide loading is defective.
Mesh Terms:
ATP-Binding Cassette Transporters, Calcium-Binding Proteins, Calreticulin, Cell Line, Glycoproteins, HLA-A Antigens, HLA-B Antigens, HLA-C Antigens, Histocompatibility Antigens Class I, Humans, Indolizines, Molecular Chaperones, Mutation, Peptides, Ribonucleoproteins, beta 2-Microglobulin
ATP-Binding Cassette Transporters, Calcium-Binding Proteins, Calreticulin, Cell Line, Glycoproteins, HLA-A Antigens, HLA-B Antigens, HLA-C Antigens, Histocompatibility Antigens Class I, Humans, Indolizines, Molecular Chaperones, Mutation, Peptides, Ribonucleoproteins, beta 2-Microglobulin
Immunity
Date: Aug. 01, 1996
PubMed ID: 8769474
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